93-156 Abstract

93-156

Short Arc Orbit Determination For Altimeter Calibration And Validation On Topex/Poseidon,

B. G. Williams*, E. J. Christensen**, D. N. Yuan***, K. C. McColl*, and R. F. Sunseri*

Abstract

TOPEX/POSIEDON (T/P) is a joint mission of United States' National Aeronautics and Space Administration (NASA) and French Centre National d'Etudes Spatiales (CNES) design launched August 10, 1992. It carries two radar altimeters which alternately share a common antenna. There are two project designated verification sites, a NASA site off the coast at Pt. Conception, CA and a CNES near Lampedusa Island in the Mediterranean Sea. Altimeter calivration and validation for T/P is performed over theese highly instrumented sites by comparing the spacecraft's altimeter radar range to computed range based on its situ measurements which include the estimated orbit position. This paper presents selected results of orbit determination over each of these sites to support altimeter verification. A short arc orbit determination technique is used to estimate a locally accurate position determination of T/P from less than one revolution of satellite laser ranging (SLR) data. This technique is relatively insensitive to gravitational and non-gravitational force modeling errors and is therefore essentially geometrical. The quality of these short arc orvits is demonstrated by covariance analysis and by comparison to orbits determined from longer arcs of data and other tracking data types, such as DORIS and Global Positioning System Demonstration Receiver (GPSDR) data.


*     Technical Group Supervisor, Navigation Systems and Applications Section, Jet Propulsion Laboratory,4800 Oak Grove Drive, Pasadena, California 91109.

**    Deputy Project Scientist for TOPEX/POSEIDON Project and Member of the Technical Staff, Tracking Systems and Applications Section, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109.

***   Member of Technical Staff, Navigation Systems and Applications Section, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109.