The X-37B launched into space on May 20 atop an Atlas V rocket on a two-year secret mission, the fourth of its kind. But -- secrecy or not -- this X-37B is also the fourth to be identified by earthling observers, with one respected hobbyist seeing the craft in orbit.

The X-37B, known officially as Orbital Test Vehicle 4, rocketed into space carrying 100 scientific samples for experimental purposes as well as a LightSail, a solar-powered exploration vehicle that's being tested for the first time on this trip. That was pretty much everything the public knew about the flight or exactly what the X-37B, which resembles an unmanned version of the space shuttle, was supposed to be doing. Until now.

"OTV 4 entered the lowest initial altitude of the program," Ted Molczan, a respected satellite watcher, told the news site Spaceflight Now in an article published Wednesday, adding that the still-orbiting satellite is flying closer to Earth than its predecessors did.