Abstract—The IRNSS (Indian Regional Navigation Satellite System) user receiver calculates its position using the timing information embedded in the navigation signal, transmitted from the IRNSS satellites. The timing information broadcasted in the navigation signal is derived from Atomic clock onboard the IRNSS satellite. A perfect and high stability frequency source is required for precise time measurement. Highly accurate time synchronization between satellite time and ground system time is also required which is synchronized through uplink broadcast navigation parameters. But there is a shift in the frequency of the atomic clock when it is transported from ground to the satellite orbit. Since the atomic clock frequency onboard the IRNSS spacecraft has a very profound impact on user position accuracy, it is appropriate to know what should be the exact frequency of atomic clock to be set before satellite launch. This frequency has to be computed by taking into account the various relativistic effects on the satellite clocks. In this paper, we compute this offset (Factory offset) for the IRNSS satellite clocks that will be set before launch of the IRNSS satellites.

Index Terms—IRNSS, relativistic effects, satellite clocks

The authors are with the Space Navigation Group, ISRO Satellite Center, Bangalore-560 017, India (e-mail: rbabu@isac.gov.in, rethika@isac.gov.in, ratnakar@isac.gov.in)

Cite: Babu R., Rethika T., and Rathnakara S. C., "Onboard Atomic Clock Frequency Offset for Indian Regional Navigation Satellite System," International Journal of Applied Physics and Mathematics  vol. 2, no. 4, pp. 270-272, 2012.