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Doppler effect analysis helped narrow Malaysian jetliner search


HONG KONG (AP) - Investigators are closer to solving an international aviation mystery thanks to a British communications satellite and classroom physics.

An analysis of faint signals sent from Malaysia Airlines Flight 370 to an Inmarsat satellite led officials to conclude the plane crashed in a remote area of the southern Indian Ocean. More precise information about the plane's position when it sent the last signals is helping authorities refine the search being undertaken by planes and ships in seas 2,500 kilometers (1,550 miles) southwest of Perth, Australia. Investigators had little to examine otherwise because other communications were lost early in the flight March 8.


Even with other communications shut down, the plane sent an automatic signal - a "ping" or a "handshake" - every hour to an Inmarsat satellite. Flight 370 completed six pings, and the time each took to be sent by the plane and received by the satellite showed the plane's range from the satellite, according to the U.K. Air Accidents Investigation Branch. This initial analysis showed the last ping came from a position along one of two vast arcs north and south from the Malaysian Peninsula.


Think of a horn being honked in a passing car. To an observer, the sound is high pitched as the car approaches and is lower after the car passes. On approach, each successive sound wave is sent from a slightly closer position to the observer. The sound waves get compressed, resulting in a higher frequency. The opposite happens as the car moves away. It's called the Doppler effect for Austrian physicist Christian Doppler, who put forward the theory in 1842.

The same effect applies to the pings, which would arrive to the satellite at a higher frequency if the plane was moving toward the satellite and decrease in frequency when moving away.

For the analysis that led to Monday's conclusion the plane had crashed, Inmarsat studied the satellite communications made while the plane was on the ground at Kuala Lumpur airport and early in its flight.

It considered aircraft performance, the satellite's fixed location and other known factors. By knowing how the Doppler effect would apply to the satellite communications, Inmarsat could calculate the possible positions, direction of travel and speed of the plane.

The company then compared its predictions to six other Boeing 777 aircraft that flew the same day, and found good agreement, according to Malaysian Defense Minister Hishammuddin Hussein. Inmarsat did not respond to repeated requests for comment from The Associated Press.

"By analyzing that you can determine speed and direction," said Joseph Bermudez Jr., chief analytics officer and co-founder of AllSource Analysis, a commercial satellite intelligence firm. And by determining the area from which the last signal was sent, then estimating fuel left, it "could give you an approximate area of where the aircraft impacted."


Inmarsat sent its data to investigators days after the plane went missing. But it continued to run its own analysis to see if it could wring out any more clues.

The company's engineers were dealing with a "totally new area," Chris McLaughlin, senior vice president of external affairs at Inmarsat, told the BBC. "This really was a bit of a shot in the dark." However, the latest information could only go so far in pinpointing the jet's location.

"We can't help you with any closer data," he said.

Gregory D. Durgin, a professor who teaches satellite communications at the Georgia Institute of Technology, said that because Inmarsat was using a different kind of satellite in a novel way, he expects it would locate the last ping from the Malaysia Airlines lane within "around 100 miles (161 kilometers) of precision."


Inmarsat Plc started out in 1979 as an intergovernmental organization with the aim of helping ships communicate while at sea. It became a private company in 1999 and listed its shares in London in 2005. Customers now include governments, airlines, broadcast media, oil and gas companies, aid agencies as well as merchant shipping. They use hand-held satellite phones, laptop size Internet devices and antennas linked to the company's 10 satellites to communicate.

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Hello Sean ;) March 25 2014 at 7:34 PM

The same way your GPS determines the speed of your car, satellite triangulation. The signals that could not be shut off that were sent to satellites can give a very good idea where the aircraft was when it went completely "off-line".

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1 reply
brian.bergbauer Hello Sean ;) March 25 2014 at 8:05 PM

The way i read it the pings were picked up by a single Inmarsat satellite. With only 1 satellite, there would be no triangulation. There would also be more than 1 possible location, each of which would cover a much larger area. Its been a while since I've taken physics so I could be totally off base, so I suppose the plane could've been hijacked by a foreign government pretending to be aliens. It would take some time to probe all of the passengers anus'.

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nephsam March 26 2014 at 12:54 AM

Most important: Nobody's talking about what the heck was that plane doing there! It was headed to Beijing, not the South Pole! :-s

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1 reply
paulaflyhigh nephsam March 26 2014 at 1:06 AM

Nephsam: my thoughts exactly!!

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KIM March 25 2014 at 10:07 PM

I have to say my gut says it landed somewhere too. I don't know why but I believe it is on land.

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1 reply
estheruthompson KIM March 25 2014 at 10:20 PM

The Radar and Satellite would have picked up the trail if it landed somewhere.

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klw4919 March 25 2014 at 8:39 PM

None of this could be determined until now? what has changed since the plane went missing?

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2 replies
mike klw4919 March 25 2014 at 8:46 PM

Have you been following this story long? You sound uninformed.

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denreilly1 klw4919 March 25 2014 at 8:47 PM

little or nothing.

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rekb March 25 2014 at 8:41 PM

Well Done Inmarsat

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sghenry4 March 26 2014 at 12:50 AM

Until aircraft parts are found that are proven to be, without question, from this plane, it could still be anywhere. We can be told anything and most of us will believe it. Show me.....

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1 reply
embroder sghenry4 March 26 2014 at 1:02 AM

I believe that no one wants to find the "smoking gun" at least not for now, this whole case was nothing but mary go round to say the least.

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woomaster March 26 2014 at 12:24 AM

Theres proof the radar was cut off and the plane went in a different direction and it never landed ,The plane may not ever be found or the people.It was a sucide flight of doom.

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1 reply
billnrth woomaster March 26 2014 at 1:17 AM

I'm thinking the plane had a fire..

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mmounteerm March 26 2014 at 12:22 AM

Thank god for British ingenuity and know how. The plane will be within a >

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Monica Escobar March 25 2014 at 8:53 PM

Sadly to say, still say all were dead before plane crashed due to depressurization. Have a gut feeling that either pilot/co-pilot planned this suicide mission in order to have a clean slate regarding their reputation. Think about it, I think either pilot killed co-pilot right after plane made U-turn or vice versa, programmed plane, depressurized plane so all could not be able to breathe, plane was flying almost 8 hours and no phone calls from anyone to family members. (meant all passengers had passed away), then eventually ended up in the Indian Ocean. Where to my understanding, if you wanted to ditch a place and for it not to be found..it would be there, Indian Ocean. It is the MOST difficult place to attempt any kind of search for plane.

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1 reply
SumBreezeHuh Monica Escobar March 25 2014 at 9:14 PM

From a separate article about in-flight cell phone usage:

...many or all of the passengers might well have been oblivious to the fact that anything was awry. There is no evidence that the takeover of the plane was violent; the view has become increasingly widespread among investigators that the captain himself diverted the plane. By this time, it was past 1 a.m., and many passengers were no doubt asleep. Apart from the lights of the occasional ship, the sea below would have been completely dark. In such a situation, without visual reference or navigational instruments, it is almost impossible to determine one’s orientation. The only way a passenger could have detected a change in course is if he happened to be watching the plane’s course on the entertainment system—but the cockpit can shut that down. “There’s the circuit breakers for all that stuff,” says retired 777 captain Gerard Baer.

At any rate, once an airliner is at 30,000 feet, cell phones no longer work. You don’t have coverage. Part of the problem is that cell tower antennae are pointed down, toward the ground, not up into the sky. If you’re over a city, with its dense cluster of coverage, you’ll have a decent chance, but not in a rural area, and even less so over the ocean.

So what about the United Flight 93 passengers? Most of their calls were made using GTE AirFones, a technology no longer in use that relied on radio waves to communicate with the ground. Malaysia Airlines offers a “air-to-ground phone” service in business class that also allows passengers to send email, but the captain can shut this down, too. Only in the later stages of United Flight 93, when the plane was nearing Washington, D.C. and below 10,000 feet, did a few cell phone calls manage to go through.

That’s not to say that a cell phone would have been completely useless in this scenario. If it were to be taken out of airplane mode, a cell phone would begin sending out signals every 20 seconds or so, trying to locate the nearest cell phone tower. (This is why it’s a good idea to put your phone on airplane mode during a flight, even if you’re not worried about disrupting navigational equipment: The constant fruitless pinging will drain your battery.) This won’t result in your phone making a connection to a network, but it’s a source of electromagnetic radiation that eavesdroppers could pick up. “If you have 200 cell phones all pinging repeatedly at 6/10ths of a watt, it would be a chorus,” says Paul Czarnecki, a pilot and cell phone network technician. “The United States has listening stations all over the world to record and digitize every signal in the air. It blows my mind that we don’t know where it is.”

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1 reply
Monica Escobar SumBreezeHuh March 25 2014 at 9:34 PM

Yes everything you mentioned makes sense however, remember most of the time plane was flying at 12, 000 feet.

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life1967d2 March 25 2014 at 11:58 PM

Was the plane. Hijacked. How could the transponder. Be turn off. Was the cockpit door locked. How was the data deleted. From the pilots flight. Simulator. That was at the pilots home. I think this tradgy. Was. Sabatoge and murder.

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