A U.S. Air Force X-37B UOV (unmanned orbital vehicle) landed October 17th under software control after 675 days in orbit. Previously an X-37B landed on June 16th 2012 after 469 days in orbit. The first mission ended on December 3rd 2010 after 224 days in orbit. The air force reports few details about the X-37B but has said it plans to launch another one in 2015.
The official endurance of the X-37B was originally about 280 days. The real endurance appears to be nearly three times that. The long endurance is largely because the X-37B carries a large solar panel, which is deployed from the cargo bay, unfolded and produces enough power to keep the X-37B up there for a long time. The air force has not reported what t the X-37B has been doing up there all this time. The air force has revealed that it is designing an X-37C, which would be twice the size of the X-37B and able to carry up to six passengers. Think of it as Space Shuttle Lite, but robotic and run by the military, not NASA.
The X-37B is a remotely controlled mini-Space Shuttle. The space vehicle, according to amateur astronomers (who like to watch spy satellites as well), appears to be going through some tests. The X-37B is believed to have a payload of about 227-300 kg (500-660 pounds). The payload bay is 2.1x1.4 meters (7x4 feet). As it returned to earth, it landed by itself (after being ordered to use a specific landing area.) The X-37B weighs five tons, is nine meters (29 feet) long and has a wingspan of 4 meters (14 feet). In contrast the Space Shuttle was 56 meters long, weighed 2,000 tons and had a payload of 24 tons.
The X-37B is a classified project, so not many additional details are available. It's been in development since 2000 but work was slowed down for a while because of lack of money. Whatever the X-37B is now doing up there has been convincing enough to get Congress to spend over a billion dollars on it. What makes the X-37B so useful is that it is very maneuverable, contains some internal sensors (as well as communications gear), and can carry mini-satellites, or additional sensors, in the payload bay. Using a remotely controlled arm, the X-37B could refuel or repair other satellites. But X-37B is a classified project, with little confirmed information about its payload or mission (other than testing the system on its first mission). Future missions will involve intelligence work, and perhaps servicing existing spy satellites (which use up their fuel to change their orbits.) The X-37B is believed capable of serving as a platform for attacks on enemy satellites in wartime. It is believed that recent missions may have also involved testing new spy satellite components in space, where the harsh environment, especially the radiation, can have unpredictable effects on microelectronics.
The X-37B also demonstrated that it could not be easily tracked while in orbit although at times the X-37B could be elusive for amateur astronomers. The international collection of amateur sky watchers have proved remarkably adept at spotting orbital objects in the past, including classified ones like the X-37B. The amateur orbital observer community has concluded that one thing the X-37B tested was how well it could constantly switch positions, and stay hidden. In that respect, the X-37B was a resounding success. That's because these amateur observers are generally very good at tracking what's up there.
One notable incident occurred in 2008 when a U.S. spy satellite fell out of orbit (apparently because of a failure in its maneuvering system). The amateur astronomers were able to track it. If this had not been an American reconnaissance satellite, there would have been no media attention to this, because 4-5 satellites a month fall back to earth. Since most of the planet is ocean, or otherwise uninhabited (humans like to cluster together), the satellites tend to come down as a few fragments, and rarely is anyone, or anything manmade, hit.
Before the Internet became widely used a decade ago, you heard very little about all these injured or worn out space satellites raining down on the planet. But with the Internet, the many thousands of amateur astronomers could connect and compare notes. It was like assembling a huge jigsaw puzzle. Many sightings now formed a pattern, and a worldwide network of observers made visible the movements of hundreds of space satellites. These objects were always visible at night, sometimes to the naked eye, but unless you knew something about orbits and such, they could be difficult to keep track of. These days, a lot of the activity is posted and discussed at http://www.satobs.org/. But the X-37B has proved elusive, and sometimes became a frustrating challenge to the amateur sky watchers. This is pleasing to American air force officials, who designed the X-37B to be elusive to terrestrial observation and the dedicated (and quite effective) amateur satellite watchers gave the X-37B quite a workout.