A group of amateur sky-watchers has succeeded in tracking the movements of a recently-launched unmanned US spaceplane.
Nine metres long with a 4.5m wingspan, the X-37B Orbital Test Vehicle was launched last month in a blaze of reticence.
The Pentagon could hardly deny it existed - takeoff was quite noticeable - but flatly refused to discuss its function.
All the USAF would say was that it was designed to provide "an 'on-orbit laboratory' test environment to prove new technology and components before those technologies are committed to operational satellite programs". Inevitably, there was speculation that the spacecraft's main purpose would be to test new space weapons.
But an international team of amateur satellite-watchers believes it's been able to track the spaceship.
"Now that we amateurs currently have it under 'control', it will be very interesting to see just how the spacecraft is manoeuvered and what its capabilities are orbit-wise," Cape Town-based Greg Roberts, one of the discoverers, told TechEye.
"I fully expect the amateur network to lose the satellite when a major change is made - if it can in fact do a major change - so it will be a case of hunting for it again. But I am reasonably confident we will acquire it again, so its likely to be a game of 'cat and mouse' for the months remaining whilst the spaceplane is in orbit."
The group reckons the spaceplane's movements suggest it may be being used to carry out surveillance and test new spy equipment.
Roberts says the spacecraft is about 255 miles up, and orbiting the earth every 90 minutes. He and his colleagues in Canada and the US have sighted it six times, in an orbit that takes it from 40 degrees north to 40 degrees south.
It's passing over the same spot on Earth every four days - the usual pattern for US imaging satellites.
And its course, Roberts says, takes it over such photogenic parts of the world as Iraq, Iran, Pakistan, Afghanistan and North Korea.
"As to just what this satellite can do is an interesting question. Obviously it will be unmanned but it has a fair sized 'cargo bay' - why ? - maybe to place other smaller satellites in orbit, or even possibly to retrieve a satellite ( friendly or otherwise?) and return it back to earth," says Roberts.
"On account of its almost Buck Rodgers/Star Trek possible orbital capability it will be an ideal reconnaissance vehicle able to change its orbit to meet the need at the time. Its also an ideal test vehicle for new developments/technologies."
The Secure World Foundation (SWF) agrees that the X-37B would be pretty useless for attacking targets on the ground, but makes perfect sense as a spy plane.
It believes the X-37B contains various sensors including radar, optical, infrared, and signals/electronic intelligence (SIGINT/ELINT) suites. It's known to have a flying time of nine months.
"One of the downsides to using satellites for collecting intelligence is that once they are launched they have a fixed set of sensors and capabilities," said Brian Weeden, SWF technical advisor and former USAF officer.
"The X-37B brings to space the capability to customise the on-board sensor package for a specific mission, similar to what can be done with US reconnaissance aircraft such as the U-2 and SR-71."