A shot of the craft after it landed at Vandenberg Air Force Base in 2012. (Courtesy photo)

A mysterious unmanned space craft touched down at Vandenberg Air Force Base this morning after spending 674 days in orbit.

The X-37B Orbital Test Vehicle was launched by the U.S. Air Force, which has kept details about the mission closely guarded. While many suspect its goal may be intelligence-related, the Air Force only said the program “supports space experimentation, risk reduction and concept of operations development for long duration and reusable space-vehicle technologies.”

For Vandenberg, situated right outside Lompoc, the successful landing affirms the base’s ability to execute big-ticket aeronautical missions.

“I’m extremely proud of our team for coming together to execute this third safe and successful landing,” Col. Keith Balts, 30th Space Wing commander, said in a press release. “Everyone, from our on console space operators to our airfield managers and civil engineers, takes pride in this unique mission and exemplify excellence during its execution.”

Boeing has only built two of the X-37B crafts, which are operated by the Air Force’s Rapid Capabilities Office. Measuring slightly more than 29 feet in length, they are the world’s smallest unmanned orbital vehicles. It weighs 11,000 pounds and has solar panels that unfurl to charge its batteries once in orbit.

Although the base has been involved with the program since 2008, this may be one of the last landings of an X-37B at Vandenberg. The Air Force has leased space at the Kennedy Space Center in Florida and has said it plans to relocate the program there. The Air Force is also looking into whether an existing runway used to land the space shuttle in Florida could be used for landing future missions.

“Officials anticipate multiple missions will be required to satisfy the test program objectives, but the exact number of missions has not been determined,” an Air Force statement said.