Space weapons designed to attack US satellites are increasingly becoming a major concern for the US military, especially electronic signal jammers used to interfere with GPS signals. Gen. John Raymond, the chief of space operations for the US Space Force, told a congressional hearing that the threat is "real and worrisome today." He pointed to China and Russia as major players pursuing technologies to "forcefully jam GPS and communications satellites."

GPS Composition and Evolution

  • GPS consists of 31 satellites (including 24 primary and backup satellites) orbiting the Earth at an altitude of 20,000 kilometers. The US Space Force manages these satellites like a global utility. GPS satellites in six orbital planes orbit the Earth twice a day, broadcasting positioning, navigation, and timing (PNT) signals that are critical to all aspects of the civilian economy and military operations.
  • The first GPS satellite, Navstar 1, was launched in 1978, and the entire constellation became operational in 1995. The military's heavy reliance on PNT data makes GPS an attractive target for adversaries, the RAND Corporation noted in a recent report.
  • A new generation of GPS satellites provides military users with a stronger signal, called the M-code. U.S. Marine Corps combat engineers use the new GPS equipment during an exercise. These stronger signals improve the safety and reliability of military operations.

　　In addition to denying GPS signals through electronic jamming attacks, foreign militaries can deceive the U.S. military using fake PNT data, a technique called spoofing. GPS disruptions can wreak havoc on all military activities involving aircraft, ships, munitions, land vehicles and ground forces. "In an intense military conflict, even brief denials and spoofing of PNT could have significant impacts if coordinated with other operations," the report said.

The methods of U.S. military is dealing with GPS weaknesses

　　To counter these vulnerabilities, the Space Force is strengthening what it calls the "GPS enterprise," which includes three parts: space satellites, ground control systems and user equipment. "We're looking at how to evolve that architecture to be more robust and resilient than it is today," said Col. Ryan Colburn, director of the Spectrum Warfare Division at the Space and Missile Systems Center.

　　The Department of Defense uses a variety of PNT technologies to supplement GPS or serve as a backup when GPS performance degrades or becomes unavailable. Some military platforms use onboard sensors to track their location and timing without using external signals. Other PNT technologies use external information sources other than GPS to determine the platform's location. For example, military fighter jets use GPS paired with an inertial navigation system so that if GPS fails, the pilot can still complete the mission. Inertial sensors and clocks allow the platform to identify its location and track time without relying on external signals. Other technologies rely on celestial and magnetic navigation to determine location. In addition, the number of satellites in low-Earth orbit that transmit PNT information is growing.

　　However, the U.S. Government Accountability Office said in a report that none of these alternative PNT technologies have reduced the U.S. military's reliance on GPS. "Alternative PNT does not appear to be a priority for the Department of Defense," said Karen Howard, director of science, technology assessment and analysis at GAO.

　　Jon Ludvigson, director of contracts and national security acquisition at the U.S. Government Accountability Office, noted that for years, Congress has questioned the Department of Defense's strategy of making GPS the core of its PNT architecture. Due to the success of GPS, “alternatives don’t really have to move forward.” However, as reliance on GPS grows, “there’s more and more concern about what it means for our operations if we lose GPS.”

　　Despite the vulnerabilities, the U.S. military has doubled down on the GPS system, continuously upgrading and diversifying PNT technologies to keep up with evolving global threats and ensure the reliability and effectiveness of national security and military operations.