MODELING GPS SATELLITE ATTITUDE VARIATION FOR PRECISE ORBIT DETERMINATION

High precision geodetic applications of the Global Positioning System (GPS) require highly precise ephemerides of the GPS satellites. An acc urate model for the non-gravitational forces on the GPS satellites is a key to high quality GPS orbit determination, especially in long arcs . In this paper the effect of the satellite solar panel orientation er ror is investigated. These effects are approximated by empirical funct ions to model the satellite attitude variation in long are orbit fit. Experiments show that major part of the long are GPS orbit errors can be accommodated by introducing a periodic variation of the satellite s olar panel orientation with respect to the satellite-Sun direction, th e desired direction for solar panel normal vector, with an amplitude o f about 1 degree and with a frequency of once per orbit revolution.