The IRIS mission

The Interface Region Imaging Spectrograph (IRIS) Small Explorer's (SMEX) science investigation is centered on three themes of broad significance to solar and plasma physics, space weather, and astrophysics. Which types of non-thermal energy dominate in the chromosphere and beyond? How does the chromosphere regulate mass and energy supply to the corona and heliosphere? How do magnetic flux and matter rise through the lower atmosphere, and what role does flux emergence play in flares and mass ejections? Here we briefly discuss the rationale for these goals, the IRIS mission and its hardware, and the current state of instrument development.