Tuesday, March 25, 2014

Using Doppler Effect helps find lost plane's path

Jet Fell Into Ocean With All Lost, Premier Says

NY Times quote:  "Guided by a principle of physics called the Doppler effect, the company, Inmarsat, analyzed tiny shifts in the frequency of the plane’s signals to infer the plane’s flight path and likely final location. The method had never before been used to investigate an air disaster, officials said."

Here's a story from cnn with a more detail on using the ping data off of satellites that revealed slight expansion or compression of the signal as the plane moved while it was transmitting.
CNN quote: "If you sit at a train station and you listen to the train whistle -- the pitch of the whistle changes as it moves past. That's exactly what we have," explained CNN Meteorologist Chad Myers, who has studied Doppler technology. "It's the Doppler effect that they're using on this ping or handshake back from the airplane. They know by nanoseconds whether that signal was compressed a little -- or expanded -- by whether the plane was moving closer or away from 64.5 degrees -- which is the longitude of the orbiting satellite."

Edit:  Here's an interesting map from the BBC showing projected path at varying speeds.  Just eyeballing things seems like course changes were designed to avoid radar - especially turning south after out of site even of military radars.

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