Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse g
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ORIGINAL ARTICLE
Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground networks Wen Huang1,2
· Benjamin Männel1 · Pierre Sakic1
· Maorong Ge1,2 · Harald Schuh1,2
Received: 29 January 2019 / Accepted: 19 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites and low Earth orbiters (LEOs) are usually performed independently. It is a potential way to improve the GNSS orbits by integrating LEOs onboard observations into the processing, especially for the developing GNSS, e.g., Galileo with a sparse sensor station network and Beidou with a regional distributed operating network. In recent years, few studies combined the processing of ground- and space-based GNSS observations. The integrated POD of GPS satellites and seven LEOs, including GRACE-A/B, OSTM/Jason-2, Jason-3 and, Swarm-A/B/C, is discussed in this study. GPS code and phase observations obtained by onboard GPS receivers of LEOs and ground-based receivers of the International GNSS Service (IGS) tracking network are used together in one least-squares adjustment. The POD solutions of the integrated processing with different subsets of LEOs and ground stations are analyzed in detail. The derived GPS satellite orbits are validated by comparing with the official IGS products and internal comparison based on the differences of overlapping orbits and satellite positions at the day-boundary epoch. The differences between the GPS satellite orbits derived based on a 26-station network and the official IGS products decrease from 37.5 to 23.9 mm (34% improvement) in 1D-mean RMS when adding seven LEOs. Both the number of the space-based observations and the LEO orbit geometry affect the GPS satellite orbits derived in the integrated processing. In this study, the latter one is proved to be more critical. By including three LEOs in three different orbital planes, the GPS satellite orbits improve more than from adding seven well-selected additional stations to the network. Experiments with a ten-station and regional network show an improvement of the GPS satellite orbits from about 25 cm to less than five centimeters in 1D-mean RMS after integrating the seven LEOs. Keywords POD · Integrated processing · Sparse ground network · GPS · LEOs · GRACE · Jason · Swarm
1 Introduction The precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites is mainly performed with ground-based observations by a dynamic approach (e.g., Montenbruck and Gill 2000; Hackel et al. 2015; Zhao et al. 2018). The weighted RMS of individual GPS orbit products provided by the International GNSS Service (IGS, Johnston et al. 2018) Analysis Centers with respect to the combined
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Wen Huang [email protected]
1
Deutsches GeoForschungsZentrum GFZ, Telegrafenberg 14473, Potsdam, Germany
2
Institute of Geodesy and Geoinformation Science, Technische Universität Berlin, Strasse
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