After six months in orbit, the U.S. Air Force X-37B UOV (unmanned orbital vehicle) is proving elusive to amateur astronomers. This international collection of sky watchers have proved remarkably adept at spotting orbital objects in the past, including classified ones like the X-37B. One notable incident occurred two years ago, 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 tend to cluster together), the satellites tend to come down as a few fragments, rarely is anyone, or anything man-made, 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 has become 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.
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), and capable of staying in orbit for 9 months. The payload bay is 2.1x1.4 meters (7x4 feet). When returned to earth, it will land 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). The Space Shuttle is 56 meters long, weighs 120 tons and has a payload of 24 tons.
The X-37B is a classified project, so not many additional details are available. It's been in development for eleven years, but work was slowed down for a while because of lack of money. A second X-37B is now being built, and is to be launched next year.
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.