Page 53 - EETimes Europe June 2021

SPECIAL REPORT: GPS/GNSS

In Fixing GPS, Timing

Is Everything

By George Leopold

lobal Navigation Satellite Systems (GNSS), particularly the vul-
nerable U.S. Global Positioning System (GPS), represent a single
point of failure that can be rendered inoperable by unintentional
Gor intentional interference. That reality, along with overdepen-
dence on the nearly five-decade–old satellite constellation, has forged a
Western consensus to accelerate development of terrestrial GPS backups
and other mitigation strategies built around complementary positioning,
navigation, and timing (PNT) technologies.
Several federal agencies are working on demonstration PNT projects
aimed at testing and developing a terrestrial backup system should GPS be
knocked out by jamming, spoofing, or interference aimed at the satellite
constellation’s inherently weak signal.
“A clear common denominator in reducing economic and safety risk expo-
sure due to dependence on GPS is to consider investment in complementary
PNT services,” notes a January 2021 assessment from the U.S. Department
of Transportation (DOT).
If GPS signals are jammed, the U.S. does not want to find itself dependent
on other GNSS constellations, such as Russia’s GLONASS or China’s Baidu
systems, which could be used to interfere with GPS. “What we want to do is
have a terrestrial system, a ground system that doesn’t depend on satel-
lites,” Diana Furchtgott-Roth, former DOT deputy assistant secretary for
research and technology, told Federal News Network in early April.
In this special report, which originally ran on EE Times, we examine the
scope of the GPS challenge and the growing roster of possible terrestrial
backup systems that would kick in if GNSS signals were blocked. We also
consider the state of underlying technologies, such as atomic clocks, that
make the entire PNT system click. ■
IMAGE: SHUTTERSTOCK George Leopold is a technology writer and an EE Times contributing editor.