And check out this fact sheet for more background on the Air Force's OTV spacecraft, which evolved from NASA's former X-37B program.

IMAGE: A United Launch Alliance Atlas V rocket with the Air Force's Orbital Test Vehicle rolls out to its Space Launch Complex-41 launch pad arriving at 11 a.m. EDT today. The OTV, also known as the X-37B, supports space experimentation, risk reduction, and concept of operations development for long duration and reusable space vehicle technologies. Photos by Pat Corkery, United Launch Alliance.