GREENBELT, Md., Jan. 18 (UPI) -- 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.