

UK satellite operator used the Doppler effect to locate MH370 - dcx
http://www.themalaysianinsider.com/malaysia/article/uk-satellite-operator-used-19th-century-physics-to-trace-missing-plane

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teuobk
Here's some intuition about how the Doppler effect can be used to find
location of a transmitter given a single receiver: objects (transmitters)
moving in a straight line that are far away from the receiver will have less
of a shift in frequency when they "pass" the receiver than objects that are
close to the receiver.

What's more, you don't actually have to wait for the transmitter to pass the
receiver: the radial velocity is what's important, and if you measure that at
several points, you can fit a curve. That will tell you how far the
transmitter is from the receiver.

Do this several times, and you can make a constellation of possible locations,
and then fit those points to a line.

Globalstar does this with its satellite phones. Their situation is easier than
with Inmarsat, because Globalstar uses fast-moving (relative to points on
Earth) LEO satellites rather than geostationary satellites. Given a single LEO
satellite on a known orbit and assuming that the phone on the ground is
stationary, a fix on position can be made relatively quickly using the Doppler
effect.

Here's a paper about how Globalstar does it:
[http://www.eng.tau.ac.il/~nadav/pdf-
files/Instant_active_pos...](http://www.eng.tau.ac.il/~nadav/pdf-
files/Instant_active_positioning_with_one_LEO_satellite.pdf)

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adrianpike
We should all take a page from this book - data storage is incredibly cheap,
and you can't predict what potential value you might get from it. Store any
data you can get your hands on, timing information, raw packets, everything.
It's easy to throw away later, but impossible to recreate if you never had it
in the first place.

~~~
danieltillett
I think this is exactly how the NSA works:)

More on topic this is pretty cool use of limited data to solve a problem - now
lets hope they can find the black box.

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ssully
This is really interesting and I appreciate knowing the technique that went
into coming up with this conclusion, but I find it kind of weird to see the
article mention that the plane crashed and killed all passengers so factually.
People need closure on this, but it seems kind of cold to speak this way about
the fate of the passengers considering we have no physical proof.

~~~
wallflower
It's kind of like when having a funeral without a body. Which is done in some
extraordinary situations.

Statistically speaking, assuming the plane's final destination was somewhere
in the Southern Indian Ocean, there are no more survivors. If the plane had
somehow landed in the Southern Indian Ocean (roiling seas, 20 to 40 foot waves
[1], pitch black - remember moonless night) and there were survivors, there
would be no more survivors two weeks later (hypothermia due to wind chill,
lack of fresh water). Also, the emergency locators in the life rafts would
have most likely sent out the distress signals upon contact with water.

The mystery of MH370 is that in most all previous cases of onboard fires,
there was some successful attempt to make a form of emergency radio contact.
Even when the ceiling was literally melting [2]. There was none with MH370.

[1] [http://www.seos-
project.eu/modules/oceancurrents/oceancurren...](http://www.seos-
project.eu/modules/oceancurrents/oceancurrents-c02-p05.html)
[http://en.wikipedia.org/wiki/Roaring_Forties](http://en.wikipedia.org/wiki/Roaring_Forties)

[2]
[http://en.wikipedia.org/wiki/Swissair_Flight_111](http://en.wikipedia.org/wiki/Swissair_Flight_111)

~~~
tzs
Minor correction: by the time the plane must have come down in the ocean, it
was after 8am, which I think is well after sunrise at that date and location.

