The Air Force's secret space plane has been up in orbit for nearly 500 days-a space endurance record. But nearly a year and a half into the mission, the Pentagon still won't say what the X-37B is doing up there, or when it might come back. The U.S. Air Force boosted the robotic X-37B atop the nose of an Atlas-5 rocket in December 2012. Since then it's orbited the Earth thousands of times, overflying such interesting places as North Korea and Iran. The U.S. Air Force will not comment on what kind of missions the X-37B does in space. The service, which doesn't mind talking about the space drone as a technological achievement, clams up when discussing actual missions. Brian Weeden, a former Air Force officer with the Space Command's Joint Space Operations Center and now at the Secure World Foundation, believes that the X-37B is primarily a test bed for new technologies. I think it is primarily an ISR (Intelligence, Surveillance and Reconnaissance) platform for testing new sensor technologies or validating new technologies." Weeden [said]. "The current [flight] has basically been in the same orbit since launch, with only the occasional maneuver to maintain that orbit. That's consistent with a remote sensing/ISR mission." The X-37B is probably testing technologies that might be incorporated into the spy satellites of the future. New cameras, radars, and other sensors could be tested in space and then brought back to Earth for study.