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1995-02-23
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SPACEBORNE IMAGING RADAR-C/X-BAND SYNTHETIC APERTURE RADAR
(SIR-C/X-SAR)
PHOTO CAPTION P-45243
Mount Everest
February 9, 1995
Radar/Optical
These are two comparison images of Mount Everest and its
surroundings, along the border of Nepal and Tibet. The peak
of Mount Everest, the highest elevation on Earth at 8,848
meters (29,028 feet), can be seen near the center of each
image. The image at the top was acquired through thick cloud
cover by the Spaceborne Imaging Radar-C/X-band Synthetic
Aperture Radar (SIR-C/X-SAR) aboard the space shuttle
Endeavour on April 16, 1994. The image on the bottom is an
optical photograph taken by the Endeavour crew under clear
conditions during the second flight of SIR-C/X-SAR on October
10, 1994. Both images show an area approximately 70
kilometers by 38 kilometers (43 miles by 24 miles) that is
centered at 28.0 degrees north latitude and 86.9 degrees east
longitude. North is toward the upper left. The colors in
the radar image were obtained using the following radar
channels: red represents the L-band (horizontally transmitted
and received); green represents the L-band (horizontally
transmitted and vertically received); blue represents the C-
band (horizontally transmitted and vertically received).
Radar illumination is from the top of the frame. The optical
photograph has been geometrically adjusted to better match
the area shown in the radar image. Many features of the
Himalayan terrain are visible in both images. Snow covered
areas appear white in the optical photograph while the same
areas appear bright blue in the radar image. The radar image
was taken in early spring and shows deep snow cover, while
the optical photograph was taken in late summer and shows
minimum snow cover. The curving and branching features seen
in both images are glaciers. The two wavelengths and
multiple polarizations of the SIR-C radar are sensitive to
characteristics of the glacier surfaces that are not detected
by conventional photography, such as the ice roughness, water
content and stratification. For this reason, the glaciers
show a variety of colors in the radar image (blue, purple,
red, yellow, white) but only appear as gray or white in the
photograph. Field data from other SIR-C/X-SAR test sites,
such as the Alpine glaciers of Austria, are being used to
help interpret data from remote regions like Mount Everest.
-----
Spaceborne Imaging Radar-C and X-band Synthetic Aperture
Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet
Earth. The radars illuminate Earth with microwaves, allowing
detailed observations at any time, regardless of weather or
sunlight conditions. SIR-C/X-SAR uses three microwave
wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3
cm). The multi-frequency data will be used by the
international scientific community to better understand the
global environment and how it is changing. The SIR-C/X-SAR
data, complemented by aircraft and ground studies, will give
scientists clearer insights into those environmental changes
which are caused by nature and those changeswhich are induced
by human activity. SIR-C was developed by NASA's Jet
Propulsion Laboratory. X-SAR was developed by the Dornier and
Alenia Spazio companies for the German space agency, Deutsche
Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian
space agency, Agenzia Spaziale Italiana (ASI), with the
Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v.(DLR),
the major partner in science, operations and data processing
of X-SAR.