NASA's Interface Region Imaging Spectrograph (IRIS) spacecraft launched at 10:27 p.m. EDT Wednesday from Vandenberg Air Force Base, Calif. The mission to study the solar atmosphere was placed in orbit by an Orbital Sciences Corporation Pegasus XL rocket. IRIS is a NASA Explorer Mission to observe how solar material moves, gathers energy and heats up as it travels through a little-understood region in the sun's lower atmosphere. This interface region between the sun's photosphere and corona powers its dynamic million-degree atmosphere and drives the solar wind. The interface region also is where most of the sun's ultraviolet emission is generated. These emissions impact the near-Earth space environment and Earth's climate.
The Pegasus XL carrying IRIS was deployed from an Orbital L-1011 carrier aircraft over the Pacific Ocean at an altitude of 39,000 feet, off the central coast of California about 100 miles northwest of Vandenberg. The rocket placed IRIS into a sun-synchronous polar orbit that will allow it to make almost continuous solar observations during its two-year mission.