Solar radiation pressure models for BDS-3 IGSO: impacts and improvement from observation geometry

Abstract The orbit quality of BDS-3 inclined geosynchronous orbit (IGSO) satellites is limited by the observation geometry as well as dynamic models. Regarding ground L-band data, the maximum nadir angle for IGSO satellites is approximately 9°. However, with BDS-3 Ka-band inter-satellite link (ISL) data, the maximum nadir angle can reach up to 45°, which significantly improves observation conditions. This study investigates the impact of ISL data on 5-parameter reduced extented CODE orbit model (ECOM1) compared with that from ground L-band data only. It is observed that the estimates of the ECOM1 parameter become more precise by using ISL data, particularly for D 0 as well as those in B direction. Y 0 bias shows noticeable thermal radiation effects for C38 and C39. The Sun-elevation angle dependent clock linear-fit residuals are reduced significantly for C39 or almost vanished for C38 and C40. By analyzing the solar radiation pressure (SRP) accelerations for the solutions with L-band only or L and ISL data, we observed that the radial acceleration differences show opposite dependency with these in the B direction. The similar phenomenon can be observed in the differences of solutions based on ECOM2 and ECOM1 with L-band data only. These reveal that the deficiency of the ECOM1 for the non-cubic satellites can be partly compensated by using better observation geometry from ISL data, as better estimates in B direction can be obtained. Based on the adjustable box-wing model, the optical coefficients of BDS-3 IGSO are calibrated with L-band and ISL measurements. By incorporating these estimates into the box-wing model used as the a priori SRP to augment ECOM1, the Sun-elevation angle dependent errors in clock offsets are mitigated. And the RMS of clock linear-fit is further reduced by approximate 1.2 cm by using the estimates from L-band and ISL data than that from L-band-only data. This demonstrates the positive contribution for ISL on SRP modeling of BDS-3 IGSO satellites.