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Following the crash of EgyptAir flight MS804 yesterday, Chris Kjelgaard examines the importance of air traffic surveillance and aircraft tracking initiatives in finding aircraft that have disappeared from radar…
…More than 250nm beyond land, today’s ground-based Automatic Dependent Surveillance-Broadcast (ADS-B) and primary/secondary radar surveillance technologies don’t work.
This is because ground stations can’t detect the ADS-B Out and other transponder GPS-based positional signals broadcast by aircraft, and the primary-radar signals bouncing off aircraft, when those aircraft are flying beyond the ground stations’ line of sight. In being able to detect airliners flying at normal cruising altitudes, this line-of-sight limit is only about 250nm away.
So any aircraft which disappears today in remote oceanic airspace isn’t likely to be found anywhere near as easily as an aircraft crashing into the Mediterranean. The Air France AF440 and Malaysia Airlines MH370 crashes show this is the case.
However, on the North Atlantic, the adoption of Aireon’s new space-based ADS-B technology by both Nav Canada and NATS, respectively the ANSPs of Canada and the UK, will allow them together to provide active ATM surveillance of almost the entire North Atlantic from February 2018.
By means of space-based ADS-B feeds from Aireon, which rely on aircraft’s ADS-B Out positional signals (broadcast twice a second) being received by rings of satellites orbiting in low earth orbits and then broadcast from the satellites down to a polar-region ground station, the two ANSPs will be able to circumvent today’s line-of-sight detection limit.
Since some 80 per cent of all aircraft crossing the North Atlantic fly through both Nav Canada’s Gander FIR and NATS’ Shanwick FIR, the two ANSPs will know at all times the exact real-time positions to within two seconds of the vast majority of aircraft traversing the North Atlantic.
If an aircraft goes missing, Nav Canada and NATS will notice the fact very quickly and will be able to narrow the location where the aircraft entered the ocean to within a very small area of sea surface.
Aireon’s space-based ADS-B technology will be able to receive ADS-B Out signals from aircraft flying anywhere over the Earth’s surface. So, theoretically, from early 2018, when Aireon’s new technology enters service, no aircraft might ever again be truly lost to those searching for it.