A robotic space plane is flying in Low Earth orbit and nobody knows why.
While intelligence gathering is widely regarded as the best explanation, no one can say for certain what it could be.
"That question implies that it has a single, rational mission. And I don't think it does," said John Pike, director of GlobalSecurity.org.
[...] The Secure World Foundation, a non-profit based in Broomfield, Colo., published a 2010 report on the craft. It speculated the space plane's most likely purpose was for intelligence gathering and said the vessel had a low probability of other uses, such as satellite repair.
Whatever its real purpose, the X-37B has very real capabilities. It travels low in orbit, staying around 177 to 804 kilometres above the Earth at a cruising speed of about 17,500mph (28,163kph).