Abstract
The orbit accuracy of the navigation satellites relies on the accurate knowledge of the forces on the spacecraft, in particular the non-conservative perturbations. This study focuses on the Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites of the regional Chinese BeiDou Navigation Satellite System (BDS-2), for which apparent deficiencies of non-conservative models are identified and evidenced in the Satellite Laser Ranging (SLR) residuals. The orbit errors derived from the empirical 5-parameter Extended CODE Orbit Model (ECOM) as well as a semi-analytical adjustable box-wing model show prominent dependency on the Sun elongation angle, even in the yaw-steering attitude mode. Hence, a periodic acceleration in the normal direction of the +X surface, presumably generated by the mismodeled thermal radiation pressure, is introduced. The SLR validations reveal that the Sun elongation angle-dependent systematic errors were significantly reduced, and the orbit accuracy was improved by 10–30% to approximately 4.5 cm and 3.0 cm for the BDS-2 IGSO and MEO satellites, respectively.
Highlights
Academic Editor: Yunbin YuanWith the launch of the latest Geostationary Earth Orbit (GEO) satellite of the ChinaBeiDou Navigation Satellite System (BDS), BDS started to provide global positioning, navigation, and timing (PNT) services with 57 active satellites at the beginning of July, 2020 [1]
For Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites with yaw-steering (YS) and orbital normal (ON) attitude mode, much more attention was paid on the yaw attitude modeling [9,10] as well as dynamic force modeling for satellites in ON mode [11,12,13]
In contrast to the results shown in Figure 1, the slope of the Satellite Laser Ranging (SLR) residuals as a function of the e angle almost vanished, which contributed to the improvements revealed by the SLR
Summary
Academic Editor: Yunbin YuanWith the launch of the latest Geostationary Earth Orbit (GEO) satellite of the ChinaBeiDou Navigation Satellite System (BDS), BDS started to provide global positioning, navigation, and timing (PNT) services with 57 active satellites at the beginning of July, 2020 [1]. With the adoption of the empirically derived SRP model for BDS GEO satellites, the radial orbit accuracy reached 10 cm as validated by Satellite Laser Ranging (SLR) [3]. For IGSO and MEO satellites with yaw-steering (YS) and orbital normal (ON) attitude mode, much more attention was paid on the yaw attitude modeling [9,10] as well as dynamic force modeling for satellites in ON mode [11,12,13]. Significant improvement was obtained for satellites in ON mode with the improved SRP model, the orbit accuracy is still worse by a factor of two compared with that in the YS mode [14]. The SLR residuals show the Sun elongation angle (i.e., the e angle between the Sun and Earth as seen from the satellite)-dependent errors related to the purely empirical 5-parameter Extended CODE Orbit model
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