Satellite connectivity provider Inmarsat has confirmed that the missing Malaysia Airlines Boeing 777 did transmit signals over its satellite and SITA’s network.
In statement released this morning Inmarsat said:
“Routine, automated signals were registered on the Inmarsat network from Malaysia Airlines flight MH370 during its flight from Kuala Lumpur. This information was provided to our partner SITA, which in turn has shared it with Malaysia Airlines. For further information, please contact Malaysia Airlines.”
Inmarsat confirmed to Get Connected that the aircraft was equipped with its “classic aero” services equipment.
This means that it would have been fitted with equipment capable of transmitting over its Inmarsat I-3/I-4 satellite network.
The “classic” Aero H, Aero H+ and Aero I services can provide packet data with speeds of up to 9.6kbps at latitudes of up to around 80 degrees north and south.
Inmarsat was the first operator to comply with the requirements of the International Civil Aviation Organization (ICAO) for global safety communications and its services support safety communications used by most of the world’s leading airlines.
The “classic aero” services enable satellite-aided air traffic control (ATC) when the aircraft is out of VHF range.
Inmarsat says it facilitates the automatic reporting of an aircraft’s real-time position, including altitude, speed and heading, via satellite to air traffic control centres.
The faster 432kbps SwiftBroadband system, which is transmitted only over Inmarsat’s I-4 satellites, is not currently certified for safety services, although testing for the certification process is understood to be ongoing.
The Wall Street Journal has reported that Malaysia Airlines’ missing jet transmitted its location repeatedly to satellites over the course of five hours after it disappeared from radar.
Authorities were ultimately able to establish two possible “arcs” for the aircraft’s last known position by measuring how long it took for the handshake signal, or signal from the Aircraft Communications Addressing and Reporting System (ACARS), to return, and the angle at which it hit the satellite.
This may have been based on the signal strength rather than the angle – a certain signal strength then giving a possible “circle of interest” in the satellite’s footprint.
Chris Mclaughlin, Snr, VP for External Affairs, Inmarsat later added that they had used the Doppler effect to calculate the aircraft’s direction. That is, they must have compared the received frequency from the aircraft with the known transmitted frequency. The small difference between the two would indicate if the aircraft was moving towards or away from the satellite.
Some news sources have said that they looked at the “speed” of the signals, but that is not true. All electromagnetic signals travel at the speed of light – it is the frequency that changes if the transmitter and receiver are moving relative to each other, similar to the “red shift” seen with galaxies that are moving away from us.