Citation
Detection of oil pollution in the Santa Barbara Channel using spaceborne sensors

Material Information

Title:
Detection of oil pollution in the Santa Barbara Channel using spaceborne sensors
Creator:
Schuetze, Jennifer Kathleen
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
Publication Date:
Language:
English
Physical Description:
vii, 85 leaves : illustrations ; 29 cm

Subjects

Subjects / Keywords:
Oil pollution of the sea -- California -- Santa Barbara Channel ( lcsh )
Scientific satellites ( lcsh )
Oil pollution of the sea ( fast )
Scientific satellites ( fast )
Pacific Ocean -- Santa Barbara Channel ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references (leaves 77-85).
General Note:
Submitted in partial fulfillment of the requirements for the degree, Master of Basic Science
Statement of Responsibility:
by Jennifer Kathleen Schuetze.

Record Information

Source Institution:
|University of Colorado Denver
Holding Location:
|Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
37832025 ( OCLC )
ocm37832025
Classification:
LD1190.L44 1997m .S38 ( lcc )

Downloads

This item has the following downloads:


Full Text
DETECTION OF OIL POLLUTION IN THE SANTA BARBARA CHANNEL
USING SPACEBORNE SENSORS
by
Jennifer Kathleen Schuetze
B.S. San Diego State University, 1993
A thesis submitted to the
University of Colorado at Denver
in partial fulfillment
of the requirements for the degree of
Master of Basic Science
lp&Z.


This thesis for the Master of Basic Science
degree by
Jennifer Kathleen Schuetze
has been approved
by
r
Randall Tagg
Willard Chappell

Date


CONTENTS
Chapter
1. Introduction, Problem Statement and Research Qustion 1
2. Review of Existing Systems 7
2.1. Earth Remote Sensing Satellites 7
2.1.1. Landsat 7
2.1.2. NOAA Series 9
2.1.3. Topex/Poseidon 12
2.1.4. SeaSat 13
2.1.5. SIR-A and SIR-B 13
2.1.6. SIR-C/X-SAR 14
2.1.7. SPOT 17
2.1.8. Cosmos and Okean 18
2 1.9. Almaz-1 19
2.1.10. JERS-1 20
2.1.11. ERS 21
2.1.12. Radarsat 23
2.2. Tromso Satellite Station 25
3. Sensors 28
v


3.1 Passive Sensors
28
3.1.1 Thermal Infra-Red 29
3.1.2. Relfected Infra-Red 3 2
3.1.3. Ultra-Violet 33
3.1.4. Visible 34
3.2. Active Sensors 34
3.2.1. Side Looking Airborne Radar 38
3.2.2. Synthetic Aperture Radar 41
3.2.3. Scattering from Ocean Waves and Wave Damping Theory 44
4. Orbital Parameters 49
4.1. Geostationary Orbits 51
4.2. Low-Earth, Non-Polar Orbits 52
4.3. Polar Orbits 54
5. Cost 59
5 1. Cost of Oil Pollution 59
5.1.1. Cost of an Oil Spill 60
5 1.2. Cost of Oil Pollution Monitoring and Response 61
5.2. Cost of a Space-Based Detection System 63
5.2.1. Cost of a Satellite 63
VI


5.2.2. Cost of a Launch
64
5.2.3. Cost of a Ground Station 65
6. Conclusions and Suggestions for Further Study 67
6.1. Sensors 67
6.2. Orbits 69
6.3. Cost 70
6.4. Suggestions for Further Study 73
6.5. Late Breaking Updates 75
Glossary 76
References 77
vii


1. Introduction, Problem Statement and Research Question
In 1994, over 19.5 million gallons of oil were spilled in 9,440 separate
incidents in U. S. navigable waters (Federal Offshore Statistics, 1996). California is
the fourth largest producer of oil in the United States, after Alaska, Texas and
Louisiana (Meyer, 1995). As of 1986, 17 percent of California's oil was produced on
the Pacific outer continental shelf, in an area called the Santa Barbara Channel. In
1969, the largest well blowout (an unintentional, uncontrolled oil flow from an oil
well) happened on platform A in the channel (Francois, 1993). This resulted in the
loss of 3.3 million gallons of oil which spilled directly into the water (Meade and
Sorensen, 1970). While this blowout happened close to 30 years ago, the dangers of
major oil pollution still exist. In 1989, the Exxon Valdez dumped approximately 11
million gallons of oil into the Prince William Sound in Alaska (Mink, 1994), which was
only the 35th largest spill ever (Etkin, 1996). Litigation concerning the latter has
lasted more than five years. Since 1969, there have been at least 13 major spills from
aging or damaged pipelines (Francois, 1993, Big spill reported in Komi region of
Russian Arctic, 1995; Fine assessed in California oil spill, 1994). From June 1979 to
February 1980, 140 million gallons spilled at the Ixtoc I well blowout in the Gulf of
Mexico, and 1991 saw the largest spill ever with approximately 240 million gallons
1


spilled from oil terminals and tankers off the coast of Saudi Arabia. Typically 100
million gallons of oil are spilled each year (Etkin, 1996).
Santa Barbara County is considered one of the most environmentally conscious
counties in the U. S. Wildlife habitats and refuges abound within it. Santa Barbara is
also sustained by the tourist and fishing industries. Each of these is affected by oil to
some extent. While fish themselves are not impacted as seriously as other animals, the
industry can be hurt by precluding fishermen from getting around oil collection booms
as well as the oil polluting the fish as the fishermen pull them through the oily
substance (Meade and Sorensen, 1970). The tourist industry may or may not be
affected depending on the extent of the pollution (Meade and Sorensen, 1970).
Wildlife, however, is put at grave risk because of spills. Bird sanctuaries near the
Milford Haven Harbor became fouled after the U. K.'s largest tanker spill in 1996
(Grounded tanker may cause U. K.'s largest oil spill, 1996). 6,900 birds of more than
25 species were found dead (Dyrynda and Symberlest, 1997). This same spill affected
numerous species of invertebrates, virtually destroying all but two individuals of a
breed of starfish unique to this area (Pearce, 1996). Research is beginning to point out
that even rehabilitation of animals after spills is not working. Only 12 percent of
rehabilitated pelicans are surviving for at least two years (Kopytoff, 1996). Other
birds are living only six to eleven days after being released from oil rehabilitation,
whereas after release from captivity for other than rehabilitation, normal life
2


expectancy is 200 days or more (Oil seals contaminated birds' fates, 1996). Another
species greatly affected by oil pollution in the Santa Barbara Channel is the Pacific
Otter. This species is on the threatened list under the Endangered Species Act of
1977. Oil affects them in two distinct ways. As they groom themselves by licking
their fur, they ingest the toxins, which result in lung and kidney failure. Secondly, oil
prevents their thick fur from trapping insulating air bubbles, and they die of
hypothermia (Bonnel, Ford and Brody, 1996, Friends of the Sea Otter, 1997).
There are 24 oil platforms, thousands of miles of oil pipelines and shipping
lanes all through the Santa Barbara Channel (Pacific OCS Map, 1996). See Figure
1.1. This area produces a substantial amount of the United States' oil. It is fair to
conclude from the history and characteristics of this region that this is an area that
remains at risk.
Tseng and Chiu (1994) note,
"the occurrence of oil spills due to accidents such as collisions or
capsizing of tankers, or blowouts of offshore oil wells, causes major
environmental hazards. Early detection, monitoring, containment and
cleanup of spills is crucial for the protection of the
environment. . remote sensing techniques provide the potential for
early detection, monitoring and tracking of oil spills."
Until recently, the U. S. Coast Guard, the agency that responds to a spill in
federal waters, employed a fixed-wing aircraft, the HU-25B "Aireye" to detect oil
spills (Aviation Week and Space Technology, 1989). These aircraft utilize two side-
3


Figure 11: Pacific OCS Region Map (Minerals Management Service)
U.S. Departnent of the Interior
Minerals Managenent Service
Pacific DCS Region
SAN PSDRO BAY
range
County
LEGEND
|| County Boundary
Federal Ecological
Preserve
Buffer Zone
Channel Islands
y!y& National Marine
Sanctuary
|*j<| Producing Lease
[7^1 Non-Producing
LJ Lease
U. S. Congressional
District Nunber
PLANNING AREAS


looking real aperture radars mounted underneath the plane to detect areas of the sea,
whose waves are dampened by oil slicks. These aircraft are only called on now to
investigate known slicks, not to detect them initially (Blalock, USCG, Conversation,
27 Feb 1997). Essentially slick detection in the Santa Barbara Channel is dependent
on alert citizens who spot the pollution and call it in to the authorities. Obviously a
major spill will bring much attention to itself. Smaller spills, however, are very easily
missed, if no regular method for detection is employed. Such spills could occur, for
example, from seepage out of platforms or traveling vessels and even pollution from
ships illegally dumping.
Challenor (1986) and Wahl, et al (1996) both agree that satellites are well
suited to a pollution monitoring role. Wahl, et al (1996) writes, "with the launch of
the European Space Agency's satellite ERS-1 in July 1991, a new tool became
available for pollution monitoring, namely the radar satellite."
In the late 1980s a project began in Norway to dedicate a satellite ground
station to the processing of these particular radar images for the purpose of oil
pollution monitoring. By 1994, this was being accomplished in real-time.
This brings about realizations and more questions. The radar satellite seems to
work for Norway to detect oil pollution. California's Central Coast seems to be at
major risk for spills and other oil pollution. Can these two observations be connected?
Can spacebome sensors effectively detect oil pollution along California's Central
5


Coast? Are there new issues to examine in applying experience gained by the
Norwegians to a different geographical location? And is it worth the cost to attempt
this?
These questions are the primary focus of this thesis. In particular, the thesis
will assess the feasibility and a cost comparison of satellite monitoring of California's
Central Coast It will identify and suggest resolution to challenges posed in designing
such a surveillance system. The assessment will be broken down into several aspects.
First, a review of the current inventory of earth remote sensing satellites will be
completed in chapter 2, including some example images, with oil slicks, if available.
This review will also look closer at Tromso Satellite Station, the site in Norway
currently fulfilling this mission. Next, chapter 3 compares the various sensors capable
of detecting oil pollution on water and an overview of the physics behind this
phenomenon. Then chapter 4 discusses the advantages and disadvantages of various
possible orbits feasible for an earth remote sensing satellite. Finally, a broad cost
comparison is presented in chapter 5 to get an idea of the amount of money spent on
satellite programs versus the amount of money spent on oil pollution prevention and
clean-up. Chapter 6 conclude this thesis by recommending the most appropriate
sensor and orbit as well as suggestions for further study.
6


2. Review of Existing Systems
Before delving into the subject of the best way to detect oil slicks, it is
important to understand what currently exists in the worlds inventory of remotes
sensing satellites. These satellites include both active radar satellites and passive
optical sensor satellites. This chapter will also include a short overview of the Tromso
Satellite Station, a ground station in Norway already fulfilling the mission of using
space based sensors for oil slick detection.
2.1. Earth Remote Sensing Satellites
2.1.1. Landsat
Landsat is a United States earth remote sensing satellite which is an integral
part of the National Aeronautics and Space Administrations (NASA) Mission to
Planet Earth. Landsat 1, the first of six, was launched in 1972. With each subsequent
generation, improvements have been made to the sensors and spacecraft themselves.
Landsat 5, launched in 1984, is currently operational. Unfortunately, Landsat 6 was
lost in a launch problem in October of 1993. Landsat 7 is expected to be launched in
May of 1998 (Space Systems Forecast, 1996).
7


Landsats are in a sun-synchronous orbit with an altitude of 705 kilometers.
This gives a repeat time of 16 days at the equator. The satellites capabilities (for
Landsat 7) include an Enhanced Thematic Mapper (7 bands) and the Sea Wide Field
Sensor. A multispectral scanner (4 bands for Landsat 5, 7 bands for Landsat 7)
provides data to 30 meter resolution (Space Systems Forecast, 1996 and Wilson,
1996).
Landsat has detected oil slicks. The MSS band 5 imaged a spill from a
blowout in 1975 (Sabins, 1987). The thematic mapper was able to detect oil after the
Exxon Valdez oil spill in Prince William Sound. Figure 2.1 is a Landsat image of an
island called Muroroa in the Pacific Ocean. Note how the cloud cover obscures the
image of the coral beneath it (Landsat-sample images, 1996).
Figure 2.1: Landsat image of Muroroa. (Landsat-sample images, 1996)
8


2.1.2. NOAA Series
The National Oceanic and Atmospheric Administration (NOAA) Polar
Orbiting Environmental Satellites carry many different sensors. Fourteen satellites
have been produced and launched since 1960. They began as weather satellites and
have had many variations.
NOAA-M is scheduled to be launched in August of 1997. Several of the
existing satellites are still operational (Stringer, et al, 1992). They are in a polar orbit
at either 833 or 870 kilometer altitude. Each has an orbital period near 102 minutes.
There are primarily five sensors carried aboard the NOAA satellites. The three that
are for earth remote sensing purposes include the Advanced Very High Resolution
Radiometer, the High Resolution Infrared Radiation Sounder and the Microwave
Sounder Unit (Space Systems Forecast, 1996). The AVHRR gathers visible and
infrared signals to measure cloud cover and surface temperature. The other two
sensors detect and measure energy in the troposphere to construct temperature
profiles of the earths surface (Scialdone, 1996).
The AVHRR, with its five channels (Advanced Very High Resolution
Radiometer, 17 Feb 1996) is on NOAA 1,9, 11, 12 and 14 satellites. AVHRR with
only four bands is on TIROS-N, NOAA 6, 8, and 10 satellites (Scialdone, 1996).
Stringer, et al (1992) and Tseng and Chiu (1994) all discuss applications of AVHRR
9


when detecting oil slicks. AVHRR did detect oil during the Valdez crisis, but because
of the resolution, the images could only represent the oil as large unresolved map
units (Stringer, et al, 1992). Tseng and Chiu (1994) found that multi-channel
composites of the data led to slick detection during several blowouts and tanker
collisions in the Persian Gulf during Desert Storm in 1991. Figure 2.2 is an AVHRR
image of California's Central Coast. Note the obscuring cloud cover.
Figure 2.2: AVHRR image
10


The Defense Meteorological Support Program (DMSP) satellites are similar in
design to the NOAA TIROS satellites. While previously an Air Force program, an
agreement made in May 1996 placed DMSP under NOAA control. These satellites
have visible and infrared sensors plus a microwave imager. Their orbit is sun
synchronous with an altitude of 830 kilometers. They have an orbital period of 101
minutes and their 3000 kilometer swath gives global coverage of clouds every six
hours (DMSP Satellite Program Description, 29 Feb, 1997). Figure 2.3 shows a
DMSP image of the United States. Cloud cover and therefore weather patterns are
deduced from these images.
Figure 2.3: DMSP image of United States.
11


2 13 TOPEX/Poseidon
TOPEX/Poseidon is a one-of-a-kind earth observation satellite. Its mission is
ocean topography and is a joint oceanographic program with France. Its primary
instruments are two radar altimeters to measure the height of the ocean surface to a
precision of 13 centimeters (Space Systems Forecast, 1996).
This satellite was launched in August 1992 into a 65 degree inclined orbit at
1334 kilometers in altitude. Its orbital period is 112 minutes and offers a repeat time
of close to ten days (Space Systems Forecast, 1996).
Figure 2.4: Topex/Poseidon Global Image. (Topex/Poseidon images, 1997)
12


2.1.4. SeaSat
SeaSat housed the first synthetic aperture radar (SAR) ever to be placed on a
spacebome platform. It was launched on 28 June 1978 into an 800 kilometer altitude,
108 degree inclined orbit. It completed 14 orbits each day and operated for 105 days
before October, when a major short circuit in the satellites electrical system ended its
mission (SeaSat 1978, 3 Dec 1996).
Scientists were very excited at the prospect of the amount of highly resolved
data SeaSat produced. Veseky and Stewart (1982) and Sabins (1987) show images
SeaSat collected containing oil spills or pollution in the Santa Barbara Channel.
SeaSat laid the ground work for future spacebome radar experiments.
215 SIR-A and SIR-B
In November 1981, three years after the demise of SeaSat, NASA launched the
Shuttle Imaging Radar or SIR-A. A synthetic aperture radar antenna was stowed in
the shuttle cargo bay and was operated when the shuttle was inverted. The data was
recorded on board the shuttle and then processed after the mission. (Sabins, 1987)
The main goal of SIR-A was to further understanding the use of radar technology to
assess geologic features (SIR-A 1982, 3 Dec 1996).
The shuttle and therefore the sensor were in a 38 degree inclined, 259
13


kilometer high orbit The swath width was 50 kilometers. This mission was only for
five days, but covered some 10 million square kilometers (Sabins, 1987).
Sabins (1987) shows a SIR-A image of the Santa Barbara Channel with oil
slicks present and identifiable. Fiscella, et al (1991) use the data to assess the sea state
based on wind conditions.
In October 1984, three years after SIR-A, another shuttle radar experiment
was conducted. SIR-B had the added benefit of tilting the radar antenna to assess the
relationship between image intensity and depression angle. All other aspects of SIR-A
and SIR-B remained the same with another exception being that the second
experiment had most images recorded digitally and downlinked during the flight.
The shuttle was in a 57 degree inclined orbit which attained three different
altitudes: 360, 257 and 224 kilometers. It was able to attain a swath width of 40
kilometers (SIR-B 1985, 3 Dec 1996). A slick in the Sea of Japan was seen accurately
by SIR-B (Bern, et al, 1993).
2 16 SIR-C/X-SAR
The next step in shuttle based radar experiments was SIR-C/X-SAR. This was
actually two distinct experiments. The package was flown twice in 1994, once in
April, then in October, aboard the Shuttle Endeavor. These experiments were highly
evolved from any other SIR experiment or any other existing radar satellite (see JERS-
14


1, ERS-1 and Cosmos, sec 2.1.10, 2.1.11, 2.1.12) (Stofan, et al, 1995).
The X-SAR was an instrument built and sponsored by a German/Italian
alliance. Its an X-band antenna with a mechanical tilt to change the depression angle.
This antenna was based off of the Germans initial radar program the Microwave
Remote Sensing Experiment (SER-C Description, 3 Dec 1996).
SIR-C offered numerous enhancements over the previous SIRs First, it had
two different arrays for C and L band transmission. Second, the panels were built in
such a way as to send and receive any configuration of polarized radiation. This
allowed comparison of the same imaged objects using the same wavelength energy
with only polarization configuration changed, in order to see the effect of polarization
on image detectibility. Third, the antennas were not physically steerable, but were
phased arrays, offering a greater range of depression angles using electronic beam
steering (SIR-C Description, 3 Dec, 1996). Finally, because of the unique electronic
beam steering as well as an ability to send out a short burst of energy rather than a
long pulse, SIR-C could operate in a mode called ScanSAR. It sends bursts at angle
one, then bursts at angle two, then angle three, then back to angle one. This
synthesizes an even larger swath width (Chang, Jin, Lou and Holt, 1996).
The shuttle operated two eleven day missions with this experiment. The
missions were in circular, 57 degree inclined, 215 kilometer high orbits (Chang, Jin,
Lou and Holt, 1996).
15


Alpers and Holt (1995) used SER.-C/X-SAR data to identify ocean
characteristics including wave-wave interaction, something affected by oil slicks. (See
section 4.2.2.3) Grade, Alpers, Bao and Huehnerfiiss (1996) used SIR-C images of
preplanned slicks to test the ability to detect them with the varied polarization
configurations. Figure 2.5 is a SIR-C image of extensive oil slicks in the Arabian Sea,
west of Bombay, India. The dark streaks are the slicks. This image covers an area 20
by 45 kilometers (Oil slicks, 1997).
Figure 2.5: SIR-C Image of Oil Pollution in the Arabian Sea. (Oil slicks, 1997)
16


217 SPOT
SPOT (Satellite pour lObservation de la Terre) is a French earth observation
satellite. The current satellite is SPOT 3. SPOT 2 is running as an on-orbit spare to
SPOT 3 while SPOT 1 was retired in July of 1993. It had be reactivated to support
growing demand of images at an earlier time. The three are in co-planar orbits
(Kaman Sciences Corp, 1994).
SPOT has primarily one type of sensor on it. Two High Resolution Visible
(HRV) imagers collect data simultaneously. The push broom imagers achieve 117
kilometer swath widths with three kilometers of overlap. SPOT is highly capable,
however, with its unique tilting mirror. Because of it, the total swath width is 950
kilometers and the same site can be imaged on seven successive days at the equator,
eleven successive days at latitudes greater than 45 degrees (Wilson, 1996). This
scanner can be operated in multi spectral mode or a high-resolution panchromatic
mode. Because of the two imagers, SPOT can often provide stereo images of the
same subject (Sabins, 1987).
The SPOT satellites are in a sun-synchronous, 824 kilometer high, 98.7 degree
inclined orbit. They have a 26 day repeat period, but with their tiltable mirrors, each
can image a site much more often than it is physically over it (Wilson, 1996). The
following image, figure 2.6 is a high resolution visible image of an industrial area.
17


2 1 8 Cosmos and Okean
The Soviets launched Cosmos-1500 in 1983 as the first side looking radar (real
18


aperture) aboard a spacecraft. Cosmos was the precursor to the Okean satellites,
which also carry the SLAR. There were four Cosmos (-1500, -1602, -1766 and -
1869), all prototypes, before the first Okean satellite was launched and operational.
Including the prototypes, there have been nine satellites launched and one in-flight
failure of a booster, destroying the tenth. The most recently launched satellite was the
first of the third generation, Sich 1, on 31 August 1995. Currently, Okean 4 and Sich
1 are still operational. The design life of these satellites is only six months. Their
primary sensor include the SLAR, two scanning radiometers and a multi-spectral
scanner. For Sich 2, plans to include a SAR have been made. Presumably because of
the expense of this sensor, the design life of the new satellites has been increased to
three years.
Currently the Okean satellites are all in an 82.6 or 82.5 degree inclined orbit of
an altitude between 632 and 669 kilometers (Wilson, 1996).
Kalymkov, et al (1985) discuss the capabilities of the SLAR aboard the
Cosmos series of spacecraft. The SLAR with its resolution of one to two kilometers,
he states, is perfect for the detection of such large scale phenomenon as oil slicks.
2.1.9. Almaz-1
Almaz-1 is the first Russian space borne SAR to make it into space and
become operational (several attempts had previously failed). It was launched in 1991
19


into a 60 degree inclined orbit at an altitude of 260 kilometers. It has a resolution of
20 meters and a swath width of only 20 kilometers. However, it can aim its coverage
area in a swath at least 350 kilometers wide (Kamann Institute, 1994). While the
Russian satellites mentioned previously have on-board processing, the amount of data
collected on board Almaz using a SAR required processers at the ground station
instead (Kalmykov, et al, 1993).
2.1.10. JERS-1
The Japanese Earth Resources Satellite contains a SAR as well as an optical
sensor package. It was launched in February of 1992 into a sun-synchronous orbit
with orbital altitude of 568 kilometers (JERS-1, 17 Feb 1997). The radar sensor has a
resolution of 18 meters and a swath width of 75 kilometers (Kalmykov, et al, 1993).
More than 140,000 SAR and 90,000 optical scenes have been returned through March
1995 (Wilson, 1996). Figure 2.7 is an image, collected by JERS-1. It is an image of a
river delta. See the following page.
20


Figure 2.7: JERS-1 image of a river delta
2.1.11. ERS
The European Space Agency (ESA) launched ERS-1, Earth Remote Sensing
Satellite-1, in July 1991. With 30 meter resolution and a 100 kilometer swath width,
21


this was the best SAR satellite ever to attain orbit (Kalmykov, et al, 1993). Its design
purpose was ice, coastal, and ocean monitoring
ERS has other sensors as well as the SAR, including an along-track scanning
radiometer for sea surface temperature measurement and an active microwave
scatterometer for wind mode readings.
ERS-2 was launched in April of 1995. The two satellites operated in opposite
sides of the same orbit for over a year when ERS-1 was placed in stand-by mode in
May 1996 (Space Systems Forecast, 1996).
ERS-1 proved very successful, completing over 20,000 orbits and reproducing
more than 600,000 different radar scenes. The data has been used to track movement
along the San Andreas fault, movement of volcanic masses and to locate and monitor
oil pollution at sea (Space Systems Forecast, 1996).
In 1991 and 1992, ESA had a project entitled utilization of SAR for detection
of oil on sea surface in which controlled spills were coordinated with ERS-1
overpasses. This brought attention to the satellites new found capability (Bjerde, et
al, 1993). Kobayashi, et al, (1993) drew similar conclusions from a similar experiment
carried out in the Sea of Japan.
Figure 2.8 is an image collected by ERS-1 of an oil spill mentioned in chapter 1
caused by the oil tanker "Sea Empress" accident on the coast of Wales (hgsystem,
1996). The image represents a 100 by 100 kilometer swath
22


Figure 2.8: ERS-1 image of oil spill of Wales, (hgsystem, 1996)
2 1.12. Radarsat
Radarsat is Canadas first space based SAR Its mission is to provide remote
sensing in the areas of ice reconnaissance, coastal surveillance, land use mapping and
agricultural and forestry monitoring (Space Systems Forecast, 1996)
Radarsat is in a sun synchronous, 98 6 degree inclined orbit at an altitude of
793 to 821 kilometers (Canadian Space Agency, 23 Jan 1997). It was launched in
November 1995 with a five year design life (Wilson, 1996)
It is unique in several aspects. First, Radarsat is primarily a commercial
23


satellite, offering radar images to the general public for a price. Second, and more
importantly, Radarsat employs ScanSAR, a mode in which it can sacrifice some
resolution to gain a much larger swath width In standard mode, it has 25 meter
resolution with 100 kilometer swath width. In ScanSAR wide mode, it has only 100
meter resolution,, but 510 kilometer swath width. Because of this unique ability,
Radarsat is considered to have an operational capability, wherein it can be used as a
central, on-going data source for a particular type of environmental monitoring rather
than providing occasional, confirmatory coverage (Gower, Vachon and Edel, 1993).
Figure 2.9 is an image collected by Radarsat of Eastern Lake Superior. Data
such as this image are used by the Canadian Ice Service (Canadian Ice Service, 1997)
Figure 2.9: Radarsat image of Eastern Lake Superior. (Canadian Ice Service, 1997)
24


2.2. Tromso Satellite Station
In 1991, shortly after ERS-1 was launched, it was shown that this satellite
could detect oil slicks on the sea. An experiment called the "Dedicated Oil Spill
Experiment," DOSE-91, was undertaken to answer certain questions about this new
radar satellite. The experimenters wanted to discover whether or not the ERS-1
satellite was capable of detecting oil and what the capabilities are relative to an
airborne system as well as the major limits regarding detection. These questions were
answered by comparing in-situ data gathered by buoys, surveillance aircraft and other
truthing methods to the satellite data (Bern, et al, 1993). The conclusions drawn
included the wind dependency for slick detection (Bern, et al, 1993).
Later in 1992, the wind dependence problem was further demonstrated
(Andersen, 25 Feb, 1997). Tromso Satellite Station began digitally processing SAR
images on a regular basis. More than 150 were analyzed (Wahl, et al, 1996). This is
when the feasibility of near real time operations was clearly demonstrated.
In 1993 the station processed more images and began to discover and address
problems in discriminating between man-made (oil) and natural slicks. In 1994, TSS
took over the daily search for slicks in ERS-1 imagery.
During the second half of 1994, over 1700 SAR images from ERS-1 were
analyzed. This station had become the world first tracking station to routinely use
25


satellite data for real-time pollution monitoring (Wahl, et al, 1996).
Currently, TSSs main objective is to give the end users information on possible
oil spills within two hours of a satellite overpass. Based on the satellites passes, aerial
surveillance can also be more effectively scheduled.
The operators have discovered several limitations of this method, some
solvable. Winds play a major role. Winds at certain low speeds cause natural slicks to
be misinterpreted as oil slicks. This is addressed by operator training. At high wind
speeds, however, the pollutant may become mixed in with the sea, making it
undetectable by radar. Consequently, meteorological and wind information are used
to aid the operators in their assessment (Andersen, 25 Feb 1997).
Figure 2 .10 is an image processed by TSS of oil pollution in the North Sea. It
is an ERS-2 image collected on July 28, 1996. A notice was immediately sent to the
Norwegion Pollution Control Authority after interpretation of this image. The two
large dark spots are slicks while the dark spot on the top right comer of the image
shows an area of low wind conditions. This image represents a 100 by 100 kilometer
swath (Ershd, 1996).
26


27


3. Sensors
There are several ways available to detect oil slicks. We have seen examples of
each of these in previous chapters. In this section we will be looking into the
principles of the two main types: passive, those sensors that detect and record energy
naturally reflected or radiated from the sensed object (Sabins, 1987) and active, those
systems which illuminate the sensed objects with their own supplied radiation (Rees,
1990). The passive systems will be further broken down into thermal and reflected
infra-red, ultra-violet and visible. The active systems discussed here will be further
broken down into two types: side-looking airborne radar and synthetic aperture radar
Side-looking airborne radar (SLAR) is an imaging radar, one in which the
intensity of radiation reaching it is a function of intensity and position on the earths
surface. Thus a two-dimensional pictoral representation of the intensity can be
constructed (Rees, 1990). Synthetic aperture radar (SAR) is a high resolution
refinement of the SLAR (Rees, 1990).
3.1. Passive Sensors
Passive sensors detect naturally occurring radiation, without supplying energy
of their own The simplest example is a camera It records wavelenths in the visible
region of the spectrum. Several satellites exist in which variations of the basic, visible
28


camera are used, including the shuttle missions, on which the astronauts photograph
the earth using the large format camera (LFC).
The underlying principle is that all objects reflect, in various wavelengths, light
supplied by the sun. These wavelengths correspond to colors. For example, violet is
approximately 0.38 to 0.44 pm, while red is from 0.62 to 0.75 pm. The variance in
wavelength reflected or emitted by the objects then corresponds to the colors detected
on the film
This very common practice is extrapolated for remote sensing purposes.
Systems have been devised to filter out visible data and to photograph other regions of
the electro-magnetic (EM) spectrum, for example, infra-red. There are some sensors
which are sensitive to only certain regions of the spectrum and detect objects emitting
only those wavelengths. When characteristic EM signatures of objects are known,
then it is easy to correlate which objects are being remotely sensed. For example, oil
in a thin film on water has a spectral signature in the 8-12 pm region, which is
considered to be thermal infra-red. This can then be detected using sensors sensitive
to those thermal infra-red wavelengths.
3.1.1 Thermal Infra-Red
Every material has properties that are unique to it. As light, or radiant energy,
strikes its surface, that energy is partially reflected, partially transmitted through the
29


material, and partially absorbed by the material. By definition, then, reflectivity plus
absorptivity plus transmitivity equal 1 (Sabins, 1987). These all depend on the
material and the wavelength of the incident energy. To understand how objects are
detected in certain spectral regions, some background must be given.
A black body is defined as a material which absorbs all radiant energy and
radiates it. Therefore its absorptivity is 1. Suppose a material has kinetic temperature
Tkin, which is the temperture a thermometer would measure when placed in direct
contact with the material. The radiant flux, Fb, or electromagnetic energy, radiated
from the material is
Fb
(3.1)
where a is 5.67 1012 W/cm2 *K4. a is the Stefan-Boltzmann constant and (3.1) is the
Stefann-Boltzmann law. Kinetic temperature can be measured for any material and
using (3.1), the black body flux is then calculated. This is an idealism, however,
because there is no material that can act as a perfect black body, absorbing all radiant
energy and radiating the full amount of energy in (3.1). A ratio has been devised: the
actual radiant flux from a material to the radiant flux of a black body. This is called
emissivity.
(3.2)
Only a black body has emissivity of 1, while all others will be less than 1. Every
30


material has an emissivity, but it is wavelength dependent, changing for different
wavelenth values. Water with a thin film of oil has an emissivity of 0.972, while pure
water has an emissivity of 0.993. The following will show how this difference in
emissivity has detectable properties.
Combining (3.1) and (3.2), we see that radiant flux for a real material is as
follows:
F, =6 <, (3.3)
Emissivity is a measurement that quantifies the ability of a material to both
radiate and absorb energy (Sabins, 1987). Material with high emissivity absorb high
amounts of incident energy, while radiating large amounts of energy. Materials with
lower emissivity absorb and radiate lower amounts of energy. Sabins (1987) shows
that the following is true:
Trad^TUn (3.4)
Using the oil measurements and assuming a temperature of 291 K, we see that the
radiant temperature of the water with oil is 288.94 K and the radiant temperature of
the water is 290.49 K. This 1.55 K difference is very detectable using a device called a
radiometer, which is a thermal IR detector, generally sensitive to temperature
differences of 0.1 C (Sabins, 1987). Based on the Planck radiation function, the
wavelength band from 3-5 pm is most sensitive to changes in temperature at about
300K, while the 8-14 pm wavelength band is sensitive to temperature changes
31


occurring between 210 and 360K (Rees, 1990). There are several different devices
which detect this change in temperature. One has a material whose resistance changes
with the change in temperature, one has potential differences change with the
temperature change, and another consists of a crystal which undergoes a redistribution
on internal charge as a result of detected temperature change (Rees, 1990).
This sensor works well during day and night. Liu, Tseng, and Chang (1996)
present a study using data from channel 4 (thermal IR) from AVHRR Polar Orbiting
Earth Sensing satellite data, clearly illuminating an oil spill on the Gulf of Oman during
the day and at night. Thermal IR, however, is limited when moisture is present in the
atmosphere due to water absorption.
This described how thermal IR sensors work. There are other passive sensors
capable of seeing oil on ocean water. These include reflected IR, ultra-violet and
visible sensors.
3 12 Reflected Infra-Red
Whereas thermal IR sensors are based on a materials emissivity, the
othersensors are based on a materials reflectance in the various spectral regions.
Reflected infra-red is an area of the spectrum in which oil has a distinct signature from
the underlying sea water as seen in figure 3.1. The AVHRR was able to detect oil
32


UV ->4* VISIBLE--*+ PHOTO. IR
WAVELENGTH
Figure 3.1: Spectral radiance of ocean water and a layer of crude oil (Sabins, 1987)
from the Exxon Valdez spill measuring reflected IR in the wavelength range 0.72 to
1.1 pm. This was not the optimum, however, and thermal IR sensors were used
predominantly (Stringer, et al, 1992).
3 13 Ultra-Violet
As seen in figure 3.1, oil and ocean water are also discemable in the UV
region. It is clearly the most sensitive as seen by the large difference in reflectance of
33


the two substances. Due to the wavelength of UV rays, however, most are absorbed
by the atmosphere. Airborne experiments to date have been successful for
discriminating oil spills using UV sensors (Sabins, 1987; Huehnerfuss, Alpers, and
Richter, 1996). However, it is not an option at altitudes higher than 1000 meters due
to the aforementioned issue (Sabins, 1987) and will not be covered in any further
detail.
3.1.4. Visible
The visible is an option, since oil is seen in the blue to green wavelengths. This
is not as effective as other wavelengths, and especially not effective on a spacebome
platform. The angle of the sunlight causes reflection on bodies of water (Lillesand and
Kiefer, 1987). Finally, visible wave-lengths are susceptible to cloud cover hindering
the field of view as well as the limitation of not being able to image during night
periods.
3.2. Active Sensors
Active systems are different from passive types in that they supply their own
energy which is to be reflected back to be detected by the sensor. Consider a
transmitter aboard the satellite that emits isotropically. A power Pt is spread over a
surface at range Rt to give a power per unit area normal to the radiation (irradiance)
34


(isotripic)
(3.5)
E =------- in Wm'2
4ttR*
Antennas are constructed to confine the radiation to a solid angle significantly less than
47t, i.e. the antenna is directional. This is represented by a gain G such that:
P
E =------*-r-G inWm'2 (directional) (3.6)
4:rRt
For an antenna of area Ae and efficiency r|, the diffraction limiterd gain is (Rees, 1990)
G =
4teActi
%2
(3.7)
where X is the wavelength of the radiation. (Efficiency takes into account resistive
losses in the antenna so that transmitterd power is r) times the source power.) For
example, an antenna of of diameter 3 meters and efficiency of 0.9 emitting at a
wavelength 3 cm (X-band) would have G equal to approximately 9 x 104.
The radiant intensity (power per unit solid angle) scattered from an object is
I = gE in Wsr'1 (3.8)
where a is the cross-section in meters squared, of the object. The solid angle
subtended by a receiver antenna of area A, at distance R* is A,/(47i:Rv2). Thus the
power received is
P
r
= i
Ar
4nR2T
(3.9)
35


filling in equations (3.8) and (3.5)
p = Ij9.
r 4tcR2 47iR2
(3.10)
If transmitter and receiver are the same antenna with area Ae,
P = oAcG P
r 16tt2R4
(3.11)
For a scattering surface of area dAs, the cross-section is proportional to dAs.
a = adAs (3.12)
where a0 is ta dimensionless number, the backscattering cross-section per unit area.
Then
P
r
Aaa
16tt2 R4 1
(3.13)
Let dA* be estimated by the resolution of the sensor. Then dAs is equal to dxrangs times
dyazimuth If dx and dy are equal and 30m, then dAs is 900 meters squared.
The x-band backscatter coefficient for the ocean surface subject to a 10 meter
per second wind is esitmated by Rees (1990) to be on the order of -20 dB for a sensor
depression angle of 30 degrees So let a-102. If the range R is 1000 kilometers, the
estimated received power for an antenna of 3 meters diameter and 5 kW peak power
using equation (3.13) is approximately 2x 10'16 Watts. We may compare this with thte
36


thermal noise power generated at the detector. This is given by
Pth = kTAv (3.14)
where K is Boltzman's constant (1.38 xlO'23 JK'1), T is the detector temperature in
Kelvin, and Av is the detector bandwidth in Hertz. This may be approximated by 1
over the bandwidth. Suppose the detector temperature is 290 K (20C) The
bandwidth is estimated by the pulsewidth x, which in turn is related to the range
resolution dx by 2dxcos0d=cx (equation (3.16)). For dx=30meters and 9d=30,
x=0.2ps. Therefore, Av is approximately 5 Mhz and P*is 2 xlO14 W. We find,
initially, that Pt/Pth is 102, that is, the received signal is buried 20dB in the sensor's
thermal noise. Vairous remedies exist. The detector can be cooled Indeed, a liquid
helium cooled detector, for which T=4K, would bring P/Po, to unity. A further
remedy is to integrate the response over N pulses. The incoherent noise will partially
cancel itself as successive pulses are summed, while the desired signal sums directly.
An improvement by a factor of N1/2 should be achieved so that a 32 times
improvement is achieved by averaging 1000 pulse returns Doppler processing of the
signal can substantially decrease the bandwidth. For further discussion of detectability
and range of radar systmes, see Stimson, Introduction to Airborne Radar (1983)
Rees (1990) states microwave scatterometry has been used extensively for
characterising geological materials, using the variation of a0 with incidence angle 0d as
37


a signature in much the same way as materials are identified in the visible band by their
spectral signature.
3.2.1. Side-Looking Airborne Radar
The side-looking airborne radar is a real aperture radar based on the principles
outlined above. Energy in the microwave range is transmitted from an antenna in
short pulses on the order of microseconds. The signal bounces off an object and
returns to the antenna. By measuring the difference in signal transmit and receive
time, the range of the object is easily calculated (Lillesand and Keifer, 1987):
SR= (3.15)
2
where SR is slant range or distance, c is the speed of light and t is the amount of time
between transmission and echo reception. The echo is recorded, and the time delay
and intensity of the return will define the image, after the velocity of the platform is
taken into account.
The next two issues are critical for the system to be able to distinguish separate
objects: range and azimuth resolutions. Range, or cross-track, resolution is that
which is perpendicular to the flight path of the platform. It is dependent on the pulse
length of the signal, which is the duration of the transmitted pulse, x. The resulting
measurement represents the slant range, while the desired measurement is the ground
38


range (Sabins, 1987). This is the actual distance between objects that can or cannot be
resolved. The equation then, for the range resolution (measuring the actual ground
range) is:
Rr =
where 0d is the depression angle,
is approximately 65 meters. See
CT
2cosOa
(3.16)
Using x = 0.2 ps and 0d= 30, the range resolution
figure 3.2:
ANTENNA
Figure 3.2: Radar resolution in the range direction. (Sabins, 1987)
The azimuth or along-track resolution is the measurement of how distant
objects must be in a direction parallel to the flight path in order to be distinguishable.
This is based on several properties. The azimuth resolution is smaller in the near range
39


than in the far range as seen in figure 3.3. This beam width is proportional to the
wavelength of the transmitted pulse and inversely proportional to antenna length:
R. =
0.7SRZ
(3.17)
where SR is slant range distance and D is antenna length. Using D=10 meters and
altitude of 800 kilometers at a 30 degree depression angle (resulting in a slant range of
923 kilometers) the azimuth resolution is 1.9 kilometers.
TARGETS C & 0 ARE NOT RESOLVED
Figure 3.3: Radar beam width and resolution in the azimuth direction. (Sabins, 1987)
This is the limiting agent of real-aperture radars. They are simple in theory and
design but limited to low altitude with very large antennas to achieve acceptable
resolution (Lillesand and Kiefer, 1987). Knowing this, synthetic aperture radars were
developed to give increased resolution with the same size antenna. Kalmykov, et al.,
40


(1993) state, however, that spacebome real aperture radars, such as those aboard the
Soviet Cosmos and Okean satellites are suited perfectly for the initial detection of such
large features as oil slicks, where as the small resolution of the SAR is better suited for
observing fine detail.
3.2.2. Synthetic Aperture Radars
A synthetic aperture radar employs the same components as a real aperture
radar (Lillesand and Kiefer, 1987), but through use of the Doppler principle and
special data processing equipment, the azimuth resolution of a very narrow beam is
synthesized, narrow beams allowing for greater distinction between objects. See
figure 3.3.
Recalling that the Doppler principle states that the frequency source (pitch) of
the sound heard differs from the frequency of the vibrating source whenever the
listener and the source are in motion relative to one another (Sabins, 1987), it is
easily applied to detection platforms in relative motion to a sensed object. As seen in
figure 3.4, the Doppler principle can be applied to this situation (Wahl, et al., 1996).
Figure 3.5 shows the synthesized length L of an antenna with actual length D. Not
only are longer antennas synthesized in a SAR system, but dependence on altitude is
not an issue (Rees, 1990). The drawback of this system, however, is the complexity of
the data received. It requires powerful processors to produce the end-product image.
41


Figure 3.4: Doppler frequency shift due to relative motion of target through radar
beam. (Sabins, 1987)
These processors are generally too large to be aboard the satellite, so large amounts of
data are transmitted to a ground station for manipulation, the data rate also being an
issue (Challenor, 1987). When SeaSat, the first satellite with a SAR, was operational,
the computers used to digitally process the data had 512 kilobytes of random access
memory, compared to personal computers today containing upwards of 32 megabytes
of RAM. This was the reason most SeaSat data was optically versus digitally
42


SYNTHETIC
BEAM
WIDTH
Figure 3.5: Resolution of SAR in the azimuth direction. (Sabins, 1987)
processed. This, however, lends itself to distortions and other problems with data
representation (Veseky and Stewart, 1982). In the early 1990s, the European Space
Agency (ESA) underestimated the processing power required to generate top quality
digital images from their original SAR satellite, ERS-1 (Clery, 1993). Great strides
are being made, however, with individual ground stations processing their own images
to the desired resolution, Tromso Satellite Station in Norway, for example (Wahl, et
al., 1996).
43


3.2.3 Scattering from Ocean Waves and Wave Damping Theory
The incidence angle, surface tension and elastic properties of the slick all play a
role in the intensity of a backscattered signal from the sea surface (Bass and Puzenko,
1994). Vesecky (1995), defining capillary waves as those with X < 1 meter, conducted
experiments and calculations and states that wave-wave interaction also play a large
role in surface film effects.
The Bragg condition states that the path difference between two incident EM
rays is equal to an integer multiple of the microwave wavelength
Aii0r AsmQ{ = nA, (3.18)
where X is the wavelength of the microwave. See figure 3.6The path difference
between ray 2 and ray 1 is Asin0r AsinG; where 0i and 0r are incident and reflected
angles and A is the distance between the waves.
There is an additional requirement for Bragg scattering of radar from the ocean
waves. The constructive interference only occurs from those waves whose crests are
perpendicular to the direction of propagation of the radar. See figures 3.7 and 3.8.
44


Figure 3.6. Bragg Scattering
Figure 3.7. Bragg scattering can occur
45


Satellite
Figure 3.8. No Bragg scattering
The Bragg phenomenon is quite analogous to scattering of light from a diffraction
grating Radar contrast in deciels is plotted against the Bragg number for different
polarisation states. Based on the plot, the predictability of detection is assessed. It is
accepted that the incidence angle 0 of 20 to 60 degrees fits into this model (Singh,
Gray, Hawkins and O'Neil, 1986).
Oil slicks are readily detectable provided they are embedded in a wave field
that satisfies the Bragg condition. The backscattering cross section is proportional to
height of the waves. The wave height is determined by an energy balance betwen
energy supply from wind and depletion due to damping and nonlinear mechanisms that
transfer energy from one wavelength to another. The bottom line is that if there is
more damping, there will be smaller waves and consequently less scattering.
Oil has long been known to damp water waves. Conswquently there's a rich
literature describing their damping, including a "classic" treatment by Levich. Recent
46


work by Cini and Lombardini (1989) express the ratio of damping of oil covered
waves to clean water waves as:
where:
y(0 =
1 2t+2t?-x+y(x+ t)
12t+ 2t? 2x +2X2
(3.19)
T=(^f
{2g7

y
(2*1*? f
e0K
4rjpw
(3.20)
(3.21)
(3.22)
oK3
f =?-=(-£
2tc 1 2n
+ gK
-y
(3.23)
where: a is surface tension, p is water density, g is acceleration of gravity, K is wave
number, rj is kinematic viscosity and tud is characteristic frequency of the film.
da

0 d(lnT)
(3.24)
where V is surface concentration In (3.19) a plus sign is for soluble films, a negative
sign for insoluble films. In this instance, the dampling function uses wave number as a
parameter
S is devised as the omni-directional spectrum, a function of frequency and is
broken down into 3 terms. Sm or energy input from the wind, Si or non-linear cross-
47


spectral transfer due to the wave-wave interaction and finally Sas, the dissipative term.
f = S + S S* (3.25)
The surface films introduced then effect each of these parameters to varying degrees,
Sj and Sds to a greater extent. Cini, Lombardini and Huehnerfuss (1983) explain how
Sm and Si are affected and show the modification of Sds based on the presence of
surface slicks. Using (3.11) and the expression
S= 4yK2 (3.26)
where 8 is the viscous energy damping coefficient, y is the kinematic viscosity and K is
the wave number, an expression is formed that fits into
$* = <55 (3.27)
where S is the steady state spectrum in the absence of losses.
These parameters give the qualitative picture of energy transfer causing
detectable damping of wave height.
48


4 Orbital Parameters
One of the most important issues, when dealing with spacebome sensors, is the
orbital characteristics of the platform. Adhering to basic orbital mechanics, there are
still numerous ways in which to configure a satellite orbit and consequently the amount
of and location of the earth observed. Larson and Wertz (1992) state that coverage, a
part of the earth the instrument can see instantaneously or over an extended period, for
a particular location is frequently a key element in mission design. The field of view
(FOV) of a sensor is the actual area the instrument can see at one time. The access
area, contrastly, is what the sensor can see if it were rotated. Although existing
systems like SPOT (Lillesand and Kiefer, 1987) and Radarsat (Gower, Vachon and
Edel, 1993) have steerable sensors, we will deal with non-steerable beams for the most
part of this discussion.
A short synopsis of relevant orbital parameters will be instrumental in
understanding the benefits and drawbacks of each of the orbits discussed later. See
figure 4.1. The inclination, i, of an orbit is the angle at which it crosses the equator.
As the satellite is traveling northward, this point is called the ascending node, Q.
Conversely, the point at which it crosses the equator traveling southward is the
descending node. One revolution about the earth, or from ascending node to ascending
49


node, is the satellites orbital or nodal period. Apogee and perigee are the points in
the orbit furthest and closest to the earth respectively.
Figure 4.1: Classical orbital elements. (Classical Orbital Elements, 1995)
Assuming a circular orbit, with eccentricity, e, equal to 0, these are identical and equal
to the altitude of the rest of the points on the orbit. When a satellite is in a circular
orbit, the semiO-major axis, a, is equal to its altitude. Consequently, as the satellite
moves around its orbit, the earth is rotating on its axis underneath it, creating a ground
trace that appears as a sine wave, rather than a repeating circle. The ground trace is
an imaginary line following the path of the satellite travelling through space, translated
onto the earth. Lastly, as the earth moves underneath the orbit, the orbit precesses
somewhat irregularly due to several other factors including the oblateness of the earth
and other physical effects.
North
Pole
X
Venial
Equinox
Vernal
Equinox
50


Using this background, unique types of orbits will be discussed: geostationary,
low-earth orbit other than polar, and polar orbits.
4 1 Geostationary Orbits
A satellite in a geostationary orbit is, as its name suggests, at rest with respect
to the rotating earth (Rees, 1990). This is made possible by putting the satellite at an
altitude where its nodal or orbital period is the same as the earths rotational period. It
has an inclination of zero. The satellite in geostationary orbit, then appears to rest at
the same longitude, directly above the equator with a distance of 22,375 miles (Rees,
1990). This is deduced by the expression.
T = 2.76(--
104km
)2
(4.1)
When the orbital period of the earth in hours is substituted for T, the answer includes
the radius of the earth, which must be subtracted. This gives the appropriate altitude
for geosynchronous orbits. This equation was arrived at by using Newton's second
law, the law of large bodies and angular velocity.
Geosynchronous orbits have the same orbital period as the earth, but have an
inclination greater than zero. This causes the satellite to drift north and south of the
equator to the latitude corresponding to the inclination, spending equal time in each
51


hemisphere. This orbit traces out a figure-8, where the ascending and descending
nodes are on the same point on the equator.
Larson and Wertz (1992) maintain that geostationary orbits are most usefully
applied to communications and weather missions. Examples include Milstar, a military
communications satellite system and Geostationary Operational Environmental
Satellite (GOES), NOAA/NASA weather satellites (Lillesand and Kiefer, 1987).
Lillesand and Kiefer (1987), Larson and Wertz (1992) and Sabins (1987) all
state that for fine detail a geosynchronous orbit is inappropriate. The desired spatial
resolution is simply not achieved from such an altitude. Due to the nature of the
mission outlined in this paper, geosynchronous orbits will no longer be considered a
candidate solution for this issue.
4.2. Low-Earth, Non-Polar Orbits
The next option with respect to orbits is low-earth, non-polar. Low-earth, for
our purposes, will be defined as having an altitude lower than 950 miles or 1500
kilometers. Several sensors which have spotted oil slicks have been in such an orbit.
SIR-A, -B, and -C/X-SAR were all shuttle campaigns in which the sensors were in this
configuration.
Using the Central Coast of California as a target, calculations can be done
based on orbital parameters to predict how often the target is within the FOV of the
52


sensor. Assuming a side looking radar (real or synthetic aperture), the footprint area
(or FOV) is approximated at:
FA =
7iD2 sin1 0
4 sin s
(4.2)
where D is the range from satellite to the toe of the footprint (FOV), 0 is the angle
between the toe and the heel of the footprint as seen from the satellite and e is the
spacecraft elevation angle. See figure 4.2.
spacecraft
Figure 4.2: Geometry of a footprint. (Larson and Wertz, 1992)
53


Orbits attain north and south latitudes corresponding to their inclinations. The
SIR-C/X-SAR campaigns had an orbital inclination of only 57. Therefore the highest
north latitude attained was 57. The altitude of these flights, by default, gave smaller
swaths, as well (Stofan, et al., 1995). The swath is the continous coverage attained by
a particular sensor.
While this low-earth, non-polar orbit has been very useful during the shuttle
campaigns, it has the drawback that the entire earth is not viewed. Only near-polar,
low-earth orbits allow for this. While such an orbit might seem appropriate for the
low latitudes of the Santa Barbara Channel, not being able to image the entire earth is
a drawback as demonstrated in future sections.
4.3. Polar Orbits
Larson and Wertz (1992) suggest that sun-synchronous orbits are best suited
for satellites for earth resource observations. A sun-synchronous orbit is one in which
the satellite will cross a given latitude at the same solar time every day (Rees,
1990). Based on an assumption that from the earth, the sun appears to rotate about
the earth with a period of one year with an angular speed of 1.991 xlO 'V1, we set that
equal to the satellite's angular speed in order to achieve an orbit where the satellite
sees the earth at the same solar time each day.
54


COS 1
7
(
1000km
)2 =-6624.6
(4.3)
By using equation (4.3) and choosing an appropriate altitude and eccentricity, the
inclination angle can be calculated (Rees, 1990).
This makes these satellites necessarily retrograde (with inclination angle of greater
than 90) with inclinations not less than 96. This orbit has been found to be
extremely useful with visible-wavelength sensors because the satellite can be placed to
look at features at a particular time of day, i.e. local early morning or high noon,
depending on mission requirements (Rees, 1990). The majority of the earth remote
sensing satellites, past and present, utilize this orbit, to include Nimbus, SPOT,
Landsat, DMSP, NOAA, TIROS and nearly SeaSat
Additionally, because of the nature of this orbit, the coverage capability is
dependent on latitude (Wahl, et al., 1996). Wahl, et al. (1996) shows that the
coverage capability at latitude <|) of a radar satellite with a fixed swath W, doing N
revolutions per day, in an orbit with inclination, is approximately
Coverage =
NW
(4.3)
where R is the radius of the earth.
55


Figure 4.2: Coverage elements
Two good examples of how this works are ERS-1 and Radarsat. ERS-1 is able to
give 36% coverage of longitudes to locations at 35 north or south latitude based on
its orbital parameters and a 400 kilometer swath width in its three day cycle. Radarsat
with its adjustable swath width can give 90% or better coverage of longitudes to all
latitudes in its 510 kilometer mode with its three day cycle..
An important issue when dealing with remote sensing satellites is repeat time,
or how often the satellite subpoint is the same. This can be easily calculated based on
orbital parameters
56


(4.4)
?u(ne-Q) = 2n^
where Pn is the nodal or orbital period, f2e is the earths rotational speed, and Q is the
satellites precession. The ratio ni/n2 when extrapolated into integers represents the
number of days taken to revisit the same location on the earths surface, ni, and the
number of revolutions taken to get there, n2. ERS-1, for example, has a revisit time of
3 days and 43 orbits (Rees, 1990).
Rees (1992) discusses that for observing rapidly changing phenomenon, short
repeat periods are preferable. While that can be difficult to attain, orbital subcycles are
employed. This is where the orbit doesnt repeat itself exactly for long periods of
time, but almost repeats itself at much shorter intervals. Rees (1990) uses ERS-1 as
an example, again using ni is 3 days and n2 is 43 orbits. Using these parameters, the
suborbital tracks or ground trace at the equator corresponds to about 930 kilometers.
(460 kilometers at 60 north or south) Using the case ni is 80 days, n2 can be 1143,
1147 or 1149. This corresponds to a suborbital track spacing of 35 kilometers at the
equator, giving much more complete coverage than the 3-day repeat orbit. However,
using n2=l 147, the satellite has made 43 orbits in 2.999 days, instead of the original 3
and is only 0.31 east of its original position, or intended position for the 3-day repeat.
This is only 34 kilometers away (at the equator). So while the satellite sub-point is not
exactly the same, a sensor with at least a 60 kilometer swath, in this example, will have
57


an approximate 3-day repeat period. This will allow the sensor to image the same
point over more consecutive days, but it will miss the same point more days as well.
An additional factor to be taken into consideration is a steerable sensor. SIR-
C/X-SAR (Chang, Jin, Lou and Holt, 1996), Radarsat (Gower, Vachon and Edel,
1993) and SPOT (Lillesand and Kiefer, 1987) all use or used steerable sensors to gain
better coverage for particular features, chosen on a real-time basis. The added feature
of variable swath width (on SIR-C and Radarsat) is also extremely useful in real-time
mission parameter changes. With the larger swath width, resolution is the trade-off.
58


5 Cost
This section is a brief comparison of the cost of a satellite, as part of an early
warning and detection system, and the cost of an oil spill and oil pollution in general.
This evaluation is not intended as a conclusive cost analysis, but rather a general study
to give an overview of the figures and determine the need for a more thorough cost
analysis.
5 1. Cost of Oil Pollution
Schriel (1989) and Sabins (1987) both state that the causes of oil pollution can
generally be divided into distinct sources, but give conflicting figures on the amounts
from each source. While Schriel (1989) has transportation at 9%, Sabins (1987)
names it as the largest source, 45%. Schriel (1989) has land run-off as the largest
polluter (50%) while Sabins (1987) has it second with 36%. Sabins (1987) names off-
shore drilling the smallest polluter at 1.5%, while Schriel (1989) names it second
highest at 32%. Looking at either scenario, it is easy to see that pollution from any
source is an issue to be dealt with. Sabins (1987) puts the total amount of oil pollution
in marine environments at 3.24 million metric tons. For purposes of cost, oil pollution
will be looked at from two angles: pollution caused by oil spills and pollution caused
by everything else, including the above-mentioned sources.
59


5 1.1 Cost of an Oil Spill
In 1969, the Santa Barbara Channel experienced one of the worst blowouts of
oil ever. An uninhibited oil and gas flow lasted for 10.5 days, with spillage and
seepage occurring intermittently for one year. Estimates put the total released for the
first 100 days at 3.25 million gallons of oil and natural gas (Meade and Sorensen,
1970).
Meade and Sorensen (1970) divide the cost of an oil spill into seven categories:
direct clean up and property damage, damage to tourism, damage to commercial
fishing, decline in real property values, damage to the marine environment, esthetic
costs and reduction in recreational opportunities for the resident population, and
finally loss of the resource itself.
The largest part of the expense was the actual clean up, costing the oil
companies 10.5 million 1969 dollars (Meade and Sorensen, 1970). This equates to
approximately 45 million 1995 dollars (u. S. Bureau of the Census, 1996). The
estimated total cost of this oil spill was 16 5 million 1969 dollars (Meade and
Sorensen, 1970), equating to 68.6 million 1995 dollars (U. S. Bureau of the Census,
1996).
This is a conservative figure for one spill that happened almost 30 years ago
The Exxon Valdez spill in March 1989 has cost Exxon $8 7 billion. This includes
actual cleanup, $2.1 billion, money to the state and federal governments for fines,
compensatory and punitive damages, and others (Mink, 1994). Even more recently, in
60


1994, 2000 barrels were spilled in Taft, California due to an aging pipeline. Although
claiming no responsibility, one corporation paid $8.3 million in direct clean up costs
and $3.2 million to the California and federal governments (Fine assessed in California
oil spill, 1994).
On top of dealing with spills when they occur, there are several federal and
California state agencies that deal with oil pollution on an everyday basis.
5.1.2. Cost of Oil Pollution Monitoring and Response
California Department of Fish and Game has an office of Oil Spill Prevention
and Response, which works closely with the federal equivalent, the U. S. Department
of the Interior's Minerals Management Service (Cooperative Agreement). Because of
the Exxon Valdez disaster, the federal government passed the Oil Pollution Act (OPA)
of 1990 (Natural Resource Damage Assessment under the OPA of 1990, 1997).
These two offices as well as the Coast Guard enforce the tenets of OPA, which require
that the natural resources be restored to their original condition and compensation be
paid for lost services as a result of oil spills (Natural Resource Damage Assessment
Under the OPA of 1990, 1997). NOAA has formed several centers charged with
damage assessment and restoration to coastal environments plagued with oil pollution
(NOAA Damage Assessment and Restoration Center Northwest, 1997). The federal
Environmental Protection Agency also plays a role in oil spill response and clean-up
61


The Minerals Management Service, charged with "regulation and supervision
of energy and mineral exploration, development and production operations on the
OCS lands" (Amendment to the Federal Budget, 1997) has a 1997 estimated budget of
$80 million just to deal with outer continental shelf (OCS) lands. Oil spill research is
specifically allocated $6.4 million.
The U. S. Coast Guard, who "detect and respond immediately and substantially
to potential or actual oil or hazardous discharges" (MSO San Francisco Fact Sheet,
1997) is allocated $242 million per year for "marine environmental protection"
(Amendment to the Federal Budget, 1997).
The Environmental Protection Agency was authorized $30 million for 1997
specifically for oil spill response (Amendment to the Federal Budget, 1997).
NOAA has a revolving account of at least $2 million annually ($14 million in
fiscal year 1996) to carry out oil and hazardous materials contingency planning and
response, natural resource damage assessment and restoration of lost natural resources
(Amendment to the Federal Budges, 1997).
Finally an oil spill liability trust fund was set up by the federal government in
compliance with a public law of 1989. A $0.05 per barrel tax for domestic or
imported oil has brought the balance of this fund to $1.236 billion. Legislation is
currently pending to raise the cap of this fund to $2.5 billion. While the tax pays into
the fund, so do penalties and fines assessed against polluters. For fiscal year 1997, it is
estimated that $374 million will be collected (with an existing balance of $997 million)
62


and only $135 million will actually be spent. This is the maximum allowable amount to
come out of this fund. So it essentially just grows larger.
The total budget for oil spill response is approximately $280 million, excluding
the $1.2 billion trust fund.
5 2 Cost of a Space-Based Detection System
The cost of a space-based detection program will be broken down into three
separate categories: the cost of the satellite itself, the cost of the launch vehicle and
the cost of the ground station support, needed to keep the satellite operational and
downlink the data.
5.2.1. Cost of a Satellite
Not being able to solicit bids from actual aerospace corporations for a
theoretical satellite, the best way to determine the cost of one is to look at how much
earth remote sensing satellites in existence originally cost. We will look at several,
including Landsat, Topex/Poseidon and the radar satellites currently in the inventory.
ERS-1, the original SAR satellite after SeaSat, cost $850 million dollars to
produce. While that one was extremely costly, ERS-2, a virtual duplicate of the first,
except for additional sensors, was one-third as much, costing $275 million (Space
Systems Forecast, 1996). Assumably, this is because the technology was no longer
breakthrough.
63


Landsat is a less expensive program. Landsat-7, currently being built is
expected to cost an estimated $200 million (Space Systems Forecast, 1996). It is not
as expensive as the radar satellites seen here.
Meteosat, another non-radar satellite, is in a geosynchronous orbit, designed
for a weather observation mission. Each of these spacecraft (those not yet built) is
expected to cost about $180 million (Space Systems Forecast, 1996).
NOAA, another series of weather satellites, cost $67 million, with follow-on
spacecraft expected at approximately $75 million (Space Systems Forecast, 1996).
Radarsat, Canada's space-based SAR, is one of the more expensive spacecraft.
The first cost $390 million (Space Systems Forecast, 1996). If the program continues
as the ERS program did, the follow-on satellites will be considerably less expensive.
Topex/Poseidon is an expensive system costing $470 million for the spacecraft
Several active microwave instruments on this platform, a design life of 12 years and
total systems redundancy each drive the price higher. Its follow-on is expected to
drop to $310 million (Space systems Forecast, 1996).
5 2 2 Cost of a Launch
The cost of a launch vehicle must be taken into consideration as the boosters
are often as expensive as the spacecraft itself. Often the same launch vehicle can cost
different amounts, based on the weight taken into orbit.
64


The Arian 4 cost $40-50 million for 1200-1600 kilograms, $55-65 million for
2000-2500 kilograms, $65-80 million for 2500-3000 kilograms and $90-110 million
for payloads greater than 3000 kilograms. Other options can be included for a price,
transportation of the spacecraft to the launch site, for example (Wilson, 1996). The
Topex/Poseidon launch on an Arian 4 cost $130 million (Space Systems Forecast,
1996).
The United States' largest expendable booster is the Titan IV, produced by
Lockheed Martin. The contract with the U. S. Air Force sets the cost of a single
booster to $190 million, not including an upper stage (Wilson, 1996).
Lockheed Martin's Atlas Centaurs has been used to launch NOAA's GOES
satellites into orbit. $200 million put three into space, averaging $67 million for each
launch (Wilson, 1996).
McDonnell Douglas Aerospace's Delta rockets come with different
specifications and different prices. A Delta 2 is available for $55 million, a Delta 3,
$75 million (Wilson, 1996).
As seen here, depending on the orbit launched into and the weight of the
spacecraft, launch could cost anywhere from $55 to 190 million.
5.2.3. Cost of a Ground Station
Without the support of a ground station, a satellite is virtually useless The
ground station is where the state of health of the satellite itself is monitored and from
65


where commands are sent to the spacecraft to complete preventative maintenance and
respond to satellite anomalies. Besides that, a ground station is where a spacecraft
will downlink mission data. In this case it would be the images from radar or optical
systems that were collected and recorded earlier in the orbit or collected at the time of
downlink.
Some satellite have complex ground station networks set up, while others only
require two or three stations. Some ground stations do double duty, acquiring data
from multiple satellites.
The United Kingdom is establishing an Earth Observation Data Center for the
processing of remote sensing data. The contract is worth $14 million for the first four
years.
ERS-1 cost $1.3 billion, to include launch, satellite and three years of ground
station support. This results in a yearly cost of approximately $100 million. Because
of ERS's complex ground segment, this money could go to up to 23 ground stations
(Space Systems Forecast, 1996). However, most of these ground stations support
other satellite programs as well.
Based on the previous information, a satellite program with an active radar
could cost approximately $600 million: $300 million for the satellite, $200 million for
the launch and $100 million for three years support from a ground station network.
Because this effort is no longer original, the cost could be considerably lower.
66


6. Conclusions and Suggestions for Further Study
Challenor (1988) states satellites "are well suited to a general monitoring role"
when it comes to oil pollution detection. Wahl, et al, (1996), Anderson (1997) and
Victorov (1996) and Gower, Vachon and Edel (1993) all state something similar in
that satellites are well suited to this role. Having established that, the question then
becomes which orbit, which sensor and can it be cost effective. While the arguments
for each of these questions were made in previous chapters, the following three
sections will submit conclusions. The final section will suggest what further studies
should be accomplished to either further support this thesis or to test other, closely
related topics.
6 1 Sensors
Referring back to section 3, it is noted that there are two main sensor types:
active and passive. Of the passive systems discussed, each has advantages and
disadvantages. Thermal and reflected infrared each have difficulties with cloud cover.
Because coastal zones are often obscured by clouds, it is imperative to find a sensor
for which clouds are not a problem. While these passive sensors have had success in
detecting oil slicks, they would be unreliable because of the overwhelming chance of
67


unfavorable weather conditions. Ultra-violet sensor do not fair well above 1000
meters, making them inappropriate for a space-based platform.
This brings our attention to active microwave sensors. Those covered include
synthetic aperture radar and side-looking airborne radar, both imaging radars. It has
been shown that the SAR on board ERS-1 and -2 has been used successfully to image
oil slicks (Wahl, et al, 1996, Victorov, 1996, Stringer, et al, 1992). The problems with
this method have also been identified. Detection using active radar is wind dependent.
Oil can only be detected with winds between 2 and 13 meters per second (Wahl, et al,
1996; Gower, Vachon and Edel, 1993). Overwhelming amounts of data are produced
using this sensor. This causes problems for both the downlink capacity and for the
computing power needed on the ground (Challenor, 1988). Limited information
concerning spacebome SLARs has been presented as very few systems employ this
sensor. While Kalmykov, et al (1993) make the argument the SLARs are very well
suited for oil slick detection due to the resolution trade-off for less computing power
required, more studies indicate synthetic aperture along with its inherent liabilities is
the sensor of choice.
Some of the known liabilities include wind dependence for detection capability,
large amounts of data encumbering the downlink data rate, mistaking natural slicks for
man-made slicks, and power limitations. Some of these have been already considered.
Operator training is one solution to two of the problems: better interpretation during
68


unusual wind conditions and fewer mistaken slicks of biogenic source (Wahl, et al,
1996; Victorov, 1996). While data rates of 1000 megabits per second were a major
issue in 1988 (Challenor, 1988), with the evolution of computer systems, this might
not be a problem anymore. It does merit further study. Finally, based on orbital
mechanics and when the satellite is in eclipse, the on-board batteries can probably
support operation of a SAR no more than 10 minutes per period. This issue also
warrants further study.
In conclusion, synthetic aperture radar meets the sensor requirements. It sees
through clouds and can have a very high resolution. In addition, those SARs with a
variable swath width are even more valuable, as a sensor can be scanning for a slick in
a lower resolution, larger swath width mode to ensure greater coverage.
6.2. Orbit
As seen in chapter 4, primarily three orbits can be offered for earth remote
sensing purposes: low-earth orbit, sun-synchronous or polar and geosynchronous.
Geosynchronous is not an option due to the limited resolution and the inability of the
signal to stay above noise levels when traveling from that distance. Low-earth orbit,
with an inclination of at least 35 degrees would cover Central California, but would be
very limiting for other geographic regions, i.e. those above 35 degrees north and
below 35 degrees south latitude. While the issue of cost has not yet been discussed,
69


multi-tasking is obviously a way to reduce cost. By limiting the total earth coverage,
the price is, be default, being driven up. Polar, sun-synchronous orbits seem to be the
choice for earth remote sensing. This issue of latitude of the Central Coast becomes a
player with this orbit. As it is fairly close to the equator, Central California will be
afforded less coverage than those locations closer to the poles (Gower, Vachon, and
Edel, 1993). This is to be dealt with by trade-offs in repeat time and sensor
swath/resolution
6.3. Cost
This thesis presented several oil spill incidents. The Santa Barbara Channel
spill of 1969 translated into $70 million and 3.3 million gallons of oil lost. The Exxon
Valdez spill cost Exxon $8.7 billion and 11 million gallons of oil.
The budget of the U. S. Government was consulted and found that $280
million is spent annually on oil spill prevention. This excludes the Oil Spill Prevention
Liability Trust Fund of $1.2 billion and any amount of money the oil companies
themselves spend on detection and monitoring.
We've seen the cost of a SAR system drop from $870 million to $275 million
because the technology was no longer original. While the average radar satellite cost
hovers around $350 million, the price has dropped considerably. Also, compared to
70


what is contained in the trust tund and what was spent on the Valdez disaster alone,
this amount pales in comparison.
According to Wahl, et al, (1996) satellite images are competitively priced.
Anderson (1997) asserts that surveillance from satellites is less expensive than that
from airborne sensors.
Finally, radar satellites were designed with different functions in mind than
detecting oil pollution. Surely multi-tasking of one will spread the cost burden to
other agencies who will utilize the data for purposes of ice mapping, wind condition
monitoring, ocean current tracking and other oceanographic related missions.
Victorov (1996) states the requirements for an early warning system include
time delay of less than one hour with coverage of traffic lanes and coastal zones,
repeat time of less than twelve hours with a 75% success rate of detecting slicks with
an area at least 0.01 square kilometers. Link, McKim and Bruizewicz (1991) state
that the "optimum sensing package for oil spill sensing form satellites would be a
system with the resolution of the TM (thematic mapper), the daily coverage of the
AVHRR and the all weather mapping capability of a SLAR." Challenor (1988) give
requirements of an active microwave sensor with a swath width in excess of 1000
kilometers and resolution of 25 meters. He suggests two satellites in different
locations of the same orbit: one leading the way with a low-resolution, large swath,
71


the second following with a steerable, high resolution sensor, able to focus on what
was detected by the first satellite.
The author agrees with Wahl, et al, (1996) who states, "it is recommended that
pollution authorities worldwide consider the use of radar satellites as an additional
source of environmental information from their coastal waters."
It has been calculated that the minimum amount of time to image a location is
2.4 days after its original imaging This is using Radarsat, ERS-1 and JERS. Because
ERS has no recording capability, it can image only where it can downlink data to a
ground station. Finally, while each satellite can only image for approximately 10
minutes per orbit, based on the satellites speeds, each only needs to radiate on the
order of seconds in order to achieve images covering the entire Santa Barbara
Channel This could become an issue, however, based on whether or not the satellites
are in eclipse. The batteries have limitations on what power they can provide to the
active instrument.
It has been mentioned that the volume of oil is most important to ascertain
when dealing with a slick. While SARs have been shown to be effective in
determining slick thickness (and therefore volume), thermal IR sensors have been
shown to be more effective. During the Valdez disaster, the initial slick stayed
relatively motionless, staying in an area of 350 square kilometers for 2.5 days before
dispersing because of wind driven sea state conditions. This represents a square with
72


18.7 kilometer legs. The platform in the Santa Barbara Channel furthest from shore is
only 16.5 kilometers away, the closest being 6 kilometers. Had Valdez happened near
any platform in the channel, the beaches would have been effected immediately. This,
again, is where the most damage occurs and the most costs are incurred. Early
warning to locate the slick and track the bulk of the oil mass is paramount to
preventing its spread towards land where it does the most damage.
Synthetic aperture radar effectively detects oil pollution in marine
environments. Knowing the orbital limitations of systems and the systems already in
service, it is recommended that these parameters be taken into account in a further
study to design a constellation with both oil pollution monitors and other data users in
mind. Funding could be solicited not only from the federal and state governments and
any other associated agencies who would use the data, but also from large oil
companies who contribute the most to cleaning up oil pollution.
6 4 Suggestions for Further Studies
While this paper was designed to bring several concepts together, further
studies are necessary to supply proof of several of the hypotheses herein.
First, dealing with the constellation itself, using existing satellites downlinked
data, and that from any future projects from any other nations, determine how many
specific platforms would give the desired coverage, resolution and repeat time. This
73


can be done only after a customer, possibly the EPA, has chosen specifications for the
detection mission. Investigate to see if existing ground stations, such as the Alaska
SAR Facility in Fairbanks, are able to handle another mission or if separate, dedicated
facilities must be built.
Second, determine by how much oil spills become more costly and harmful as
they go undetected for hours or days. This will also include a model for how the
majority of the oil travels, based on prevailing winds and currents, and when it will
reach shore causing the most damage. This will further enforce the cost effectiveness
issue.
Third, once a platform has been chosen, ground station and booster secured,
and the actual cost in terms of time is deduced, conduct a succinct cost analysis to
verity the cost effectiveness.
Finally, probe users to see if any other data could be useful. This could include
ice mapping, current monitoring and even land-based applications.
These further studies will provide proof to the hypothesis that the volatile
California Central Coast as well as other coastal areas can be effectively monitored for
oil pollution by satellites, presumably in a cost-effective manner.
74


6.5. Late Breaking Updates
In a conversation with John Barry, engineer and program manager for Boeing
Aerospace, on 30 March 1997, it was discovered that the United States government is
currently investigating a radar satellite initial concept. Several corporations have been
invited to submit proposals for the concept of an unclassified constellation of radar
satellites.
75


Glossary
Terms Definition
Advanced Very High Resolution Radiometer Thermal ER sesor aboard NOAA Polar Orbiting Environmental Satellites
Depression angle Angle betwen flight path of instrument and slant range
High Resolution Infrared Sounder Unit IR sensor aboard NOAA POES
Microwave Sounder Unit Passive microwave sensor aboard NOAA POES
Multi-spectral Scanner Sensor aboard Landsat, detecting in different wavelengths
On-orbit spare Satellite which is not currently being used, but is still in its orbit and can be reactivated
Push-broom imagers Sensor type on board SPOT, scanning continually
Thematic Mapper Thermal IR sensor aboard Landsat
Wave-wave interaction When waves intersect one another
76


References
Alaska SAR f acility (ASF) data center document. (1995, Oct 24).
http://asf.ww,v.:ilaska.edu/datacenters_documents/asf_datacenter.html. (7 April 1997)
Alpers, W. and Holt, B. (1995). Imaging of ocean features by SIR-C/X-SAR: an
overview. 1995 International Geoscience and Remote Sensing Symposium, 2, 1588-
1590.
Alpers, W. and Huehnerfuss, H. (1989, May 13). The damping of ocean waves by
surface films: a new look at an old problem. Journal of Geophysical Research, 94,
6251-6265.
Alpers, W. (1983). Imaging ocean surface waves by synthetic aperture radar-a
review. In Allan, T. D. (ed.), Satellite Microwave Remote Sensing, 107-119.
Chicester: Ellis Horwood Limited.
Andersen, J. H. Oil spill monitoring by use of radar satellites and sircraft.
http://www.tss.no/oilserv/brosjyr.html. (25 February 1997).
Appendix to the Budget of the United States Government. (Fiscal Year 1997).
Washington, D. C.: U. S. Government Printing Office.
ASF (1996). Supported satellites characteristics.
http://www.asf.alaska.ecu/reference_documents/source_references/orbits.html. (11
April 1997).
Basic Petroleum Book. (1987). American Petroleum Institute
Bass, F. G. and Puzenko, S. A. (1994). Detection of oil spills on the sea using radar
measurements. Journal of Electromagnetic Waves and Appliations, vol 8, #7, 859-
870.
Bate, R. R., Mueller, D. D., and White, J. F. (1971). Fundamentals of
Astrodynamics. New York: Dover Publications, Inc.
77


Bern, T. I., Wahl, T., Anderssen, T. and Olsen, R. (1993, March). Oil spill detection
using satellite based SAR: experience from a field experiment. Photogrammetric
Engineering and Remote Sensing, vol 59, #3, 423-428.
(1995, Jan 2). Big spill reported in Komi region of Russian Arctic. The Oil and Gas
Journal, vol 93, #1. 30.
Bjerde, K. W., Schistad Solberg, A. H. and Solberg, R. (1993). Oil spill detection in
SAR imagery. 1993 International Geoscience and Remote Sensing Symposium. 943-
945.
Bonnell, M. L., Ford, R. G., and Brody, A. J. (1996, Dec). Assessing the threat of oil
spills to southern sea otters. Endangered Species Update, vol 13, #12. 38.
Canadian Ice Service. Radar sat image of the month.
http://www.dow.on.doe.ca/ice/picmonth/radarsat.html. (11 April 1997).
Canadian Space Agency. Radarsats FAQ: most frequently asked questions.
http://radarsat.spac.gc.ca/eng/radarsat/faq.html. (23 January 1997).
Canadian Space Agency. Radarsats specification sheet.
http://radarsat.spac.gc.ca/eng/radarsat/specification_sheet.html. (23 January 1997).
Challenor, P. G. (1988). The future role of satellites. In Lodge, A. E., (ed.) The
Remote Sensing of Oil Slicks, 143-147. Chicester: John Wiley and Sons, Ltd.
Chang, C. Y., Jin, M. Y., Lou, Y. and Holt, B. (1996; September). First SIR-C
scansar results. IEEE Transactions on Geoscience and Remote Sensing, vol 34, #5,
1278-1281.
Cini, R., Lombardini, P. P. and Huehnerfuss, H. (1983). Remote sensing of marine
slicks utilizing their influence on wave spectra. International Journal of Remote
Sensing, vol4,#l, 101-110.
Clery, D. (1993, June 18). ERS-1 give europeans new views of the oceans. Science,
260, 1742-1743.
Coast Guard radar images are key to tracking oil spills. (1989, April 10). Aviation
Week and Space Technology, 18.
78


Cooperative Agreement. California Department of Fish and Game Office of Oil Spili
Prevention and Response and U. S. Department of Interiors Minerals Management
Service Pacific OCS Region. Camarillo, CA: Minerals Management Service.
DMSP Satellite Program Description.
Http://web.ngdc.noaa.gov/dmsp/source/dmspdesc.html. (26 February 1997).
Dundee Satellite Station Advanced Very High Resolution Radiometer (AVHRR)
http/Avww.sat.dundee.ac.uk/avhrr.html. (17 February 1997).
Dyrynda, P. and Symberlist, R. (1997, Feb 1). Casualty statistics for birds.
http://www.swan.ac.ak/biosci/empress/birds/stats.htm. (11 April 1997).
Elachi, C. (1987). Spacebome Radar Remote Sensing: Applications and Techniques.
New York: The Institute of Electrical and Electronics Engineers, Inc. Press.
Ershd. (1995, Nov 28). Oproto (Portugal) October 94.
http://gds.esrin.esa.it/0xc0tafc3d_0x0005e065. (11 April 1997).
Ershd. (1996, Jul 25). Isle of Amrum (Germany) June96.
Http://gds.esrin.esa.it/0xc0tafc3d_0x000703be. (11 April 1997).
Ershd. (1996, July 26). North Sea July 96.
http://gds.esrin.it/0xc06afc3d_0x00070408. (11 April 1997).
Etkin, D. S. (1996). Oil spill basics: a prime for students. Oil Spill Intelligence
Report, http://www.cutter.eom/osir/osirbasc.htm#yearly. (11 April 1997).
(1994, Aut 29). Fine assessed in California oil spill. The Oil and Gas Journal, vol 92,
#35. 38-39.
Fiscella, B., Lombardini, P. P., Trivero, P., Cappa, C. and Pavese, P. (1989, March
29). Model of mesoscale wind field obtained from SAR marine images. II Nuovo
Cimento, vol I2c, #6, 787-797.
Fiscella, B., Lombardini, P. P., Trivero, P., Pavese, P. and Cappa, C. (1991, March-
April). Western Mediterranean wind field deduced from SIR-A SAR images. II
Nuovo Cimento, vol 14c, #2, 127-133.
79


Flament, P., Carance, R., Holt, B. and Bernstein, R. (1995). Multi-frequency and
interferometric SAR mapping of wind-driven mesoscale oceanic processes off northern
California and in the lee of the island of Hawaii. 1995 International Geoscience and
Remote Sensing Symposium, 2, 1120-1122.
Francois, D. K. (1993). Federal offshore statistics. OCSReport, 141-145.

Friends of the Sea Otter. Oil: the number 1 threat to sea otters.
http://www.seaotters.org/oil.html. (11 April 1997).
Gade, M., Alpers, W., Bao, M. and Huehnerfuss, H. (1996). Measurements of the
radar backscatter over different oceanic surface films during the SIR-C/X-SAR
campaigns. 1996 International Geoscience and Remote Sensing Symposium, 860-
862.
Goodman, R. H. (1988). Application of the technology in North America. In Lodge,
A. E. (ed.) The Remote Sensing of Oil Slicks, 39-61. Chicester: John Wiley and
Sons, Ltd.
Gower, J. F. R., Vachon, P. W. and Edel, H. (1993, Noverber-December). Ocean
applications of radarsat. Canadian Journal of Remote Sensing, vol 19, #4, 372-383.
(1996, Feb 26). Grounded tanker may cause U.K.'s largest oil spill. The Oil and Gas
Journal, vol 94, #9. 34.
Hgsystem. (1996, Mar 1). Wales (U. K.) 15 february 1996.
http://gds.esrin.it/0xc06afc3d_0x00064479. (11 April 1997).
Hover, G. L. (1993, July). Evaluating technologies of oil spill surveillance. Sea
Technology, 45-53.
Huehnerfuss, H., Alpers, W. and Richter, K. (1986). Discrimination between crude
oil spills and monomolecular sea slicks by airborne radar and infrared radiometer-
possibilities and limitations. International Journal of Remote Sensing, vol 7, #8,
1001-1013.
Implementation of the oil pollution act of 1990.
http://www.mms.gov/omm/osm/opa90.html. (1 March 1997).
80


Japanese Earth Resources Satellite-1.
http://nasa.eoc.nasda.go.jp/guide/satellite/satdata/jers_e.html. (17 February 1997).
Johannessen, J. A., Lyzenga, D. R., Shuchman, R., Espedal, H. and Holt, B. (1995).
Mulit-ffequency SAR observations of ocean surface features off the coast of Norway.
1995 International Geoscience and Remote Sensing Symposium, 2, 1328-1330.
Johnson, N. L. and Rodvold, D. M. (1993). Europe and Asia in Space. Colorado
Springs: Kaman Sciences Corporation.
Kalmykov, A. I., Efimov, V. B., Kavelin, S. S., Kurekin, A. S. Nelepo, B. A., and
Pickugin, A. P., et al. (1985). The radar system of the cosmos-1500 satellite. Soviet
Journal of Remote Sensing, 4(5), 827-840.
Kalmykov, A. I., Velichko, S. A. Tsymbal, V. N., Keleshov, Yu. A., Weinmann, J. A.
and Jurkevich, I. (1993). Observations of the marine environment from spacebome
side-looking real aperture radars. Remote Sensing Environment, 45, 193-208.
Kobayashi, T. Okamoto, K., Masuko, H., Nakamura, K., Horie, H. and Kumagai, H.
(1993). Artificial oil pollution detection and wave observation in the sea adjacent to
Japan by ERS-1 SAR images. 1993 International Geoscience and Remote Sensing
Symposium, 946-948.
Kopytoff, V. G. (1996, Nov 12). Birds rescued in spill do poorly, study finds. The
New York Times, C4.
Krapez, J. C. and Cielo, P. (1992, August 15). Optothermal evaluation of oil film
thickness on water. Journal of Applied Physics, vol 72, #4, 1255-1261.
(1996, Nov 13) Landsat-sample images.
http.V/www.eurimage.it/Products/LS/Msample-images.html. (11 April 1997).
Lichtenegger, J. (1994, Dec 16). Using ERS-1 SAR images for oil spill surveillance.
http:gds.esrin.it/0xc0tafc3d_0x0002b774. (11 April 1997).
Lillesand, T. M. and Kiefer, R. W. (1987). Remote Sensing and Image Interpretation.
(2nd ed ). New York: John Wiley and Sons.
Link, L. E., McKim, H. and Bruzewics, A. (1991, May-June) Remote sensing of the
Persian Gulf oil spill. Army Research, Development and Acquisition Bulletin, 19-21.
81


Liu, A. K., Tseng, W. Y. and Chang, S. Y. -S. (1996). Wavelet analysis of AVHRR
images for feature tracking. 1996 International Geoscience and Remote Sensing
Symposium, 85-87.
Lodge, A. E. (1989). The Remote Sensing of Oil Slicks. Chicester: John Wiley and
Sons.
Lombardini, P. P., Fiscella, B., Trivero, P., Cappa, C. and Garrett, W. D. (1989).
Modulation of the spectra of short gravity waves by sea surface films: slick detection
and characterization with a microwave probe. Journal of Atmospheric and Oceanic
Technology, 6, 882-890.
Marine Minerals. U. S. Department of the Interior Minerals Management Service.
Herndon, VA: Minerals Management Service.
Mead, W. J. and Sorensen, P. E. (1970, December 16) The economic cost of the
Santa Barbara oil spill. Santa Barbara Oil Symposium, 183-226.
Meyer, S. (ed.). (1995). Energy Statistics Sourcebook, 10th ed Tulsa: Pennwell
Publishing Company.
Mink, N. (1994, Oct 24). Were partying hearty (litigants profit from Exxon Valdez
oil spill). Forbes, vol 154, #10. 84-85.
MMS: Ensuring Safety on the OCS. U. S. Department of the Interior Minerals
Management Service. Herndon, VA: Minerals Management Service.
MSO San Francisco fact sheet, http://iserver2.tcpet.uscg.mil/msosf. (1 Mar 1997).
Murphy, D. W. (1995). Definition of the orbital elements.
http://sgra.jpl.nasa.gov/html_dwm/pg/pg_release/nodel7.html. (11 April 1997).
NOAA damage assessment and restoration center.
http://www.darchw.noad.gov/index.shtml. (1 Mar 1997).
Natural resource damage assessment under the oil pollution act of 1990.
http://www.darcnw.noaa.gov/opa.htm. (1 Mar 1997).
82


Ohmsett: The National Oil Spill Response Test Facility. U. S. Department of the
Interior Minerals Management Service. Herndon, VA: Minerals Management
Service.
(1996, Nov 16). Oil seals contaminated birds' fates. Science News, vol 150, #20.
314.
Oil slicks, http://www.jpl.nasa.gov/radar/sircxsar/oilsk.html. (11 April 1997).
Oil-Spill Prevention and Research. U. S. Department of the Interior Minerals
Management Service. Herndon, VA: Minerals Management Service.
Pacific OCS Operations. (1996, October 9). U. S. Department of the Interior
Minerals Management Service Pacific OCS Region. Pacific OCS Platforms.
http://www.mms.gov/omm/pacific/production/plfintro.html. (9 March 1997).
Peace, F. (1996, Aug 10). Oily legacy lingers aftermiraclecleanup. New Scientist,
no 2042. 6.
Rees, W. G. (1992). Orbital subcycles for earth remote sensing satellites.
International Journal of Remote Sensing, vol 13, #5, 825-833.
Rees, W. G. (1990). Physical Principles of Remote Sensing. Bristol. Cambridge
University Press.
Romero, J. (1995, April 14). Congresswoman Seastrand to Oversee Signing of
Memorandum of Agreement Between California's Office of Oil Spill Prevention and
Response and the U. S. Minerals Management Service. MMSNews Release.
http://www.mms.gov/omm/pacific/public/osprmoa.html. (9 March 1997).
Romero, J. (1996, February 21). MMS Awards $1.4 Million for California Offshore
Oil and Gas Evergy Resources Study. MMS News Release.
http://www.mms.gov/omm/pacific/public/cooger.html. (9 March 1997).
Sabins, F. F. (1987). Remote Sensing Principles and Interpretation. (2nd ed.). New
York: W. H. Freeman and Company.
83


Scialdone, J. N. (1996). AVHRR GAC, LAC and HRPT Level lb Data Set [POL 90-
90 180-180], http://www.saa.noaa.fov:8000/dif7anhrr 1 b-dif.html. (3 November
1996).
Scialdone, J. N. (1996). TOVS MSU, SSU and HIRS/2 Level lb Data Set [OL 90-90
180-180], http://www.saa.noaa.gov:8000/dlf7tovs 1 b-dif.html. (3 November 1990).
SeaSat 1978. http://southport.jpl.nasa.gov/scienceapps/seasat.html. (3 December
1996) .
Shestopalov, Y. K. (1993, September). The statistical treatment of passive
microwave data. IEEE Transactions on Geoscience and Remote Sensing, vol 31, #5,
1060-1065.
Singh, K. P., Gray, A. L. Hawkins, R. K. and ONeil, R. A. (1986, September). The
influence of surface oil on c- and ku-band ocean backscatter. IEEE Transactions on
Geoscience and Remote Sensing, volGE-24, #5, 738-743.
Sir-A 1982. http://southport.jpl.nasa.gov/scienceapps/sira.html. (3 December 1996).
Sir-B 1985. http://southport.jpl.nasa.gov/scienceapps/sirb.html. (3 December 1996).
Sir-C description, http://www.jpl.nasa.gov/sircxsar/sc-oilskgif. (3 December 1996).
Space Systems Forecast. (1996). Newton Connecticut: Forecast Intemational/DMS.
Stofan, E. R., Evans, D. L., Schmullius, C., Holt, B., Plant, J. J. and vanZyl, J., et al.
(1995, July). Overview of results of spacebome imaging radar-C, X-band synthetic
aperture radar (SER-C/X-SAR). IEEE Transactions on Geoscience and Remote
Sensing, vol 33, #4, 817-827.
Stringer, W. J., Dean, W. G., Guritz, R. H., Garbeil, H. M., Groves, J. E. and Ahlnaes,
K. (1992). Detection of petroleum spilled from the MV Exxon Valdez. International
Journal of Remote Sensing, vol 13, #5, 799-824.
Topex/Poseidon images, http://www.jpl.nasa.gov/podaac.w960104.gif. (7 April
1997) .
Tseng, W. Y. and Chiu, L. S. (1994). AVHRR observations of Persian Gulf oil spills.
1994 International Geoscience and Remote Sensing Symposium, 779-782.
84


U. S. Bureau of the Census. (1996). Stastical Abstract of the United States, 116th
ed. Washington, D. C.: U. S. Government Printing Office.
Vesecky, J. F. (1995). Surface film effects on the radar cross section of the ocean
surface. 1995 International Geoscience and Remote Sensing Symposium, 2, 1375-
1377.
Veseky, J. F. and Stewart, R. H. (1982, April 30). The observation of ocean surface
phenomena using imagery from the SEAS AT synthetic aperture radar: an assessment.
Journal of Geophysical Research, vol 87, #C5, 3397-3430.
Victorov, S. V. (1996). Regional Satellite Oceanography. Bristol, PA: Taylor and
Francis.
Wismann, V. (1993). Radar signatures of mineral oil spills measured by an airborne
multi-frequency radar and the ERS-1 SAR. 1993 International Geoscience and
Remote Sensing Symposium. 940-942.
Wolfe, D. A. (1994). The fate of thre oil spilled from the Exxon Valdez.
Environmental Science and Technology, vol 28, #13. 561-567.
Working for Americas Energy Future and a Quality Environment. US. Department
of the Interior Minerals Management Service. Washington, D. C .: Minerals
Management Service.
Your boat, your oil spill, http://www.tcpet.uscg.mil/msosfrdstlm/smspill.htm. (4
March 1997).
85


Full Text
Schuetze, Jennifer Kathleen, Master of Basic Science
Detection of Oil Pollution in the Santa Barbara Channel using Spacebome Sensors
Thesis directed by Dr. Randall Tagg
ABSTRACT
The Central Coast of California including the Santa Barbara Channel are
responsible for seventeen percent of California's oil porduction. The danger for oil
pollution and detrimental effects on tourism and the environment is very high. In
Norway, a satellite station downlinks radar satellite data to scan for possible oil
pollution in the North Sea waters along Norway's coast. Can their knowledge be
applied to California's situation? This thesis examines three major aspects in applying
this technology: the appropriate sensor, the appropriate orbit and the cost
effectiveness of such a project.
After reviewing several passive sensors, it appears that synthetic aperture radar
is the most effective for this mission. This sensor detects the difference in wave
heights caused by the wave damping properties of oil on ocean water. Sun-
synchronous orbit is found to be appropriate, after several orbits are considered. A
review of basic orbital mechanics is accomplished and repeat time and coverage are
dealt with more extensively. These parameters are affected greatly by the orbit and
determine how often one geographic location can be viewed by an orbiting spacecraft.
A cost comparison is completed and finds that a spacecraft system costs a fraction of
what is spent on oil pollution clean up. Finally, an analysis based on existing assets,
ERS-2, JERS-1 and Radarsat, is done to find best and worst case scenarios for
coverage of the Central Californian coastline. It is found that not only could the U. S.
begin completing this mission using existing resources (ground stations and satellites),
but it should add satellites of its own for total coverage, repeating at a desirable
interval.
This abstract accurately represents the content of the candidate^ thesis. I recommend
its publication.
Signed]
Tagg
IV



PAGE 1

DETECTION OF Oll.POLLUTION IN THE SANTA BARBARA CHANNEL USING SPACEBORNE SENSORS by Jennifer Kathleen Schuetze B.S San Diego State University, 1993 A thesis submitted to the University of Colorado at Denver in partial fulfillment of the requirements for the degree of Master of Basic Science

PAGE 2

This thesis for the Master ofBasic Science degree b y Jennifer Kathleen Schuetze has been approved by Randall Tagg Willard Chappell Date

PAGE 3

Schuetze, Jennifer Kathleen, Master ofBasic Science Detection of Oil Pollution in the Santa Barbara Channel using Spacebome Sensors Thesis directed by Dr. Randall Tagg ABSTRACT The Central Coast of California including the Santa Barbara Channel are responsible for seventeen percent of California's oil porduction The danger for oil pollution and detrimental effects on tourism and the environment is very high In Norway, a satellite station downlinks radar satellite data to scan for possible oil pollution in the North Sea waters along Norway's coast. Can their knowledge be applied to California's situation? This thesis examines three major aspects in applying this technology: the appropriate sensor, the appropriate orbit and the cost effectiveness of such a project. After reviewing several passive sensors it appears that synthetic aperture radar is the most effective for this mission This sensor detects the difference in wave heights caused by the wave damping properties of oil on ocean water. Sun synchronous orbit is found to be appropriate after several orbits are considered A review ofbasic orbital mechanics is accomplished and repeat time and coverage are dealt with more extensively These parameters are affected greatly by the orbit and determine how often one geographic location can be viewed by an orbiting spacecraft A cost comparison is completed and finds that a spacecraft system costs a fraction of what is spent on oil pollution clean up Finally an analysis based on existing assets ERS-2 JERS-1 and Radarsat, is done to find best and worst case scenarios for coverage of the Central Californian coastline It is found that not only could the U. S begin completing this mission using existing resources (ground stations and satellites) but it should add satellites of its own for total coverage, repeating at a desirable i nterval. This abstract accurately represents the content of the valll\.U\J" .. its publication i v

PAGE 4

CONTENTS Chapter 1 Introduction Problem Statement and Research Qustion 2 Review of Existing Systems 7 2. 1 Earth Remote Sensing Satellites 7 2 1 1 Landsat 7 2 1 2 NOAA Series 9 2 .1.3. Topex/Poseidon 12 2 1.4 SeaSat 13 2 .1.5. SIR-A and SIR-B 13 2 1 6 SIR-C/X-SAR 14 2 1.7 SPOT 17 2 1.8 Cosmos and Okean 18 2 1.9 Almaz-1 19 2 1.10 JERS-1 20 2 1.11. ERS 21 2 1 12. Radarsat 23 2 2 Tromso Satellite Station 25 3 Sensors 28 v

PAGE 5

3 1 Passive Sensors 3 1 1 Thermal Infra-Red 3 1 2 Relfected InfraRed 3 1 3 UltraViolet 3 1.4 Visible 3 .2. Active Sensors 3.2.1 Side Looking Airborne Radar 3 2 2 Synthetic Aperture Radar 3 2 3 Scattering from Ocean Waves and Wave Damping Theory 4 Orbital Parameters 4 1 Geostationary Orbits 4 2 Low-Earth Non-Polar Orbits 4 3 Polar Orbits 5 Cost 5 1 Cost of Oil Pollution 5 1 1 Cost of an Oil Spill 5 1.2 Cost of Oil Pollution Monitoring and Response 5.2 Cost of a Space-Based Detection System 5 .2 .1. Cost of a Satellite vi 28 29 32 33 34 34 38 41 44 49 51 52 54 59 59 60 61 63 63

PAGE 6

5 2.2. Cost of a Launch 5.2 3 Cost of a Ground Station 6 Conclusions and Suggestions for Further Study 6 .1. Sensors 6 2 Orbits 6 3 Cost 6.4 Suggestions for Further Study 6 .5. Late Breaking Updates Glossary References V II 64 65 67 67 69 70 73 75 76 77

PAGE 7

1 Introduction, Problem Statement and Research Question In 1994, over 19 5 million gallons of oil were spilled in 9, 440 separate incidents in U. S navigable waters (Federal Offshore Statistics, 1996) California is the fourth largest producer of oil in the United States after Alaska, Texas and Louisiana (Meyer, 1995) As of 1986 17 percent of California's oil was produced on the Pacific outer continental shelf, in an area called the Santa Barbara Channel. In 1969, the largest well blowout (an unintentional, uncontrolled oil flow from an oil well) happened on platform A in the channel (Francois, 1993) This resulted in the loss of 3 3 million gallons of oil which spilled directly into the water (Meade and Sorensen, 1970) While this blowout happened close to 30 years ago, the dangers of major oil pollution still exist. In 1989, the Exxon Valdez dumped approximately 11 million gallons of oil into the Prince William Sound in Alaska (Mink 1994 ), which was only the 35th largest spill ever (Etkin 1996) Litigation concerning the latter has lasted more than five years Since 1969 there have been at least 13 major spills from aging or damaged pipelines (Francois 1993 ; Big spill reported in Komi region of Russian Arctic, 1995 ; Fine assessed in California oil spill 1994) From June 1979 to February 1980, 140 million gallons spilled at the Ixtoc I well blowout in the Gulf of Mexico and 1991 saw the largest spill ever with approximately 240 million gallons 1

PAGE 8

spilled from oil terminals and tankers off the coast of Saudi Arabia Typically 100 million gallons of oil are spilled each year (Etkin 1996) Santa Barbara County is considered one of the most environmentally conscious counties in the U. S Wildlife habitats and refuges abound within it. Santa Barbara is also sustained by the tourist and fishing industries Each of these is affected by oil to some extent. While fish themselves are not impacted as seriously as other animals the industry can be hurt by precluding fishermen from getting around oil collection booms as well as the oil polluting the fish as the fishermen pull them through the oily substance (Meade and Sorensen, 1970). The tourist industry may or may not be affected depending on the extent ofthe pollution (Meade and Sorensen 1970) Wildlife however, is put at grave risk because of spills Bird sanctuaries near the Milford Haven Harbor became fouled after the U. K. 's largest tanker spill in 1996 (Grounded tanker may cause U.K.'s largest oil spill 1996). 6 900 birds of more than 25 species were found dead (Dyrynda and Symberlest 1997) This same spill affected numerous species of invertebrates virtually destroying all but two individuals of a breed of starfish unique to this area (Pearce 1996) Research is beginning to point out that even rehabilitation of animals after spills is not working Only 12 percent of rehabilitated pelicans are surviving for at least two years (Kopytoff 1996) Other birds are living only six to eleven days after being released from oil rehabilitation whereas after release from captivity for other than rehabilitation normal life 2

PAGE 9

expectancy is 200 days or more (Oil seals contaminated birds' fates, 1996) Another species greatly affected by oil pollution in the Santa Barbara Channel is the Pacific Otter This species is on the threatened list under the Endangered Species Act of 1977 Oil affects them in two distinct ways As they groom themselves by licking their fur they ingest the toxins which result in lung and kidney failure Secondly oil prevents their thick fur from trapping insulating air bubbles and they die of hypothermia (Bonnel Ford and Brody 1996 ; Friends ofthe Sea Otter 1997) There are 24 oil platforms thousands of miles of oil pipelines and shipping lanes all through the Santa Barbara Channel (Pacific OCS Map 1996) See Figure 1.1. This area produces a substantial amount of the United States' oil It is fair to conclude from the history and characteristics of this region that this is an area that remains at risk. Tseng and Chiu (1994) note "the occurrence of oil spills due to accidents such as collisions or capsizing of tankers or blowouts of offshore oil wells causes major environmental hazards Early detection monitoring containment and cleanup of spills is crucial for the protection of the environment. . remote sensing techniques provide the potential for early detection, monitoring and tracking of oil spills Until recently the U. S Coast Guard the agency that responds to a spill in federal waters employed a fixed-wing aircraft the HU-25B "Aireye" to detect oil spills (Aviation Week and Space Technology 1989) These aircraft utilize two side-3

PAGE 10

'"1'1 .., (!) -"'d () 8-i () 0 () C/) 0 ::l 3:: ::l (!) .., e. Vl 3:: 00 (!) s (!) ::l ..... C/) (!) $ () (!) '-" !ldlii!Ml U S Dl>pClr"tMent of "the lntttrlor" M l ne-rClls Mo.no.gPMtnt Servlctt Pacific OCS Region c....L....& .............. f f f ................ CALIFORNIA SGnto Bo.rbo.ro Coun t y @ SAN PEDRO BAY Vntura County @ E3 r::::n 83 @j B 8 @ LEGEND County Boundary F ederol Ecological Preserve Buffer Zone Channel Islands No t lonol Morine Sonctuory Producing Leose Non-Producing Leose U S Congressional D istrict NuMber PACIFIC OCS REGION PLANNING AREAS

PAGE 11

looking real aperture radars mounted underneath the plane to detect areas of the sea whose waves are dampened by oil slicks These aircraft are only called on now to investigate known slicks not to detect them initially (Blalock, USCG, Conversation 27 Feb 1997) Essentially slick detection in the Santa Barbara Channel is dependent on alert citizens who spot the pollution and call it in to the authorities Obviously a major spill will bring much attention to itself Smaller spills, however, are very easily missed if no regular method for detection is employed. Such spills could occur for example, from seepage out of platforms or traveling vessels and even pollution from ships illegally dumping Challenor (1986) and Wahl et al (1996) both agree that satellites are well suited to a pollution monitoring role Wahl, et al (1996) writes, "with the launch of the European Space Agency's satellite ERS-1 in July 1991 a new tool became available for pollution monitoring namely the radar satellite In the late 1980s a project began in Norway to dedicate a satellite ground station to the processing of these particular radar images for the purpose of oil pollution monitoring. By 1994 this was being accomplished in real-time This brings about realizations and more questions The radar satellite seems to work for Norway to detect oil pollution California's Central Coast seems to be at major risk for spills and other oil pollution Can these two observations be connected? Can spaceborne sensors effectively detect oil pollution along California's Central 5

PAGE 12

Coast? Are there new issues to examine in applying experience gained by the Norwegians to a different geographical location? And is it worth the cost to attempt this? These questions are the primary focus of this thesis In particular the thesis will assess the feasibility and a cost comparison of satellite monitoring of California's Central Coast. It will identify and suggest resolution to challenges posed in designing such a surveillance system The assessment will be broken down into several aspects First a review of the current inventory of earth remote sensing satellites will be completed in chapter 2 including some example images, with oil slicks if available This review will also look closer at Tromso Satellite Station the site in Norway currently fulfilling this mission Next, chapter 3 compares the various sensors capable of detecting oil pollution on water and an overview of the physics behind this phenomenon Then chapter 4 discusses the advantages and disadvantages of various possible orbits feasible for an earth remote sensing satellite Finally a broad cost comparison is presented in chapter 5 to get an idea of the amount of money spent on satellite programs versus the amount of money spent on oil pollution prevention and clean-up Chapter 6 conclude this thesis by recommending the most appropriate sensor and orbit as well as suggestions for further study 6

PAGE 13

2 Review of Existing Systems Before delving into the subject of the best way to detect oil slicks, it is important to understand what currently exists in the world s inventory of remotes sensing satellites These satellites include both active radar satellites and passive optical sensor satellites This chapter will also include a short overview of the Tromso Satellite Station, a ground station in Norway already fulfilling the mission of using space based sensors for oil slick detection. 2. 1 Earth Remote Sensing Satellites 2 1 1 Landsat Landsat is a United States earth remote sensing satellite which is an integral part ofthe National Aeronautics and Space Administration s (NASA) Mission to Planet Earth Landsat 1 the first of six was launched in 1972 With each subsequent generation, improvements have been made to the sensors and spacecraft themselves Landsat 5 launched in 1984 is currently operational. Unfortunately Landsat 6 was lost in a launch problem in October of 1993 Landsat 7 is expected to be launched in May of 1998 (Space Systems Forecast 1996) 7

PAGE 14

Landsats are in a sun-synchronous orbit with an altitude of 705 kilometers. This gives a repeat time of 16 days at the equator. The satellite s capabilities (for Landsat 7) include an Enhanced Thematic Mapper (7 bands) and the Sea Wide Field Sensor A multispectral scanner ( 4 bands for Landsat 5, 7 bands for Landsat 7) provides data to 30 meter resolution (Space Systems Forecast 1996 and Wilson, 1996) Landsat has detected oil slicks The MSS band 5 imaged a spill from a blowout in 1975 (Sabins, 1987) The thematic mapper was able to detect oil after the Exxon Valdez oil spill in Prince William Sound. Figure 2.1 is a Landsat image of an island called Muroroa in the Pacific Ocean Note how the cloud cover obscures the image of the coral beneath it (Landsat-sample images, 1996) Figure 2 1 : Landsat image of Muroroa (Landsat-sample images 1996) 8

PAGE 15

2 1 .2. NOAA Series The National Oceanic and Atmospheric Administration (NOAA) Polar Orbiting Environmental Satellites carry many different sensors Fourteen satellites have been produced and launched since 1960 They began as weather satellites and have had many variations NOAA-M is scheduled to be launched in August of 1997 Several of the existing satellites are still operational (Stringer, et al, 1992) They are in a polar orbit at either 833 or 870 kilometer altitude Each has an orbital period near 102 minutes There are primarily five sensors carried aboard the NOAA satellites The three that are for earth remote sensing purposes include the Advanced Very High Resolution Radiometer, the High Resolution Infrared Radiation Sounder and the Microwave Sounder Unit (Space Systems Forecast, 1996) The A VHRR gathers visible and infrared signals to measure cloud cover and surface temperature The other two sensors detect and measure energy in the troposphere to construct temperature profiles ofthe earth's surface (Scialdone, 1996) The A VHRR, with its five channels (Advanced Very High Resolution Radiometer, 17 Feb 1996) is on NOAA 7, 9, 11, 12 and 14 satellites AVHRR with only four bands is on TIROS-N, NOAA 6, 8, and 10 satellites (Scialdone, 1996) Stringer, et al (1992) and Tseng and Chiu (1994) all discuss applications of AVHRR 9

PAGE 16

when detecting oil slicks A VHRR did detect oil during the Valdez crisis but because of the resolution the images could only represent the oil as large unresolved map units (Stringer, et al, 1992) Tseng and Chiu (1994) found that multi-channel composites of the data led to slick detection during several blowouts and tanker collisions in the Persian Gulf during Desert Storm in 1991. Figure 2 2 is an A VHRR image of California's Central Coast. Note the obscuring cloud cover. Figure 2 2 : A VHRR image 10

PAGE 17

The Defense Meteorological Support Program (DMSP) satellites are similar in design to the NOAA TIROS satellites While previously an Air Force program an agreement made in May 1996 placed DMSP under NOAA control. These satellites have visible and infrared sensors plus a microwave imager. Their orbit is sun synchronous with an altitude of 83 0 kilometers They have an orbital period of 1 01 minutes and their 3000 kilometer swath gives global coverage of clouds every six hours (DMSP Satellite Program Description 29 Feb, 1997) Figure 2.3 shows a DMSP image of the United States Cloud cover and therefore weather patterns are deduced from these images Figure 2 3 : DMSP image ofUnited States 11

PAGE 18

2 .1.3. TOPEX/Poseidon TOPEX/Poseidon is a one-of-a-kind earth observation satellite Its mission is ocean topography and is a joint oceanographic program with France Its primary instruments are two radar altimeters to measure the height of the ocean surface to a precision of 13 centimeters (Space Systems Forecast 1996) This satellite was launched in August 1992 into a 65 degree inclined orbit at 1334 kilometers in altitude Its orbital period is 112 minutes and offers a repeat time of close to ten days (Space Systems Forecast 1996) ..JPL Tut.M .. N/\SI\ ......... .__ _.s,_. .............. Figure 2.4 : Topex/Poseidon Global Image (Topex/Poseidon images, 1997 ) 12

PAGE 19

2 1.4 SeaSat SeaSat housed the first synthetic aperture radar (SAR) ever to be placed on a spacebome platform It was launched on 28 June 1978 into an 800 kilometer altitude 108 degree inclined orbit. It completed 14 orbits each day and operated for 105 days before October when a major short circuit in the satellite s electrical system ended its mission (SeaSat 1978 3 Dec 1996) Scientists were very excited at the prospect of the amount ofhighly resolved data SeaSat produced Veseky and Stewart (1982) and Sabins (1987) show images SeaSat collected containing oil spills or pollution in the Santa Barbara Channel. SeaSat laid the ground work for future spacebome radar experiments 2 .1.5. Sffi-A and Sffi-B In November 1981, three years after the demise of SeaSat NASA launched the Shuttle Imaging Radar or SIR-A. A synthetic aperture radar antenna was s t owed in the shuttle car g o ba y and was operated when the shuttle was inverted The data was recorded on board the shuttle and then processed after the mission. (Sabins 1987) The main goal of SIR-A was to further understanding the use of radar technology to assess g eologic features (SIR-A 1982 3 Dec 1996) The shuttle and therefore the sensor were in a 38 degree inclined 259 13

PAGE 20

kilometer high orbit. The swath width was 50 kilometers. This mission was only for five days but covered some 10 million square kilometers (Sabins 1987) Sabins (1987) shows a SIR-A image of the Santa Barbara Channel with oil slicks present and identifiable Fiscella, et al ( 1991) use the data to assess the sea state based on wind conditions In October 1984 three years after SIR-A, another shuttle radar experiment was conducted SIR-B had the added benefit of tilting the radar antenna to assess the relationship between image intensity and depression angle All other aspects of SIR-A and SIR-B remained the same with another exception being that the second experiment had most images recorded digitally and downlinked during the flight. The shuttle was in a 57 degree inclined orbit which attained three different altitudes : 360 257 and 224 kilometers It was able to attain a swath width of 40 kilometers (SIR-B 1985 3 Dec 1996) A slick in the Sea of Japan was seen accuratel y by SIR-B (Bern, et al, 1993) 2 1 6 SIR-C/X-SAR The next step in shuttle based radar experiments was SIR-C/X-SAR This was actually two distinct experiments The package was flown twice in 1994 once in April then in October aboard the Shuttle Endeavor. These experiments were highly evolved from any other SIR experiment or any other existing radar satellite (see JERS-14

PAGE 21

1 ERS-1 and Cosmos sec 2 1.10 2 1.11, 2.1.12) (Stofan et al, 1995). The X-SAR was an instrument built and sponsored by a German/Italian alliance It's an X-band antenna with a mechanical tilt to change the depression angle This antenna was based off of the German's initial radar program the Microwave Remote Sensing Experiment (SIR-C Description 3 Dec 1996) SIR-C offered numerous enhancements over the previous SIRs F ir st it had two different arrays for C and L band transmission Second, the panels were built in such a way as to send and receive any configuration of polarized radiation This allowed comparison of the same imaged objects using the same wavelength energy with only polarization configuration changed in order to see the effect of polarization on image detectibility Third, the antennas were not physically steerable but were phased arrays offering a greater range of depression angles using electronic beam steering (SIR-C Description, 3 Dec 1996) Finally because of the unique electronic beam steering as well as an ability to send out a short burst of energy rather than a long pulse SIR-C could operate in a mode called ScanSAR It sends bursts at angle one then bursts at angle two, then angle three then back to angle one Thi s synthesizes an even larger swath width (Chang Jin, Lou and Holt 1996) The shuttle operated two eleven day missions with this experiment. The missions were in circular 57 degree inclined 215 kilometer high orbits (Chang, Jin Lou and Holt 1996) 15

PAGE 22

Alpers and Holt (1995) used SIR-C/X-SAR data to identify ocean characteristics including wave-wave interaction something affected by oil slicks (See section 4 2 2 3) Gade Alpers Bao and Huehnerfuss (1996) used SIR-C images of preplanned slicks to test the ability to detect them with the varied polarization configurations Figure 2 5 is a SIR-C image of extensive oil slicks in the Arabian Sea west ofBombay, India The dark streaks are the slicks. This image covers an area 20 by 45 kilometers (Oil slicks 1997) Figure 2 5 : SIR-C Image of Oil Pollution in the Arabian Sea (Oil slicks 1997) 16

PAGE 23

2 1.7 SPOT SPOT (Satellite pour !'Observation de la Terre) is a French earth observation satellite The current satellite is SPOT 3 SPOT 2 is running as an on-orbit spare to SPOT 3 while SPOT 1 was retired in July of 1993 It had be reactivated to support growing demand of images at an earlier time The three are in co-planar orbits (Kaman Sciences Corp 1994) SPOT has primarily one type of sensor on it. Two High Resolution Visible (HR. V) imagers collect data simultaneously The push broom imagers achieve 117 kilometer swath widths with three kilometers of overlap SPOT is highly capable however, with its unique tilting mirror Because of it the total swath width is 950 kilometers and the same site can be imaged on seven successive days at the equator, eleven successive days at latitudes greater than 45 degrees (Wilson, 1996) This scanner can be operated in multi spectral mode or a high-resolution panchromatic mode. Because of the two imagers, SPOT can often provide stereo images of the same subject (Sabins 1987). The SPOT satellites are in a sun-synchronous, 824 kilometer high 98 7 degree inclined orbit. They have a 26 day repeat period, but with their tiltable mirrors, each can image a site much more often than it is physically over it (Wilson 1996) The following image, figure 2 6 is a high resolution visible image of an industrial area 17

PAGE 24

Figure 2 6 : Spot image of industrialized area 2 1 8 Cosmos and Okean The Soviets launched Cosmos-1500 in 1983 as the first side looking radar (real 18

PAGE 25

aperture) aboard a spacecraft Cosmos was the precursor to the Okean satellites which also cany the SLAR There were four Cosmos ( -1500 -1602 -1766 and 1869) all prototypes before the first Okean satellite was launched and operational. Including the prototypes there have been nine satellites launched and one in-flight failure of a booster destroying the tenth The most recently launched satellite was the first of the third generation, Sich 1 on 31 August 1995 Currently Okean 4 and Sich 1 are still operational. The design life of these satellites is only six months. Their primary sensor include the SLAR, two scanning radiometers and a multi-spectral scanner For Sich 2 plans to include a SAR have been made Presumably because of the expense of this sensor the design life of the new satellites has been increased to three years Currently the Okean satellites are all in an 82 6 or 82.5 degree inclined orbit of an altitude between 632 and 669 kilometers (Wilson, 1996) Kalymkov et al (1985) discuss the capabilities of the SLAR aboard the Cosmos series of spacecraft The SLAR with its resolution of one to two kilometers he states is perfect for the detection of such large scale phenomenon as oil slicks 2 1.9 Almaz-1 Almaz-1 is the first Russian space borne SAR to make it into space and become operational (several attempts had previously failed) It was launched in 1991 19

PAGE 26

into a 60 degree inclined orbit at an altitude of 260 kilometers It has a resolution of 20 meters and a swath width of only 20 kilometers However, it can aim its coverage area in a swath at least 350 kilometers wide (Kamann Institute, 1994) While the Russian satellites mentioned previously have on-board processing, the amount of data collected on board Almaz using a SAR required processers at the ground station instead (Kalmykov, et al, 1993) 2 1.10 JERS-1 The Japanese Earth Resources Satellite contains a SAR as well as an optical sensor package It was launched in February of 1992 into a sun-synchronous orbit with orbital altitude of568 kilometers (JERS-1, 17 Feb 1997) The radar sensor has a resolution of 18 meters and a swath width of75 kilometers (Kalmykov et al, 1993). More than 140,000 SAR and 90 000 optical scenes have been returned through March 1995 (Wilson, 1996) Figure 2 7 is an image, collected by JERS-1. It is an image of a river delta See the following page 20

PAGE 27

JERSl SAR 20-Jll.J92 0416 -335 1 2 5 2 1 Figure 2 7 : JERS-1 image of a river delta 2 1.11. ERS The European Space Agency (ESA) launched ERS-1 Earth Remote Sensing SatelliteI in July 1991. With 30 meter resolution and a 100 kilometer swath width 21

PAGE 28

this was the best SAR satellite ever to attain orbit (Kalmykov et al, 1993) Its design purpose was ice coastal and ocean monitoring ERS has other sensors as well as the SAR including an along-track scanning radiometer for sea surface temperature measurement and an active microwave scatterometer for wind mode readings ERS-2 was launched in April of 1995. The two satellites operated in opposite sides of the same orbit for over a year when ERS-1 was placed in stand-by mode in May 1996 (Space Systems Forecast, 1996). ERS-1 proved very successful completing over 20 000 orbits and reproducing more than 600 000 different radar scenes The data has been used to track movement along the San Andreas fault, movement of volcanic masses and to locate and monitor oil pollution at sea (Space Systems Forecast 1996) In 1991 and 1992 ESA had a project entitled utilization of SAR for detection of oil on sea surface in which controlled spills were coordinated with ERS-1 overpasses This brought attention to the satellite s new found capability (Bjerde et al, 1993) Kobayashi et al, (1993) drew similar conclusions from a similar experiment carried out in the Sea of Japan Figure 2 8 is an image collected by ERS-1 of an oil spill mentioned in chapter 1 caused by the oil tanker "Sea Empress" accident on the coast of Wales (hgsystem 1996) The image represents a 100 by 100 kilometer swath 22

PAGE 29

Figure 2 8 : ERS-1 image of oil spill ofWales. (hgsystem 1996) 2 1 .12. Radarsat Radarsat is Canada s first space based SAR Its mission is to provide remote sensing in the areas of ice reconnaissance coastal surveillance land use mapping and agricultural and forestry monitoring (Space S y stems Forecast 1996) Radar sat is in a sun synchronous, 98 6 degree inclined orbit at an altitude of 793 to 821 kilometers (Canadian Space Agency 23 Jan 1997) It was launched in November 1995 with a five year design life (Wilson 1996) It is unique in several aspects First Radarsat is primarily a commercial 23

PAGE 30

satellite offering radar images to the general public for a price Second and more importantly, Radarsat employs ScanSAR, a mode in which it can sacrifice some resolution to gain a much larger swath width In standard mode, it has 25 meter resolution with 100 kilometer swath width In ScanSAR wide mode, it has only 100 meter resolution but 510 kilometer swath width Because of this unique ability, Radarsat is considered to have an operational capability wherein it can be used as a central, on-going data source for a particular type of environmental monitoring rather than providing occasional confirmatory coverage (Gower, Vachon and Edel 1993) Figure 2.9 is an image collected by Radarsat of Eastern Lake Superior Data such as this image are used by the Canadian Ice Service (Canadian Ice Service 1997) Figure 2 9 : Radarsat image of Eastern Lake Superior (Canadian Ice Service 1997) 24

PAGE 31

2 2 Tromso Satellite Station In 1991 shortl y after ERS-1 was launched it was shown that this satellite could detect oil slicks on the sea An experiment called the "Dedicated Oil Spill Experiment," DOSE-91 was undertaken to answer certain questions about this new radar satellite The experimenters wanted to discover whether or not the ERS-1 satellite was capable of detecting oil and what the capabilities are relative to an airborne system as well as the major limits regarding detection These questions were answered by comparing in-situ data gathered by buoys surveillance aircraft and other truthing methods to the satellite data (Bern, et al 1993) The conclusions drawn included the wind dependency for slick detection (Bern et al, 1993) Later in 1992 the wind dependence problem was further demonstrated ( Andersen 25 Feb, 1997) Tromso Satellite Station began digitally processing SAR images on a regular basis More than 150 were analyzed (Wahl et al 1996) This is when the feasibility of near real time operations was clearly demonstrated In 1993 the station processed more images and began to discover and address problems in discriminating between man-made (oil) and natural slicks In 1994, TSS took over the daily search for slicks in ERS-1 imagery During the second half of 1994 over 1700 SAR images from ERS-1 were analyzed This station had become the world first tracking station to routinel y use 25

PAGE 32

satellite data for real-time pollution monitoring (Wahl, et al, 1996) Currently TSSs main objective is to give the end users information on possible oil spills within two hours of a satellite overpass Based on the satellite's passes aerial surveillance can also be more effectively scheduled The operators have discovered several limitations of this method some solvable Winds pla y a major role Winds at certain low speeds cause natural slicks to be misinterpreted as oil slicks This is addressed by operator training At high wind speeds, however the pollutant may become mixed in with the sea, making it undetectable by radar Consequently meteorological and wind information are used to aid the operators in their assessment (Andersen 25 Feb 1997) Figure 2 .10 is an image processed by TSS of oil pollution in the North Sea It is an ERS-2 image collected on July 28 1996. A notice was immediately sent to the Norwegion Pollution Control Authority after interpretation of this image The two large dark spots are slicks while the dark spot on the top right comer of the image shows an area of low wind conditions This image represents a 100 by 100 kilometer swath (Ershd 1996) 26

PAGE 33

Figure 2 .10 ERS-2 image of oil pollution in the North Sea (Ershd 1996 ) 27

PAGE 34

3 Sensors There are several ways available to detect oil slicks We have seen examples of each of these in previous chapters In this section we will be looking into the principles of the two main types : passive those sensors that detect and record energy naturally reflected or radiated from the sensed object (Sabins 1987) and active those systems which illuminate the sensed objects with their own supplied radiation (Rees, 1990). The passive systems will be further broken down into thermal and reflected infra-red ultra-violet and visible The active systems discussed here will be further broken down into two types : side-looking airborne radar and synthetic aperture radar Side-looking airborne radar (SLAR) is an imaging radar one in which the intensity of radiation reaching it is a function of intensity and position on the earth's surface Thus a two-dimensional pictoral representation of the intensity can be constructed (Rees 1990) Synthetic aperture radar (SAR) is a high resolution refinement ofthe SLAR (Rees 1990) 3 1 Passive Sensors Passive sensors detect naturally occurring radiation without supplying energy of their own The simplest example is a camera It records wavelenths in the visible region of the spectrum. Several satellites exist in which variations of the basic, visible 28

PAGE 35

camera are used including the shuttle missions, on which the astronauts photograph the earth using the large format camera (LFC) The underlying principle is that all objects reflect in various wavelengths light supplied by the sun These wavelengths correspond to colors For example, violet is approximately 0 38 to 0.44llm, while red is from 0 62 to 0 .75 llm The variance in wavelength reflected or emitted by the objects then corresponds to the colors detected on the film. This very common practice is extrapolated for remote sensing purposes Systems have been devised to filter out visible data and to photograph other regions of the electro-magnetic (EM) spectrum, for example, infra-red There are some sensors which are sensitive to only certain regions of the spectrum and detect objects emitting only those wavelengths When characteristic EM signatures of objects are known, then it is easy to correlate which objects are being remotely sensed For example, oil i n a thin film on water has a spectral signature in the 8-12 llm region which is considered to be thermal infra-red This can then be detected using sensors sensitive to those thermal infra-red wavelengths 3.1.1. Thermal Infra-Red Every material has properties that are unique to it. As light or radiant energy, strikes its surface that energy is partially reflected, partially transmitted through the 29

PAGE 36

material and partially absorbed by the material By definition, then, reflectivity plus absorptivity plus transmitivity equal 1 (Sabins 1987) These all depend on the material and the wavelength of the incident energy To understand how objects are detected in certain spectral regions some background must be given A black body is defined as a material which absorbs all radiant energy and radiates it. Therefore its absorptivity is 1 Suppose a material has kinetic temperature T kin which is the temperture a thermometer would measure when placed in direct contact with the material The radiant flux Fb or electromagnetic energy radiated from the material is (3. 1) where cr is 5 67 -12 W/cm2 K4 cr is the Stefan-Boltzmann constant and (3.1) is the Stefann-Boltzmann law Kinetic temperature can be measured for any material and using (3 1 ) the black body flux is then calculated This is an idealism, however because there is no material that can act as a perfect black body, absorbing all radiant energy and radiating the full amount of energy in (3 1 ) A ratio has been devised: the actual radiant flux from a material to the radiant flux of a black body. This is called emissivity (3. 2) Only a black body has emissivity of 1 while all others will be less than 1 Every 30

PAGE 37

material has an emissivity, but it is wavelength dependent changing for different wavelenth values Water with a thin film of oil has an emissivity of 0. 972 while pure water has an emissivity of 0 993 The following will show how this difference in emissivity has detectable properties. Combining (3 1) and (3 2) we see that radiant flux for a real material is as follows : F = E ark. r tn (3. 3) Emissivity is a measurement that quantifies the ability of a material to both radiate and absorb energy (Sabins 1987) Material with high emissivity absorb high amounts of incident energy, while radiating large amounts of energy Materials with lower emissivity absorb and radiate lower amounts of energy Sabins (1987) shows that the following is true : (3.4) Using the oil measurements and assuming a temperature of291 K, we see that the radiant temperature of the water with oil is 288 94 K and the radiant temperature of the water is 290.49 K. This 1 .55 K difference is very detectable using a device called a radiometer, which is a thermal IR detector, generally sensitive to temperature differences of 0 1 C (Sabins 1987) Based on the Planck radiation function, the wavelength band from 3-5 Jlm is most sensitive to changes in temperature at about 300K while the 8-14 Jlm wavelength band is sensitive to temperature changes 31

PAGE 38

occurring between 210 and 360K (Rees, 1990) There are several different devices which detect this change in temperature One has a material whose resistance changes with the change in temperature, one has potential differences change with the temperature change and another consists of a crystal which undergoes a redistribution on internal charge as a result of detected temperature change (Rees, 1990) This sensor works well during day and night. Liu Tseng, and Chang (1996) present a study using data from channel4 (thermal IR) from A VHRR Polar Orbiting Earth Sensing satellite data clearly illuminating an oil spill on the Gulf of Oman during the day and at night. Thermal IR, however, is limited when moisture is present in the atmosphere due to water absorption This described how thermal IR sensors work. There are other passive sensors capable of seeing oil on ocean water These include reflected IR, ultra-violet and visible sensors 3 1.2 Reflected Infra-Red Whereas thermal IR sensors are based on a material s emissivity the othersensors are based on a material's reflectance in the various spectral regions Reflected infra-red is an area of the spectrum in which oil has a distinct signature from the underlying sea water as seen in figure 3 1 The A VHRR was able to detect oil 32

PAGE 39

i w (.) z:
PAGE 40

the two substances Due to the wavelength ofUV rays however most are absorbed by the atmosphere Airborne experiments to date have been successful for discriminating oil spills using UV sensors (Sabins 1987 ; Huehnerfuss Alpers and Richter 1996) However it is not an option at altitudes higher than 1000 meters due to the aforementioned issue (Sabins 1987) and will not be covered in any further detail 3 .1.4. Visible The visible is an option since oil is seen in the blue to green wavelengths This is not as effective as other wavelengths and especially not effective on a spacebome platform The angle of the sunlight causes reflection on bodies of water (Lillesand and Kiefer 1987) Finally visible wave-lengths are susceptible to cloud cover hindering the field of view as well as the limitation of not being able to image during night periods 3 2 Active Sensors Active systems are different from passive types in that they supply their own energy which is to be reflected back to be detected by the sensor Consider a transmitter aboard the satellite that emits isotropically A power P1 is spread over a surface at range Rt to give a power per unit area normal to the radiation (irradiance) 34

PAGE 41

(isotripic) (3. 5) Antennas are constructed to confine the radiation to a solid angle significantly less than 4n, i e the antenna is directional This is represented by a gain G such that: p E t G w -2 = m m 2 4nRt (directional) (3. 6) For an antenna of area Ae and efficiency 11, the diffraction limiterd gain is (Rees 1990) (3. 7) where A is the wavelength of the radiation (Efficiency takes into account resistive losses in the antenna so that transmitterd power is 11 times the source power ) For example an antenna of of diameter 3 meters and efficiency of 0 9 emitting at a wavelength 3 em ( X-band) would have G equal to approximatel y 9 x 104 The radiant intensity (power per unit solid angle) scattered from an object is I = crE in Ws(1 (3. 8) where cr is the cross-section in meters squared of the object. The solid an g le subtended by a receiver antenna of area A at distance Rr is Aj( 4nRv 2 ) Thus the power received is (3. 9) 35

PAGE 42

filling in equations (3. 8) and (3. 5) Ar --a 4nR2 r If transmitter and receiver are the same antenna with area Ae, For a scattering surface of area dAs, the cross-section is proportional to dAs. (3. 10) (3. I I) (3. 1 2) where (i is ta dimensionless number the backscattering cross-section per unit area Then (3. 13) Let dAs be estimated by the resolution of the sensor Then dAs is equal to dXrangs times dyazimuth. If dx and dy are equal and 30m, then dAs is 900 meters squared The x-band backscatter coefficient for the ocean surface subject to a 10 meter per second wind is esitmated by Rees (1990) to be on the order of -20 dB for a sensor depression angle of30 degrees So let cr0=10 -2 If the rangeR is 1000 kilometers the estimated received power for an antenna of 3 meters diameter and 5 kW peak power using equation (3. 13) is approximately 2x 10-16 Watts We may compare this with thte 36

PAGE 43

thermal noise power generated at the detector This is given by (3.14) where K is Holtzman's constant (1.38 x10-23 JK-1 ) Tis the detector temperature in Kelvin, and v is the detector bandwidth in Hertz This may be approximated by 1 over the bandwidth Suppose the detector temperature is 290 K (20C) The bandwidth is estimated by the pulsewidth t, which in tum is related to the range resolution dx by 2dxcos8d=ct (equation (3. 16)) For dx=30meters and 8d=3 0 t = 0 2!ls Therefore approximately 5 Mhz and Pthis 2 x10-14 W We find initially, that P/Pth is 10-2 that is the received signal is buried 20dB in the sensor's thermal noise Vairous remedies exist. The detector can be cooled Indeed a liquid helium cooled detector, for which T=4K, would bring P/Pth to unity A further remedy is to integrate the response over N pulses The incoherent noise will partially cancel itself as successive pulses are summed, while the desired signal sums directly An improvement by a factor ofN112 should be achieved so that a 32 times improvement is achieved by averaging 1000 pulse returns. Doppler processing of the signal can substantially decrease the bandwidth For further discussion of detectabilit y and range of radar systmes see Stimson Introduction to Airborne Radar (1983) Rees (1990) states "microwave scatterometry has been used extensively for characterising geological materials using the variation of (l with incidence angle ed as 37

PAGE 44

a signature in much the same way as materials are identified in the visible band by their spectral signature." 3 2 1 Side-Looking Airborne Radar The side-looking airborne radar is a real aperture radar based on the principles outlined above Energy in the microwave range is transmitted from an antenna in short pulses on the order of microseconds The signal bounces off an object and returns to the antenna By measuring the difference in signal transmit and receive time the range ofthe object is easily calculated (Lillesand and Keifer, 1987) : SR=ct 2 (3. 15) where SR is slant range or distance c is the speed of light and t is the amount of time between transmission and echo reception The echo is recorded, and the time delay and intensity of the return will define the image, after the velocity of the platform is taken into account. The next two issues are critical for the system to be able to distinguish separate objects : range and azimuth resolutions. Range or cross-track, resolution is that which is perpendicular to the flight path of the platform. It is dependent on the pulse length of the signal, which is the duration of the transmitted pulse, 't. The resulting measurement represents the slant range while the desired measurement is the ground 38

PAGE 45

range (Sabins 1987) This is the actual distance between objects that can or cannot be resolved The equation then for the range resolution (measuring the actual ground range) is: R = cr r 2cosBd (3. 16) where ed is the depression angle Using 't = 0 2 llS and ed = 30, the range resolution is appro xi mately 65 meters See figure 3 2 : ANTENNA DEPRESSION ANGlE. "I 500 .,. .. 0.1 x 1o-6sec RANGE DIRECTION .,. c Rr 2 COl')' c 3 x 1o& m ste1 TARGETS Rr .. 18m (at -y= 350) C & DARE RESOlVED F igure 3 2 : Radar resolution in the range direction (Sabins 1987) The azimuth or along-track resolution is the measurement of how distant objects must be in a direction parallel to the flight path in order to be distinguishable This is based on several properties The azimuth resolution is smaller in the near range 39

PAGE 46

than in the far range as seen in figure 3 3 This beam width is proportional to the wavelength of the transmitted pulse and inversel y proportional to antenna length : R = 0 .7SRA a 0 (3. 17) where SR is slant range distance and Dis antenna length Using D =IO meters and altitude of 800 kilometers at a 30 degree depression angle (resulting in a slant range o f 923 kilometers) the azimuth resolution is 1.9 kilometers ANTENNA DISTANCE AB DISTANCE CD 35m TAR6ETS A & 8 AR RESOLVED TARGETS C &. 0 ARE NOT RESOLVED F igure 3 3 : Radar beam width and resolution in the azimuth direction (Sabins 1987) This is the limiting agent of real-aperture radars They are simple in theory and design but limited to low altitude with very large antennas to achieve acceptable resolution (Lillesand and Kiefer 1987) Knowing this synthetic aperture radars were developed to give increased resolution with the same size antenna Kalmyko v, et al. 40

PAGE 47

(1993) state however, that spacebome real aperture radars such as those aboard the Soviet Cosmos and Okean satellites are suited perfectly for the initial detection of such large features as oil slicks where as the small resolution of the SAR is better suited for observing fine detail 3 2 2 Synthetic Aperture Radars A synthetic aperture radar employs the same components as a real aperture radar (Lillesand and Kiefer 1987) but through use ofthe Doppler principle and special data processing equipment, the azimuth resolution of a very narrow beam is synthesized, narrow beams allowing for greater distinction between objects See figure 3 3 Recalling that "the Doppler principle states that the frequency source (pitch) of the sound heard differs from the frequency of the vibrating source whenever the listener and the source are in motion relative to one another (Sabins 1987) it is easily applied to detection platforms in relative motion to a sensed object. As seen in figure 3.4, the Doppler principle can be applied to this situation (Wahl et al. 1996) Figure 3 5 shows the synthesized length L of an antenna with actual length D Not only are longer antennas synthesized in a SAR system but dependence on altitude is not an issue (Rees 1990) The drawback of this system however is the complexity of the data received It requires powerful processors to produce the end-product image 41

PAGE 48

NEAR RANGE / FAR RANGE Figure 3 4 : Doppler frequency shift due to relative motion oftarget through radar beam (Sabins 1987) These processors are generally too large to be aboard the satellite, so large amounts of data are transmitted to a ground station for manipulation, the data rate also being an issue (Challenor 1987) When SeaSat the first satellite with a SAR, was operational the computers used to digitally process the data had 512 kilobytes of random access memory, compared to personal computers today containing upwards of32 megabytes of RAM This was the reason most SeaS at data was optically versus digitally 42

PAGE 49

_ j SYNTHETIC f BEAM WIDTH NEAR RANGE FAR RANGE Figure 3 5: Resolution of SAR in the azimuth direction (Sabins 1987) processed This however, lends itself to distortions and other problems with data representation (Veseky and Stewart 1982) In the early 1990s the European Space Agency (ESA) underestimated the processing power required to generate top quality digital images from their original SAR satellite ERS-1 (Clery 1993) Great strides are being made however with individual ground stations processing their own images to the desired resolution Tromso Satellite Station in Norway for example (Wahl et al., 1996) 43

PAGE 50

3 2 3 Scattering from Ocean Waves and Wave Damping Theory The incidence angle surface tension and elastic properties of the slick all play a role in the intensity of a backscattered signal from the sea surface (Bass and Puzenko 1994) Vesecky (1995) defining capillary waves as those with A < 1 meter conducted experiments and calculations and states that wave-wave interaction also play a large role in surface film effects The Bragg condition states that the path difference between two incident EM rays is equal to an integer multiple of the microwave wavelength (3. 18) where A is the wavelength of the microwave. See figure 3 6The path difference between ray 2 and ray 1 is Asin9r Asin9i where 91 and Sr are incident and reflected angles and A is the distance between the waves There is an additional requirement for Bragg scattering of radar from the ocean waves The constructive interference only occurs from those waves whose crests are perpendicular to the direction of propagation of the radar. See figures 3 7 and 3 8 44

PAGE 51

Figure 3 6 Bragg Scattering Satellite Figure 3 7 Bragg scattering can occur 45

PAGE 52

Satellite Figure 3 8 No Bragg scattering The Bragg phenomenon is quite analogous to scattering of light from a diffraction grating Radar contrast in deciels is plotted against the Bragg number for different polarisation states Based on the plot the predictability of detection is assessed It is accepted that the incidence angle e of 20 to 60 degrees fits into this model (Singh, Gray Hawkins and O'Neil 1986) Oil slicks are readily detectable provided they are embedded in a wave field that satisfies the Bragg condition The backscattering cross section is proportional to height of the waves The wave height is determined by an energy balance betwen energy supply from wind and depletion due to damping and nonlinear mechanisms that transfer energy from one wavelength to another The bottom line is that if there is more damping there will be smaller waves and consequently less scattering Oil has long been known to damp water waves Conswquently there's a rich literature describing their damping, including a "classic" treatment by Levich Recent 46

PAGE 53

work by Cini and Lombardini ( 1989) express the ratio of damping of oil covered waves to clean water waves as : where : y(f) 1 2r+2i -x+ y(x+ r) 1 2r+ 2i2x+2>i r =(-Wo j 2w E K2 x = o "--------;-(2ryul j E 0 K y=-4rypw aK 3 -+gK UJ p l f=-=(-' 27r 27r (3 .19) (3. 20 ) (3. 21) (3. 22) (3.23 ) where : cr is surface tension p is water density g is acceleration of gravity K is wave number 11 is kinematic viscosity and m0 is frequency of the film du E---o -d(lnr) (3. 24) where r is surface concentration In ( 3 19) a plus sign is for soluble films a negative sign for insoluble films In this instance, the dampling function uses wave number as a parameter S is devised as the omni-directional spectrum a function of frequency and is broken down into 3 terms sin or energy input from the wind snl or non-linear cross-47

PAGE 54

spectral transfer due to the wave-wave interaction and finally Sds, the dissipative term 85 -=5. + 51-Sd iJt m n s (3. 25) The surface films introduced then effect each of these parameters to varying degrees Sin and Sds to a greater extent. Cini Lombardini and Huehnerfuss (1983) explain how Sin and Sn1 are affected and show the modification of Sds based on the presence of surface slicks Using (3. 11) and the expression (3. 26) where 8 is the viscous energy damping coefficient y is the kinematic viscosity and K is the wa v e number an e x pression is formed that fits into (3. 27) where S is the steady state spectrum in the absence of losses These parameters give the qualitative picture of energy transfer causing detectable damping of wave height. 48

PAGE 55

4. Orbital Parameters One of the most important issues, when dealing with spaceborne sensors is the orbital characteristics of the platform Adhering to basic orbital mechanics, there are still numerous ways in which to configure a satellite orbit and consequently the amount of and location of the earth observed Larson and Wertz (1992) state that coverage a part of the earth the instrument can see instantaneously or over an extended period for a particular location is frequently a key element in mission design The field of view (FOV) of a sensor is the actual area the instrument can see at one time The access area contrastly, is what the sensor can see if it were rotated Although existing systems like SPOT (Lillesand and Kiefer, 1987) and Radarsat (Gower, Vachon and Edel, 1993) have steerable sensors, we will deal with non-steerable beams for the most part of this discussion A short synopsis of relevant orbital parameters will be instrumental in understanding the benefits and drawbacks of each of the orbits discussed later See figure 4 .1. The inclination i of an orbit is the angle at which it crosses the equator. As the satellite is traveling northward this point is called the ascending node n Conversely, the point at which it crosses the equator traveling southward is the descending node One revolution about the earth or from ascending node to ascending 49

PAGE 56

node is the satellite s orbital or nodal period Apogee and perigee are the points in the orbit furthest and closest to the earth respectively. \ \. Raa e =-a X Equinox North Pole z Orbit J Plane J-. -----_ I )o-Y fquator X Equinox Figure 4 1 : Classical orbital elements (Classical Orbital Elements 1995 ) Assuming a circular orbit with eccentricity e equal to 0 these are identical and equal to the altitude of the rest of the points on the orbit. When a satellite is in a circular orbit the serniO-major axis a, is equal to its altitude Consequently as the satellite mo v es around its orbit the earth is rotating on its axis underneath it creating a ground trace that appears as a sine wave rather than a repeating circle The ground trace is an ima gi nary line following the path of the satellite travelling through space translated onto the earth Lastly as the earth moves underneath the orbit the orbit precesses somewhat irregularly due to several other factors including the oblateness of the earth and other physical effects 50

PAGE 57

Using this background, unique types of orbits will be discussed : geostationary low-earth orbit other than polar and polar orbits 4 1 Geostationary Orbits A satellite in a geostationary orbit is as its name suggests, at rest with respect to the rotating earth" (Rees 1990) This is made possible by putting the satellite at an altitude where its nodal or orbital period is the same as the earth's rotational period It has an inclination of zero The satellite in geostationary orbit then appears to rest at the same longitude directly above the equator with a distance of22, 375 miles (Rees 1990) This is deduced by the expression: T = 2.76( a ;t 104km (4 1) When the orbital period of the earth in hours is substituted forT, the answer includes the radius ofthe earth which must be subtracted This gives the appropriate altitude for geosynchronous orbits. This equation was arrived at by using Newton's second law the law oflarge bodies and angular velocity Geosynchronous orbits have the same orbital period as the earth but have an inclination greater than zero This causes the satellite to drift north and south of the equator to the latitude corresponding to the inclination, spending equal time in each 51

PAGE 58

hemisphere This orbit traces out a :figure-8 where the ascending and descending nodes are on the same point on the equator. Larson and Wertz (1992) maintain that geostationary orbits are most usefully applied to communications and weather missions Examples include Milstar, a military communications satellite system and Geostationary Operational Environmental Satellite (GOES), NOAA/NASA weather satellites (Lillesand and Kiefer 1987) Lillesand and Kiefer (1987) Larson and Wertz (1992) and Sabins (1987) all state that for fine detail a geosynchronous orbit is inappropriate The desired spatial resolution is simply not achieved from such an altitude Due to the nature of the mission outlined in this paper, geosynchronous orbits will no longer be considered a candidate solution for this issue 4 2 Low-Earth, Non-Polar Orbits The next option with respect to orbits is low-earth, non-polar Low-earth, for our purposes will be defined as having an altitude lower than 950 miles or 1500 kilometers Several sensors which have spotted oil slicks have been in such an orbit. SIR-A, -B and -C/X-SAR were all shuttle campaigns in which the sensors were in this configuration Using the Central Coast of California as a target, calculations can be done based on orbital parameters to predict how often the target is within the FOV of the 52

PAGE 59

sensor. Assuming a side looking radar (real or synthetic aperture), the footprint area (or FOV) is approximated at: nD2 sin2 9 FA=-----4 sinE (4.2) where Dis the range from satellite to the toe of the footprint (FOV), 8 is the angle between the toe and the heel of the footprint as seen from the satellite and E is the spacecraft elevation angle See figure 4 2 spacecraft earth Figure 4 2 : Geometry of a footprint. (Larson and Wertz 1992) 53

PAGE 60

Orbits attain north and south latitudes corresponding to their inclinations The SIR-C/X-SAR campaigns had an orbital inclination of only 57. Therefore the highest north latitude attained was 57. The altitude ofthese flights by default gave smaller swaths as well (Stofan, et al. 1995) The swath is the continous coverage attained by a particular sensor. While this low-earth, non-polar orbit has been very useful during the shuttle campaigns, it has the drawback that the entire earth is not viewed Only near-polar low-earth orbits allow for this While such an orbit might seem appropriate for the low latitudes of the Santa Barbara Channel, not being able to image the entire earth is a drawback as demonstrated in future sections 4 3. Polar Orbits Larson and Wertz (1992) suggest that sun-synchronous orbits are best suited for satellites for earth resource observations A sun-synchronous orbit is one in which the satellite will cross a given latitude at the same solar time every day (Rees, 1990). Based on an assumption that from the earth, the sun appears to rotate about the earth with a period of one year with an angular speed of 1.991 xlO -7s-\ we set that equal to the satellite's angular speed in order to achieve an orbit where the satellite sees the earth at the same solar time each day 54

PAGE 61

( ass )t = -6624.6 cosi lOOOkm (1-e2 ) 2 (4 3) By using equation (4 3) and choosing an appropriate altitude and eccentricity the inclination angle can be calculated (Rees 1990) This makes these satellites necessarily retrograde (with inclination angle of greater than 90 ) with inclinations not less than 96 This orbit has been found to be extremely useful with visible-wavelength sensors because the satellite can be placed to look at features at a particular time of day i e local early morning or high noon depending on mission requirements (Rees 1990) The majority of the earth remote sensing satellites past and present utilize this orbit to include Nimbus SPOT Landsat DMSP NOAA, TIROS and nearly SeaSat. Additionally because of the nature of this orbit, the coverage capability is dependent on latitude (Wahl et al., 1996). Wahl et al. (1996) shows that the coverage capability at latitude cj) of a radar satellite with a fixed swath W doing N revolutions per day in an orbit with inclination is approximatel y NW Coverage = -----;======= (4 3) where R is the radius of the earth 55

PAGE 62

Figure 4 2 : Coverage elements Two good examples of how this works are ERS-1 and Radarsat. ERS-1 is able to give 36% coverage oflongitudes to locations at 35 north or south latitude based on its orbital parameters and a 400 kilometer swath width in its three day cycle Radarsat with its adjustable swath width can give 90% or better coverage of longitudes to all latitudes in its 51 0 kilometer mode with its three day cycle .. An important issue when dealing with remote sensing satellites is repeat time, or how often the satellite subpoint is the same. This can be easily calculated based on orbital parameters 56

PAGE 63

P (Q Q) = 2n!!L N e nz (4.4) where P N is the nodal or orbital period n e is the earth's rotational speed and n is the satellite s precession The ratio ntln2 when extrapolated into integers represents the number of days taken to revisit the same location on the earth s surface nt and the number of revolutions taken to get there n2 ERS-1 for example has a revisit time of 3 days and 43 orbits (Rees 1990) Rees (1992) discusses that for observing rapidly changing phenomenon, short repeat periods are preferable While that can be difficult to attain orbital subcycles are employed This is where the orbit doesn t repeat itself exactly for long periods of time but almost repeats itself at much shorter intervals Rees (1990) uses ERS-1 as an example again usin g n1 is 3 days and n2 is 43 orbits Using these parameters the suborbital tracks or ground trace at the equator corresponds to about 930 kilometers (460 kilometers at 60 north or south) Using the case ntis 80 days n2 can be 1143 1147 or 1149 This corresponds to a suborbital track spacing of35 kilometers at the equator giving much more complete coverage than the 3-day repeat orbit. However using n2= 1147 the satellite has made 43 orbits in 2 999 days instead ofthe original 3 and is only 0 .31 east of its original position or intended position for the 3-day repeat. This is only 34 kilometers away (at the equator) So while the satellite sub-point is not exactly the same a sensor with at least a 60 kilometer swath in this example will have 57

PAGE 64

an approximate 3-day repeat period This will allow the sensor to image the same point over more consecutive days but it will miss the same point more days as well An additional factor to be taken into consideration is a steerable sensor SIR C/X-SAR (Chang, Jin Lou and Holt 1996) Radarsat (Gower, Vachon and Edel 1993) and SPOT (Lillesand and Kiefer 1987) all use or used steerable sensors to gain better coverage for particular features chosen on a real-time basis The added feature ofvariable swath width (on SIR-C and Radarsat) is also extremely useful in real-time mission parameter changes With the larger swath width, resolution is the trade-off 58

PAGE 65

5 Cost This section is a brief comparison of the cost of a satellite as part of an early warning and detection system, and the cost of an oil spill and oil pollution in general This evaluation is not intended as a conclusive cost analysis but rather a general study to give an overview of the figures and determine the need for a more thorough cost analysis 5 1 Cost of Oil Pollution Schriel (1989) and Sabins (1987) both state that the causes of oil pollution can generally be divided into distinct sources, but give conflicting figures on the amounts from each source While Schriel (1989) has transportation at 9% Sabins (1987) names it as the largest source 45% Schriel (1989) has land run-off as the largest polluter (50%) while Sabins (1987) has it second with 36% Sabins (1987) names off shore drilling the smallest polluter at 1 5% while Schriel ( 1989) names it second highest at 32% Looking at either scenario it is easy to see that pollution from any source is an issue to be dealt with Sabins ( 1987) puts the total amount of oil pollution in marine environments at 3 24 million metric tons. For purposes of cost oil pollution will be looked at from two angles : pollution caused by oil spills and pollution caused by everything else, including the above-mentioned sources 59

PAGE 66

5.1 1 Cost of an Oil Spill In 1969 the Santa Barbara Channel experienced one of the worst blowouts of oil ever An uninhibited oil and gas flow lasted for 10 5 days, with spillage and seepage occurring intermittently for one year Estimates put the total released for the first 100 days at 3 25 million gallons of oil and natural gas (Meade and Sorensen, 1970) Meade and Sorensen (1970) divide the cost of an oil spill into seven categories : direct clean up and property damage damage to tourism damage to commercial fishing decline in real property values damage to the marine environment esthetic costs and reduction in recreational opportunities for the resident population, and finally loss of the resource itself The largest part of the expense was the actual clean up costing the oil companies 10 5 million 1969 dollars (Meade and Sorensen, 1970) This equates to approximately 45 million 1995 dollars (u S Bureau ofthe Census 1996) The estimated total cost ofthis oil spill was 16. 5 million 1969 dollars (Meade and Sorensen 1970) equating to 68 6 million 1995 dollars (U. S Bureau of the Census 1996) This is a conservative figure for one spill that happened almost 30 years ago The Exxon Valdez spill in March 1989 has cost Exxon $8 7 billion. This includes actual cleanup $2 1 billion, money to the state and federal governments for fines compensatory and punitive damages and others (Mink, 1994) Even more recently in 60

PAGE 67

1994 2000 barrels were spilled in Taft, California due to an aging pipeline Although claiming no responsibility, one corporation paid $8 3 million in direct clean up costs and $3. 2 million to the California and federal governments (Fine assessed in California oil spill 1994). On top of dealing with spills when they occur, there are several federal and California state agencies that deal with oil pollution on an everyday basis 5 1 .2. Cost of Oil Pollution Monitoring and Response California Department of Fish and Game has an office of Oil Spill Prevention and Response, which works closely with the federal equivalent the U. S. Department of the Interior's Minerals Management Service (Cooperative Agreement). Because of the Exxon Valdez disaster, the federal government passed the Oil Pollution Act (OPA) of 1990 (Natural Resource Damage Assessment under the OP A of 1990 1997) These two offices as well as the Coast Guard enforce the tenets of OP A, which require that the natural resources be restored to their original condition and compensation be paid for lost services as a result of oil spills (Natural Resource Damage Assessment Under the OPA of 1990 1997). NOAA has formed several centers charged with damage assessment and restoration to coastal environments plagued with oil pollution (NOAA Damage Assessment and Restoration Center Northwest 1997) The federal Environmental Protection Agency also plays a role in oil spill response and clean-up 61

PAGE 68

The Minerals Management Service, charged with "regulation and supervision of energy and mineral exploration development and production operations on the OCS lands" (Amendment to the Federal Budget 1997) has a 1997 estimated budget of $80 million just to deal with outer continental shelf (OCS) lands Oil spill research is specifically allocated $6.4 million The U. S Coast Guard who "detect and respond immediately and substantially to potential or actual oil or hazardous discharges" (MSO San Francisco Fact Sheet 1997) is allocated $242 million per year for "marine environmental protection" (Amendment to the Federal Budget 1997) The Environmental Protection Agency was authorized $30 million for 1997 specifically for oil spill response (Amendment to the Federal Budget, 1997) NOAA has a revolving account of at least $2 million annually ($14 million in fiscal year 1996) to carry out oil and hazardous materials contingency planning and response natural resource damage assessment and restoration of lost natural resources (Amendment to the Federal Budges 1997) Finally an oil spill liability trust fund was set up by the federal government in compliance with a public law of 1989 A $0 .05 per barrel tax for domestic or imported oil has brought the balance of this fund to $1. 236 billion Legislation is currently pending to raise the cap of this fund to $2 5 billion. While the tax pays into the fund so do penalties and fines assessed against polluters For fiscal year 1997 it is estimated that $374 million will be collected (with an existing balance of$997 million) 62

PAGE 69

and only $13 5 million will actually be spent. This is the maximum allowable amount to come out of this fund So it essentially just grows larger The total budget for oil spill response is approximately $280 million excluding the $1.2 billion trust fund 5 2 Cost of a Space-Based Detection System The cost of a space-based detection program will be broken down into three separate categories : the cost of the satellite itself the cost of the launch vehicle and the cost of the ground station support needed to keep the satellite operational and downlink the data 5 2 .1. Cost of a Satellite Not being able to solicit bids from actual aerospace corporations for a theoretical satellite the best way to determine the cost of one is to look at how much earth remote sensing satellites in existence originally cost. We will look at several including Landsat Topex/Poseidon and the radar satellites currently in the inventory ERS-1 the original SAR satellite after SeaSat cost $850 million dollars to produce While that one was extremely costly ERS-2 a virtual duplicate of the first except for additional sensors was one-third as much costing $275 million (Space Systems Forecast 1996) Assumably this is because the technology was no longer breakthrough 63

PAGE 70

Landsat is a less expensive program. Landsat-7, currently being built is expected to cost an estimated $200 million (Space Systems Forecast, 1996) It is not as expensive as the radar satellites seen here Meteosat, another non-radar satellite is in a geosynchronous orbit, designed for a weather observation mission Each of these spacecraft (those not yet built) is expected to cost about $180 million (Space Systems Forecast, 1996) NOAA, another series ofweather satellites, cost $67 million, with follow-on spacecraft expected at approximately $75 million (Space Systems Forecast 1996) Radarsat, Canada's space-based SAR, is one of the more expensive spacecraft The first cost $390 million (Space Systems Forecast, 1996). Ifthe program continues as the ERS program did, the follow-on satellites will be considerably less expensive Topex/Poseidon is an expensive system costing $470 million for the spacecraft Several active microwave instruments on this platform, a design life of 12 years and total systems redundancy each drive the price higher. Its follow-on is expected to drop to $310 million (Space systems Forecast, 1996) 5 2 2 Cost of a Launch The cost of a launch vehicle must be taken into consideration as the boosters are often as expensive as the spacecraft itself. Often the same launch vehicle can cost different amounts, based on the weight taken into orbit. 64

PAGE 71

The Arian 4 cost $40-50 million for 1200-1600 kilograms $55-65 million for 2000-2500 kilograms $65-80 million for 2500-3000 kilograms and $90-110 million for payloads greater than 3000 kilograms Other options can be included for a price transportation ofthe spacecraft to the launch site for e x ample (Wilson, 1996) The Topex!Poseidon launch on an Arian 4 cost $130 million (Space Systems Forecast 1996) T he United States' lar g est e x pendable booster is the Titan IV, produced b y Lockheed Martin The contract with the U. S Air Force sets the cost of a single booster to $190 million not includin g an upper stage (Wilson, 1996) Lockheed Martin's Atlas Centaurs has been used to launch NOAA' s GOES satellites into orbit. $200 million put three into space averaging $67 million for each launch (Wilson, 1996) McDonnell Douglas Aerospace s Delta rockets come with different specifications and different prices. A Delta 2 is available for $55 million a Delta 3 $75 million (Wilson 1996) As seen here depending on the orbit launched into and the weight o f the spacecraft launch could cost anywhere from $55 to 190 million 5 2 3 Cost of a Ground Station Without the support of a ground station a satellite is virtually useless The ground station is where the state of health of the satellite itself is monitored and from 65

PAGE 72

where commands are sent to the spacecraft to complete preventative maintenance and respond to satellite anomalies Besides that a ground station is where a spacecraft will downlink mission data In this case it would be the images from radar or optical systems that were collected and recorded earlier in the orbit or collected at the time of downlink Some satellite have comple x ground station networks set up while others only require two or three stations Some ground stations do double duty acquiring data from multiple satellites The United Kingdom is establishing an Earth Observation Data Center for the processing of remote sensing data The contract is worth $14 million for the first four y ears ERS-1 cost $1.3 billion to include launch satellite and three years of ground station support This results in a yearly cost of approximately $100 million Because of ERS's complex ground segment this money could go to up to 2 3 ground stations (Space Systems Forecast 1996) However most ofthese g round stations support other satellite programs as well Based on the previous information a satellite program with an active radar could cost approximatel y $600 million : $300 million for the satellite $200 million for the launch and $100 million for three years support from a ground station network Because this effort is no longer original the cost could be considerably lower. 66

PAGE 73

6 Conclusions and Suggestions for Further Study Challenor (1988) states satellites "are well suited to a general monitoring role" when it comes to oil pollution detection Wahl, et al, (1996), Anderson (1997) and Victorov (1996) and Gower Vachon and Edel (1993) all state something similar in that satellites are well suited to this role Having established that the question then becomes which orbit, which sensor andean it be cost effective While the arguments for each of these questions were made in previous chapters the following three sections will submit conclusions. The final section will suggest what further studies should be accomplished to either further support this thesis or to test other closely related topics 6 .1. Sensors Referring back to section 3 it is noted that there are two main sensor types : active and passive Of the passive systems discussed each has advantages and disadvantages Thermal and reflected infrared each have difficulties with cloud cover. Because coastal zones are often obscured by clouds it is imperative to find a sensor for which clouds are not a problem While these passive sensors have had success in detecting oil slicks, they would be unreliable because of the overwhelming chance of 67

PAGE 74

unfavorable weather conditions Ultra-violet sensor do not fair well above 1000 meters making them inappropriate for a space-based platform This brings our attention to active microwave sensors Those covered include synthetic aperture radar and side-looking airborne radar both imaging radars It has been shown that the SAR on board ERS-1 and -2 has been used successfully to image oil slicks (Wahl, et al 1996 ; Victorov 1996 ; Stringer et al, 1992) The problems with this method have also been identified Detection using active radar is wind dependent. Oil can only be detected with winds between 2 and 13 meters per second (Wahl et al, 1996 ; Gower, Vachon and Edel 1993) Overwhelming amounts of data are produced using this sensor This causes problems for both the downlink capacity and for the computing power needed on the ground (Challenor 1988) Limited information concerning spaceborne SLARs has been presented as very few systems employ this sensor While Kalmykov et al (1993) make the argument the SLARs are very well suited for oil slick detection due to the resolution trade-off for less computing power required more studies indicate synthetic aperture along with its inherent liabilities is the sensor of choice Some of the known liabilities include wind dependence for detection capability large amounts of data encumbering the downlink data rate mistaking natural slicks for man-made slicks and power limitations Some of these have been already considered Operator training is one solution to two of the problems : better interpretation during 68

PAGE 75

unusual wind conditions and fewer mistaken slicks of biogenic source (Wahl et al, 1996 ; Victorov 1996) While data rates of 1000 megabits per second were a major issue in 1988 (Challenor 1988) with the evolution of computer systems this might not be a problem anymore It does merit further study Finally based on orbital mechanics and when the satellite is in eclipse the on-board batteries can probably support operation of a SAR no more than 10 minutes per period This issue also warrants further study In conclusion synthetic aperture radar meets the sensor requirements It sees through clouds and can have a very high resolution In addition those SARs with a variable swath width are even more valuable as a sensor can be scanning for a slick in a lower resolution larger swath width mode to ensure greater coverage 6 2 Orbit As seen in chapter 4 primarily three orbits can be offered for earth remote sensing purposes : low-earth orbit sun-synchronous or polar and geosynchronous. Geosynchronous is not an option due to the limited resolution and the inability of the signal to stay above noise levels when traveling from that distance Low-earth orbit with an inclination of at least 3 5 degrees would cover Central California but would be very limiting for other geographic regions i e those above 35 degrees north and below 3 5 degrees south latitude While the issue of cost has not yet been discussed 69

PAGE 76

multi-tasking is obviousl y a way to reduce cost. By limiting the total earth coverage the price is be default being driven up Polar sun-synchronous orbits seem to be the choice for earth remote sensing This issue of latitude of the Central Coast becomes a player with this orbit. As it is fairly close to the equator Central California will be afforded less covera g e than those locations closer to the poles (Gower Vachon, and Edel 1993) This is to be dealt with by trade-offs in repeat time and sensor swath/resolution 6 3 Cost This thesis presented several oil spill incidents. The Santa Barbara Channel spill of 1969 translated into $70 million and 3 3 million gallons of oil lost. The Exxon Valdez spill cost Exxon $8 7 billion and 11 million gallons of oil The budget of the U. S Government was consulted and found that $280 million is spent annuall y on oil spill pre v ention This excludes the Oil Spill Prevention Liability Trust Fund of $1. 2 billion and any amount of mone y the oil companies t hemselves spend on detection and monitoring We've seen the cost of a SAR system drop from $870 million to $275 million because the technolo gy was no longer original. While the average radar satellite cost hovers around $ 3 50 million the price has dropped considerabl y Also compared to 70

PAGE 77

what is contained in the trust fund and what was spent on the Valdez disaster alone this amount pales in comparison According to Wahl et al, (1996) satellite images are competitively priced. Anderson (1997) asserts that surveillance from satellites is less expensive than that from airborne sensors Finally radar satellites were designed with different functions in mind than detecting oil pollution Surely multi-tasking of one will spread the cost burden to other agencies who will utilize the data for purposes of ice mapping, wind condition monitoring ocean current tracking and other oceanographic related missions Victorov (1996) states the requirements for an early warning system include time delay of less than one hour with coverage of traffic lanes and coastal zones repeat time ofless than twelve hours with a 75% success rate of detecting slicks with an area at least 0 .01 square kilometers Link, McKim and Bruizewicz (1991) state that the 11 optimum sensing package for oil spill sensing form satellites would be a system with the resolution of the TM (thematic mapper) the daily coverage ofthe A VHRR and the all weather mapping capability of a SLAR 11 Challenor ( 1988) give requirements of an active microwave sensor with a swath width in excess of 1000 kilometers and resolution of 25 meters He suggests two satellites in different locations of the same orbit: one leading the way with a low-resolution large swath 71

PAGE 78

the second following with a steerable high resolution sensor able to focus on what was detected by the first satellite The author agrees with Wahl et al, (1996) who states "it is recommended that pollution authorities worldwide consider the use of radar satellites as an additional source of environmental infonnation from their coastal waters It has been calculated that the minimum amount oftime to image a location is 2.4 da y s after its original imaging This is using Radarsat ERS-1 and JERS Because ERS has no recording capability it can image only where it can downlink data to a ground station Finally while each satellite can only image for approximately 10 minutes per orbit, based on the satellites speeds, each only needs to radiate on the order of seconds in order to achieve images covering the entire Santa Barbara Channel. This could become an issue however, based on whether or not the satellites are in eclipse The batteries have limitations on what power they can provide to the active instrument. It has been mentioned that the volume of oil is most important to ascertain when dealing with a slick. While SARs have been shown to be effective in detennining slick thickness (and therefore volume) thennal IR sensors have been shown to be more effective During the Valdez disaster the initial slick stayed relatively motionless staying in an area of 3 50 square kilometers for 2 5 days before dispersing because of wind driven sea state conditions This represents a square with 72

PAGE 79

18. 7 kilometer legs The platform in the Santa Barbara Channel furthest from shore is only 16. 5 kilometers away the closest being 6 kilometers Had Valdez happened near any platform in the channel the beaches would have been effected immediately. This again is where the most damage occurs and the most costs are incurred Early warning to locate the slick and track the bulk of the oil mass is paramount to preventing its spread towards land where it does the most damage Synthetic aperture radar effectively detects oil pollution in marine environments Knowing the orbital limitations of systems and the systems already in service it is recommended that these parameters be taken into account in a further study to design a constellation with both oil pollution monitors and other data users in mind. Funding could be solicited not only from the federal and state governments and any other associated agencies who would use the data but also from large oil companies who contribute the most to cleaning up oil pollution 6.4 Suggestions for Further Studies While this paper was designed to bring several concepts together further studies are necessary to supply proof of several of the hypotheses herein First dealing with the constellation itself using existing satellites downlinked data, and that from any future projects from any other nations, determine how many specific platforms would give the desired coverage resolution and repeat time This 73

PAGE 80

can be done only after a customer possibly the EPA, has chosen specifications for the detection mission Investigate to see if existing ground stations such as the Alaska SAR Facility in Fairbanks are able to handle another mission or if separate dedicated facilities must be built. Second determine by how much oil spills become more costly and harmful as they go undetected for hours or days This will also include a model for how the majority of the oil travels based on prevailing winds and currents and when it will reach shore causing the most damage This will further enforce the cost effectiveness ISSUe Third once a platform has been chosen ground station and booster secured and the actual cost in terms of time is deduced conduct a succinct cost analysis to verity the cost effectiveness Finally probe users to see if any other data could be useful. This could include ice mapping current monitoring and even land-based applications These further studies will provide proof to the hypothesis that the volatile California Central Coast as well as other coastal areas can be effectively monitored for oil pollution by satellites presumably in a cost-effective manner. 74

PAGE 81

6.5 Late Breaking Updates In a conversation with John Barry engineer and program manager for Boeing Aerospace on 30 March 1997, it was discovered that the United States government is currently investigating a radar satellite initial concept. Several corporations have been invited to submit proposals for the concept of an unclassified constellation of radar satellites 75

PAGE 82

Glossary Terms Definition Advanced Very High Resolution Thermal IR sesor aboard NOAA Polar Radiometer Orbiting Environmental Satellites Depression angle Angle betwen flight path of inst rument and slant range High Resolution Infrared Sounder Unit IR sensor aboard NOAA POES Microwave Sounder Unit Passive microwave sensor aboard NOAAPOES Multi-spectral Scanner Sensor aboard Landsat detecting in different wavelengths On-orbit spare Satellite which is not currently being used but is still in its orbit and can be reactivated Push-broom imagers Sensor type on board SPOT scanning continually Thematic Mapper Thermal IR sensor aboard Landsat Wave-wave interaction When waves intersect one another 76

PAGE 83

References Alaska SAR (ASF) data center document (1995 Oct 24) http://asf W \ 'f'.-'i.:.tlaska edu/datacenters documents/asf_ datacenter.html (7 April 1997 ) Alpers W. and Holt, B (1995) Imaging of ocean features by SIR-C/X-SAR : an overv1ew 19 95 International Geoscience and Remote Sensing Symposium, 2, 15881590 Alpers W and Huehnerfuss, H. (1989, May 13) The damping of ocean waves by swface films : a new look at an old problem. Journal of Geophysical Research, 94, 6251-6265 Alpers, W (1983) Imaging ocean surface waves by synthetic aperture radar-a review In Allan, T. D (ed ), Satellite Microwave Remote Sensing, 107-119 Chicester : Ellis Horwood Limited Andersen, J. H. Oil spill monitoring by use of radar satellites and sircraft http://www tss no/oilserv/brosjyr.html (25 February 1997) Appendix to the Budget of the United States Government. (Fiscal Year 1997) Washington, D. C : U. S Government Printing Office ASF (1996) Supported satellites' characteristics http : //www asf alaska ecu/reference documents/ source references/ orbits html ( 11 April1997) Basic Petroleum Book. (1987) American Petroleum Institute Bass, F G and Puzenko, S A. (1994) Detection of oil spills on the sea using radar measurements Journal of Electromagnetic Waves and Appliations, vol8, #7, 859870 Bate, R. R., Mueller, D D and White, J. F (1971) Fundamentals of Astrodynamics New York: Dover Publications, Inc. 77

PAGE 84

Bern, T. 1., Wahl, T., Anderssen, T. and Olsen, R. (1993, March) Oil spill detection using satellite based SAR : experience from a field experiment. Photogrammetric Engineering and Remote Sensing, vol 59, #3, 423-428 (I995, Jan 2) Big spill reported in Komi region of Russian Arctic The Oil and Gas Journal, vol93, #1. 30 Bjerde, K. W Schistad Solberg, A. H. and Solberg, R. (I993). Oil spill detection in SAR imagery. 1993 International Geoscience and Remote Sensing Symposium. 943945. Bonnell, M L., Ford, R. G., and Brody, A J. (I996, Dec) Assessing the threat of oil spills to southern sea otters Endangered Species Update, vol 13, # 12. 3 8 Canadian Ice Service. Radarsat image of the month http://www.dow on.doe ca/ice/picmonth/radarsat.html. (II April I997) Canadian Space Agency Radarsat's FAQ : most frequently asked questions http :1 /radarsat. spac gc ca/eng/radarsatlfaq html (23 January 1997) Canadian Space Agency Radars.at's specification sheet. http://radarsat.spac.gc ca/eng/radarsatlspecification_sheet.html (23 January 1997) Challenor, P G. (I988). The future role of satellites In Lodge, A E., (ed ) The Remote SensingofOil Slicks, I43-I47. Chicester : John Wiley and Sons, Ltd. Chang, e Y., Jin, M Y., Lou, Y. and Holt, B. (I996; September) First SIR-C scansar results IEEE Transactions on Geoscience and Remote Sensing, vol 34, #5, I278-I281. Cini, R., Lombardini, P P and Huehnerfuss, H. (I983). Remote sensing of marine slicks utilizing their influence on wave spectra International Journal of Remote Sensing, vol4, #1, IOI-110 Clery, D (1993, June 18). ERS-1 give europeans new views of the oceans Science, 260, 1742-1743 Coast Guard radar images are key to tracking oil spills (1989, April 10) Aviation Week and Space Technology, 18. 78

PAGE 85

Cooperative Agreement. California Department ofFish and Game Office of Oil Spill Prevention and Response and U. S Department of Interior's Minerals Management Service Pacific OCS Region Camarillo, CA: Minerals Management Service DMSP Satellite Program Description Http://web ngdc .noaa. gov/dmsp/source/drnspdesc html (26 February 1997) Dundee Satellite Station Advanced Very High Resolution Radiometer (A VHRR) http//www sat.dundee ac uk/avhrr html (17 February 1997) Dyrynda P and Symberlist, R. (1997, Feb 1) Casualty statistics for birds http://www swan.ac ak/biosci/empress/birds/stats htm (11 April 1997) Elachi, C (1987). Spacebome Radar Remote Sensing: Applications and Techniques. New York : The Institute of Electrical and Electronics Engineers Inc Press Ershd (1995, Nov 28) Oproto (Portugal) October '94. http://gds esrin esa.it/Oxc0tafc3d_Ox0005e065 (11 April1997) Ershd (1996, Jul25). Isle of Amrum (Germany) June 96. Http://gds.esrin esa.it/Oxc0tafc3d Ox000703be. (11 April 1997) Ershd (1996, July 26) North Sea July '96. http://gds esrin.it/Oxc06afc3d Ox00070408 (11April1997) Etkin, D S. (1996). Oil spill basics : a prime for students Oil Spill Intelligence Report http://www cutter com/osir/osirbasc.htm#yearly (11 April1997) (1994 Aut 29) Fine assessed in California oil spill. The Oil and Gas Journal vo/92, #35. 38-39 Fiscella, B Lombardini P P Trivero, P Cappa, C. and Pavese P (1989 March 29) Modei of mesbscale wind field obtained from SAR marine images II Nuovo Cimento, vo/12c, #6, 787-797 Fiscella, B Lombardini, P P Trivero, P., Pavese, P and Cappa, C. (1991 March April) Western Mediterranean wind field deduced from SIR-A SAR images II Nuovo Cimento, vo/J4c, #2, 127-133. 79

PAGE 86

Flament P Carance, R., Holt, B and Bernstein, R. (1995) Multi-frequency and interferometric SAR mapping of wind-driven mesoscale oceanic processes off northern California and in the lee of the island ofHawaii 1995 International Geoscience and Remot e Sensing Symposium 2 1120-1122. Francois D K. (1993) Federal offshore statistics OCS Report, 141-145 Friends of the Sea Otter Oil : the number 1 threat to sea otters http : //www seaotters org/oil html (11 Aprill997). Gade M Alpers W., Bao M and Huehnerfuss H. (1996) Measurements ofthe radar backscatter over different oceanic surface films during the SIR-C/X-SAR camprugns 1996 International G e o s cience and Remot e Sensing Symposium, 860862 Goodman R. H (1988) Application of the technology in North America In Lodge A E (ed ) The Remote SensingofOil Slicks, 39-61. Chicester : John Wiley and Sons Ltd Gower J. F R., Vachon P W and Edel H. (1993 Noverber-December) Ocean applications ofradarsat. C anadian Journal of Remote Sen s ing, vol19, #4, 372-383 (1996 Feb 26) Grounded tanker may cause U.K.'s largest oil spill. The Oil and Ga s Journal vol94, #9 34 Hgsystem (1996 Mar 1) Wales (U K.) 15 february 1996 http : / / gds esrin.it/Oxc06afc3d Ox00064479 (II April1997) Hover G L. (1993 July) Evaluating technologies of oil spill surveillance Sea Tec hnolo gy, 45-53 Huehnerfuss H., Alpers W and Richter, K. (1986) Discrimination between crude oil spills and monomolecular sea slicks by airborne radar and infrared rad i ometer possibilities and limitations Int e rnational Journal of R e mot e Sensing, vo l 7 #8, 10011013 Implementation of the oil pollution act of 1990 http://www mms gov/omm/osm/opa90.html (1 Marc h 1997) 80

PAGE 87

Japanese Earth Resources SatelliteI http://nasa.eoc. nasda .go. jp/guide/satellite/satdata/jers e html (17 February 1997) Johannessen, J. A, Lyzenga, D R, Shuchman, R., Espedal, H and Holt, B (1995) Mulit-frequency SAR observations of ocean surface features off the coast ofNorway 1995 International Geoscience and Remote Sensing Symposium, 2, 1328-1330 Johnson, N L. and Rodvold, D M (1993). Europe and Asia in Space. Colorado Springs : Kaman Sciences Corporation Kalrnykov A 1., Efimov V B. Kavelin S S., Kurekin A S Nelepo B. A., and Pickugin, A P., et al (1985) The radar system ofthe cosmos-1500 satellite. Soviet Journal of Remote Sensing, 4(5), 827-840. Kalmykov A 1., Velichko, S A Tsymbal, V N Keleshov, Yu. A, Weinmann, J. A. and Jurkevich, I. (1993) Observations ofthe marine environment from spaceborne side-looking real aperture radars Remote Sensing Environment 45 193-208 Kobayashi, T Okamoto, K. Masuko, H., Nakamura, K. Horie, H. and Kumagai H. (1993 ) Artificial oil pollution detection and wave observation in the sea adjacent to Japan by ERS-1 SAR images 1993 International Geoscience and Remote Sensing Symposium 946-948. Kopytoff, V G. (1996, Nov 12) Birds rescued in spill do poorly, study finds The New York Times C4. Krapez J. C and Cielo P (1992, August 15). Optothermal evaluation of oil film thickness on water. Journal of Applied Physics vol72, #4, 1255-1261. (1996, Nov 13) Landsat-sample images http : I /www. eurirnage it/Products!LS/Msample-images. htrnl ( 11 April 1997) Lichtenegger, J. (1994, Dec 16). Using ERS-1 SAR images for oil spill surveillance http : gds esrin.it/Oxc0tafc3d Ox0002b774 (II April 1997). Lillesand T M and Kiefer, R. W. (1987). Remot e Sensing and Image Interpretation. (2nd ed ) New York: John Wiley and Sons. Link, L. E., McKim, H. and Bruzewics A. (1991 May-June) Remote sensing ofthe Persian Gulf oil spill Army Research, Development and Acquisition Bull e tin 19-21 81

PAGE 88

Liu, A K., Tseng W Y. and Chang S Y. -S (1996) Wavelet analysis of AVHRR images for feature tracking 1996 International Ge oscience and Remot e Sensing Symposium 85-87 Lodge A E (1989) The Remot e Sensin g of Oil S licks. Chicester : John Wiley and Sons. Lombardini P P Fiscella, B ., Trivero, P ., Cappa C. and Garrett W. D ( 1989) Modulation of the spectra of short gravity waves by sea surface films : slick detection and characterization with a microwave probe Journal of Atmospheric and O c eanic Technology 6, 882-890 Marine Minerals. U. S Department ofthe Interior Minerals Management Service Herndon, VA: Minerals Management Service Mead W J. and Sorensen, P E (1970 December 16) The economic cost of the Santa Barbara oil spill Santa Barbara Oil Symposium, 183-226 Meyer, S (ed ) (1995) Energy Statistics Sourc e book lOth ed Tulsa : Pennwell Publishing Company Mink, N (1994, Oct 24) We're partying hearty (litigants profit from Exxon Valdez oil spill) Forbes vol154, # 10. 84-85 MMS: Ensuring Safety on the OCS. U.S. Department of the Interior Minerals Management Service Herndon, VA: Minerals Management Service MSO San Francisco fact sheet. http://iserver2 tcpet.uscg mil/msosf. (1 Mar 1997) Murphy D. W (1995) Definition ofthe orbital elements http://sgra jpl.nasa gov/html dwm/pg/pg_release/node17 html (II April 1997) NOAA damage assessment and restoration center. http://www darchw noad gov/index shtml. (I Mar 1997) Natural resource damage assessment under the oil pollution act of 1990 http://www darcnw noaa gov/opa htm (1 Mar 1997) 82

PAGE 89

Ohmsett: The National Oil Spill Response Test Facility. U. S Department of the Interior Minerals Management Service. Herndon, VA: Minerals Management Service (1996, Nov 16) Oil seals contaminated birds' fates. Science News vol150, #20. 314 Oil slicks http : //www.jpl.nasa gov/radar/sircxsar/oilsk html (11 April1997) Oil-Spill Prevention and Research. U. S Department of the Interior Minerals Management Service Herndon, VA: Minerals Management Service Pacific OCS Operations (1996, October 9). U. S. Department of the Interior Minerals Management Service Pacific OCS Region Pacific OCS Platfonns http : //www mms gov/ornrnlpacific/production/plfintro.html. (9 March 1997). Peace F. (1996 Aug 10) Oily legacy lingers after 'miracle' cleanup. New Scientist no 2042. 6 Rees W G (1992) Orbital subcycles for earth remote sensing satellites International Journal of Remote Sensing, val 13 #5, 825-833 Rees, W G (1990) Physical Principles of Remote Sensing. Bristol: Cambridge University Press Romero J. (1995, April14) Congresswoman Seastrand to Oversee Signing of Memorandum of Agreement Between California's Office of Oil Spill Prevention and Response and the U. S Minerals Management Service AfMS News Release. http://www mms gov/omm/pacific/public/osprmoa.html (9 March 1997) Romero, J. (1996, February 21) MMS Awards $1.4 Million for California Offshore Oil and Gas Evergy Resources Study Mlv!S News Release. http://www mms gov/omm/pacific/public/cooger html (9 March 1997) Sabins, F F (1987) Remote Sensing Principles and Interpretation. (2nd ed.). New York: W H. Freeman and Company 83

PAGE 90

Scialdone, J. N. (1996) A VHRR GAC, LAC and HRPT Level I b Data Set [POL 9090 180-180]. http://www. saa.noaa fov:8000/dif/anhrr1b-difhtml (3 November 1996) Scialdone, J. N (1996). TOYS MSU, SSU and illR.S/2 Level I b Data Set [OL 90-90 180-180]. http://www.saa noaa.gov : 8000/dlf/tovs1b-difhtml (3 November 1990) SeaS at 1978 http : I /southport.jpl. nasa gov/ scienceapps/seasat. html. (3 December 1996) Shestopalov, Y K. (1993, September) The statistical treatment ofpassive microwave data IEEE Transactions on Geoscience and Remote Sensing, vol31, # 5 1060-1065 Singh, K. P Gray, A L. Hawkins, R. K. and O'Neil, R. A (1986 September) The influence of surface oil on cand ku-band ocean backscatter. IEEE Transactions on Geoscience and Remote Sensing, vol GE-24, #5, 738-743 Sir-A 1982 http://southport.jpl.nasa gov/scienceapps/sira html (3 December I996) Sir-B 1985 http://southport.jpl.nasa gov/scienceapps/sirb html (3 December 1996) Sir-C description http : //www.jpl.nasa.gov/sircxsar/sc-oilskgif (3 December 1996) Space Systems Forecast. (1996) Newton Connecticut: Forecast Intemational/DMS Stofan, E R Evans, D L., Schmullius, C., Holt, B., Plant J. J. and vanZyl, J., et al. (1995, July) Overview of results ofspacebome imaging radar-C X-band synthetic aperture radar (SIR-C/X-SAR) IEEE Transactions on Geoscience and Remote Sensing, vol 33 #4, 817-827 Stringer, W J., Dean, W G Guritz, R. H., Garbeil, H. M Groves, J. E and Ahlnaes K. (1992) Detection of petroleum spilled from the MV Exxon Valdez International Journal of Remote Sensing, vol13, # 5 799-824 Topex/Poseidon images http://www jpl.nasa gov/podaac.w960104 .gif (7 April 1997) Tseng, W Y. and Chiu, L. S (1994) A VHRR observations of Persian Gulf oil spills. 1994 International Geoscience and Remote Sensing Symposium 779-782 84

PAGE 91

U. S Bureau ofthe Census (1996) Stastical Abstract of the United States 116th ed Washington, V C.: U S Government Printing Office. Vesecky J. F. (1995). Surface film effects on the radar cross section ofthe ocean surface 1995 International Geoscience and Remote Sensing Symposium 2, 13751377 Veseky, J. F and Stewart, R. H. (1982, April30) The observation of ocean surface phenomena using imagery from the SEASAT synthetic aperture radar : an assessment. Journal of Geophysical Research vol87, # C5, 3397-3430 Victorov S V. (1996) Regional Satellite Oceanography Bristol P A: T aylor and Francis Wismann, V (1993) Radar signatures of mineral oil spills measured by an airborne multi-frequency radar and the ERS-1 SAR 1993 International Geosci e nc e and R e mot e Sensing Symposium 940-942 Wolfe D A (1994) The fate ofthre oil spilled from the Exxon Valdez Environmental Science and Technology, vol28, #13. 561-567 Working for America s Energy Future and a Quality Environment U.S. Department of the Interior Minerals Management Service Washington, D C.: Minerals Management Service Your boat your oil spill http://www tcpet.uscg mil/msosfldstlrn/smspill htm (4 March 1997) 85