GRACE builds on the heritage of the German Space Agency’s Challenging Minisatellite Payload (CHAMP) mission in the area of Earth gravity field measurements. The revolutionary new configuration for GRACE—using two satellites following one another on the same orbital track—is expected to improve the accuracy of gravity field measurements dramatically. The European Space Agency plans to launch the Gravity Field and Steady-State Ocean Circulation (GOCE) mission in 2006 as part of its Living Planet Programme. The sensor’s measurements of the gravity field will complement those made by GRACE. The science community believes that even more accurate gravity measurements may be possible in the future as new technologies are developed. One possibility involves replacing the microwave ranging system on GRACE with a laser ranging system. This would allow for even more precise distance measurements than GRACE can obtain and thereby increase the accuracy of the resulting gravity field measurements.
The ESSP Program
A component of NASA’s Earth Science Enterprise (ESE), Earth System Science Pathfinder (ESSP) Missions are intended to address unique, specific, highly-focused scientific issues and provide measurements required to support Earth science research. The ESSP missions are an integral part of a dynamic and versatile program consisting of multiple space flights to study Earth system science. The ESSP program is characterized by relatively low- to moderate-cost, small to medium-sized missions that are capable of being built, tested, and launched in short time intervals. These missions are capable of supporting a variety of scientific objectives related to Earth science, including the atmosphere, oceans, land surface, polar ice regions, and solid Earth. Investigations include developing and operating remote-sensing instruments and conducting research investigations using data obtained from these instruments. Subsequent launches are planned over the next few years. A Program Manager located at Goddard Space Flight Center is responsible for overall management of the ESSP Program. Each individual mission is led by a Principal Investigator (PI) who oversees all aspects of the mission, from ensuring science accuracy to making sure the mission stays on budget and on time.
GRACE was the first ESSP mission to launch, and is a joint partnership between the National Aeronautics and Space Administration (NASA) in the United States and the Deutsches Zentrum für Luft und Raumfahrt (DLR) in Germany. The Principal Investigator is from the University of Texas Center for Space Research (UTCSR) and the Co-Principal Investigator is from the GeoForschungsZentrum (GFZ). NASA’s Jet Propulsion Laboratory (JPL) has responsibility for the Project Management of GRACE, and NASA’s Goddard Space Flight Center maintains responsibility for Mission Management.