New Delhi: The X-37B unmanned robotic `mini shuttle` landed at California`s Vandenberg Air Force Base on Saturday morning at 5:48 a.m. PDT (8:48 a.m. EDT, 1248 GMT). The landing drew X-37B program`s second-ever spaceflight to closure, a mission that lasted more than 15 months with objectives that remain shrouded in secrecy.
The US Air Force`s X-37B, is an unmanned reusable spacecraft built by Boeing that has spent more than a year on a classified mission in space.
Measuring 29 feet in length and having a 15-foot wingspan, the unmanned reusable X-37B Orbital Test Vehicle looks like a miniature version of NASA`s now retired space shuttles. The craft, which is 8.9 metres long and 4.5 metres wide, has a payload bay roughly the size of a pickup truck.
The spacecraft, which was launched from Cape Canaveral Air Force Station in Florida in March 2011, conducted in-orbit experiments during the 15-month clandestine mission, officials said. It was second such autonomous landing at the Vandenberg Air Force Base, 130 miles northwest of Los Angeles. Earlier, in 2010, an identical unmanned spacecraft returned to Earth after seven months and 91 million miles in orbit.
The shuttle`s homecoming was set in motion when the stubby-winged robotic X-37B fired its engine to slip out of orbit, then pierced through the atmosphere and glided down the runway like an airplane.
The spacecraft went into orbit on March 5, 2011, but as was the case during its first launch in 2010, very little has been known about its mission. That has led to speculation that the spacecraft is involved in intelligence gathering operations or the testing of new technologies.