“Soyuz” - “Mir” Orbital Flight GPS/GLONASS Experiment

Vladimir Branets, Mikhail Mikhailov, Yuri Stishov, Sergey Klyushnikov, Sergey Filatchenkov, Nicolai Mikhailov, Sergey Pospelov, Mikhail Vasilyev

Abstract:	The paper presents the results of the first GPS/GLONAS experiment performed during the Russian piloted space mission. The combined GPS/GLONASS receiver ASN-2401P has been installed on the manned space ship “Soyuz-TM28” and was used to obtain experimental data during its orbital flight in August – December 1998. The receiver components used in the experiment will become core elements of the navigation receiver of Russian mod-ule of International Space Station “Alpha” and Russian space ships. Raw pseudorange and carrier phase measurements, along with the position, velocity and time (PVT) results have been recorded during the autonomous flight of “Soyuz-TM28”, rendezvous operations, as well as during the docked to “Mir” flight. Analysis of the flight data, in-cluding comparison of the ASN-2401P data with the data of Motorola’s Viceroy GPS receiver installed on board the “Mir” station, is presented in the paper. The accuracy assessment of the ASN-2401P snapshot PVT solutions with combined GPS/GLONASS meas-urements compared to the data of the orbit determined from the same measurements is presented. An orbit de-termination (OD) SW primarily developed by Soft Nav Ltd. for autonomous OD on board the satellite with GPS measurements was used during the assessment. Process-ing of the results has demonstrated that weighted least-square GPS/GLONASS PVT solutions become signifi-2303 cantly more accurate with the increase of the number of GLONASS signals involved in the solutions. The error sources limiting the ultimate accuracy of GPS/GLONASS orbital navigation are examined and discussed. Multipath errors have been experimentally evaluated. For this, differences between C/A-code meas-ured pseudoranges (PR) and accumulated delta-ranges (ADR) measured on signal carrier have been analyzed. The analysis demonstrated an episodic growth of mul-tipath errors especially during the approach phase of the flight. Such errors may become the dominating factor limiting the accuracy of relative spacecraft navigation with code measurements. Spectral characteristics of the multipath error were found to be favorable for PRs smoothing, together with ADR measurements. Unfortu-nately, PR-ADR differences have been found to diverge very fast (up to 0.8 m/s at negative elevations). Necessity for orbital applications of more sophisticated PR smoothing algorithms than those normally used on the ground is discussed in brief. The experimental results make a significant contribution to the development of GPS/GLONASS receivers to be used in future Russian program of piloted space flights.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	2303 - 2312
Cite this article:	Branets, Vladimir, Mikhailov, Mikhail, Stishov, Yuri, Klyushnikov, Sergey, Filatchenkov, Sergey, Mikhailov, Nicolai, Pospelov, Sergey, Vasilyev, Mikhail, "“Soyuz” - “Mir” Orbital Flight GPS/GLONASS Experiment," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 2303-2312.
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