NASA spacecraft readied for sun study

A spacecraft that will study the little-understood lower levels of the sun\'s atmosphere has been fully assembled and final testing is under way, NASA says. The Interface Region Imaging Spectrograph or IRIS spacecraft, set to launch in April, will use high-resolution images and data to unravel how matter, light and energy move from the sun\'s 10,240-degree F surface to its 1.8-million degree outer atmosphere, the corona, the space agency said Friday. Such movement powers solar flares and coronal mass ejections to create space weather that can affect Earth. \"This is the first time we\'ll be directly observing this region since the 1970s,\" said Joe Davila, IRIS project scientist at NASA\'s Goddard Space Flight Center in Greenbelt, Md. \"We\'re excited to bring this new set of observations to bear on the continued question of how the corona gets so hot.\" The spacecraft will carry a single instrument, an ultraviolet telescope combined with an imaging spectrograph. The data it gathers will be sent back to Earth where state-of-the-art 3-D numerical modeling will be conducted with supercomputers such as the Pleiades computer at the Ames Research Center in Moffett Field, Calif., NASA said. The IRIS observatory will launch from Vandenberg Air Force Base, Calif., and will fly in a sun-synchronous polar orbit for ongoing solar observations during a two-year mission.