The Instrument on NASA's GRACE Mission: Augmentation of GPS to Achieve Unprecedented Gravity Field Measurements

Charles Dunn, Willy Bertiger, Garth Franklin, Ian Harris, Gerhard Kruizinga, Tom Meehan, Sumita Nandi, Don Nguyen, Tim Rogstad, J. Brooks Thomas and Jeff Tien

Abstract:	The Gravity Recovery and Climate Experiment (GRACE) mission is an international collaboration that uses high-precision global positioning system (GPS) measurements, augmented by micron-level inter-satellite links, in combination with a precision accelerometer, to produce gravity field maps of the Earth that are orders of magnitude more precise than current state of the art. GRACE also measures temporal variations in the Earth’s gravity field. The mission is an international collaboration between NASA and Deutsches Zentrum für Luftund Raumfahrt eV (DLR). NASA supplied the twin GRACE satellites and the instrumentation. The DLR supplied the launch services and mission operations. JPL manages the Project for NASA, and the Principal Investigator is from the University of Texas at Austin. JPL provided the satellites and instrumentation with principal support from Astrium, Gmbh, Space Systems / Loral, Technical University of Denmark, Office National d'Éstudes et de Recherches Aérospatiales and Johns Hopkins University Applied Physics Laboratory. This paper will describe the design and on-orbit performance of the GRACE Instrument Processing Unit (IPU) that integrates most of the critical science functions required by the GRACE mission to perform its gravity science and atmospheric radio occultation tasks. Requirements and design of the IPU subsystems (GPS, K/Ka-band cross link transceiver, star camera, accelerometer, and ultra-stable oscillator) will be discussed along with the approach to ground testing of the high performance instrument and comparisons with data collected in Earth orbit during the first few months of the mission.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	724 - 730
Cite this article:	Dunn, Charles, Bertiger, Willy, Franklin, Garth, Harris, Ian, Kruizinga, Gerhard, Meehan, Tom, Nandi, Sumita, Nguyen, Don, Rogstad, Tim, Thomas, J. Brooks, Tien, Jeff, "The Instrument on NASA's GRACE Mission: Augmentation of GPS to Achieve Unprecedented Gravity Field Measurements," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 724-730.
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