The X-37B is a robotic spacecraft which resembles NASA's old space shuttle. In fact, it started as a NASA project in 1999 before being transferred to the United States Department of Defense in 2004. The X-37B has been orbiting Earth off and on since April 2010, with some flights lasting as long as 780 days in orbit.
"I only wish the seeing had been better so I could get more details," says Smith. Maybe next time. Thanks in part to the efforts of amateur satellite observers, we usually know where the X-37B is. Local flyby predictions may be found at Heaven's Above.