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NASA's Sun probe IRIS is readied for launch

Paul Sutherland, Feature writer
Apr 22, 2013, 7:00 UTC

Sen—In recent years, a number of space probes have greatly increased our understanding of how our home star, the Sun, behaves. However much remains to be learned.

NASA's latest mission, called IRIS, is currently being prepared for launch in just a few weeks time to discover more about what drives the Sun and to help scientists predict space weather.

IRIS - the Interface Region Imaging Spectrograph - is a NASA Small Explorer Mission that aims to observe how solar material moves, gains energy and heats up in the Sun's lower atmosphere.

It was delivered to Vandenberg Air Force Base in California last week to be fitted inside an Orbital Sciences Pegasus rocket that will be launched from a L-1011 carrier aircraft on 28 May at the earliest.

Solar scientists have only recently begun to find clues to explain an odd aspect of solar dynamics. They want to explain how material flowing from the Sun's surface, or photosphere, actually becomes considerable hotter as it gets further from the Sun and enters its atmosphere, or corona. This seems contrary to common sense.

IRIS mission scientist Joe Davila, of NASA's Goddard Space Flight Center in Greenbelt, Maryland, said: “IRIS will contribute significantly to our understanding of the interface region between the sun's photosphere and corona. This region is crucial for understanding how the corona gets so hot.”

IRIS will fly with a single instrument aboard, an ultraviolet telescope fitted with a multi-channel imaging spectrograph that will help scientists better understand the physical processes occurring above sunspots on the Sun's photosphere. Previous missions such as NASA's now-retired Transition Region and Coronal Explorer (TRACE) have recorded images of this dramatic activity.

Eric Ianson, IRIS mission manager at Goddard, said: “With the high-resolution images from IRIS, scientists will be able to use advanced computer models to unravel how matter, light, and energy move from the sun’s 6,000 Kelvin surface to its million Kelvin corona.

IRIS in orbit

An impression of how IRIS will look in orbit. Credit: NASA

“Scientists will be able to combine data from NASA’s IRIS and Solar Dynamics Observatory and the NASA/JAXA Hinode missions to obtain a more comprehensive understanding of the sun’s atmosphere.”

IRIS's ultraviolet telescope will zoom in on the two layers of the Sun's atmosphere closest to its surface, called the chromosphere and the transition region. In this violently dynamic zone, hot and cold plasma are mixed over an area that stretches from the Sun's surface to several thousand miles high.

Tracking the movement of material and energy through this region will be a crucial part of understanding the Sun's dynamics.

Space scientists hope it will help explain what causes the ejection of solar material, from the steady stream of the solar wind to the explosive eruptions such as flares and coronal mass ejections (CMEs) that can hurl material out into space, threatening satellites and power grids and sparking the aurora.

A video shows how IRIS will be launched and deployed to observe the Sun. Credit: NASA