Missing plane: Searching from space may help
High-definition satellite imagery would seem to be an ideal tool to use in the multinational hunt for a passenger jet that simply vanished nearly a week ago with hundreds of people on board.
Satellites can deliver incredibly detailed images of large swathes of open ocean that can then be scanned on a computer screen for any potential wreckage, seemingly delivering a technological advantage in the hunt for missing Malaysia Airlines flight MH370.
But does searching from space really work?
Hopes of a breakthrough in the investigation were raised briefly this week, when a Chinese government agency released three grainy satellite images it said showed unidentified "floating objects" in the "suspected crash area" of the Boeing 777, which disappeared with 239 people, including six Australians and two New Zealanders, on board.
The pictures, taken by the Gaofen-1 satellite, showed what appeared to be three large floating objects in the South China Sea, about 226 kilometres from the last recorded transponder signal in the waters north-east of Kuala Lumpur and south of Vietnam.
But Malaysian authorities later discounted the theory that the items were remnants of the aircraft.
Malaysia's civil aviation chief, Datuk Azharuddin Abdul Rahman, said surveillance aircraft examined the area identified by the satellite images on Thursday.
"There is nothing. We went there, there is nothing," he said.
Associate Professor Linlin Ge, from the University of NSW's School of Civil and Environmental Engineering, believes that satellite remote sensing can deliver many advantages over traditional air and sea searches using ships and aircraft.
In an article on The Conversation website, published before the Chinese satellite images were discounted, Dr Ge said metallic structures such as the wreckage of a plane could be easily visible on radar images, while satellite imaging radar could also "see" through any cloud and take images day and night.
He said satellites orbited the earth at a height of between 200 and 900 kilometres, and could cover a large area, between 100,000 and 250,000 square kilometres, with a single image collected in only a few seconds.
"It would take an aircraft between 1.5 and 34 hours to cover the same area. A ship will take much longer," he wrote.
"Another advantage of satellites is that, once in orbit, the cameras and radar sensors on board are always on standby. They can be switched on immediately, as soon as the space agencies are informed of an accident, and can be pointed straight at the area around the last known co-ordinates of the aircraft.
"This also makes them much quicker to respond to incidents such as an air crash than the air and sea search vessels."
Dr Ge said there were some limitations, such as if a plane crashed on land and the wreckage was obscured by dense tropical forest.
But in response to the article, Geoffrey Dell, an associate professor in accident investigation and forensics at Central Queensland University, said that "if something sounds too good to be true, it probably is".
"It'll be a while yet before the watershed moment when digital imagery will fully supplant the tedious, hard yards of physical searching, which has been the hallmark of SAR [search-and-rescue] activities for the past 50 years or more," he wrote on The Conversation.
"While the notion of being able to examine hundreds of thousands of square kilometres of ocean, in short order, seems like it'd be just what the doctor ordered, I think the real challenges associated with the practical application of the technology might yet be just beyond our present capability."
Associate Professor Dell said complex algorithms were needed to synthesise areas of interest from digital imagery and, without this, people would need to visually examine all of the images, which would take a long time.
"However, the crowdsourcing of hundreds of thousands of volunteers might make a valuable contribution with the use of effective and reliable algorithms to consolidate consensus tagging of areas of interest," he wrote.
"Albeit, even then, if an area of interest is identified, someone will have to fly out there and take a look. Doubtless it will still [take] significant effort and be a difficult and time-consuming process."
A timeline of events in the disappearance of a Malaysia Airlines jetliner which vanished from radar screens on a flight from Kuala Lumpur to Beijing on Saturday.
Sydney Morning Herald