On track to revolutionise global air traffic

Steve Nichols looks at how space-based receivers are revolutionising the global air traffic surveillance system.

Aireon is currently deploying a global, space-based air traffic surveillance system for automatic dependent surveillance-broadcast (ADS-B) equipped aircraft.
ADS-B is ‘automatic’ because it requires neither pilot nor other inputs. It is ‘dependent’ because it depends on data from the aircraft’s navigation system.
Pioneered originally in the USA, an ADS-B-equipped aircraft finds its own position using a global navigation satellite system (GNSS), typically GPS, and periodically broadcasts this position and other information to ground stations and other aircraft equipped with ADS-B.
In 2018, Aireon says it will provide the first global air traffic surveillance system using a satellite-based ADS-B network that makes it possible to extend visibility across the entire planet.
Aireon is working with Iridium Communications to place ADS-B receivers on 66 of its active Iridium NEXT satellites, with a further six in-orbit spares and nine ground spares.
Iridium announced the successful launch of its first 10 Iridium NEXT satellites with Aireon ADS-B receivers into low-Earth orbit in January. Iridium says further deployments are planned and, at the time of writing, the second 10 satellites were targeted for launch.
Iridium NEXT is replacing the company’s existing constellation of satellites with more powerful capabilities, including Aireon’s space-based global real-time aircraft surveillance and tracking service.
Don Thoma, Aireon CEO, said its satellite-based ADS-B service would operate globally, even over the poles, thanks to Iridium’s low-Earth orbiting satellites.
“Aireon is working with 10 air navigation service providers (ANSPs) to test and implement the new service,” Thoma said.
He added that the improved routeing capabilities Aireon’s ADS-B service would enable, especially over the North Atlantic, means that up to $350 million a year could be saved in fuel costs alone.
“And that doesn’t take into account the savings in terms of carbon dioxide and NOX emissions.”
ADS-B-equipped aircraft broadcast their precise position in space via a digital datalink (the global interoperable frequency is 1090MHz) along with other data, including ground speed, altitude, and whether the aircraft is climbing, or descending.
Receivers integrated into the air traffic control system or installed aboard other aircraft provide users with an accurate depiction of real-time aviation traffic, both in the air and on the ground – although this does require additional equipment to be installed on the aircraft.
Unlike conventional radar, ADS-B works at low altitudes and on the ground, so that it can be used to monitor traffic on the taxiways and runways of an airport. It’s also effective in remote areas or in mountainous terrain where there is no radar coverage, or where coverage is limited.
One of the greatest benefits of ADS-B is its ability to provide the same real-time information to both pilots in aircraft cockpits and ground controllers, so that, for the first time, ADS-B-equipped aircraft can both ‘see’ the same data, as long as all aircraft in the vicinity are similarly equipped.
It also benefits from its relative low cost when compared to other surveillance systems, such as radar, its high accuracy, and the fact that it can also support other airborne surveillance applications, which will enable many future updates.
The safety benefits of ADS-B are huge and include improved visual acquisition, especially for general aviation under visual flight rules (VFR) and reduced runway incursions.
There are two commonly recognised types of automatic dependent surveillance for aircraft applications.
ADS-B Out transmits GPS-based position and other aircraft or vehicle information and implementation is now mandated in 2020. ADS-B In allows transmitted signals to be received by other aircraft as well as ground stations, but this is not part of the 2020 mandate.
There is no mandate for ADS-B In. However, this optional In capability, which receives the tracking data for display in the cockpit, should be a popular upgrade, since it can clearly enhance situational awareness by giving pilots a view of the same basic traffic data that ground controllers are monitoring on their scopes.