On the ramp of Vandenberg Air Force Base in California a Boeing 737 aircraft waits to accompany Orbital Sciences.

On the ramp of Vandenberg Air Force Base in California, a Boeing 737 aircraft waits to accompany Orbital Sciences’ L-1011 aircraft when it takes off with NASA’s Interstellar Boundary Explorer, or IBEX, spacecraft and Pegasus XL rocket. The L-1011 will head for the Reagan Test Site at Kwajalein Atoll in the South Pacific. The 737 will fly ahead of the L-1011 as a pathfinder. Launch vehicle engineers are aboard in the unlikely event their expertise is needed. The IBEX satellite will make the first map of the boundary between the Solar System and interstellar space. IBEX is targeted for launch Oct. 19. The Pegasus rocket will be dropped from under the wing of the L-1011 over the Pacific Ocean to carry the spacecraft approximately 130 miles above Earth and place it in orbit. Photo credit: NASA/Randy Beaudoin, VAFB