JET PROPULSION LABORATORY

CALIFORNIA INSTITUTE OF TECHNOLOGY

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

PHOTO CAPTION P-43891 April 13, 1994

Mammoth/C-band multipol

This image is a false-color composite of the Mammoth Mountain

area in the Sierra Nevada Mountains, California. The image is

centered at 37.6 degrees north latitude and 119.0 degrees west

longitude. The area is approximately 11.5 kilometers by 78.3

kilometers (7.2 by 48.7 miles) in size. The image was acquired

by the Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar

(SIR-C/X-SAR) aboard space shuttle Endeavour on its 40th orbit,

April 11, 1994. The city of Mammoth Lakes is visible in the

bottom right portion of the scene. In this color representation,

red is C-band HV-polarization, green is C-band VV-polarization

and blue is the ratio of C-band VV to C-band HV. Blue areas are

lakes or slopes facing away from the radar illumination. Yellow

represents areas of dry, old snow as well as slopes facing

directly the radar illumination.

At the time of the SIR-C overflight, the sky conditions were

partially cloudy, with low and cold air temperatures. Total snow

depth is about 1 to 1.5 meters (3 to 5 feet). The current snow

accumulation is only about 40 percent of the average for the

season. The most recent snowfall in the area covered the entire

area with about 30 centimeters (14 inches) of fresh dry snow.

Above 3,000 meters (10,000 feet) elevation the snowpack is dry.

Below that elevation, the snowpack has a layered structure.

Snow hydrologists are using SIR-C/X-SAR data to determine both

the quantity of water held by seasonal snowpack and the amount of

snow melting.

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SIR-C/X-SAR 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, in conjunction

with aircraft and ground studies, will give scientists clearer

insights into those environmental changes which are caused by

nature and those changes which 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 fur Luft und Raumfahrt e.v. (DLR), the major

partner in science, operation and data processing of X-SAR.

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