PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contact: Mary A. Hardin
FOR IMMEDIATE RELEASEJuly 15, 1996
FUTURE TOPOGRAPHIC RADAR MISSION WILL MAP 80% OF THE EARTH
A Space Shuttle mission scheduled to be flown in May 2000
will carry a specially modified radar system that will produce
the most accurate and complete topographic map of Earth's surface
ever assembled.
The planned 11-day mission, called the Shuttle Radar
Topography Mission (SRTM), is a cooperative project between NASA
and the Defense Mapping Agency of the U.S. Department of Defense.
A formal memorandum of understanding to develop and conduct the
mission was finalized on July 8.
The mission is designed to collect three-dimensional
measurements of nearly 80 percent of the Earth's land surface,
except near the poles, with an accuracy of better than 16 meters
(53 feet). The regions to be mapped are home to about 95 percent
of the world's population.
SRTM will use the same radar instrument that comprised the
Spaceborne
Imaging Radar-C (SIR-C) that flew twice on Space Shuttle
Endeavour in 1994. To
collect the topographic images, engineers will add an almost 60-
meter-long (200-foot) mast, additional C-band imaging antennas,
and improved tracking and navigation devices.
The mast, which was developed using the design for the truss
structure of the International Space Station, will extend
sideways from the orbiter's cargo bay. The antennae at the tip
will allow the system to acquire stereo-like radar images of
Earth's surface through a technique called interferometry. Such
space-based interferometry was successfully tested during SIR-C's
second flight.
Scientists will then use the 3-D images to generate
computer versions of topographic maps, called digital elevation
models, that can be used for a large number of scientific,
civilian and military applications.
"Excepting measurements from weather satellites, the
topographic information
produced from this mission will be the most universally useful
data set about Earth that NASA has ever produced," according to
NASA Program Scientist Dr. Miriam Baltuck. "Possible applications
range from scientific uses such as planetary geophysics or
hydrologic drainage system modeling, to more realistic flight
simulators for military aircraft, to commercial uses like better
locations for cellular phone towers and improved maps for
backpackers."
Traditionally, topographic maps have been generated
from stereo pairs of photographs acquired from high-altitude
aircraft and satellites. However, such optical systems cannot
penetrate the cloud cover that blankets nearly 40 percent of the
Earth's surface. In some tropical regions the cloud cover is
virtually continuous and, as a
result, significant portions of Earth’s surface have never been
mapped in detail.
"We have a better global map of Venus than we do for
the Earth," said Dr. Michael Kobrick, co-originator of the SRTM
mission concept at NASA's Jet Propulsion Laboratory. "Since
radars can see right through clouds, SRTM's 11-day flight will
give us enough data to produce an image of the Earth 30 times
more precise than any that currently exist -- and the best part
is that the image will be in 3-D."
The Defense Mapping Agency (DMA), Fairfax, VA, plans to
use the radar
data to fulfill a joint defense requirement for a digital global
terrain elevation map with data points spaced approximately every
30 meters (100 feet). The DMA currently holds a digital terrain
map over 65 percent of the Earth's land mass with data points
every 100 meters (330 feet). Completion of this data set has
been hampered by a lack of cloud-free photos over major portions
of the world.
The SRTM mission will be implemented by the Jet Propulsion
Laboratory for NASA's Office of Mission to Planet Earth,
Washington, DC.
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7/15/96 MAH
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