Abstract:

Care of the phase wind-up correction should be reasonably taken in precise point positioning. In practice, correct computation of phase wind-up relies mainly upon the information about the satellite attitude, which should be modeled differently when satellites undergo eclipsing. Different GPS satellite types would be subject to different eclipsing periods. For instance, GPS ⅡR satellites can experience noon and midnight turn maneuvers, GPS ⅡF satellites suffer from noon maneuver and shadow crossing, and GPS Ⅱ/ⅡA satellites may further experience post-shadow recovery periods when compared to ⅡF ones. As for the BDS non-GEO satellites, one should take into account the attitude control switching between the nominal and the orbit-normal mode. This paper presents a model enabling the attitude to be correctly computed for both eclipsing as well as non-eclipsing satellites. Numerical tests using real data are then performed in order to verify our model presented. As far as the filtered residuals are concerned, it is found that, their maximum residual could exceed 20 cm during the eclipsing periods. This problem is fortunately solvable when use of our model has been made, since the residuals reduce to below 5 cm. It should be noted that, our numerical results may be slightly different when we use precise satellite orbit and clock products delivered by different Analysis Centers. Furthermore, the shadow crossing period takes typically up to 1 hour for GPS Ⅱ/ⅡA satellites, during which the yaw attitude is controlled entirely by the positive yaw bias (Ⅱ/ⅡA of0.5°). The Ⅱ/ⅡA post-shadow recovery periods, covering about 30 minutes, still cannot be fully modeled; the data collected within this period should thereby be excluded.

Key words: precise point positioning, phase wind-up, satellite attitude model