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.

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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.