Abstract
The Astronomical Institute of the University of Bern (AIUB) has been performing GPS-based Precise Orbit Determination (POD) for a large variety of Low Earth Orbit (LEO) satellites since two decades. Traditionally, LEO orbits have been generated by a reduced-dynamic POD strategy using the Bernese GNSS Software, replacing an explicit modeling of non-gravitational forces by dedicated empirical orbit parametrizations. This LEO POD strategy can be advanced by two main developments: on the one hand, use is made of the GNSS Observation-Specific Bias (OSB) and clock products provided by the Center for Orbit Determination in Europe (CODE), allowing for the resolution of single-receiver GNSS carrier-phase ambiguities. On the other hand, the main focus of this article, a refined satellite non-gravitational force modeling strategy is constructed to reduce the amount of empirical parameters used to compensate for force modeling deficiencies. LEO POD is first performed for Sentinel-3, a satellite formation currently consists of two identical satellites −3A and −3B, which experience a similar in-flight environment and allow for direct POD performance comparisons. A third satellite Swarm-C, which flies at a lower altitude and has a more sophisticated surface geometry, is selected to validate the robustness of the new POD strategy. As a result, both the internal consistency checks and external orbit validations suggest superior orbit quality obtained for the three satellites for a time span of 1.5 years (7 June, 2018 to 31 December, 2019). The ambiguity resolution adds strong constraints to the orbits and the satellite non-gravitational force modeling leads to more tightly constrained (towards zero) pseudo-stochastic empirical parameters. The final orbit solutions agree with external orbit solutions and independent satellite laser ranging measurements at levels of sub-cm, indicating approximately 20% improvement w.r.t. the nominal reduced-dynamic orbit solutions. This suggests potential benefits to the space geodesy community that always pursues best-possible satellite orbits.
Highlights
:: spheric density models is less than 10% during the selected period (Bruinsma, 2015), and no significant impacts on the Precise Orbit Determination (POD) performances are witnessed in Bernese GNSS Software (BSW) when estimating scale factors and Piece-wise Constant Accelerations (PCAs)
This article investigates the latest development of the Bernese GNSS Software for low Earth orbit satellite precise orbit determination
Three main non-gravitational forces - solar radiation pressure, Earth radiation pressure and aerodynamic force - are modeled as the sum of independent plate-wise surface force acting on a satellite macro-model
Summary
Low Earth Orbit (LEO) satellites have significantly broadened our space exploration eyesight by successfully fulfilling various designated scientific tasks during the past years They often necessitate Precise Orbit Determination (POD) products and many investigations have proven the GPS-based. Hackel (2019) suggested a refined satellite non-gravitational force modeling strategy, which supported further investigation into the so-called single-receiver Integer Ambiguity Resolution (IAR) done by (Montenbruck et al., 2018a). Molina et al (2019) evaluated the GPS L2C tracking performance of the Sentinel-3B GPS receiver and compared it with that of the Sentinel-3A satellite during their so-called tandem phase These methodology improvements will be beneficial to a broader LEO POD community. The major improvements for the LEO POD are the single-receiver IAR and the non-gravitational force modeling, which is the focus of this article.
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