The science behind search for missing MH370

The science behind search for missing MH370

As a physicist, I was excited to see how a complicated problem involving the search for Malaysia Airlines Flight MH370 was solved using very limited data.

Scientists thinking out of the box formulated a solution using well-known scientific principles in a fine example of scientific creativity. In the case of MH370, which disappeared on March 8, the radar transponder and the aircraft's Communication Addressing and Reporting System (ACARS) were mysteriously switched off about an hour after take-off, when it was over the South China Sea.

ACARS is the system that feeds information about the aircraft's location, altitude, speed and heading to a ground station, either directly by radio waves or via a satellite link.

Without this information, an aircraft cannot normally be located once it is out of range of civilian radar.

In this case, however, military radar detected MH370 changing course and heading west, with its last known radar contact somewhere between the Strait of Malacca and the Andaman Sea.

Six "pings", or handshakes, one every hour, between the aircraft and a satellite known as Inmarsat 3-F1 also suggested that the aircraft remained in the air for another five hours before its fuel was depleted.

Assuming a maximum cruising speed of 450 knots, this produced an enormous search area with a radius of more than 4,000km.

Inmarsat 3-F1 is a geostationary communication satellite located at longitude 64.5 degrees east, 35,800km above the equator.

The aircraft's response to the satellite's hourly "pings" would normally contain at least the aircraft's position and heading. But in this case, the signal was empty because ACARS was not active.

How then, were the scientists and engineers at Inmarsat, the company that operates the communication satellite, able to determine that MH370 headed towards the southern Indian Ocean?

They began by making use of the time delay between the satellite sending out the ping and the response from the aircraft to figure out the distance of the aircraft from the satellite.

However, timing alone could not pinpoint the aircraft's location. At most, an arc on the earth's surface equidistant from the satellite could be drawn.

Together with the estimation of the minimum and maximum speed of the aircraft, the possible final location of the plane was narrowed down to two "corridors".

One extended northwards into Central Asia, and the other one went south to the Indian Ocean. This information was released to the public on March 15.

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