Precise Seasat ephemeris from laser and altimeter data

Abstract

The determination of a precise Seasat ephemeris has required improvements in the modeling of the gravitational and nongravitational forces acting on the satellite. Because laser range data were used as the primary ground-based tracking measurement, the limited data distribution in July and August, 1978, necessitated the use of other data to achieve an improved ephemeris. Consequently, the Seasat altimeter data were used to provide improved data distribution in the ocean region. In this study, an 18-day continuous ephemeris was used to determine a degree and order 26 gravity field and other geodetic parameters from laser range, altimeter and altimeter crossover measurements. The resulting 18-day ephemeris had an estimated accuracy of the radial component of 34 cm RMS. The modeling of the nongravitational parameters included radiation parameter coefficients and atmospheric resistance parameters. The resulting ephemeris has been further evaluated using radio tracking data, including S-band data, and these results will be discussed.