China should put aside doubts and act quickly to recover flight MH370's black box, Chinese scientists say.
Answers to vital questions such as why the plane veered off course from Kuala Lumpur to Beijing on March 8 and out over the southern Indian Ocean, would probably be found in the plane's rugged recording devices, but China needed more information to find them, scientists said.
They said information released by Malaysian authorities had been vague or incomplete, impeding the search.
Professor Fu Xiongjun, an image and signal processing researcher with the Beijing Institute of Technology, said he had doubts about the Malaysian government's search capabilities and hence its announcement. But the conclusion by Western experts that the flight came to a tragic end 2,500 kilometres southwest of Perth had to be accepted.
Yin Junjun, a research fellow on radar signal interpretation with Tsinghua University in Beijing, said that to find the Boeing 777, investigators would need data from at least three satellites to fix its last co-ordinates.
She said if data was recovered from fewer than three, calculations about the plane's location would be unreliable, if not impossible to make.
"Malaysian authorities have made a very definite conclusion on the plane's loss, and I believe it because they have data from more than one satellite," Yin said.
She said the technique of tracking planes with satellite "pings" was based on science that was two centuries old.
Austrian physicist Christian Doppler proposed in 1842 that an observer could detect an object's position based on a change in sound wave frequency. It's the theory that helps drivers detect if a siren is approaching or retreating. The shifting frequency, known as the Doppler effect, can determine an object's relative speed.
Using that principle, satellites can help determine a plane's location. Each hour a satellite received a "ping" from the missing plane and recorded a brief pulse of electromagnetic waves. Yin said that by analysing the wave patterns, investigators might be able to pin down the location.
"The method is simple in theory, but difficult in practice," she said.
Professor Wang Xiuming, a geophysicist with the Chinese Academy of Sciences' Institute of Acoustics, said that given the breadth of the search zone, the plane might not be found without years of effort and at a very high price.
High-resolution sonar imagers can identify objects as long as five metres on the ocean floor at more than 3,000 metres deep, but they can only scan an area about a dozen kilometres wide. Searching the entire floor area would require many ships and many years.
Even the best sonar images are not clear enough to identify plane wreckage, so a search team would need to lower a deep-sea submersible with a camera, which would be costly and time- consuming.
"If the government is determined to find the plane, we will find it sooner or later," Wang said.
But time is working against investigators.
Jiang Yan, chief engineer with the Shanghai Salvage Company under the Ministry of Transport, told China Central Television that China did not have the ability to retrieve wreckage or black boxes from a depth beyond three kilometres.
"Only the United States, Norway or France have the technology and experience," he said. "After April, the weather in the area will become so bad that most search efforts will have to be postponed."
Professor Fu Xiongjun, an image and signal processing researcher at the Beijing Institute of Technology, said that using the raw data, Chinese researchers might reach the same conclusion as Malaysian officials.
"From the first day, China had a dilemma. Most of the passengers on the plane are Chinese but we have made the least discoveries," Fu said. "The embarrassing situation was probably why the government urged Malaysia to be more transparent and asked for the satellite data."