NASA’s next scientific satellite, which is scheduled for launch June 26, will
provide the most detailed look ever at the sun’s lower atmosphere or interface
region.

The Interface Region Imaging Spectrograph (IRIS) mission will
observe how solar material moves, gathers energy, and heats up as it travels
through this largely unexplored region of the solar atmosphere. The interface
region, located between the sun’s visible surface and upper atmosphere, is where
most of the sun’s ultraviolet emission is generated. These emissions impact the
near-Earth space environment and Earth’s climate.

The IRIS spacecraft
was designed and built by Lockheed Martin’s Advanced Technology Center in Palo
Alto, Calif. It will launch aboard an Orbital Sciences Corp. Pegasus XL rocket
deployed by the company’s L-1011 aircraft from Vandenberg Air Force Base on the
central California coast.

“IRIS data will fill a crucial gap in our
understanding of the solar interface region upon joining our fleet of
heliophysics spacecraft,” said Jeffrey Newmark, NASA’s IRIS program scientist in
Washington. “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.”

IRIS carries an
ultraviolet telescope that feeds a multi-channel imaging spectrograph. The
satellite is the first mission designed to use an ultraviolet telescope to
obtain high-resolution images and spectra every few seconds and provide
observations of areas as small as 150 miles across the sun.

“Previous
observations suggest there are structures in this region of the solar atmosphere
100 to 150 miles wide, but 100,000 miles long,” said Alan Title, IRIS principal
investigator at Lockheed Martin. “Imagine giant jets like huge fountains that
have a footprint the size of Los Angeles and are long enough and fast enough to
circle Earth in 20 seconds. IRIS will provide our first high-resolution views of
these structures along with information about their velocity, temperature and
density.”

After launch, IRIS will travel in a polar, sun-synchronous
orbit around Earth, crossing nearly directly over the poles in such a way that
it moves over the equator at the same local time each day. The spacecraft will
orbit at an altitude range of 390 miles to 420 miles. This orbit allows for
almost continuous solar observations on IRIS’ two-year mission.

NASA’s
Ames Research Center in Moffett Field, Calif., will provide IRIS mission
operations and ground data systems. The Norwegian Space Centre in Oslo, Norway,
will provide regular downlinks of science data. NASA’s Launch Services Program
at the agency’s Kennedy Space Center is responsible for launch management.

IRIS is a NASA Small Explorer Mission, which the agency’s Goddard Space
Flight Center in Greenbelt, Md., manages for the Science Mission Directorate in
Washington. The goal of the Explorers Program is to provide frequent flight
opportunities for world-class scientific investigations from space utilizing
innovative, streamlined and efficient management approaches within the
heliophysics and astrophysics science areas.

Other IRIS contributors
include the Smithsonian Astrophysical Observatory in Cambridge, Mass.; Montana
State University in Bozeman, Mont.; Stanford University in Stanford, Calif.; and
the University of Oslo in Norway.