How a new satellite constellation could allow us to track planes all over the globe

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.”

When pilots fly over these low-coverage areas, air traffic controllers keep planes very far apart — putting about 30 to 100 miles of space in between them, says Thoma. Additionally, planes flying internationally often follow predetermined routes until they get to better surveillance coverage. That leaves little room for flexibility. “You can see it’s a big conga line of airplanes going across the north Atlantic,” Thoma says. “They get on that, they stay at the same distance and the same speed. There’s very little variability to climb to a more efficient altitude because there’s so much traffic on those routes.”

But the Aireon ADS-B payloads on board Iridium NEXT could give air traffic controllers more options. Iridium NEXT consists of 66 satellites, with nine spares in orbit. All of these vehicles are flying in a regimented formation over the Earth’s poles, which lets them cover the entire Earth at all times. Because of their high vantage point, about 484 miles up, the Aireon ADS-B technology can see farther out than ground-based stations. One satellite can collect information being broadcast 2,174 miles away, says Thoma.

Originally, Iridium and Aireon hoped to complete the NEXT constellation a couple years ago, but a series of delays and scheduling problems pushed back the first launch to 2017. It’s an issue that pushed back Aireon’s payday; until their tech was fully deployed in space, they couldn’t generate revenue from their tracking services. But over the last two years, SpaceX has launched the Iridum NEXT satellites in batches of 10, and Aireon has been slowly testing out its new ADS-B capability as new spacecraft come online. Of the last 10 that were launched, six of those will be part of the operational constellation, and Aireon announced today that it has received control of the payloads on those last few satellites. Now, Aireon will spend the upcoming weeks testing out the now complete ADS-B satellite system. The goal is to go live with the system by the spring.

If it all works as planned, the Iridium satellites will receive information from planes. That info then gets transmitted to a data center in Virginia operated by Aireon. From there, Aireon throws out any redundant messages, as it’s possible multiple satellites will receive the same information from a plane. The company then determines which airspace a plane is in and sends over the information to the relevant air traffic control organization. That process, end to end, lasts less than two seconds, says Thoma.

After the system is certified for use, Aireon will roll out the capability to its first customers, which include Canada’s air traffic organization, Nav Canada, and the United Kingdom’s air traffic control, NATS — both of which have invested in Aireon. The European Aviation Safety Agency is also evaluating the system, and the FAA has tested out the service over Caribbean airspace. “The FAA believes that space-based ADS-B (SBA) holds promise as a global, seamless surveillance capability,” an FAA spokesperson said in a statement to The Verge. “We are exploring technology-proving activities to evaluate the potential use of space-based ADS-B, in strong partnership with stakeholders.”

Ultimately, rolling out this capability is going to take time. Air traffic controllers will need to train their personnel on how to use and process all of this new information that they didn’t have before. “Think about it, in many cases, the controllers could never see the aircraft before,” says Thoma. “So they were using procedural methods for keeping aircraft safely apart for controlling aircraft.” With more detailed knowledge of the planes’ positions, air traffic controllers could potentially provide more efficient routes to airlines, saving on fuel and the amount of greenhouse gases that are pumped into the atmosphere. And planes could have more flexibility if they need to deviate from a planned course over the ocean, due to weather or some other concern.

Knowing where planes are at all times has the potential to make skies safer. But the system is still dependent on the plane continuously broadcasting its position. In the case of Malaysia Airlines Flight 370, which went missing over the Indian Ocean, there’s evidence that the avionics on board the aircraft had been turned off at some point. But Thoma argues that with the new space-based ADS-B, flight controllers would know the exact moment that information stops broadcasting.

“That information is extremely helpful pinpointing the location of an aircraft in distress or crash situation and help their search and rescue organizations,” says Thoma. “It really gets back to those first principles: it’s always better to see the airplanes.”

And now with airplanes all over the world equipped with ADS-B, everyone may be able to see planes with Aireon’s technology. The deadline for the FAA’s ADS-B mandate is January 1st, 2020, and any US aircraft not equipped by then will effectively be grounded. Though the FAA hasn’t fully committed to ADS-B from space yet, the US will soon have a lot of airplanes that will be shouting out their location at all times. And Aireon’s payloads are always overhead, listening in.