NASA's Sun Satellite IRIS Ready for Launch

IRIS, NASA's newest satellite, was declared ready for flight Wednesday in preparation for takeoff the following day from Vandenberg Air Force Base near Lompoc, Calif.

Designed to provide the most detailed look yet at the Sun's lower atmosphere, the launch of the satellite, which was initially planned for Wednesday, hit a snag when the launch range lost electricity when an equipment failure at a utility substation darkened much of the central coast.

With everything now going according to plan, however, the satellite is planned to launch at 7:27 p.m. PDT on an Orbital Sciences Corporation Pegasus XL rocket.

The drop of the rocket from Orbitals L-1011 carrier aircraft will occur over the Pacific Ocean at an altitude of 39,000 feet, approximately 100 miles northwest of Vandenberg off the central cost of California, south of Big Sur, according to a NASA press release.

Scientists plan on placing IRIS in a polar, sun-synchronous orbit around Earth at an altitude range of 390 to 420 miles where it will 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, drives the solar wind and is also where most of the Sun's ultraviolet emission that impacts the near-Earth space environment and Earth's climate is generated.

Equipped with an ultraviolet telescope capable of obtaining high-resolution images and spectra every few seconds, Jeffrey Newmark, NASA's IRIS program scientist in Washington, said scientists will gain insight through the satellite that has been simply unavailable up to this point.

"IRIS data will fill a crucial gap in our understanding of the solar interface region upon joining our fleet of heliophysics spacecraft," he said in a news release. "For the first time we will have the necessary observations for understanding how energy is delivered to the million-degree outer solar corona and how the base of the solar wind is driven."