The US Air Force's top-secret X-37B spacecraft is set to land sometime in the next few days at the Vandenberg Air Force Base.
[[mario cart]] It will be the US' first ever autonomous re-entry and runway landing.
"Space professionals from the 30th Space Wing will monitor the de-orbit and landing of the Air Force's first X-37B, called the Orbital Test Vehicle 1 (OTV-1)," says the Air Force in a statement.
"While the exact landing date and time will depend on technical and weather considerations, it is expected to occur between Friday, December 3, and Monday, December 6, 2010."
Amateur astronomers have had a high old time tracking the movements of the elusive craft. At one point it seemed to disappear, until a South African skywatcher spotted it in a new orbit five days later.
The landing date was to be expected, given that the craft has been aloft since April and one of the few known facts about it is that it has a 270-day maximum flight time.
The 4.9 ton spacecraft looks rather like a miniature space shuttle. It measures a little under nine meters long and has a wingspan of 4.3 meters. It's currently in orbit at around 180 miles high.
Its true purpose has been the cause of much debate. The military says the mission was intended to test guidance, navigation and control systems for autonomous orbital flight. Inevitably, though, there has been speculation that it could be used for other, more aggressive purposes.
Another x-37B is currently under construction and is expected to launch next spring.