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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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strugglinfamfund March 25 2014 at 7:19 PM

prayers for all involved

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txblkleon March 25 2014 at 11:30 PM

Trucking companies such as FEDX, UPS and other trucking companies have GPS system installed in the vehicles so they track the were-bout of the vehicles all the time. How come the airliner companies and the military do not have the GPS system to know where the planes are at any time. The GPS data can be recorded from takeoff to landing, and the GPS system cannot be accessed while the plane is flying. It cannot be that expensive if the trucking industry is using it. However, if the same unit is put in a aircraft the cost would be quadrupled.

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1 reply
sbren20979 txblkleon March 25 2014 at 11:46 PM

Still a good idea in the aftermath of this crash.

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crrunch March 25 2014 at 11:31 PM

And so the world is still waiting for hard evidence.

Flag Reply +2 rate up
suzanp99 March 25 2014 at 7:32 PM

Inmarsat is all we have. Every conspiracy theory is worthless. Someone in China has to convince these poor families, their loved ones have gone on. Malaysia did everything they could as soon as they became aware of any data. Is it less than Europe or the US would know, who, what, where, why, and how????maybe, maybe not.

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John Hall March 25 2014 at 7:32 PM

if you're smarter than them. why haven't revealed what has happened to the airplane?

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1 reply
lovieperkins John Hall March 25 2014 at 7:56 PM

why would the enmey want to tell you anything ?????? A seething pot of Islamic extremists is Malaysia, the longer the wild goose chase and stall the better for them to do their planned wicked stage 2......

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gsun25sun March 25 2014 at 9:27 PM

Has anyone looked in the Lake Victoria area. There r little islands there with a lot of thing that do not look right. They need to check it out. Just saying

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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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ritacyphe March 25 2014 at 9:26 PM

You have to Sign In first to leave a comment."WHY" did the pilots wife and family leave the home the day before the flight? Did they move out? If so, why?

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1 reply
tony ritacyphe March 25 2014 at 9:57 PM

Prob just felt like doing it.

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xpphil12 March 25 2014 at 9:21 PM

Some people on this site wake up to a new world every morning.Meaning they start each and every day from square one as if it were their first day on earth,they accumulate no knowledge over time.Actually some of their comments are funny as hell so it's not a total bust.

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Blessed March 26 2014 at 2:37 AM

So many countries, all came together to help the Families of 239 passengers and they're still working to solve the issue at hand. If no one else can say " Thank You " , I do. I'm sure other posters as well, would say the same were it their own loved one gone to the seas. Bless the people who are solving this puzzle, to bring answers whilst knowing the very answers that are sought, won't bring back the loved ones. You are doing a wonderful job.

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