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HMS Elusive

作者:樊回塥    发布时间:2019-03-08 04:15:06    

By Duncan Graham-Rowe IF SOME reports are to be believed, China can now pinpoint the position of British and American nuclear submarines. But while Beijing may have got its hands on classified data showing how they might be tracked from space, experts contacted by New Scientist say that China almost certainly remains in the dark about the movements of the West’s submarines. Last week, Jon Kyl, a Republican member of the US Senate Intelligence Committee, announced that details of a classified research project were given to China in 1997 by Peter Lee, a physicist then working for the aerospace and electronics company TRW in Redondo Beach, California. The project, which aims to detect submarines using satellite radar, is run by the Lawrence Livermore National Laboratory, also in California. Ian Robinson, an expert on remote sensing at the University of Southampton, says that the basic technology has been in use for some 20 years. He uses it to study the internal waves that occur at the ocean’s thermocline, the region where warm surface waters form a boundary with the colder, denser waters of the deep ocean. Movements of the thermocline cause tiny variations in sea level, which can be detected by sensitive radars mounted on satellites such as the European Space Agency’s ERS-2. The US military possesses similar satellites. And in theory, they could track submerged submarines. These tend to travel just below the thermocline, which lies anywhere between 10 and 200 metres below the surface, because this is where they are least visible to sonar. A submarine’s wake could disrupt the thermocline, amplifying its internal waves and causing a displacement of water at the surface (see Diagram). However, this would only be easily detectable if the submarine was at the right depth, and moving in the right speed and direction in relation to ocean currents. It would be “a bit of a hit or miss affair”, says Robinson. Reports suggesting that subs can be detected “miles” below the surface are certainly untrue, experts say. Andy Best, a sonar expert at Marconi Underwater Systems near Portsmouth, says most military submarines don’t descend to such depths. The US Navy’s Los Angeles sub, for example, can only dive to 450 metres. Civilian remote sensing experts concede that scientists working on the classified project may have developed sophisticated signal-processing software to improve the likelihood of spotting a submarine’s wake. But even if this technology is better developed than they suspect, China won’t be able to make much use of it. At present,

 

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