On the ramp of Vandenberg Air Force Base aircraft awaits departure for the Kwajalein Atoll and Pegasus XL rocket.

On the ramp of Vandenberg Air Force Base in California, Orbital Sciences’ L-1011 aircraft awaits departure for the Kwajalein Atoll, a part of the Marshall Islands in the Pacific Ocean, with NASA’s Interstellar Boundary Explorer, or IBEX, spacecraft and Pegasus XL rocket. The Pegasus is attached under the wing of the aircraft for launch. Departing from Kwajalein, 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. Then, the spacecraft’s own engine will boost it to its final high-altitude orbit (about 200,000 miles high) — most of the way to the Moon. The IBEX satellite will make the first map of the boundary between the Solar System and interstellar space. IBEX science will be led by the Southwest Research Institute of San Antonio, Texas. IBEX is targeted for launch over the Pacific Oct. 19. Photo credit: NASA/Randy Beaudoin, VAFB