A security system consisting of balloon-mounted sensors listening for satellites and cell towers could save lives if the aircraft’s GPS signals are jammed or interrupted. Scientists are testing an alternative to the Global Positioning System (GPS) that uses phone signals to serve as an emergency backup for pilots in case standard onboard equipment jams or malfunctions.

The 31 active GPS satellites orbit the Earth twice a day, emitting precise signals that receivers on the ground can receive and analyze to determine how far away the satellites are. GPS devices use data from three satellites to determine the user’s exact location.

Although GPS is very reliable (the Federal Aviation Administration (FAA) certifies that it is within seven meters 95% of the time), it is not free from problems. In and around conflict zones, GPS connectivity cannot be trusted and can be blocked by attackers. Hackers can also “spoof” GPS signals to give pilots misleading information about their location or direction of travel. GPS systems can also malfunction or stop working altogether. Losing GPS signal on a commercial aircraft could put everyone on board at risk.

GPS systems can also malfunction or stop working altogether. Losing GPS signal on a commercial aircraft could put everyone on board at risk.

“The consequences of losing GPS could be felt throughout society,” said lead study author Jennifer Sanderson, an electrical engineer and navigation algorithms expert at Sandia National Laboratories.

The project, led by researchers at Sandia National Laboratories and Ohio State University, aims to create a reliable safety net for onboard navigation systems that uses a floating receiver to detect radio waves from communications satellites and base stations relative to aircraft. It then uses this information to provide navigation data to pilots.

Signals that can be used for navigation, even though this is not their purpose, are known as “opportunity signals” by scientists working in this field. They can rely on processes like:
The Doppler effect, in which waves are compressed or stretched depending on whether they are approaching or moving away from a particular point to determine position and speed.

In this case, researchers attached antenna payloads to weather balloons and deployed them among satellites and towers, sending them into the stratosphere (a layer of Earth’s atmosphere about 4 to 31 miles (6 to 50 kilometers) above the planet’s surface) to detect targets. their individual signals. These payloads could theoretically serve as emergency beacons should the pilot lose GPS signals.

Currently, researchers must manually determine which satellites are sending which signals based on available reference data. The team will then look to use algorithms that will allow payloads to automatically identify satellites and how this relates to the user’s location and speed in real time.

“While we are still processing flight data, we believe our preliminary findings indicate that we detected cell tower beacons at our peak altitude of approximately 82,000 feet. [25 000 м]said Sanderson. “If these signals are clear enough for navigation, it will significantly change what we think is possible for alternative navigation.”

While previous tests of the technology were conducted at altitudes between 5,000 and 7,000 feet (1,500-2,100 m), this new project sent payloads to altitudes of 80,000 feet (24,300 m). If a payload could reliably return navigation data from this altitude, it could have real advantages for air travel.

Although payloads float at higher altitudes to better receive signals from both communications satellites and cell towers far below, this is not a foolproof method. Satellites focus radio waves on Earth to get the best signal on the ground, so strong signals are not guaranteed at balloon altitude. Researchers will need to gradually improve detection capabilities and speed to account for this possibility of error.