Pegasus Launches NASA's IRIS Spacecraft

L-1011 with Pegasus Onboard NASA's Interface Region Imaging Spectrograph (IRIS) spacecraft was successfully launched at 10:27 p.m...

L-1011 with Pegasus Onboard

NASA's Interface Region Imaging Spectrograph (IRIS) spacecraft was successfully launched at 10:27 p.m. EDT Wednesday from Vandenberg Air Force Base, California, by Orbital Sciences Corporation's Pegasus XL air launched rocket.
The IRIS spacecraft was deployed into its targeted orbit approximately 400 miles above the Earth.
Pegasus rocket was air launched by Orbital’s L-1011 “Stargazer” carrier aircraft, a modified Lockheed L-1011 TriStar passenger aircraft. Following a one-hour preplanned positioning flight, the Pegasus rocket was released at approximately 40,000 feet from L-1011 carrier aircraft at 7:27 p.m. (PDT). The first stage ignition occured approximately five seconds after release.
After a 13-minute powered flight sequence, Pegasus launched the 440-pound IRIS satellite into its polar, sun-synchronous Earth orbit.

Pegasus Released

IRIS is a NASA Small Explorer (SMEX) mission designed 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 that impacts the near-Earth space environment and Earth’s climate.
The launch of IRIS marks the 45th overall mission for the Pegasus program. Its launch history now includes 42 launches to orbit, which collectively have deployed more than 80 satellites for Earth and space science missions overseen by NASA; military and technology demonstration spacecraft for the U.S. Department of Defense; and communications and imaging satellites for commercial customers. Pegasus technology has also been used to launch three hypersonic flight experiments in Earth’s stratosphere for NASA’s HyperX program.
The sun-synchronous polar orbit will allow it to make almost continuous solar observations during its two-year mission.
Pegasus is a winged space launch vehiclecapable of carrying small, unmanned payloads (443 kilograms (980 lb)) into low Earth orbit.
Stargazer is capable of carrying a 23,000 kilograms (51,000 lb) payload to an altitude of 12,800 metres (42,000 ft).