A NASA F-18 and an Orbital Sciences L-1011 carrier aircraft taxi to the runway at Vandenberg Air Force Base, Calif., before taking off on a mission to launch NASA's IRIS spacecraft into low-Earth orbit. IRIS, short for Interface Region Imaging Spectrograph, was launched aboard an Orbital Sciences Pegasus XL rocket released from the L-1011. Photo credit: VAFB/ Randy Beaudoin