There was at least one problem undermining the certainty of Abbott’s assertion. Though the NTSB’s process worked for generating a likely path to the south, it could also be used just as effectively to create a path to the north. The satellite data itself is ambiguous—it provides no clues about which direction the plane is moving. So when the NTSB was plotting out a route to the south, it was also effectively plotting a mirror route, symmetrical to the first, that stretched northward along the Himalayas and on to Kazakhstan.
U.S. and Malaysian officials were said to favor the southern route, but some people (including me) argued that the northern route was more plausible. It allowed for a denouement in which whoever was in control of the plane came out alive. But there was really no way to tell until an aircraft or identifiable wreckage came to light. The satellite data was inherently ambiguous.
Or at least, that’s what many of us thought. But somehow the clever engineers at Inmarsat managed to squeeze one more drop from the thimbleful of data contained in those pings. They’ve been a little cagey about how exactly they did it, so I turned to communications-satellite pioneer Mike Exner, president and CEO of Radiometrics Corp., to explain how he thought they extracted more information.
“This is an old satellite,” Exner said. “When satellites start to run out of hydrazine, you can’t keep them exactly geostationary.” Instead of keeping perfectly still above a certain spot, the satellite begins to slowly wobble. Over the course of the day, it makes a narrow figure eight around a central spot located on the Earth’s equator.
“It’s a small effect,” Exner says, “And normally you’d overlook it.” But in the hunt to overcome the symmetry of the ping data, Inmarsat likely realized that it could use the wobble of the satellite to its advantage. The satellite itself, depending on where it is in its orbit, will have a different relative motion compared to a northbound and a southbound plane. That relative motion can be detected as a Doppler effect, the frequency change you hear when a train whistle that’s coming towards you dips in pitch as it whooshes past. The effect was subtle and difficult to tease out of the data, but when Inmarsat ran simulations, it found that the amount of Doppler effect observed in the MH370 data matched the predictions for the southern route and not the northern one. Comparisons with other flights whose location and speed were known supported that conclusion. That’s the finding that the Malaysian prime minister reported.
So do we know now where MH370 went? Not exactly. The path that the plane is presumed to have taken still depends on the speed that the plane is presumed to have been flying. Inmarsat generated routes based on two different airspeeds—400 knots and 450 knots—and came up with end points that are hundreds of miles apart.
For his part, Exner believes the range of route possibilities is even larger than Inmarsat’s projections suggest. He points out that MH370 was detected diving to 12,000 feet before disappearing from Malaysian military radar. A Boeing 777 going 310 knots at 12,000 feet burns a bit less fuel than one going 440 knots at 30,000 feet, so there’s no question it could have stayed aloft that long. The resulting flight profile is still consistent with Inmarsat’s ping distance and Doppler data, but results in a track that is much shorter and curves to the east near the south coast of Sumatra and Java.
Even though Inmarsat’s presumed approach makes sense and its calculations seem credible, that is not to say that its results are necessarily accurate. Before scientists publish a finding, it must undergo peer review by independent authorities in the field. Inmarsat has declared itself absolutely confident in its results and says that its results were “peer-reviewed” by the British government, but showing one’s work to self-chosen sympathetic colleagues is not peer review. Until Inmarsat’s findings are looked over by a truly independent panel of experts, it will be hard to have unequivocal confidence in the report.
And if searchers don’t start finding wreckage in the current search area soon, it might be time to revise some basic assumptions—and start to look in a different place.