UPDATE 4.20PM: How investigators figured where MH370 can possibly be.. Malaysian authorities disclosed that satellites picked up faint electronic pulses from the passenger jet after it went missing from radar systems, but the signals or pings gave no information about where the stray jet was heading and little else about its fate. A “ping” is an indication that the aircraft’s maintenance troubleshooting systems are ready to communicate with satellites. Tim Farrar, a satellite communications consultant, who founded California-based technology consultancy firm He said an aircraft has two types of contact that was last sighted – a radar transponder and a satellite ping – but both are not linked to the other. He compared the radar transponder with the planes “Bluetooth”. The military radar transponder should be able to locate the plane the same way a bat navigates by echolocation – it sends out an amplified signal that will reflect off the metal of the plane and returns with additional information such as the planes identification. Radar should be able to pick up on the location of any vessel with a transponder, especially military radars which are much more sensitive than civilian radars, he said. But military radar systems are looking for hostile forces and have missed civilian aircraft in the past, said Farrar Even with its transponders turned off, a plane could still be connected to the Inmarsat network which received affirmative “pings” from the aircraft terminal that it was still active. Farrar then brought out the big question: can the Inmarsat network accurately show where the plane was located? According to him, the terminal which MH370 had onboard seemed to be a Swift64, which he said is not among the latest SwiftBroadband terminals which had yet to be approved for aeronautical safety services. The Swift64 uses a global beam to maintain network registration and receive “pings” and this makes it harder to rule out locations compared with if it was using regional beams. Accuracy was already compromised through the global beam, said Farrar, but looking at the position it was in, there were two potential ways to measure its location on that vast global beam. The first is to look at the time delay of transmission from signal to satellite, which will determine a range from the sub-satellite point that will narrow down a circle on the Earths surface. The second is to measure the power level of the signal received by the satellite. If you know the transmission power accurately enough and know how much power was received, you can estimate the angle it came from. This again would produce a similar range from the sub-satellite point, expressed as a circle on the Earth’s surface. We can see that the search locations are based on exactly these curves at a given distance from the sub-satellite point.
Posted on: Sun, 16 Mar 2014 08:32:30 +0000
Trending Topics
Recently Viewed Topics
© 2015