According to NASA’s aviation safety reporting system-a forum where aviation professionals can anonymously share near misses and safety tips, the number of reports addressing GPS signal loss or disruption for private and commercial aircraft has increased.
What is GPS and what is its significance?
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radio navigation system owned by the US government and operated by the United States Space Force. It operates independently of any telephonic or Internet reception and provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.
The GPS is basically a civilian version of the global navigation satellite systems (GNSS)-first devised by the U.S. military in the 1960s. Most airplanes now carry Automatic Dependent Surveillance-Broadcast (ADS-B) transponders, which use GPS to calculate and broadcast their altitude, heading, and speed. Private pilots use digital charts on tablet computers, while GPS data underpins autopilot and flight-management computers.
The GPS service is controlled by the United States government, which can selectively deny access to the system or degrade the service at any time.
Hence, several countries are in the race of setting up their own dedicated global or regional satellite navigation systems:
- The Russian Global Navigation Satellite System (GLONASS) was developed contemporaneously with GPS, although it suffered from incomplete coverage of the globe until the mid-2000s.
- China’s Beidou satellite navigation system began global services in 2018 and finished its full deployment in 2020
- The European Union has its own Galileo Satellite Navigation System
- The Indian Regional Navigation Satellite System (IRNSS), developed by India, with the operational name – “NavIC “
- The Japanese have developed the Quasi-Zenith Satellite System (QZSS)-a GPS satellite-based augmentation system to enhance GPS’s accuracy in Asia-Oceania, with satellite navigation independent of GPS and scheduled for 2023.
Can GPS be jammed?
Yes, and quite easily so. How?
Apparently, it is a relatively uncomplicated process that involves the production of an RF signal strong enough to drown out the transmissions from GPS satellites. The subject of a GPS jamming attack will be instantly aware that something is wrong, as the system will be unable to produce a geolocation result.
The vast majority of incidents involving GPS-based navigation systems either experience a total loss of signal or, more alarmingly — incorrect aircraft position reporting.
Reportedly, undisclosed Federal Aviation Administration (FAA) data for a few months in 2017 and 2018 point to hundreds of aircraft losing GPS reception in the vicinity of military tests. Air Traffic Control (ATC), search and rescue operations, the electric grid and mobile phone services are all vulnerable to GPS jamming fallout.
Yet another, a more insidious form of attack – involves a deliberate mimicking of the form of transmissions from GPS satellites, tricking the receiver into believing that it has been sent information as expected.
To give a perspective, it involves location information being sent to the GPS receiver which is clearly false and may/may not be immediately clear to the user that they are being spoofed, but, it nonetheless stops them from using their GPS for its intended purpose. In other words, it is a more targeted form of jamming.
There have been over 90 ASRS (Aviation Safety Report System) reports detailing GPS interference in the United States, most of which were filed in 2019 and 2020.
Loss of life can happen because air traffic control and a flight crew believe their equipment are working as intended, but are in fact leading them into the side of the mountain. Had we not noticed, that flight crew and the passengers would be dead. I have no doubt.said an air traffic controller referring to an aircraft incident in Idaho (August 2018) flying in smoky conditions and which apparently suffered GPS interference from military tests
Reportedly, the military is known to jam GPS signals to develop its defence (s) against GPS jamming.
Planned electronic-attack (EA) testing occasionally causes interference to GPS based flight operations, and impacts the efficiency and economy of some aviation operationsSaid a 2013 military report
Why would the military interfere with such a safety-critical system?
The GPS is exceedingly vulnerable to attack. these signals are diminished before they hit the ground. And quite surprisingly, building an electronic warfare system to disrupt these weak signals is apparently easy.
Detune the oscillator in a microwave oven and you’ve got a super powerful jammer that works over many kilometerssays Todd E Humprheys-director of the Radio navigation Laboratory at the University of Texas at Austin
In most of the cases reported, the loss of GPS was deemed an emergency. Pilots have veered off-course, accidentally entered military airspace, have been unable to manoeuvre, and lost their ability to navigate when close to other aircraft. Many pilots required the assistance of air traffic control to continue their flights.
Jamming incidents have never been specific to the US alone.
On October 16, there was a report from Flight Service Bureau Bulletin, warning of serious GPS interference at France’s Marseille-Provence airport.
In May 2016, Egyptian civil aviation authorities sent an internal alert warning pilot about malicious attempts at GPS signal jamming near Cairo airport.
Very recently, the French Civil Aviation Authority (DGAC) raised the alarm about the Russian military jamming satellite navigation systems around Ukraine. Additionally, the EASA has identified four areas where the GNSS jamming intensified since February 24, 2022-the Kaliningrad region and the Baltic Sea, the eastern part of Finland, the Black Sea, and the Eastern Mediterranean area.
The loss of GNSS data could also affect aircraft terrain avoidance and wind shear alerting systems.
All being said, the aviation industry is cognizant of the vulnerabilities of GPS, and actions are being taken to address them proactively.
The FAA’s Air Traffic Organization (ATO), for example, notes on its website that the agency is actively working with the U.S. Department of Defense to mitigate vulnerabilities and to make sure augmentation systems can detect and mitigate concerns.
COVER: IEEE Spectrum