Receiver Inter-Constellation Time Offset at Low Earth Orbit: An Experiment with Bobcat-1, the Ohio University CubeSat

Zachary Arnett, Ryan McKnight, Sabrina Ugazio, and Frank van Graas

Peer Reviewed

Abstract:	On October 2nd, 2020, Bobcat-1, the Ohio University CubeSat, launched as part of NASA’s Educational Launch of Nanosatellites (ELaNa 31), on the Cygnus NG-14 mission. Bobcat-1 was deployed from the International Space Station on November 5th, 2020, with the primary mission of evaluating the in-space performance of inter-constellation time offset determination. This paper will focus on the evaluation of Bobcat-1’s receiver inter-constellation time offset, with a particular focus on its stability over time; the value is estimated by comparison with the broadcast inter-constellation time offset. Results obtained so far suggest that the Bobcat-1 offset is within a 2 ns error bound. The estimate above is the result of multiple data collections performed over three months (September 2021–December 2021). The applied estimation techniques are described here, with a focus on the environmental and receiver hardware errors. Note that the focus of this paper is on the Galileo-to-GPS time offset (GGTO), which is the first step in validating the feasibility of the work and the applied methods to enable further analysis of other interconstellation time offsets. Bobcat-1 measurements include GLONASS, BeiDou, and QZSS multi-frequency measurements as well, which will be included in future analysis.
Published in:	Proceedings of the 2022 International Technical Meeting of The Institute of Navigation January 25 - 27, 2022 Hyatt Regency Long Beach Long Beach, California
Pages:	844 - 855
Cite this article:	Arnett, Zachary, McKnight, Ryan, Ugazio, Sabrina, van Graas, Frank, "Receiver Inter-Constellation Time Offset at Low Earth Orbit: An Experiment with Bobcat-1, the Ohio University CubeSat," Proceedings of the 2022 International Technical Meeting of The Institute of Navigation, Long Beach, California, January 2022, pp. 844-855. https://doi.org/10.33012/2022.18176
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