UK-based telecommunications testing company Spirent’s spoof detection and alerting software will initially be used on mobile devices in civil aircraft cockpits. The company also wants to work with avionics companies on certified equipment, and air navigation service providers, who also want to be able to spot Global Navigation Satellite System (GNSS) spoofing. Spirent’s spoofing detection service is mature, and it will be marketing a product soon.
Jeremy Bennington, vice president of precision navigation and timing (PNT) for Spirent, is leading the effort for the company from his home office in Utah. Spirent’s 1,500 clients are in aerospace, defense, transportation, communications, government and other sectors across five continents.
“GNSS spoofing is going to impact civil airspace and not just be isolated to areas of conflict,” he says. “The issue of GPS integrity is not going away and will become more prevalent in the decades ahead.” Bennington is currently giving briefings on GNSS spoofing to airline associations and airline pilot unions, pan-European air traffic management organization EUROCONTROL, aviation equipment standards body Eurocae andd US regulator FAA.
According to Bennington, there are hundreds of GPS spoofing incidents every day and many are affecting airline and business jets. Spirent plans to identify areas where spoofing is occurring and map it on mobile devices. This application would be for situational awareness, but the areas would be depicted on aeronautical charts on mobile devices.
Spirent would offer this as a data service that can be integrated with any provider’s cockpit -mobile app software. Certified avionics will take several years to develop, but Spirent plans to work with avionics companies that require support to develop the equipment. The company will use ADS-B data in the cockpit to detect spoofing.
Understanding spoofing
“Spoofing is insidious because a false GPS signal produces an incorrect position that is used by the cockpit navigation systems, and that is a big problem,” Bennington says.
There are several spoofing techniques. A circle spoof makes an aircraft’s position appear to be over an airport that may be hundreds of miles away. This type of spoof is used by national authorities to counter illegal drone activity by making the drone’s navigation system conclude it is over an airport and must land or not take off. Counter-drone spoofing is used by Israel and Ukraine but could become ubiquitous as many nations fear the incursion of hostile drones for surveillance or military attack.
Spirent’s laboratory research facilities have the highest available continuous dynamic range for evaluating GNSS jamming. The company also has an advanced test solution for mission-critical military systems that are designed to engage in navigation warfare.
Spirent is now using its testing infrastructure to examine the rapidly emerging GNSS spoofing threat in detail. The company is using anechoic chambers, lab bench testing and an open sky test range to examine ways to alert aircrews to spoofing and develop mitigation measures.
The company also works with Low Earth Orbit (LEO) satellite companies with its PNT services business. It also has an advanced PNT simulation system which can handle most signal sources in a single test platform. This supports, among other things, PNT signal requirements for autonomous aircraft.
LEO signals for navigation are being developed by the European Space Agency (ESA), Geely in China, Xona which is developing a network of navigation Cubesats, OneWeb and TrustPoint which is building a global positioning and timing service. LEO communications signals from the Starlink constellation could also be used if Elon Musk’s company certifies its signals. Starlink provides non-GNSS location services for smartphone users so certifying signals could be a next step, according to Bennington.
Predicting signal drop-out
Spirent’s GNSS Foresight cloud-based forecasting service and risk analysis tool accurately predicts where and when uncrewed vehicles, air taxis and drones can operate safely and dependably beyond visual line of sight (BVLOS). “Accurate, reliable GNSS performance is a key enabler of the game-changing innovations that are shaping our future – including autonomous drones and air taxis,” says Bennington.
GNSS Foresight provides a 3D map and forecasts when and where GNSS signal reception can support a safe flight in unpredictable urban and suburban areas where GNSS signals can be blocked by buildings. It provides GNSS line-of-sight and non-line-of-sight for every square meter of ground and meter of altitude every second by relying on precision GNSS orbital models.
According to Bennington GNSS technology is subject to impediments, and it is difficult to operate without added solutions like Spirent’s Foresight. With Spirent’s precision modeling, operators of uncrewed drones and aircraft can plan routes of flight and determine the best times and locations to fly whether operating visually or under BVLOS.
Decision-making to support autonomous aircraft operations is backed by high speed data and Spirent’s safety risk management focuses on the probability and severity of GPS degradation. Foresight can calculate GNSS availability up to three days in the future from the surface to 100m (330ft) above the ground.
Spirent has also worked with drone delivery companies and has built digital twins to model operations to make sure a drone can deliver a package from a warehouse to a residential neighborhood safely. The company plans to use this capability to help defeat spoofing by loading historical data and determining if an aircraft was spoofed. That data will be used to develop an app for a tablet or by an avionics company to upgrade or make certified avionics.
Development roadmap
However, the path to certified avionics will be long and expensive. It will start with software patches before being integrated into new hardware. Upgraded avionics will be able to share information with other aircraft. A key question is if avionics that can defeat jamming and spoofing will be affordable.
Bennington says the three stages of development for the aviation community will be situational awareness of where spoofing is occurring, followed by ways to avoid and mitigate it. Finally there will be improved avionics and solutions like using LEO satellites for navigation.
The aviation industry currently does not have a solution for spoofing. When GPS is jammed and can’t find a signal it fails, and the pilot uses other ground-based navaids or INS (Inertial Navigation System).
The major challenge is that the INS-only position is not readily available in airline cockpits, according to Logan Scott, a GPS consultant. It may be possible to obtain it, but the airlines haven’t figured out how to get to it yet. Bennington notes that general aviation aircraft not equipped with inertial will immediately use the spoofed position in their GPS navigation systems.
When GPS spoofing occurs, airline aircrews should turn off GPS systems, the Ground Proximity Warning System and Terrain Avoidance and Warning System. With Required Navigation Performance (RNP) as well as Area Navigation (RNAV) approaches unavailable, they should use alternate modes of navigation and realize that terrain and traffic alert systems will be compromised, determine where the aircraft is being directed by a spoofed position and know when they can resume normal operations.
Crews should also realize that ADS-B will likely transmit false data to ATC and airline dispatch, and that they may have to manually reset clocks. “All this increases crew workload and removes layers of safety that could lead to an accident,” Bennington says.
Terrain ahead
None of the airline simulation training companies are offering pilots instruction about how to recognize and react to GPS spoofing, according to Scott.
Spirent can determine how existing avionics behave when spoofed and the impact on other systems in the cockpit as well as what updates are possible for existing avionics. It plans to determine which alternative solutions can provide RNP 0.3 globally independent from GNSS.
However, ADS-B relies on GPS and will show the spoofed position, according to Bennington. In addition, Enhanced Ground Proximity Warning System (EGPWS) may set off false alarms and not provide terrain warnings. With GPS spoofing occurring now in Turkey and India where there is lots of mountainous terrain, a dangerous degradation to safety exists.
The Emergency Locator Transmitter may also be using the wrong position which would delay response in the event of an aircraft crash. Bennington believes that the autopilot and attitude and heading reference system can also fail. Some GPS systems can’t be reset in flight including those on Challenger and Falcon jets, while Collins systems can be reset, according to Bennington. Once the aircraft is on the ground, maintenance can clear the system memory.
Spirent wants to mark areas of GPS spoofing for pilots and show where the flight track enters that area. Big course corrections due to spoofing are easy for pilots to spot. Gradual changes are harder to spot but the good news is this is harder to do, and a spoofer must target your specific aircraft, according to Bennington.
Spirent’s PNT X simulation system is available to test complex PNT systems for autonomy, safety, efficiency and precision. It handles various signals including L-band, S-Band and alternative signals and military signals. The system is designed to expedite development cycles for the military, governments and aerospace enterprises. \\
