Gliding in on autopilot, the unmanned spacecraft touched down at California’s Vandenberg Air Force Base around 1248 GMT. The landing marks the end of X-37B’s fifteen month haul, and only its second venture into space. Just what it was doing up there all this time remains top secret.
The successful landing was announced by the USAF on the Vandenberg website, but the statement gave little away.
“Team Vandenberg has put in over a year’s worth of hard work in preparation for this landing and today we were able to see the fruits of our labor,” said Col. Nina Armagno, 30th Space Wing commander at Vandenberg. “I am so proud of our team for coming together to execute this landing operation safely and successfully.”
Vandenberg also said that the spacecraft had conducted “on-orbit experiments” during its 469 days in orbit – more than double the 225 days spent in space by OTV-1, X-37B’s sister ship. What experiments were performed exactly was not illuminated on.
Launched back in March 2011, X-37B was initially meant to only stay in orbit for around 270 days. However, the USAF extended the mission, calling the mission a “spectacular success”.
“With the retirement of the space shuttle fleet, the X-37B OTV program brings a singular capability to space technology development,” said X-37B programme manager Lt. Col. Tom McIntyre in a statement. “The return capability allows the Air Force to test new technologies without the same risk commitment faced by other programs. We’re proud of the entire team’s successful efforts to bring this mission to an outstanding conclusion.”
Speculation over the purpose of X-37B has been running rampant. Some have speculated that X-37B may deliver a space-based weapon into space, capable of either targeting positions on Earth or destroying enemy satellites.
Others have suggested that X-37B could be spying on the new Chinese space station, Tiangong.
"Space-to-space surveillance is a whole new ball game made possible by a finessed group of sensors and sensor suites, which we think the X-37B may be using to maintain a close watch on China's nascent space station," the editor of the British Interplanetary Society's magazine Spaceflight Dr David Baker told the BBC in January.
However, owing to the speed of both the spacecraft and the space station rushing past each other at thousands of metres a second, surveillance would prove tricky.
"I would go as far as to say, 'no chance'," said Brian Weeden of the Secure World Foundation. “If the U.S. really wanted to observe Tiangong, it has enough assets to do that without using X-37B.”
National security analyist John Pike suggested that the plane was simply "part of a strategic deception program", adding "I don't think this thing has a mission that would go beyond bewildering the Chinese.”
"It looks good; it sounds neat and everything. I assume they put little space experiments, some damn little camera in there. I'm sure the payload bay is chock full of little goodies they're flying on an opportunity basis.
"But, if the thing was actually useful for some national purpose, it would have flown a long time ago because somebody would have been hot to trot."
Amateur astronomers discovered last May that the first X-37B flew over North Korea, Iran, Iraq, Pakistan and Afghanistan, strengthening the argument that the craft is being used for high-tech espionage purposes.
However, more pragmatic analysts have suggested that the extended flight was simply a job-saving exercise. By showing off X-37B’s incredible fuel efficiency, the USAF may be able to stave off budget cuts coming in during 2013-2017 that would consign the office that developed the X-37B to the dole queue.