NIST confirms STL as reliable timing source, even indoors

Study by U.S. government agency responsible for maintaining national time scale shows that Satelles provides a signal that is independent of GNSS and delivers exceptional timing stability

Following a detailed performance study in 2020, the U.S. National Institute of Standards and Technology (NIST) determined that Satellite Time and Location (STL) is a reliable source of timing highly consistent with Coordinated Universal Time (UTC). The secure STL services are provided by Satelles Inc.

STL is based on a signal independent from GPS and other GNSS. The STL service was able to deliver this consistent performance in a deep indoor environment where GNSS signals did not reach.

The results of the study were shared by Elizabeth Donley, chief of the Time and Frequency Division at NIST, in a keynote speech at the Workshop on Synchronization and Timing Systems (WSTS) conference on April 1.

Donley articulated the details of the NIST study, in which a GPS-disciplined clock and a Satelles EVK-2 evaluation unit with a quartz oscillator were compared to UTC for 50 days. In this evaluation, the GPS device received its signal from an outdoor antenna, whereas the Satelles device was connected to an indoor antenna in a deep indoor environment where GNSS signals were not able to reach.

Time deviation calculations estimated the stability of the two signals with respect to the UTC time scale. Based on one day of averaging, the GPS instability was less than two nanoseconds, and the STL instability was only slightly higher at under three nanoseconds (see chart). These measurements demonstrated that STL delivers stability comparable to GNSS and does so in an indoor location where GPS signals usually cannot penetrate.

Image: NIST

STL delivers a positioning, navigation and timing (PNT) service from satellites in low Earth orbit (LEO) to back up or augment GPS and other GNSS. The evaluation by NIST confirms that users of PNT-reliant applications can obtain accurate and reliable timing without using GNSS.

“We are thrilled that NIST has performed these independent tests that confirm what we have long known, which is that STL delivers an independent timing source that is reliable and highly consistent with UTC,” said Gregory Gutt, president and CTO of Satelles. “This report complements and reinforces the findings of the U.S. Department of Transportation, which identified STL as a top-ranked PNT system in its technology demonstration report released earlier this year, and showed STL to be the only solution that demonstrated a wide-area timing capability that works indoors and out.”