A newly completed constellation of satellites is poised to provide unprecedented tracking of the hundreds of thousands of aircraft that soar over the Earth every day. It’s a type of global coverage that’s never been fully realized before, but it has the potential to influence how air traffic is managed throughout the world.
The satellite constellation is Iridium NEXT, and it consists of 75 vehicles — 66 operational ones and nine spares. A SpaceX Falcon 9 rocket launched the last batch of 10 satellites for the system on January 11th, out of California, and yesterday Iridium declared the constellation complete. The main function of Iridium NEXT is to provide global telecommunications coverage. But each satellite in the constellation is also equipped with a special receiver, technology that will eventually make it possible to track every single airplane flying in the sky — no matter where they are on Earth.
These small packages, called automatic dependent surveillance-broadcast (ADS-B) receivers, are designed to receive crucial information that many planes broadcast out in real time, details that include the craft’s location, its speed, and altitude. The satellites can then beam that information to air traffic controllers on the ground. That way, airlines and countries have up-to-date information on where every plane is traveling.
It’s a significant upgrade over the current system. Airlines have been been using ADS-B technology for the last decade, but without receivers in space, the only way air traffic controllers have been able to get these broadcasts from airplanes is through receiver towers located on the ground. While there are more than 600 of these towers located all over the Earth, they cannot receive every broadcast from every plane — especially for vehicles flying over oceans or continents with fewer receivers. “When you fly over to Europe or Asia, you’re looking at the seat-back map on the plane and think you know where you are,” Don Thoma, the CEO of Aireon, which owns and operates the receivers on Iridium’s satellites, tells The Verge . “And you think everyone else knows where you are, but the reality is you know where you are, the pilot knows where the plane is, but air traffic control is getting updated very infrequently.”
But the satellites in the Iridium NEXT constellation are positioned so that they can receive every broadcast from any plane with ADS-B technology. “Instead of having towers that are fixed on the ground and planes fly over them, this basically has satellites with receivers on board that are flying over the airplanes and collecting all that information at a very precise level,” says Thoma.
And the constellation’s completion is nicely timed, as the world is making ADS-B the gold standard. In 2010, the US Federal Aviation Administration (FAA) mandated that all aircraft operating in the US need to be equipped with ADS-B technology. And Australia and Europe also recently mandated that all regulation aircraft be outfitted with boxes that can transmit ADS-B. These mandates, coupled with the new satellite capability, will soon give air traffic controllers a lot more information to work with. “With the greater situational awareness, it’s an inherently safer system,” Adam Moya, senior product marketing director for safety systems at Honeywell Aerospace, tells The Verge . “Because people can be more aware of where every aircraft is — knowledge is power from that regard.”
Those mandates haven’t all gone into effect yet, which means that plenty of planes not equipped with ADS-B are still in the air. Without that tech, most air traffic controllers still use radar to track planes in their airspace. Typically, ground-based stations bounce radio waves off of the skin of planes or they’ll send signals to a plane’s onboard transponder to figure out the vehicle’s location. This system relies on input from the ground in order to work, and it’s limited in range, too.
ADS-B doesn’t require that outside ping. If an airplane has an ADS-B Out transponder, it will automatically and continuously send out information about its coordinates, all of which are calculated via the Air Force’s GPS satellites. This is usually more accurate than radar, according to the FAA. But ADS-B still runs into the same limitations of relying on ground-based stations. Each tower can only receive signals from about 250 miles away. Roughly 70 percent of the Earth’s surface is covered in ocean, leaving huge swaths of ocean unmonitored. Plus, there aren’t many ADS-B towers in remote locations, either.
“There’s that limitation that there has to be a ground station to listen to it,” says Moya. “You can’t do that effectively over water and certain areas. You also have line of sight issues. So you have to have so many ground stations in a certain area so it can be seen by an aircraft.”