Analysis by the British satellite company Inmarsat and the UK's Air Accidents Investigation Branch (AAIB) was cited on Monday by the Malaysian prime minister as the source of information that has narrowed the location where the Malaysia Airlines flight MH370 may have crashed into the southern Indian Ocean to a corridor a couple of hundred miles wide.
The analysis follows fresh examination of eight satellite "pings" sent by the aircraft between 1.11am and 8.11am Malaysian time on Saturday 8 March, when it vanished from radar screens.
The prime minister, Najib Razak, said: "Based on their new analysis, Inmarsat and the AAIB have concluded that MH370 flew along the southern corridor, and that its last position was in the middle of the Indian Ocean, west of Perth.
"This is a remote location, far from any possible landing sites. It is therefore with deep sadness and regret that I must inform you that, according to this new data, flight MH370 ended in the southern Indian Ocean."
He added that they had used a "type of analysis never before used in an investigation of this sort".
The new method "gives the approximate direction of travel, plus or minus about 100 miles, to a track line", Chris McLaughlin, senior vice-president for external affairs at Inmarsat, told Sky News. "Unfortunately this is a 1990s satellite over the Indian Ocean that is not GPS-equipped. All we believe we can do is to say that we believe it is in this general location, but we cannot give you the final few feet and inches where it landed. It's not that sort of system."
McLaughlin told CNN that there was no further analysis possible of the data. "Sadly this is the limit. There's no global decision even after the Air France loss [in June 2009, where it took two years to recover the plane from the sea] to make direction and distance reporting compulsory. Ships have to log in every six hours; with aircraft travelling at 500 knots they would have to log in every 15 minutes. That could be done tomorrow but the mandate is not there globally."
Since the plane disappeared more than two weeks ago, many of the daily searches across vast tracts of the Indian Ocean for the aircraft have relied on Inmarsat information collated halfway across the world from a company that sits on London's "Silicon Roundabout", by Old Street tube station.
Using the data from just eight satellite "pings" after the plane's other onboard Acars automatic tracking system went off at 1.07am, the team at Inmarsat was initially able to calculate that it had either headed north towards the Asian land mass or south, towards the emptiest stretches of the India Ocean.
Inmarsat said that yesterday it had done new calculations on the limited data that it had received from the plane in order to come to its conclusion. McLaughlin told CNN that it was a "groundbreaking but traditional" piece of mathematics which was then checked by others in the space industry.
The company's system of satellites provide voice contact with air traffic control when planes are out of range of radar, which only covers about 10% of the Earth's surface, and beyond the reach of standard radio over oceans. It also offers automatic reporting of positions via plane transponders. It is possible to send route instructions directly to the cockpit over a form of text message relayed through the satellite.
Inmarsat was set up in 1979 by the International Maritime Organisation to help ships stay in touch with shore or call for emergency no matter where they were, has provided key satellite data about the last movements of MH370.
Even as the plane went off Malaysian air traffic control's radar on 8 March, Inmarsat's satellites were "pinging" it.
A team at the company began working on the directions the plane could have gone in, based on the responses. One pointed north; the other, south. But it took three days for the data to be officially passed on to the Malaysian authorities; apparently to prevent any more such delays, Inmarsat was officially made "technical adviser" to the AAIB in its investigation into MH370's disappearance.
Inmarsat's control room in London, like some of its other 60 locations worldwide, looks like a miniature version of Nasa: a huge screen displays the positions of its 11 geostationary satellites, and dozens of monitors control and correct their positions. A press on a key can cause the puff of a rocket on a communications satellite 22,236 miles away, nudging its orbit by a few inches this way or that.
More prosaically, Inmarsat's systems enable passengers to make calls from their seats and also to use Wi-Fi and connect to the internet while flying.
If the plane has its own "picocell" essentially a tiny mobile phone tower set up inside the plane then that can be linked to the satellite communications system and enable passengers to use their own mobile phones to make calls, which are routed through the satellite and back to earth.
After its creation, Inmarsat's maritime role rapidly expanded to providing connectivity for airlines, the media, oil and gas companies, mining and construction in remote areas, and governments.
Privatised at the end of the 1990s, it was floated on the stock market in 2004, and now focuses on providing services to four main areas: maritime, enterprise (focused on businesses including aviation), civil and military work for the US government, and civil and military work for other governments. The US is the largest government client, generating up to a fifth of its revenues of about £1bn annually. The firm employs about 1,600 staff.
- Charles Arthur, technology editor The Guardian
This graphic from The Telegraph indicates the suspected flight path of MH370 and the location of the past week's debris sightings and searches:
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