The US Air Force launched its X-37B orbital spaceplane on Apr 22. The
Atlas V 501 rocket put the X-37B in low Earth orbit about 17 min after
launch. The orbit is probably somewhere in the 430-450 km range with an
inclination between 28 and 40 deg, possibly around 33 deg. The Centaur
AV-012 rocket separated at 0010 UTC on Apr 23 and then made a second
burn at 0035 UTC to deplete its remaining fuel, sending it into solar
orbit. The Atlas V is overpowered for missions like these, so the
Centaur ends up with lots of extra propellant. An escape-orbit disposal
was also used for the final stage from the AV-017 DMSP launch last year.
AV-012 appears to be the first United States space vehicle in solar
orbit whose orbit around the Sun is officially secret.