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Weddell Sea/ScanSAR
Two radar images are shown i
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10/26/95
| Date |
10/26/95 |
| Description |
Two radar images are shown in this composite to compare the size of a standard spaceborne radar image (small inset) to the image that is created when the radar instrument is used in the ScanSAR mode (large image). The predominant image shows two large ocean circulation features, called eddies, at the northernmost edge of the sea ice pack in the Weddell Sea, off Antarctica. The eddy processes in this region play an important role in the circulation of the global ocean and the transportation of heat toward the pole. The large image is the first wide-swath, multi- frequency, multi-polarization radar image ever processed. To date, no other spaceborne radar sensors have obtained swaths exceeding 100 kilometers (62 miles) in width. This developmental image was produced at NASA's Jet Propulsion Laboratory by the Alaska SAR Facility's ScanSAR processor system, using radar data obtained on October 5, 1994, during the second flight of the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR- C/X-SAR) onboard the space shuttle Endeavour. The image is oriented approximately east-west, with a center location of around 56.6 degrees south latitude and 6.5 degrees west longitude. Image dimensions are 240 km by 350 km (149 miles by 218 miles). The smaller image inset (upper right edge) was obtained by SIR-C/X-SAR on October 6, 1994, and covers a portion of the same ice features that are shown in the large image. The inset image dimensions are 18 km by 50 km (11 miles by 31 miles). The ocean eddies have a clockwise (or cyclonic) rotation and are roughly 40 km to 60 km (25 miles to 37 miles) in diameter. The dark areas are new ice and the lighter green areas are small sea- ice floes that are swept along by surface currents, both of these areas are shown within the eddies and to the south of the eddies. First year seasonal ice, typically 0.5 meter to 0.8 meter (1.5 feet to 2.5 feet) thick, is shown in the darker green area in the lower right corner. The open ocean to the north is uniformly bright and appears blue, due to high winds making the surface rough. The colors in both images were obtained using the following radar channels: red is C-band vertically transmitted and vertically received, green is L-band horizontally transmitted and vertically received, and blue is L-band vertically transmitted and vertically received. The ScanSAR processor is being designed for implementation in 1996 at NASA's Alaska SAR Facility, located at the University of Alaska, Fairbanks, and will produce digital images from the forthcoming Canadian RADARSAT satellite, since its C-band horizontally transmitted, horizontally received polarization radar routinely obtains data over a considerable range of swath-widths and resolutions, including the important wide-swath (300 km to 500 km/186 miles to 310 miles) mode. ##### |
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Antarctic Peninsula
The Antarctica Peninsula is
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2/20/01
| Date |
2/20/01 |
| Description |
The Antarctica Peninsula is the furthest north extension of the Antarctic continent and is exposed to slightly warmer climate conditions than the greater continent. This mosaic from the 2000 Antarctic Mapping Mission shows most of the peninsula. The blue line is the coastline seen in the 1997 Antarctic Mapping Mission. The broad Larsen Ice Shelf lies to the east, extending into the Weddell Sea, and smaller ice shelves including the Wordie and George VI are in the southwest corner. The northern Larsen Shelf has been retreating since the 1960s, with major collapses in the 1990s. Warming in both the air and ocean underlying the ice shelves leads to increased fracturing and eventually calving of the ice shelf fronts into icebergs. The 1995 Larsen calving events were due to anomalously warm summer temperatures in the early 1990s. The warming noted in the Antarctica Peninsula, as measured from several research stations located there, is not sufficient to affect the thicker and more extensive West Antarctic ice shelves to the south on the main continent. The two RADARSAT mosaics from 1997 and 2000 Antarctic imaging campaigns provide highly accurate snapshots of this rapidly changing region of the greater Antarctic continent. The Antarctic Mapping Mission is a joint project between NASA and the Canadian Space Agency. The project is led by Ohio State University in Columbus in partnership with the Alaska Synthetic Aperture Radar (SAR) Facility at the University of Alaska Fairbanks, NASA's Jet Propulsion Laboratory, Pasadena, Calif., and the Vexcel Corporation, Boulder, Colo. The Canadian Space Agency's RADARSAT-1 satellite carries a synthetic aperture radar, an imaging radar sensor that operates at C-band (5.3 GHz frequency) with horizontal transmit-horizontal receive polarization from an orbital altitude of about 800 kilometers (500 miles. The 1997 Antarctic Mapping Mission took place between Sept. 19 and Oct. 14 and mapped the entire Antarctic continent. The 2000 Antarctic Mapping Mission lasted from Sept. 3 to Nov. 4 and obtained complete coverage of Antarctica north of 82 degrees south latitude. Photo Credit: Canadian Space Agency/NASA/Ohio State University, Jet Propulsion Laboratory, Alaska SAR Facility # # # # # |
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