Future Topographic Radar Shuttle Mission Will Map 80% of the Earth

[Ron Baalke]

Douglas Isbell
Headquarters, Washington, DC July 15, 1996
(Phone: 202/358-1753)

Mary Hardin
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-5011)

Kathleen Neary
Defense Mapping Agency, Fairfax, VA
(Phone: 703/275-8677)

RELEASE 96-140

FUTURE TOPOGRAPHIC RADAR SHUTTLE MISSION WILL MAP 80 PERCENT 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
the 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 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
the Shuttle Endeavour in 1994. To collect the topographic
images, engineers will add an almost 200-foot long mast,
additional C-band imaging antennae, 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 the Earth's surface through a technique
called interferometry. Such Shuttle-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 the 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 our planet'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,
Pasadena, CA. "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 100 feet (30 meters). The DMA
currently holds a digital terrain map over 65 percent of the
Earth's land mass with data points every 330 feet (100
meters). 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.

-end-

NOTE TO EDITORS: Media representatives interested in
obtaining photos to accompany this release should fax their
request on company letterhead to the NASA Imaging Branch at
202/358-4333.

B&W SRTM Artist Conception: 96-H-452; Color 96-HC-452
B&W SRTM/Swath Comparison: 96-H-453; Color 96-HC-453