The search for missing Malaysia Airlines flight MH370 is pushing satellite technology to its limits, says an Australian satellite expert.
At any given time there are over 1000 active satellites hurtling around the earth but when it comes to locating a specific object, even one as big as a plane, it isn't simply a matter of pointing the satellite in the right direction.
While the majority of satellites in the sky are for communication purposes, orbiting at a height of tens of thousands of kilometres in order to maintain a static position relative to the earth, there are a few dozen that have the right sensors and suitable orbit radius to capture images of the earth at a level of detail that can be suitably analysed.
According to university researchers, the most able satellites for a search-and-rescue task hover at an altitude of around 700 kilometres and move at a pace of six to eight km/sec or tens of thousands of kilometres an hour, circumnavigating the earth several times a day.
However, being in the right place at the right time isn't enough, said Matthew Adams, manager at Landgate's satellite remote sensing services, who said that despite their celestial presence satellites can still be obscured by worldly elements.
"You can't see through cloud with an optical satellite," Dr Adams said. "It's like if you're flying on a plane when it's foggy: you look down but can't see the ground."
The other factor that determines the image quality is the resolution, with some satellites capable of producing images where a single pixel (dot) represents 25 cm on the ground. This is about the same scale of a thumbnail image, smaller than a passport photo, which become grainy as you zoom into a particular area.
And before producing a complete image, satellites must complete several passes of an area spanning several kilometres.
It's far from a perfect science, he said.
"This effort is really pushing technology to its limit because you're not expecting to find a whole plane, you're looking for debris of various size," he said.
It's like if you're flying on a plane when it's foggy.
It also helps to be looking in the right spot.
On Friday the Australian Maritime Safety Authority announced the search was being redirected 1100 kilometres north to a 319,000 square kilometres patch of ocean about 1850 kilometres west of Perth.
The Australian Geospatial-Intelligence Organisation, formerly the Defence Imagery and Geospatial Organisation, would re-task satellites to the new image area, identified based on new credible leads in the search for the missing Malaysia Airlines flight MH370.
Dr Adams also said a similar co-ordinated effort took place a few weeks ago via the international charter: space and major disasters' network.
Days after the plane went missing, the Chinese requested the Charter's 20-plus member countries, including Australia, redirect their satellites to the region to locate the missing aircraft.