GRACE is a joint project between the National Aeronautics and Space Administration ( NASA ) and the Deutsches Zentrum für Luft- und Raumfahrt ( DLR ). The mission has been proposed in 1996 jointly by the University of Texas at Austin, Center for Space Research ( UTCSR ), the German Research Centre for Geosciences ( GFZ ) and the Jet Propulsion Laboratories (JPL) in Pasadena. GRACE was selected in 1997 as second mission in NASA's Earth System Science Pathfinder ( ESSP ) program. As an innovation, the Principal Investigator Prof. Byron Tapley (UTCSR) and his team are ultimately responsible for developing the flight mission hardware from selection to a launch-ready condition, for accomplishing the scientific objectives and delivering the proposed measurements to the broader Earth science community and general public as expediently as possible. Co -Principal Investigator of the mission is Dr. Frank Flechtner (GFZ). Project management and systems engineering activities are carried out by JPL.
The primary science objective of the GRACE mission is to measure the Earth’s gravity field and it’s time variability with unprecedented accuracy. The increase in accuracy has been achieved by utilizing two satellites following each other on the same orbital track. To consider precise attitude and non-gravitational forces both satellites are equipped with star cameras and accelerometers. The position and velocity of the satellites is measured using onboard GPS antennae and (for validation purposes) SLR retro-reflectors. Additionally, the twin satellites are interconnected by a K-band microwave link to measure the exact separation distance and its rate of change to an accuracy of better than 0.1 µm/s. These measurements are directly coupled to the seasonal and sub-seasonal variations in the continental hydrological cycle, to ice mass loss in the large glacier systems in Greenland or Antarctica, to long wavelength ocean circulation processes or to the transport of ocean heat to Earth’s poles. Additionally, GRACE provides the time variability of the Earth’ overall external shape, the geoid. Consequently, since its launch in March 2002 this fundamental dataset has enabled dramatic improvements of seasonal and inter-annual climate change estimates.
The secondary science objective of the GRACE mission is to obtain about 150 very precise globally distributed vertical temperature and humidity profiles of the atmosphere per day using the GPS radio occultation technique.
The GRACE project is promoted by the Space Agency of the German Research Center for Aeronautics and Space (DLR) with funding of the German Federal Ministry of Economics and Technology (BMWi) based on a resolution of the German Bundestag with support code 50 EE 1027.
GRACE ground segment operations are co-funded by ESA. Therefore, ESA is supporting the continuation of the measurements of mass redistribution in the Earth system.
Prof. Dr. Frank Flechtner
Head of Section 1.2:
Global Geomonitoring and Gravity Field
building A17 room 00.12
tel. +49 331 288-1130
c/o DLR Oberpfaffenhofen
Münchner Str. 20
building 126 room 113
tel. +49 8153 90832 10