For nearly two years, a classified space plane has orbited the Earth.
Soon, it’s coming down.
The X-37B, called the Orbital Test Vehicle, is one of two space planes operated by the U.S. Air Force since 2010. Both resemble the Space Shuttle and, like it, have a cargo bay.
However, the X-37B is much smaller, at 5.5 tons, than the shuttle, which weighed more than 75 tons. They also fly unmanned, which the shuttle couldn’t do.
The space planes are launched into orbit atop a rocket and then glide down for a landing. The primary landing site, Vandenberg Air Force Base in California, began preparing for a landing Monday.
Mission control is based at Schriever Air Force Base in Colorado Springs, Colorado.
The X-37 vehicle is used to test orbital capabilities, according to the Air Force. But the missions themselves are classified. The current X-37 has been in orbit since December of 2012.
On Oct. 8, NASA entered an agreement with the Air Force to house the X-37 at the same Kennedy Space Center facility that once housed the Space Shuttle.
The X-37B is built by Boeing Phantom Works. It began as a NASA project in 1999 before being transferred to the Air Force in 2004.
Watch the X-37 in action in this Newsy video:
Gavin Stern is a national digital producer for the Scripps National Desk. Follow him on twitter at @GavinStern or email him at email@example.com