Session B1a: GNSS Integrity and Augmentation

Characterization of Recent GPS Satellite Clock Jumps
Rebecca Wang, Yu-Fang Lai, Juan Blanch, Stanford University; Dennis Akos, University of Colorado Boulder; Eric Phelts, Todd Walter, Stanford University
Location: Beacon A
Date/Time: Tuesday, Jan. 23, 1:50 p.m.

Peer Reviewed

This year, a new fault case presented in the January 25, January 28, and July 10, 2023 clock jumps in the GPS constellation. Fault events in the global navigation satellite system (GNSS) affect the accuracy of positioning solutions, but are accounted for through standardized specifications such as those provided in the GPS Standard Positioning Service Performance Standard (GPS SPS PS). However, performance characterization of new and existing satellites in the navigation constellation is necessary to both validate these specifications and inform future design improvements. The Wide Area Augmentation System (WAAS) observed the January 25 and July 10, 2023 faults exhibiting unexpected instantaneous jumps in its clock measurement at a one second sampling frequency affecting only the code phase component. However, the carrier phase component did not demonstrate the same jump. Through comparison of positioning solutions from several different receiver makes, it appeared that the carrier phase component was also affected by these jumps, but were not detected as expected by the carrier tracking loop in the WAAS receiver. Consequently, differences in signal tracking and logic between different receivers become apparent in light of this new anomalous event. This paper examines this fault in greater detail and reports insights into the reaction by receivers to the event which will also inform next-generation receiver signal tracking designs.