Working with hourly pings that had no meta-data — no GPS, no distance, no speed, no heading — satellite company Inmarsat was able to determine the last known location for Flight MH370. Targeted searches in projected flight path area have turned up possible debris sightings.
Inmarasat is a mobile satellite communications company. Their SwiftBroadband service are the most widely used satellite operator in the aviation sector, covering safety communications, weather and flight updates, and in-flight email, internet, and phone services. That means that the missing flight MH370 sent out a ping to the Inmarasat satellites every hour.
Inmarsat had five hours of pings with no meta-data to work with, an indication that the plane was powered on but lacking any GPS, distance, or speed data beyond. In the words of their senior vice-president Chris McLaughlin, "So this really was a bit of a shot in the dark and it's to the credit of our scientific team that they came up and managed to model this."
Location arcs for the missing flight, created by data from the Inmarsat satellite, and provided by the Office of Malaysian PM
The pings were used to extrapolate a last-know-location. That location was then extended into north-south arcs that would be traversed by a straight-line flight, narrowing the search area. The Inmarsat engineering team then compared to records of pings from previous Malaysia Airlines Boeing 777 aircraft. By looking at the frequency spectrum of the ping transmissions, they modelled how the frequency might change slightly as the plane travels through the sky. The frequency of pings shifted as predicted by the Doppler effect, compressing radio waves in the direction of motion and confirming that Flight MH370 took the southernly arc.
The Doppler Effect compresses waves in the direction of motion, and extends them in the reverse direction. Image credit Doleron
The BBC interviewed oceanographer Dr. Simon Boxall, who outlined just how complex it is to pull this much information out of so little data:
"The algorithms and the techniques [Inmarsat] have applied to try and locate - to within a certain area - where the last transmission was made is really quite phenomenal - but also quite tragic because it does show this plane was heading to an open area of ocean.
They've probably crammed almost a year's worth of research into maybe a couple of weeks, so it's not a routine calculation they would ever, ever make.
They've been looking at all the signals they have, all the recordings they have, and processing that many times over to try and pinpoint where the plane's signal came from. Technologically it's really quite astounding."
Ocean models were used to predict how any debris from the plane would drift from the flight lines, and a new area was outlined to focus searches. Australian, Chinese and French search teams have spotted suspected floating material during fly-overs of the regions. However, the material needs to be collected to confirm if it is from the flight or not. The material is spread out over too large of an area for all of it to be related to the flight.
However, even knowing where to search doesn't make this a simple problem to find the black box that could tell us what happened to the ill-fated flight. Going back to the BBC interview with Dr. Boxall, we just don't know that part of the ocean very well:
"It doesn't have a strong interest in terms of the resources on the seabed. We've probably got better maps of the Moon's surface than this part of the seabed."
That the region is so far from land means that search operations will be complicated by lengthly returns-to-base for refuelling. Even so, the combination of using old technology in new ways to direct efforts paired with possible debris sightings is a strong argument that we're looking in the right place.
For more on the search for Flight MH370, the BBC is maintaining well-organized coverage with minimal speculation. For a more light-hearted take on the various conspiracy theories popping up about the flight, join the group discussion on CNN's black hole theory.