Utilizing TWSTFT in a Passive Configuration

Carsten Rieck, Per Jarlemark, and Kenneth Jaldehag

Abstract:	In this paper we suggest the passive usage of Two Way Satellite Time and Frequency Transfer (TWSTFT). In a passive configuration a receiver observes, possibly multiple, codes sent by the active users of a TWSTFT-network. Common view observations of the same signals by a pair of observers can be used to compare their local clocks. Similar to GNSS, the users need to know their local coordinates and the orbit of the satellite in order to reduce the measurements by the geometry. As the orbit is usually poorly known, it is essential to establish an infrastructure that provides the users with satellite ephemerides and appropriated correction models. In this initial study we use the ranging measurements performed by the active European network to TELSTAR 11N in order to estimate precise satellite positions. Residual ranges of the position estimates are well below 1 m. Based on the precise satellite positions and other regular TWSTFT measurements an extended Kepler description of the orbit is determined, which can be used to estimate ranges from the satellite to a passive user at arbitrary station positions and arbitrary epochs. A passive use of TWSTFT will enable us to increase the number of measurements without increasing the noise level on the transponder. It will also reach out to a new group of users, both commercial and scientific, which will benefit from current and future developments of TWSTFT. NMIs will be able to offer an independent method for robust distribution of their national time scales.
Published in:	Proceedings of the 48th Annual Precise Time and Time Interval Systems and Applications Meeting January 30 - 2, 2017 Hyatt Regency Monterey Monterey, California
Pages:	219 - 234
Cite this article:	Rieck, Carsten, Jarlemark, Per, Jaldehag, Kenneth, "Utilizing TWSTFT in a Passive Configuration," Proceedings of the 48th Annual Precise Time and Time Interval Systems and Applications Meeting, Monterey, California, January 2017, pp. 219-234. https://doi.org/10.33012/2017.15002
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