GPS Multipath Effects During the Shuttle to MIR Rendezvous for the STS-84 Flight Atlantis

Guillerrno Ortega, Emilio Mora, Carrnelo Carrascosa

Abstract:	The multipath effect is the physical phenomenon by which a GPS satellite signal can be spitted in several: direct, reflected and diffracted. These signals bounce around in the surroundings of the antenna before getting into the receiver. The cause of multipath is the presence of surfaces allowing the bouncing effect. The multipath effect produces a corruption in the direct GPS signal both in the carrier phase and in the pseudorange degrading the accuracy of the system. The goal of this paper is to report results about the multipath effects caused during the rendezvous and docking between the Shuttle Atlantis and the Russian space station MIR. The flight under study is the STS-84, which took place between May 15 and May 24 in 1997. The article starts with a description of the involvement of the European Space Agency (ESA) in the setup and control of the GPS experiment on-board Atlantis. GPS measurements were taking using several receivers on board the Orbiter and the MIR station. The paper continues explaining the ESA on going efforts to study, characterize, and mitigate multipath effects in GPS measurements as a crucial part of the relative GPS techniques involved in fiture flights to the International Space Station (1SS). Next, the paper details the information available for the multipath study: the data collected during the STS-84 flight, the data post-processing of the raw GPS data from the orbiter done at ESA, and the available software tools to analyze multipath. Finally, based on the previous correlation, the paper discusses the impact in the applicability of relative GPS techniques in future rendezvous space scenarios.
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:	1017 - 1024
Cite this article:	Ortega, Guillerrno, Mora, Emilio, Carrascosa, Carrnelo, "GPS Multipath Effects During the Shuttle to MIR Rendezvous for the STS-84 Flight Atlantis," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1017-1024.
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