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How Satellite Company Inmarsat Tracked Down MH370
mdsolar (1045926) writes "Malaysian Prime Minister Najib Razak has announced that, based on satellite data analysis from UK company Inmarsat, Malayian Airlines flight MH370 ended in the southern Indian Ocean, and no one on board survived. 'Effectually we looked at the doppler effect, which is the change in frequency, due to the movement of a satellite in its orbit. What that then gave us was a predicted path for the northerly route and a predicted path the southerly route,' explained Chris McLaughlin, senior vice president of external affairs at Inmarsat. 'What we discovered was a correlation with the southerly route and not with the northern route after the final turn that the aircraft made, so we could be as close to certain as anybody could be in that situation that it went south. Where we then went was to work out where the last ping was, knowing that the aircraft still had some fuel, but that it would have run out before the next automated ping. We don't know what speed the aircraft was flying at, but we assumed about 450 knots.' Inmarsat passed the relevant analysis to the UK Air Accidents Investigation Branch (AAIB) yesterday. The cause of the crash remains a mystery."
We still have no idea exactly where the aircraft is, how it went down, or what to do now.
How come the frequency information of the signal received by the satellite was saved? What is the purpose of saving all that data in normal operations?
The communications system in question is likely based on TDMA (Time Division Multiple Access). While I have not worked with Inmarsat systems, all the other satcom systems I have worked with log each connection, and various pieces of information regarding the connection. One of these parameters that is logged is the frequency offset (ie the difference between the expected and actual frequency). This is useful from a troubleshooting perspective as it allows you to spot transmitter and receiver components that are drifting out of specification. Some of the more advanced satellite systems (iDirect) will actually log the geographic coordinates of the uplink site, as this plays into the timing requirements for the network. Unfortunately, Inmarsat isn't this aggressive with their timing, so time of flight isn't an issue).
And why did it take three weeks to do that analysis?
This is pure speculation on my part, but I would wager they had to go back through significant amounts of logs in order to characterize the transmitter and receiver components on that particular aircraft. The doppler effect is going to be subtle compared to the thermal drift of the transmitter, so they need to factor that out before they can get at the thermal drift. Also every oscillator and transmitter is different, so they would need to characterize the transmitter that is on that specific aircraft (which is now of course missing).
...si hoc legere nimium eruditionis habes...
Which is why they waited literally days before asking the international community for help? Seriously, significant progress didn't begin until the other countries were allowed to start helping.
The first few days the obvious extrapolations from the normal flight path was searched, and that search was not only conducted by Malaysia, so other countries were involved from the beginning. When they realised things were not as simple as that they asked for more international help. I fail to see what they did wrong, even in hindsight.
The Indian ocean is very deep, it is a remote location and two weeks have passed already. This black box will be harder to find than that of the Air France flight which got lost over the Atlantic. Back then they said that the sender of the black box will run for a month. I don't believe that they will find it this time.
There's no doubt that they'll find it, the question is when. As we speak, the remains of MH 370 are sitting on the bottom of the ocean, under 5,000 meters of water, and they're not going anywhere. Nothing is disturbing the wreckage, so it will just sit there for months, years, or decades until someone comes along. The Titanic sat on the seafloor for 73 years until new technologies made it possible to locate the wreckage, and yet it was remarkably well-preserved given how long it had been underwater. I doubt it will take 73 years- technology has advanced a lot, and continues to advance- but even if it does, the plane will be waiting.
Whether anything useful comes out of the flight data recorders or not is another issue. After 2 years, the data recorders from the Air France flight still worked, I don't know if anyone really knows how long the data would still be good. Solid state memory is pretty indestructible, so if the chips can survive being immersed in saltwater, maybe a long time. The bigger issue is whether the pilot shut down the recorders as well. In the SilkAir crash, the pilot or copilot shut down the flight data recorder and cockpit voice recorder before deliberately putting the plane into a dive. Whoever hijacked this plane seems to have wanted its fate to be a mystery, so there is a real possibility that he shut off the recorders as well. If so, we may find the crashed plane, but if so, we'll never know anything more than what we know now.
As for former P3 tacco, I give the following input: Only better and slower airborne asset is a helicopter. Given the remote location, the only way to get them to the search area would be by ship (destroyer (only a few helos, or aircraft carrier (many helos, but might not be available) So, what other choices do you have? Multi engine fixed wing search aircraft are the only way you could get coverage in this area. So the balance becomes how much area you can cover with radar and visual search patterns. You could search closer with surface ships, but you are talking alot of craft to cover a similar area, plus the lag time to gather them and get them to the location.