Space GNSS Receiver for In-Orbit Demonstration of PPP
The current approach for precise orbit determination (POD) with GNSS is based on the collection of code and carrier phase measurements from space GNSS receivers and computation of precise orbit with ground post-processing tools. This approach is currently adopted in multiple missions (e.g. Earth Observation LEO missions), but it has the principal limitation of not being in real time. This limitation is currently not a limiting factor for Earth observation missions, but is definitely a problem for advanced concepts such as formation flying, autonomous docking and rendezvous and high autonomy of spacecraft.
The availability of real-time on-board centimetre-level position accuracy in space would open the door to myriad applications, one clear market being the envisaged LEO constellations as e.g. OneWeb.
Centimetre-level accuracy is currently achievable on ground via RTK and PPP. While RTK relies on the corrections provided by a ground station in proximity to the user terminal, PPP is based on the dissemination of precise orbit and clock information for GNSS satellites via geostationary satellites (current approach for the majority of the commercial providers of PPP services). This approach can be adopted in space. In addition, the space usage has the great advantage of being bounded by a relative stable dynamic (orbital dynamic) with respect to a ground user whose dynamic cannot be easily predicted. Finally, the troposphere does not impact space users and the effect of the ionosphere can be removed with dual frequency or through accurate modelling, so potentially the accuracy that can be achieved is higher than the ground users.
The concept of real-time high-precision PPP in space for POD is novel and it would be of great interest to demonstrate its applicability for space users through:
- analysis of the new concept of real-time POD algorithms using PPP techniques and both kinematic and dynamic sequential Kalman filter approaches (adopting the more advanced force models for orbit propagation);
- design and development of a complete receiver ready for an IOD (In Orbit Demonstration) cubesat-like mission in order to prove the concept in space;
- identification of potential space mission of opportunities for IOD;
- supporting the demonstration of Space Service Volume (SSV) for European GNSS.
The tasks to be performed will include:
- conceptual analysis and adaptation of PPP techniques to POD real-time space users;
- receiver design encompassing identification of hardware platform capable to perform GNSS processing of dual frequency Galileo and GPS signals and assessment of characterisation aspects needed for POD (e.g. antenna phase centre characterisation);
- receiver development including hardware testing for integration of all hardware components in a cubesat-size board;
- receiver testing with real signals;
- identification of IOD missions that would allow in-space proof of concept;
- demonstration of Space Service Volume (SSV) for European GNSS.
The development of this receiver will allow proof of concept for cubesat missions (which are relatively more accessible than other bigger missions). For use in typical ESA missions (e.g. from microsatellites to standard LEO spacecraft) further activities will have to be performed to achieve EQM level, based on standard ECSS requirements.
Name: Fugro Norway AS
Last Updated: 12/03/2019 14:47