ENHANCING PRECISE ORBIT DETERMINATION OF COMPASS WITH INTER-SATELLITE OBSERVATIONS

This paper puts forward a new concept of Inter-Satellite Observations (ISOs). ISOs can be classified into inside-layer (ILOs) and cross-layer observations (CLOs). ILOs denote inter-satellite two-way ranging observations (TWROs). CLOs denote the observations between satellites of different orbit heights, such as MEO-GEO and MEO-IGSO. GEO and IGSO observations can be obtained through MEO-borne receivers as designed in low-orbit satellites. Using integrated adjustment of satellite-ground observations (SGOs) and ISOs, satellite geometry can be strengthened and orbit accuracy is significantly improved. Upon the above thought, orbit determination simulations are performed in three scenarios (using SGOs, using SGOs and CLOs, and using SGOs and TWROs) according to the satellite constellation of the Chinese COMPASS satellite navigation system. The orbit results are assessed by position dilution of precision (PDOP), three-dimensional RMS of the estimated orbits and the simulated reference orbits. The results show that, using only one-day SGOs from 7 regional stations in China, three-dimensional RMS of GEOs, IGSOs and MEOs are respectively reduced from 6.7 m, 1.3 m and 7.9 m to 0.7 m, 0.8 m and 1.3m when CLOs with beam angle of 42 degrees are added; Orbit accuracies are better than 20cm when TWROs with beam angle of 45 degrees and 30cm amplitude period term systematic error are added.