Validating the Timing Performance Improvement from Ionospheric Corrections on Iridium PNT Receivers with STL - Time Service that Utilizes only Signals from Low Earth Orbit Satellites

We present the timing accuracy improvement from ionospheric corrections on Iridium® PNT receivers by validating the timing service (STL - Time) against UTC(NIST), the timing reference at the National Institute of Standards and Technology (NIST) in Boulder, Colorado, with and without ionospheric corrections for a duration of 40 days. Iridium PNT is a mature low Earth orbit (LEO) based timing and location service that is commercially available worldwide. This paper focuses on LEO receiver time and measuring its stability and accuracy improvements from ionospheric corrections. The data show that a LEO receiver with a miniature atomic clock (MAC) oscillator provides a stable timing solution with an average time offset close to zero, a maximum offset to UTC (NIST) less than 40 ns and Maximum Time Interval Error (MTIE) less than 80 nanoseconds over a period of 40 days without ionospheric corrections. Adding ionospheric corrections to the receivers timing solution improves its MTIE performance by up to 30 ns resulting in MTIE close to 60 ns providing timing accuracy approaching grandmaster level performance (PRTC-B, MTIE < 40 ns). The time deviation (TDEV) of the LEO receiver is around 6 ns at one day of averaging and the Allan deviation (ADEV) less than 2 × 10-14 at 5 × 105 seconds continuing to average down with or without ionospheric corrections. These results show that a LEO receiver maintains a highly accurate and stable timing solution in scenarios where Global Navigation Satellite Systems (GNSS) signals cannot be received at a user's location.