Malaysian airliner's path ultimately tracked by satellite pings' Doppler shift
Thanks to data from a satellite communications provider, we now have a clear picture of Malaysian Airlines flight 370’s tragic final destination, plus or minus 100 miles. Unfortunately, that position is at the bottom of the Southern Indian Ocean. Using a scientific model based on the Doppler shift in signals from MH377 (another Malaysian Airlines' flight) and other aircraft following similar routes, engineers at Inmarsat were able to narrow the area of search for the missing aircraft to an area in the Indian ocean west of Perth, Australia.
The Inmarsat satellite that picked up the “pings” from the aircraft, Inmarsat-3 F1, was launched in 1996. It has no positioning system capabilities aboard, but it has a geostationary orbit at 64.5 degrees east longitude. Based on its relatively fixed position, engineers were able to narrow the location of the plane down with an initial analysis of the Doppler effect on the signal from the flight’s pings and the plane’s approximate altitude. That early analysis showed that the plane had to be within two possible arcs: one to the north, which would have taken it over land, and one to the south over the ocean. After that information was provided to Malaysian officials on March 12, Inmarsat engineers continued to perform analysis of the data by creating models for how the signal would have been shifted by the Doppler effect over the northern and southern paths.