Real‐time Precise Orbit Determination for FY‐3C and FY‐3D Based on BDS and GPS Onboard Observation

The code multipath error associated with elevation in BDS-2 is one of the main factors whose impact on the precision of real-time reduced-dynamic precise orbit determination (POD) using spaceborne multi-global navigation satellite systems (GNSS) observation data for FengYun-3C (FY-3C) and FengYun-3D (FY-3D) satellites. The aim is to construct a code multipath piece-wise linear error model and analyse the contribution of BDS-2 to the performance of low earth orbit POD. Conclusions are drawn out from the experimental results: (1) the real-time POD average precision of FY-3C and FY-3D is improved by about 11% and 12% after the correction of BDS-2 code multipath error; (2) Due to the small number of available BDS-2 satellites and the limited accuracy of geostationary earth orbit (GEO) satellite real-time orbit products, the precision of the real-time overlapping comparison for FY-3C/FY-3D by using the BDS-2 onboard observation data can only reach the decimetre level. However, with the BDS-2 signal capture capability of the FY-3D onboard GNSS Occultation Sounder upgraded, the average precision of the BDS-2-based POD for FY-3D is better than that of FY-3C in each direction and with 10% improvement in the average 3 dimensional-root mean square (3D-RMS); (3) Cases of onboard global positioning system (GPS), GPS + BDS-2 (with GEO), and GPS + BDS-2 (without GEO) for real-time POD can meet 5-8 cm precision requirement. The average 3D-RMS of the real-time POD for FY-3C/FY-3D, which utilises onboard GPS + BDS-2 data is inferior only to GPS data, owing to the influence of the orbit accuracy of GEO satellites. However, after excluding the influence of GEO satellites, the average result (3D-RMS) of the real-time POD for FY-3C (6.11 cm) and FY-3D (5.95 cm) is better than those of other cases.