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GPS Faces Danger Signals as System Turns 25 Years Old

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GPS Blodgett

By Dr. Brian Blodgett
Faculty Member, Homeland Security, American Military University

In late April, the Global Positioning System (GPS) turned 25 years old. GPS is so ingrained in our lives that we easily forget about its role in our society. Yet it is vital to our critical infrastructures, our military and our daily life.

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As U.S. Space Force explains, GPS is a network of 31 satellites that transmit signals which receiving devices use to determine a geographic location through trilateration.

GPS determines our geographic location and a critical fourth dimension that many are unaware of – time. Each GPS satellite contains multiple atomic clocks that send extremely precise time data to receivers. The receivers decode that information so that an electronic time device can determine the correct time to within 100 billionths of a second.

GPS and Critical Infrastructures

The GPS timing component is critical, according to the Department of Homeland Security, since it is a component in all 16 of our critical infrastructure sectors. Presidential Policy Directive 21 (PPD-21) lists the following as our critical infrastructures:

An error in critical infrastructure microseconds can lead to a cascading failures and throw off the entire network.

Todd Humphreys, an associate professor of aerospace engineering at the University of Texas at Austin, told Scientific American that the U.S. National Space-Based Positioning, Navigation and Timing (PNT) Advisory Board worries “that a foreign adversary or terrorist group could coordinate multiple jamming and spoofing attacks against GPS receivers and severely degrade the functionality of the electric grid, cell-phone networks, stock markets, hospitals, airports, and more—all at once, without detection.”

Defense Department Worries about Foreign Threats to US GPS

The Department of Defense is also worried — and has been for years — about the spread and increasing capability of jamming systems, mainly those of China and Russia.

Russia has already proven its ability to jam the Global Navigation Satellite System (GNSS) flying over its territory. It is also suspect of jamming neighboring countries as well. GNSS is a generic name for the various satellites that send positioning and timing data. Our GPS is just one of the many different sets of satellites that can provide this data.

As early as 2016, China appeared to have shown a willingness to interfere with our military drones when the U.S. was conducting surveillance missions in the Spratly Islands in the South China Sea.

Experts also believe that Iran and North Korea may have the capability to disrupt GPS signals.

American Civilian Use of GPS Jammers Also a Problem

There is also a domestic GPS jammer threat. While the Federal Communications Commission (FCC) made GPS jammers illegal in the United States, they still exist.

In 2015, pilots flying into Northeast Philadelphia Airport reported losing their GPS navigational signals as they approached the runway. The culprit was a truck driver parked in a nearby lot who was disabling a tracking device in the vehicle using a GPS jammer he had purchased.

Securing Our GPS Capabilities

In 2018, Congress passed the National Timing Resilience and Security Act (NTRSA) to create a backup system for our GPS by the end of 2020. President Trump signed the bill into law in December, just months before Diana Furchtgott-Roth took office as the Deputy Assistant Secretary for Research and Technology (OST-R) at the Department of Transportation (DOT).

Since Furchtgott-Roth joined the DOT in February 2019, she has worked to meet the requirements of the NTRSA. That includes the need to establish a complementary and backup system that users can access when the GPS is not available or when signals need reinforcing. The need for such a measure has been a DOT presidential policy requirement since President George W. Bush signed a Presidential Directive in 2004 on U.S. Space-Based Positioning, Navigation, and Timing.

That same month, Trump issued an Executive Order on Strengthening National Resilience through Responsible Use of Positioning, Navigation, and Timing Services.

Furchtgott-Roth told GPS World, “We can’t have GPS signals be a single point of failure for transportation and other critical infrastructure sectors.”

Her first hurdle was that congressional funding for the creation of a backup GPS system went instead to the Department of Defense, although Transportation was the lead agency. This resulted in a delay of the Positioning, Navigation and Timing (PNT) demonstration until March 2020.

PNT Demonstration

Eleven companies have demonstrated their backup systems and are awaiting the opportunity to submit their requests for proposals (RFPs). These companies and their specialties are:

  • TRX, positioning via an inertial measurement units technologies
  • Skyhook, positioning via Wi-Fi, cell ranging and a very large proprietary database of site locations technologies
  • OPNT, timing via Timing Fiber & White Rabbit protocol technologies
  • Seven Solutions, timing via Timing Fiber & White Rabbit protocol technologies
  • NextNav, positioning and timing via Metropolitan Beacons technologies
  • Globalstar-Echo Ridge, positioning and timing via using Global Star LEO constellation of 24 satellites
  • PhasorLab, positioning via fixed reference nodes or ad-hoc mobile mesh network
  • Hellen Systems, timing via eLoran and proprietary receiver and reference systems
  • UrsaNav, timing via eLoran signal transmissions
  • Serco, timing via eLoran signal transmissions
  • Satelles, positioning over the Iridium constellation

To Furchtgott-Roth, timing is everything and will be the first component of our GPS backup. However, she said, “It is not going to provide resilient positioning and navigation for drones, autonomous vehicles, and all our other transportation needs. America must have a combination of systems available that, when used together, will be very difficult to disrupt.”

Karen Van Dyke, who leads PNT efforts in Furchtgott-Roth’s office, told GPS World: “GPS has become an invisible utility that so many of our technologies depend upon. Providing a complementary and/or backup capability ensures users have PNT even when GPS is disrupted. It may also help protect the signals themselves by deterring malicious actors who might otherwise want to jam or spoof GPS.”

FCC Action Threatens Our GPS

In late April, the FCC approved Ligado’s “application to deploy a low-power terrestrial nationwide network in the L-Band that will primarily support 5G and Internet of Things services.”

Ligado is an American satellite communication company, formerly known at LightSquared, that operates the SkyTerra 1 satellites. The company is developing a satellite-terrestrial network to support the emerging 5G market and the Internet of Things (IoT) applications. Ligado’s SkyTerra 1 satellite is “specifically designed to provide robust mobile connectivity to small, low-power devices throughout North America. As part of the 5G future, our satellite network will meet the critical IoT requirements of service ubiquity, service continuity and service scalability.”

Ligado will use the 1526-1536 MHz, 1627.5-1637.5 MHz and 1646.5-1656.5 MHz bands.

GPS satellites transmit data on the 1227.60 and 1575.42 MHz frequencies. There is a significant amount of concern that the use of 1526-1536 MHz and the 1627.5-1637.5 MHz bands might interfere with the GPS’s frequency. The FCC approval includes several items that Ligado must do with regard to the placement of its ground sites and their use of the frequencies; there is still concern about the usage of these bands.

Esper Voices Opposition to Ligado License

Last November, Secretary of Defense Mark Esper spoke out in opposition to the Ligado license, stating that “there are too many unknowns and the risks are far too great to federal operations to allow Ligado’s proposed system to proceed. All independent and scientifically valid testing and technical data shows the potential for widespread disruption and degradation of GPS services from the proposed Ligado system. This could have a significant negative impact on military operations, both in peacetime and war.”

General David Goldfein, chief of staff of the U.S. Air Force, said he is concerned about this approval, because it will cause disruptions to the GPS system. Goldfein also mentioned that he had discussed the issue with General John Raymond, the chief of Space Operations and the commander of U.S. Space Command, who was also concerned.

The Department of Homeland Security also came out against the FCC action. DHS “recommended the FCC deny the Ligado license and remains concerned that an approval creates a high degree of uncertainty for our public and private sector partners, many of whom, along with the departments of Homeland Security, Defense and Transportation, rely on precise and uninterrupted positioning, navigation and timing (PNT) data from the GPS to ensure the security and resilience of their infrastructure.”

Most other federal departments also voiced opposition to Ligado’s use of the L-Band frequencies. However, with the FCC having granted Ligado the use of the three frequency bands, what steps the GPS community will take will depend on what decisions the community arrives at after the members examine different mitigation steps to ensure that the GPS signals are not disrupted. What steps they may take then remain unknown.

About the Author

Dr. Brian Blodgett is an alumnus of American Military University who graduated in 2000 with a master of arts in military studies and a concentration in land warfare. He retired from the U.S. Army in 2006 as a Chief Warrant Officer after serving over 20 years, first as an infantryman and then as an intelligence analyst. Dr. Blodgett is a 2003 graduate of the Joint Military Intelligence College where he earned a master’s of science in strategic intelligence with a concentration in South Asia. He graduated from Northcentral University in 2008, earning a doctorate in philosophy in business administration with a specialization in homeland security.

Dr. Blodgett has been a part-time faculty member, a full-time faculty member and a program director. He is currently a full-time faculty member in the School of Security and Global Studies and teaches homeland security and security management courses.

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