At 10, GRACE continues defying, anddefining, gravity19 March 2012, By Alan Buis

On March 17, 2002, NASA and the German AerospaceCenter (DLR) launched the Gravity Recovery andClimate Experiment (GRACE), a novel space missionthat has given scientists a new understanding ofchanges in Earth's natural systems.

(PhysOrg.com) -- Just as the lead characters in thepopular Broadway musical "Wicked" sing aboutdefying gravity, the low-Earth orbiting twinspacecraft of NASA's Gravity Recovery andClimate Experiment (GRACE) continue to defygravity 10 years after launch, while also continuingto help define it. Along the way, they've alsoproduced an amazing array of breakthroughscience that is giving us a new understanding ofchanges in Earth's natural systems.

Launched from Northern Russia on March 17,2002, on what was designed to be a three- to five-year mission, GRACE continues its task of makingdetailed measurements of Earth's gravity field. Itdoes so by noting minute changes in gravitationalpull caused by local changes in Earth's mass.Masses of ice, air, water and solid Earth can bemoved by weather patterns, seasonal change,climate change and even tectonic events such aslarge earthquakes. To track these changes,GRACE uses GPS and a microwave rangingsystem to measure micron-scale variations in the

220-kilometer (137-mile) separation between thetwo spacecraft, developed by NASA's JetPropulsion Laboratory, Pasadena, Calif.

Before the launch of NASA's Gravity Recovery andClimate Experiment (GRACE) in 2002, scientists'knowledge of Earth's gravity field was based upondecades of data from geodetic satellites (left image).

These measurements are used to produce monthly gravity maps that are more than 100 times moreprecise than previous models, providing theresolution necessary to characterize how Earth'sgravity field varies over time and space, and overland and sea. The data have substantially improvedthe accuracy of techniques used byoceanographers, hydrologists, glaciologists,geologists and climate scientists.

"GRACE essentially demonstrated a new form ofremote sensing for climate research that has turnedout even better than we hoped," said GRACEProject Scientist Michael Watkins of JPL "Werealized early on in the design of GRACE that wecould measure the gravity field well enough toobserve the critical indicators of climate change - sea level rise and polar ice melt."

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GRACE observations have revealed dramatic changes inEarth's ice, including major reductions in Greenland's icemass, as shown in this animation covering the years2003 to 2011. Credit: NASA/JPL-Caltech/University ofTexas Center for Space Research

GRACE is a joint mission with the GermanAerospace Center (DLR) and the GermanResearch Center for Geosciences (GFZ), inpartnership with the University of Texas atAustin. During its first decade of operations, themission has made remarkable contributions tomany scientific disciplines, expanding ourknowledge of ice loss from the polar ice sheets andmountain glaciers, groundwater storage on land,sea level variations and large-scale oceancirculation, to name but a few.

GRACE also pioneered the study technique nowbeing used by NASA's Gravity Recovery andInterior Laboratory (GRAIL) mission, which recentlybegan mapping the gravitational field of the moonto learn about its internal structure and compositionin unprecedented detail. GRAIL data will alsoprovide a better understanding of how Earth andother rocky planets in the solar system formed andevolved.

While the measurements of Earth's ice mass loss havebeen most dramatic in Greenland, GRACE data areshowing that Earth's other, even larger, polar ice sheet inAntarctica is not immune to the effects of Earth'schanging climate either. Credit: University of Texas atAustin Center for Space Research

In June 2010, NASA and DLR signed anagreement to continue GRACE through 2015-a full10 years past the planned mission duration.Recognizing the importance of extending this long-term dataset, NASA has approved the developmentand launch of the GRACE Follow-On mission, alsodeveloped jointly with Germany, and planned forlaunch in 2017.

Provided by JPL/NASA

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APA citation: At 10, GRACE continues defying, and defining, gravity (2012, March 19) retrieved 30August 2018 from https://phys.org/news/2012-03-grace-defying-gravity.html

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