Every spotted debris, that gave rise to initial hopes of finding the plane, were analysed and verified. Unfortunately, they were all ruled out as being from the missing plane.
The mystery of the ill-fated plane deepened after the Australian Transport Safety Bureau (ATSB) on May 29 discounted the vicinity of the four acoustic detections recorded by Bluefin-21 in that area.
The acoustic detection recorded on April 5 and 8 was initially said to be from the plane’s black-box and provided some hope in deciphering what may have transpired onboard. Flight MH370 was enroute to Beijing, China on March 8 when it lost contact with ground one hour into flight.
FINDINGS FROM INMARSAT’S RAW DATA
Finding the plane in the world’s third largest ocean is like looking for a needle in the haystack. More than anything else, one may ask whether the authorities involved are looking at the right place? Thus, is it imperative to continue the search in the Southern Indian Ocean based on the data provided by satellite owner and operator, Inmarsat?
New York-based CNN Aviation Analyst and science journalist, Jeff Wise in an email interview with Bernama provided some insight into the data provided by Inmarsat based on the pings received by the satellites.
He began by saying the frequency that the electronic “pings” were received at, were not quite what they should have been, given all that Inmarsat knew about the system.
“They were able to calculate that the discrepancy was due to the fact that the satellite’s orbit had a slight wobble to it. The amount that this (wobble) changed the transmission frequency matched a plane in the southern hemisphere, but not the northern hemisphere”, he said.
He explained this further in his article, “Where The Missing Plane Went”, published in the ‘Slate’, a United States English language online current affairs and culture magazine, in which he said in the case of MH370, the satellite communication equipment was programmed to assume that the Inmarsat satellite was orbiting over a fixed position at the equator.
However, in fact, its orbit has a slight wobble. During the hours the plane went missing, the satellite was above the equator, moving first north, and then south with increasing speed. This error in calculating the satellite’s position means that the plane’s electronics failed to correctly compensate for its own velocity”, he said.
UNDERSTANDING INMARSAT’S DATA
Wise said that the easier way to understand the nature of the Inmarsat data is to imagine that a drunken man taking a motorboat and going around on a pond in a thick fog.
You’re standing on the shore and want to know where he is. You have a foghorn, and that every time you blast it, he immediately blasts his foghorn in reply.
The sound of his foghorn tells you two things. First, knowing the speed of sound and the man’s reaction time, you can work out how far away he is by how long long it takes for you to hear his foghorn blast.
“You won’t know his exact location, but you’ll know the radius of an arc that he is in. In the case of the Inmarsat data, this would correspond to the so-called ping rings, the final one being the famous northern and southern arcs”, he explained.
According to Wise, the second clue that can be gleaned from the man’s foghorn is the frequency of the sound, which will tell whether he’s going away from or coming toward the shore.
This, he said, is thanks to the Doppler Effect, the same phenomenon that makes a train whistle sound higher-pitched when it’s coming closer and then suddenly lower once it zooms past.
“If you know the original frequency of the man’s foghorn, the difference between that and the pitch of the sound you receive will let you determine his speed, whether he is moving closer or further away, but not his total velocity. In the case of MH370, the equivalent data is called burst frequency offset (BFO)”, he noted.
WHY FINALLY THE SOUTHERN INDIAN OCEAN?
“Understanding all this, we can at last make sense of the mysterious BFO chart, which the authorities did not include any BFO or ping timing numbers when they released their report on March 25.
“Essentially, if we derive the distances from the timing offset, and the instantaneous speeds from the frequency offset, we have two solid sets of clues as to how the plane was moving”, he noted.
According to Wise, just after the plane disappeared from radar, the plane’s position error would have made a northbound plane’s transmission frequency too high, then after a few hours the satellite velocity error would have made it too low.
Conversely, he said, in the early hours after its disappearance, position error would have made a southbound plane’s frequency too low, but then satellite velocity error would have gradually made it get higher.
“Because the satellite’s velocity error becomes so dominant toward the end of the flight, and because that error varies strongly with the latitude at which the plane happened to be, the BFO value basically tells you where along the final ‘ping arc’ the plane was when it neared the end of its flight.
“And this, we can assume, is why the authorities have been searching the particular stretch of ocean they’re looking at now”, he added.
Thus, with the available data, and for the time being, the Southern Indian Ocean corridor is the right place to look for the plane.