MH370: It may be the “best available” but is the evidence really “overwhelming”?

It does not add to the confidence when the story keeps changing. Tha last reported words from the cockpit were not “All right, good night” from the co-pilot but ” Goodnight. Malaysian three seven zero”  and it is not yet finalised as to who spoke the words.

I noticed today that Tony Abbott was quoted as saying that

“The accumulation of evidence is that the aircraft has been lost and it has been lost somewhere in the south of the Indian Ocean,” he told reporters at the Perth military base coordinating the search.

“That’s the absolutely overwhelming wave of evidence and I think that Prime Minister Najib Razak was perfectly entitled to come to that conclusion, and I think once that conclusion had been arrived at, it was his duty to make that conclusion public.”

But as far as I am aware the evidence of its location south west of Perth in the Indian Ocean is entirely – and solely – based on the analysis of routine communication signals between the ACARS system on the plane and Inmarsat’s satellite.

Slate: On the morning of Saturday, March 8, MH370 replied seven times to these pings, saying, in effect, “Yes, I’m here.” The line was open for the plane to communicate with the outside world. But the system that generates the messages themselves, called ACARS, had been shut off. So nothing else was communicated between the satellite and the plane.

…. When Inmarsat pinged it at 8:11 a.m. and received MH370’s reply, the amount of time it took the plane to respond allowed investigators to calculate its distance from the satellite. This did not correspond to a specific location but to an arc of possible locations across Central Asia in the north and the Indian Ocean to the south. … 

Could analysis of the six earlier pings narrow down the route that the plane had taken? ……  The first ping coincided more or less with the time when MH370 slipped out of range of Malaysia’s military radar. So we have a starting point. By knowing the interval to the next ping, and by estimating the plane’s speed, we can arrive at a distance traveled during that time. Given the radius of the next arc, it’s a simple matter to calculate a route by angling the distance traveled to meet up with that arc.

When the NTSB ran the numbers, the resulting plot showed the plane winding up in a remote part of the Indian Ocean, and that’s where searchers began focusing their efforts. …… 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. 

….. the clever engineers at Inmarsat managed to squeeze one more drop from the thimbleful of data contained in those pings. …….. 

“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 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 ….

Numbers don’t lie. But any analysis requires assumptions to be made and the results of mathematical analysis are only as good as the assumptions made. The analysis is based on the satellite’s wobble. Somewhere in the analysis Inmarsat also had to take account of the history of how ACARS systems on Malaysian Airlines flights had communicated with their wobbling satellite. That suggests that there is variation in how systems on different aircraft react. There is no reason to suspect that the assumptions made in this case were in error but there must be a quite substantial error band.

But apart from these signals and their analysis there is no corroborating evidence of any kind. No debris so far. No black box signal. The only “eye-witness” accounts of “something”, were off the Vietnam coast and over the southern part of the Maldives!

I suppose Tony Abbott was just supporting the Malaysian PM.

It is one piece of evidence and it may be the best evidence available, but I am far from certain that the evidence available is as yet “overwhelming”. I suppose that only finding debris from the aircraft could provide that.


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