PRN-21 Carrier Phase Perturbations Observed by WAAS

S. Gordon, K. Shallberg, S. Ericson, J. Grabowski, T. Morrissey, F. Lorge

Abstract:	PRN-21 experienced numerous periods of anomalous or degraded performance over the past three years where the Wide Area Augmentation System (WAAS) set this satellite Not Monitored or increased the User Differential Range Error (UDRE). Setting the satellite to Not Monitored or to a higher UDRE value limits the utility of this satellite in the WAAS service. Investigation of these events indicated PRN-21 exhibited carrier range perturbations that sometimes resulted in receiver subframe parity failures, adjustments of L1 and L2 carrier of approximately half cycle over a few seconds, or complete loss of carrier tracking. These subframe and carrier tracking anomalies were investigated and were also observed in other receivers besides those used in the WAAS network. These anomalous PRN-21 events have been occurring approximately twice per month and are observed and tracked by normal WAAS system monitoring. PRN-21 is a GPS Block II-R satellite that was launched on March 31, 2003. Other GPS satellites exhibit similar carrier phase behavior but they typically are GPS Block II-A satellites and events do not occur with this frequency. This paper characterizes the events occurring with PRN-21 and shows that PRN-21 exhibits this anomalous behavior more frequently than other GPS satellites. It is anticipated this paper will be of interest to others that perform precision processing of GPS data as well as those that monitor GPS satellite performance.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	1236 - 1243
Cite this article:	Gordon, S., Shallberg, K., Ericson, S., Grabowski, J., Morrissey, T., Lorge, F., "PRN-21 Carrier Phase Perturbations Observed by WAAS," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 1236-1243.
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