1 Recent Advances in the Analysis of SAR Data of the Polar Oceans
5
improved spatial resolution of 11-18 m (depending on swath width)with a much wider
swath coverage that could be adjusted from 40 km to 280 km.
On July 17, 1991, the European Space Agency launched the first European remote sensing satellite (ERS-l) carrying a C-band VV (vertically polarized receive and transmit)
SAR. ERS-l was the first spaceborne SAR mission to provide a sufficient quantity of data
with enough reliability to be useful for larger-scale applications. The Alaska SAR Facility in the US was constructed to receive ERS-l data with the purpose of providing SAR
data of the polar regions to the US science community. ERS-l data has a nominal resolution of 25 m but with a limited swath width of 100 km. ERS-2, a copy of ERS-l, was
launched in April 21, 1995. At the time of writing, the two satellites are operating in tandem mode which provides I-day repeat observations of regions covered by the sensor.
The Japanese launched JERS-l (Japanese Earth Resources Satellite) in 1992. JERS-l
was primarily intended for research purposes and returned to the original L-band of
SEASAT and a relatively narrow 70-km swath. JERS-l suffered a partial failure of its
power system shortly after launch but it was still delivering data in 1996.
After a lengthy development program, Canada launched its RADARSAT on November 4, 1995. One mission objective of RADARS AT is the operational monitoring of the
sea ice cover. Of primary significance for this role is its ScanSAR mode which provides
a 500-km-wide swath with 100-m resolution. This wide swath provides a high repeat
imaging capability, essential for monitoring of ice-covered waters. At this time, large
volumes of image data are being acquired by RADARSAT.
The future of spaceborne imaging radars for continuous monitoring ice conditions
is promising with several missions well into their planning and development stages.
Canada plans to launch RADARSAT -2, a copy of its predecessor, around the year 2000.
Investment in the development RADARSAT-3, a new generation SAR satellite scheduled for launch about 2005, has commenced. The European Space Agency intends to
launch ENVISAT in 1998 with a C-band "advanced" SAR (ASAR) that will have a swath
width of approximately 400 km and resolution similar to that of the ERS and
RADARSAT radars. NASA has funded the initial design studies of LIGHTSAR with the
intent to demonstrate the feasibility of using the latest technology for implementation
of an advanced SAR system. The exact configuration and mission objectives are being
defined at the time of this writing.
1.3
Analysis of Sea Ice SAR Data
If the full RADARSAT data collection capability is realized, starting in 1997, investigators of the polar regions and of global climate as well as the operational community
will begin receiving routine high resolution data on the Arctic and Southern Oceans.
RADARSAT could acquire more than 60 min data daily (approximately 60 gigabytes of
image data). To effectively utilize these data sets and to generate useful conclusions,
automated or semiautomated data analysis tools and algorithms are necessary for
reduction of these image datasets into geophysical fields which are more useful for the
general science community: manual analysis of this volume of data will no longer be
affordable or feasible because of the sheer size of the data sets.
High resolution SAR data provide observations of a number of sea ice variables: ice
motion, ice type! concentration and surface changes. Procedures for interpretation of SAR
5
improved spatial resolution of 11-18 m (depending on swath width)with a much wider
swath coverage that could be adjusted from 40 km to 280 km.
On July 17, 1991, the European Space Agency launched the first European remote sensing satellite (ERS-l) carrying a C-band VV (vertically polarized receive and transmit)
SAR. ERS-l was the first spaceborne SAR mission to provide a sufficient quantity of data
with enough reliability to be useful for larger-scale applications. The Alaska SAR Facility in the US was constructed to receive ERS-l data with the purpose of providing SAR
data of the polar regions to the US science community. ERS-l data has a nominal resolution of 25 m but with a limited swath width of 100 km. ERS-2, a copy of ERS-l, was
launched in April 21, 1995. At the time of writing, the two satellites are operating in tandem mode which provides I-day repeat observations of regions covered by the sensor.
The Japanese launched JERS-l (Japanese Earth Resources Satellite) in 1992. JERS-l
was primarily intended for research purposes and returned to the original L-band of
SEASAT and a relatively narrow 70-km swath. JERS-l suffered a partial failure of its
power system shortly after launch but it was still delivering data in 1996.
After a lengthy development program, Canada launched its RADARSAT on November 4, 1995. One mission objective of RADARS AT is the operational monitoring of the
sea ice cover. Of primary significance for this role is its ScanSAR mode which provides
a 500-km-wide swath with 100-m resolution. This wide swath provides a high repeat
imaging capability, essential for monitoring of ice-covered waters. At this time, large
volumes of image data are being acquired by RADARSAT.
The future of spaceborne imaging radars for continuous monitoring ice conditions
is promising with several missions well into their planning and development stages.
Canada plans to launch RADARSAT -2, a copy of its predecessor, around the year 2000.
Investment in the development RADARSAT-3, a new generation SAR satellite scheduled for launch about 2005, has commenced. The European Space Agency intends to
launch ENVISAT in 1998 with a C-band "advanced" SAR (ASAR) that will have a swath
width of approximately 400 km and resolution similar to that of the ERS and
RADARSAT radars. NASA has funded the initial design studies of LIGHTSAR with the
intent to demonstrate the feasibility of using the latest technology for implementation
of an advanced SAR system. The exact configuration and mission objectives are being
defined at the time of this writing.
1.3
Analysis of Sea Ice SAR Data
If the full RADARSAT data collection capability is realized, starting in 1997, investigators of the polar regions and of global climate as well as the operational community
will begin receiving routine high resolution data on the Arctic and Southern Oceans.
RADARSAT could acquire more than 60 min data daily (approximately 60 gigabytes of
image data). To effectively utilize these data sets and to generate useful conclusions,
automated or semiautomated data analysis tools and algorithms are necessary for
reduction of these image datasets into geophysical fields which are more useful for the
general science community: manual analysis of this volume of data will no longer be
affordable or feasible because of the sheer size of the data sets.
High resolution SAR data provide observations of a number of sea ice variables: ice
motion, ice type! concentration and surface changes. Procedures for interpretation of SAR