Iridium Satellites Launch a New Era of Global Tracking

And that may help investigators locate aircraft that go missing.

Iridium satellites
The Virginia-based company Aireon operates receivers on a newly completed constellation of Iridium satellites that relay heading, speed, and altitude information from aircraft in real time.

Five years after Malaysia Airlines Flight 370, a Boeing 777 destined for Beijing, vanished after a nighttime departure from Kuala Lumpur International Airport, airline passengers around the world are still wondering if operators have made any progress to more closely track airliners, especially when they’re flying where ground radar is non-existent, over open water, or in mountainous areas.

Not only did the crew of MH370 stop responding to radio calls, but the aircraft’s transponder also shut down, making tracking nearly impossible. If not for raw data received from an Inmarsat satellite attempting to contact the flight, rescue and recovery teams would have been clueless about where to begin. While data were scarce, MH370 is believed to have gone down in the Indian Ocean.

New technologies like automatic dependent surveillance broadcast, or ADS-B, are at the heart of a new worldwide air traffic control system provided by McLean, Virginia-based Aireon. ADS-B equipment already installed on most aircraft transmits heading, speed, and altitude information. In the past, ADS-B signals were picked up only by ground stations that happened to be in line-of-sight range. Those signals can now be picked up by ADS-B receivers on board a new $3 billion constellation of 66 satellites recently launched by Iridium Communications.

Iridium says the idea to include an ADS-B receiver on its satellites emerged from German tests a decade ago in which similar receivers were attached to high-altitude balloons. Iridium sells access to ADS-B data to Aireon and its partner FlightAware, who then deliver tracking information to major air traffic control organizations around the globe like NavCanada, ENAV (Italy), NATS (U.K.), the Irish Aviation Authority (IAA) and Naviair (Denmark). The FAA will begin operational trials at the end of the year in the Caribbean region. Currently, air traffic control (ATC) facilities receive some ADS-B signals when those towers are within range of an ADS-B ground station.

While Aireon’s new ADS-B satellite receiver system was created primarily to improve ATC efficiency in remote regions, a side benefit is that the satellites also deliver position updates from aircraft every half second. With more precise position reports, ATC will be able to reduce separation standards in remote areas: over the ocean and in mountainous regions. That means increased efficiency for all aircraft. And of course, ADS-B works everywhere. ADS-B capabilities will be required on all airliners operating in and out of the United States by the end of this year and will represent the vanguard of efforts to replace aging ground-based ATC radars.

Not all cloud linings are silver, however. ADS-B position and tracking data are transmitted back to Earth through sophisticated aircraft transponders. Should that equipment stop transmitting for any reason, such as a power failure or a pilot’s intentional act, as some believe happened on board MH370, even ADS-B position signals would not get through. Some experts say emergency transponders that can’t be switched off in flight could be an answer.

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This story is a selection from the June/July issue of Air & Space magazine

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