17 March 2002
U.S., Germany Launch Twin "Water-Sensing" Satellites
(Joint mission will map Earth's water mass) (730)
NASA and the German Center for Air and Space Flight today successfully
launched the Gravity Recovery and Climate Experiment, or "Grace,"
mission into Earth orbit on March 17 from a Russian launch facility.
The mission, comprised of identical twin satellites, will precisely
measure Earth's shifting water masses and map their effects on Earth's
gravity field.
Following is the text of the NASA March 17 press release:
(begin text)
National Aeronautics and Space Administration
NASA News Release
March 17, 2002
Scientists Say 'Grace' as Water-Sensing Satellites Lift Off
NASA and the German Center for Air and Space Flight today successfully
launched the Gravity Recovery and Climate Experiment, or "Grace,"
mission into Earth orbit at 1:21:27 a.m. Pacific time from Russia's
Plesetsk Cosmodrome.
The mission, comprised of identical twin satellites, will precisely
measure Earth's shifting water masses and map their effects on Earth's
gravity field.
The five-year Grace mission -- the first launch of NASA's Earth System
Science Pathfinder program -- will be a scientific boon to researchers
who study Earth with space-based instruments. The monthly gravity maps
generated by Grace will be up to 1,000 times more accurate than those
currently in use, substantially improving the accuracy of many
techniques used by oceanographers, hydrologists, glaciologists,
geologists and other scientists to study phenomena that influence
climate. These phenomena range from shallow and deep ocean currents,
water movement on and beneath Earth's surface, and the movement and
changing mass of ice sheets, to sea-level heights, sea-level rise and
changes in the structure of the solid Earth.
Under partly cloudy, cold skies, the Grace twins lifted off on a
Russian Rockot launch vehicle. Riding nearly 160,000 kilograms
(approximately 350,000 pounds) of thrust, the rocket headed northward
over the Arctic Ocean and Alaska, then south across the Pacific Ocean
and Antarctica before heading north again over Africa and Europe. At
85 minutes, 38 seconds into the mission-or 2:47 a.m. Pacific time --
the satellites separated from the launch vehicle's third stage above
Africa into a polar orbit 500 kilometers (311 miles) above Earth.
Ground controllers successfully acquired the spacecraft's signal from
the German Space Operations Center's ground tracking station in
Weilheim, Germany at 2:49 a.m. Pacific time. Initial telemetry reports
received by the Grace team show both satellites to be in excellent
health.
Following separation, the leading Grace satellite began pulling away
from the trailing satellite at a relative speed of about 0.5 meters
(1.6 feet) per second. Over the course of the next four days, the
satellites will be spaced 220 kilometers (137 miles) apart- a little
more than the distance between Los Angeles and San Diego.
As they race around the globe 16 times a day, the satellites will
sense minute variations in Earth's surface mass below and
corresponding variations in Earth's gravitational pull. Regions of
slightly stronger gravity will affect the lead satellite first,
pulling it slightly away from the trailing satellite. By measuring the
constantly changing distance between the two satellites using an
extremely sensitive microwave ranging system and combining that data
with precise positioning measurements from Global Positioning System
instruments, scientists will be able to construct a precise Earth
gravity map.
During the next two and a half weeks, basic satellite operations will
be established. During a subsequent three-week commissioning phase,
Grace's science instruments and supporting systems will be powered up,
evaluated and calibrated. The performance of the Grace system for
measuring Earth gravity will then be validated over the following six
months. The mission then enters its observational phase, during which
routine operational data products will be made available to
scientists.
Additional information about the Grace program is available on the
Internet at: http://www.csr.utexas.edu/grace.
Grace is a joint partnership between NASA and the German Center for
Air and Space Flight (Deutsches Zentrum fur Luft und Rumfahrt, or
DLR).
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the U.S.
portion of the project for NASA's Office of Earth Science, Washington.
Science data processing, distribution, archiving and product
verification are managed under a cooperative arrangement between JPL
and the University of Texas' Austin-based Center for Space Research in
the United States and Germany's Earth Research Center (or
GeoForschungsZentrum).
JPL is a division of the California Institute of Technology in
Pasadena.
(end text)
(Distributed by the Office of International Information Programs, U.S.
Department of State. Web site: http://usinfo.state.gov)
|
NEWSLETTER
|
|
Join the GlobalSecurity.org mailing list
|
|
|
