L-1011 Drop-Launches NASA's Newest Solar Satellite

By Michael Mecham mecham@aviationweek.com
Source: AWIN First
June 28, 2013
Credit: NASA

NASA reports “a great insertion orbit” for its newest orbiting telescope for studying the Sun’s dynamic temperature bands, which was drop-launched from a former airliner off the central California coast at 7:28 p.m. PDT June 27.

The Interface Region Imaging Spectrograph (IRIS) spacecraft is to operate from about a 400-mi.-high Sun-synchronous orbit, from which it will study solar and plasma physics, space weather and astrophysics to gain a better understanding of how the Sun’s internal convective flows power its atmospheric activity. Spikes in that activity can interrupt electrical grids and disrupt communications satellites.

The launch used a three-stage Orbital Sciences Pegasus XL booster dropped from Orbital’s L-1011 flying at 39,000 ft. about 100 mi. northwest of Vandenberg AFB, Calif. The mission operations center at NASA’s Ames Research Center reported that the solar array deployment and initial systems operations are all nominal.

The mission’s $170 million budget assumes a nominal two-year mission, but there is every likelihood the spacecraft’s 20-cm (8-in.) ultraviolet telescope and spectrograph can operate much longer, given the initial reading on its orbital placement. Principal Investigator Alan Title, a senior fellow at the Lockheed Martin Advanced Technology Center in Palo Alto, Calif., notes that when 1998’s Transition Region and Coronal Explorer mission, another study of the solar photosphere, got an excellent Pegasus placement it lasted for 12 years and was only turned off when a replacement mission was launched.

NASA has been studying the Sun for decades but IRIS will create an unprecedented image scrapbook of solar activity. Its telescope will record the ultraviolet light emitted in the transitional region that stretches from its surface, where temperatures are a mere 10,000F, to its corona, or upper atmosphere, where they reach several million degrees.

Just why the solar atmosphere heats so dramatically in this fashion will be the core of the IRIS studies. There are many thoughts on the subject, including that enormous stores of energy are released by the Sun’s magnetic fields, that energy jets travel through the transitional region, or that powerful acoustic waves are involved.

Spacecraft checkout will take about two months before science operations will begin.

IRIS is a 140-kg. (300 lb.), disk-shaped spacecraft with a power rating of 200 watts. Protruding from the disk is the 3-meter (9.8-ft.) ultraviolet telescope built by the Smithsonian Astrophysical Observatory.

Its multi-channel imaging spectrograph, built by Lockheed Martin Sensing and Exploration Systems from a design collaboration with Montana State University, will observe in the extreme ultraviolet, between 1,200-3,000 angstroms, far higher than previous missions.

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