Comparison and generalization of GNSS satellite attitude models

Sebastian Strasser, Simon Banville, Andreas Kvas, Sylvain Loyer, Torsten Mayer-Gürr

Research output: Contribution to conferenceAbstract


Global navigation satellite system (GNSS) constellations such as GPS, GLONASS, Galileo, and BeiDou and the Japanese regional system QZSS apply various satellite attitude modes during eclipse season, which is the period when the Sun is close to the orbital plane of the satellite. Due to different satellite manufacturers and technological advances over time, these modes can vary between constellations but also between different satellite types within a constellation. For some constellations, namely Galileo and QZSS, the satellite attitude law has been officially published by the satellite operator. For most other GNSS satellite types, researchers have developed attitude models, for example using reverse kinematic precise point positioning, that approximate the actual attitude behaviour.

Outside of eclipse seasons, GNSS satellites generally apply either a nominal yaw-steering or an orbit normal attitude law. While both modes point the antennas towards Earth, the former yaws the satellite around the antenna axis to point the solar panels towards the Sun, while the latter always keeps a fixed yaw angle. When a satellite applying a yaw-steering law is in eclipse season and close to the orbit noon or midnight point, it may have to yaw faster than physically possible to keep the nominal attitude. The various attitude modes used by the satellites aim to prevent this scenario by applying a modified attitude law during this period, for example by yawing at a constant rate around orbit noon/midnight or by switching to orbit normal mode.

Comparisons of attitude files generated by analysis centers of the International GNSS Service (IGS) within the scope of its 3rd reprocessing campaign show significant differences in some cases. This contribution compares all available attitude models with the aim of finding similarities that allow for generalization, which in turn simplifies the implementation of the various attitude modes into GNSS software packages. The developed functions have been implemented into the open-source software GROOPS (, which makes them publicly available and documented.
Original languageEnglish
Publication statusPublished - 28 Apr 2021
EventEuropean Geosciences Union General Assembly 2021: EGU 2021 - Virtuell
Duration: 19 Apr 202130 Apr 2021


ConferenceEuropean Geosciences Union General Assembly 2021
Abbreviated titleEGU21
Internet address

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