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.
How ‘groundbreaking’ number crunching found path of Flight 370
Monday’s announcement by Malaysia’s Prime Minister acknowledging that missing Flight 370 ended in the southern Indian Ocean opens the door to a big question: How did new number crunching confirm the Boeing 777’s path?
Now we know for sure “there’s no way it went north,” said Inmarsat Senior Vice President Chris McLaughlin.
Malaysian Prime Minister Najib Razak said Monday that the plane was last tracked over the middle of the Indian Ocean, west of Perth, Australia. Malaysian Airlines has informed passengers’ relatives that “all lives are lost,” a relative told CNN.
Monday’s announcement brings new questions about the mystery that has captivated the planet for more than two weeks. It also provoked a call that all airliners be constantly tracked.
The mathematics-based process used by Inmarsat and the UK’s Air Accidents Investigation Branch (AAIB) to reveal the definitive path was described by McLaughlin as “groundbreaking.”
“We’ve done something new,” he said.
Here’s how the process works in a nutshell: Inmarsat officials and engineers were able to determine whether the plane was flying away or toward the satellite’s location by expansion or compression of the satellite’s signal.
What does expansion or compression mean? You may have heard about something called the Doppler effect.
“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 latitude of the orbiting satellite.”
Each ping was analyzed for its direction of travel, Myers said. The new calculations, McLaughlin said, underwent a peer review process with space agency experts and contributions by Boeing.