DATA from a satellite was used to try to locate missing flight MH370 after it mysteriously disappeared, but it was later discovered it had a “wobble” in its orbit which skewed the data.
The Malaysia Airlines jet vanished from radar on March 8, 2014, with 239 people on board and, to this day, has not been discovered. However, official investigators have concluded that its most likely location now is at the bottom of the Indian Ocean. This was calculated using signals exchanged between MH370 and satellite 3F1, owned by British telecommunications company Inmarsat.
However, an issue was later discovered with 3F1’s data.
The satellite was old: launched in 1996, it was only meant to be in operation for around 13 years.
Running on for 5 years longer than planned, the satellite had run low on fuel it required to stay precisely on location above the equator.
According to Jeff Wise, author of The Plane That Wasn’t There, the satellite was “wobbling” during the time it was receiving signals from MH370.
During the hours the jet was missing, 3F1 was north of the equator, moving first to the north and then swinging back to the south.
Signals sent to satellites are supposed to account for sources of error, such as the movement of the aeroplane.
Mr Wise said: “One source of error is the simple fact that the aeroplane moves - a so-called Doppler Effect.
“Just as a train whistle rises in pitch when it's coming towards you, an aeroplane that’s flying towards the satellite will produce a signal that is of the designated bandwidth.
The problem with this in the case of MH370 is that the signal sent to 3F1 was sending off signals based on where the satellite was supposed to be, not where it actually was, and assuming it was not moving relative to the earth’s surface.
When the plane first disappeared from radar, the angular distance between where the satellite was and where the plane thought it was was reportedly around three degrees.
This is enough to generate a velocity error of 20 knots.
As the hours passed and the plane flew further away from the satellite, this effect became less pronounced but another source of error was growing.
Satellite 3F1 was accelerating along a path towards the southern hemisphere, which would also skew the data it was receiving from MH370.
Mr Wise added: “The satellite communication equipment was programmed to assume the satellite was orbiting over a fixed position to the equator, but in fact 3F1’s orbit has a slight wobble.
All this means that Inmarsat’s calculations will have some error caused by this, making it more difficult to find exactly where the plane’s wreckage is located.