GPS/IMU/Laser Space Mission for Global Change Sensing and 21st Century Satellite Control

David M. Gleason

Abstract:	RAMOS (Russian -erican Observational Satellites) is a mission scheduled for the late 90’s involving two co-polar orbiting spacecraft at an altitude of about 400 km and a nominal separation of about 500 km. The optimal integration of precise multiple antenna GPS receivers, advanced cryogenic inertial measurement units (IMUs), and ultra stable frequency laser platforms on two such platforms is the basis for a multi-faceted experiment to 1)sense geodynamic gravitational changes and 2)substantially improve a variety of temporal geophysical models. Such models will make the Air Force Satellite Control Network’s orbit prediction process more accurate which in turn will reduce the number (and cost) of ground-to- satellite radar range tracking measurements needed in subsequent least squares statistical orbit determinations orfits. Tracking the phases of the dual frequency signals of occulting GPS satellites can be used to infer and improve models of the ionospheric and tropospheric temperature, refractivity, pressure, electron density and scintillation effects. Such enhanced atmospheric models will make the ground-based tracking measurements (and accompanying orbit fits) more accurate. The use of differential GPS observations, as external updates in an elaborate Kalman filter optimally integrating the three data types, puts a bound on the low frequency IMU and laser error build-up. In the filter, the GPS, IMU and laser data aid each other to estimate the low satellites’ position and orientation to centimeter and arc second levels.
Published in:	Proceedings of the 1994 National Technical Meeting of The Institute of Navigation January 24 - 26, 1994 Catamaran Resort Hotel San Diego, CA
Pages:	671 - 678
Cite this article:	Gleason, David M., "GPS/IMU/Laser Space Mission for Global Change Sensing and 21st Century Satellite Control," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 671-678.
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