* "Doppler effect" helped determine doomed flight's path
* Pings only received by one satellite, triangulation
* Company says its technology should be used more widely
By Paul Sandle
LONDON, March 24 Britain's Inmarsat used
a wave phenomenon discovered in the nineteenth century to
analyse the seven pings its satellite picked up from Malaysia
Airlines Flight MH370 to determine its final
The new findings led Malaysian Prime Minister Najib Razak to
conclude on Monday that the Boeing 777, which disappeared more
than two weeks ago, crashed thousands of miles away in the
southern Indian Ocean, killing all 239 people on board.
The pings, automatically transmitted every hour from the
aircraft after the rest of its communications systems had
stopped, indicated it continued flying for hours after it
disappeared from its flight path from Kuala Lumpur to Beijing.
From the time the signals took to reach the satellite and
the angle of elevation, Inmarsat was able to provide two arcs,
one north and one south that the aircraft could have taken.
Inmarsat's scientists then interrogated the faint pings
using a technique based on the Doppler effect, which describes
how a wave changes frequency relative to the movement of an
observer, in this case the satellite, a spokesman said.
Britain's Air Accidents Investigation Branch was also
involved in the analysis.
The Doppler effect is why the sound of a police car siren
changes as it approaches and then overtakes an observer.
"We then took the data we had from the aircraft and plotted
it against the two tracks, and it came out as following the
southern track," Jonathan Sinnatt, head of corporate
communications at Inmarsat, said.
The company then compared its theoretical flight path with
data received from Boeing 777s it knew had flown the same route,
he said, and it matched exactly.
The findings were passed to another satellite company to
check, he said, before being released to investigators on
The paucity of data - only faint pings received by a single
satellite every hour or so - meant techniques like triangulation
using a number of satellites or GPS (Global Positioning System)
could not be used to determine the aircraft's flight path.
Stephen Wood, CEO of All Source Analysis, a satellite
analytic firm, said it seemed that the investigators had
narrowed down the area substantially. "But it's still a big area
that they have to search," he said.
The incident is likely to spur a review of aviation rules,
especially related to communications equipment and the ability
to turn off a plane's transponder, he added.
But it is too early to say what that would entail because it
remains unknown what caused the plane to divert from its
"This type of incident will cause everyone who flies
airplanes commercially with passengers to be really pressed for
a whole new line of ways to keep track of their precious cargo,"
said Wood, a former U.S. intelligence officer who headed the
analysis unit of DigitalGlobe Inc, a satellite imagery
firm, until July 2013.
Inmarsat said for a relatively low cost its satellites could
keep tabs on flights and provide the data exchanged between the
air and the ground to help organise routes to save time and
Its systems, which are widely used in shipping, have been
embedded into surveillance and communications technologies that
allow air traffic controllers to build up a picture of where
aircraft are, and to better manage routes.
"If you have that (...) capability you get a preferred
routing at the right altitude that makes your aircraft more fuel
efficient, but if you don't have it you have to fly lower and
get less priority in air-traffic control," he said.
The system is used in planes in the North Atlantic,
Inmarsat's vice-president for aeronautics, David Coiley, told
Reuters earlier this month, but it is not commonly used in all
parts of the world.
Sinnatt said on Monday that such a facility would cost about
$10 per flight. "It is something we have been pushing the
industry to do because it significantly adds to safety," he
said. Other satellite providers are also developing tracking
(Additional reporting by Alwyn Scott in New York; Editing by