RGPS Post-flight Analysis of ARP-K Flight Demonstrations

Gérard Moreau, Hervé Marcille

Abstract:	Through the ARP (ATV Rendezvous Pre-development) project, ESA is demonstrating European mastering of the critical technologies involved in the GNC of the future Automated Transfer Vehicle (ATV) to the International Space Station (ISS). This pre-development program aims at developing a full scale prototype of the ATV GNC software based on ATV candidate sensors such as the ARP-GPS receiver (by Laben, for the long range part) and the optical RendezVous Sensor (final approach). On the navigation side, this involves the development and validation of a Relative GPS filter (RGPS), used to derive accurate relative navigation estimates based on simultaneous raw data obtained from the chaser (ATV) and target (ISS) GPS receivers. The development of this RGPS filter has first been validated through extensive performance simulations, as well as ground validation including the actual ARP-GPS receiver equipment fed by a GPS stimulator. The last key validation was based on three flight demonstrations to gather GPS data from an actual space environment during Shuttle rendezvous operations. The Flight Demonstration 1 (Nov-Dec 96 on STS 80) has provided such data during the STS/Orfeus-Spas rendezvous, while the Flight Demonstrations 2 and 3 (respectively May 97 on STS 84 and Sep-Oct 97 on STS 86) were performed during Shuttle's approach and departure from the MIR station, recording the Laben (integrated on the Shuttle) and Motorola GPS receiver (placed on-board MIR) data for on-ground post-processing with the RGPS algorithms. This paper presents the overall post-flight analysis results. In particular the assessment of the accuracy of the flight data is reviewed. The post-flight analysis shows the robustness of the RGPS navigation algorithms (the use of pseudo-range measurements only is possible if the carrier phase data are not available) and the very good accuracy of the compact RGPS Kalman filter (8 states). Finally, the flight results enable to assess the representativity level of the GPS S/W model developed for ground simulations.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1957 - 1966
Cite this article:	Moreau, Gérard, Marcille, Hervé, "RGPS Post-flight Analysis of ARP-K Flight Demonstrations," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1957-1966.
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