The Effects of the January 2016 UTC Offset Anomaly on GPS-Controlled Clocks Monitored at NIST

Abstract

Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS-controlled clocks to be in error by approximately-13 µs on January 25-26, 2016. The erroneous UTC offset information was broadcast by 15 GPS satellites, or half of the available constellation, during the anomaly. This paper discusses the technical reasons for the UTC offset anomaly, its effect on clocks controlled by GPS satellites (hereafter referred to as GPS clocks), and how it was detected at the National Institute of Standards and Technology (NIST). It then discusses the impact of the UTC offset anomaly on GPS clocks maintained and monitored by NIST, including clocks located in Boulder, Colorado and those at remote locations. Some analysis is presented of the effects of the UTC offset anomaly on GPS clocks located at 19 sites in North, Central, and South America.

A resilient architecture for the realization and distribution of coordinated universal time to critical infrastructure systems in the United States :

“…One simple way to do this is to compare the received GNSS time to a GNSS-independent time code. The January 2016 incident produced a sufficiently small error that could only be detected by comparisons to time sources that had microsecond-level resolution and accuracy, such as UTC(NIST) [112]. However, time errors caused by spoofing are likely to be much larger, and the freely accessible time codes described in this section are capable of detecting millisecond-level and larger errors.…”

“…These errors are exceptionally rare, especially in the case of GPS, but can happen. One example is the approximate 13 µs error in the UTC offset parameters that were broadcast by half of the GPS satellites on January 25-26, 2016 [112]. A second way is spoofing, which is an attack by a radio transmitter located near the target that interferes with the legitimate GNSS signal and delivers false information.…”

Multiple GPS Fault Detection and Isolation Using a Graph-SLAM Framework

“…The space and control segment based anomalies require a few hours to be rectified due to the lack of satellite visibility from the ground station. Some of the most recent real-world incidents reporting satellite faults are listed as follows: non-standard codes were transmitted by a satellite (SV49) [7] in 2017 and wrong timing offsets were broadcast by multiple satellites [8] in 2016. In addition, detailed documentation regarding various satellite faults that have occurred in the past decade are listed in the literature [9].…”

Asynchronous WAM with Irregular Pulse Repetition

“…However, there is still some possibility of system failure or intentional GPS signal jamming and spoofing. For example, the clock failure on one GPS satellite in January 2016 (incorrect time offset information caused by a wrong configuration) (Kovach et al, 2016; Yao et al, 2017) caused a malfunction of many GPS-based time/frequency clocks making them unreliable for tens of hours (Chronos Technology, 2016). Even if we take into account that the probability of such failure is low, the possibility of intentional or accidental jamming of the GPS signals may be an important issue.…”