Amateur astronomers have glimpsed beneath a cloak of secrecy shrouding the military's miniature robotic space shuttle, which was launched last month on a trial run.
The robotic spaceship, which resembles a miniature space shuttle, has spent an unprecedented 15 months in orbit.
On Friday evening, the Air Force's second top secret Orbital Test Vehicle is scheduled to launch from Cape Canaveral Air Force Station in Florida.
The hush-hush mission of a robotic miniature space shuttle, known in military parlance as the "Orbital Test Vehicle," or X-37B, is heading for a California landing this week, the Air Force said Tuesday.
The military's classified mini-space shuttle landed itself just after dawn on Saturday at Vandenberg Air Force Base, Calif.
The Air Force says it is using the experimental space plane to test technologies, but provides no details.
The Air Force's secrecy-shrouded unmanned space plane returned to Earth early Friday.