The NIXT, or Normal Incidence X-ray Telescope, was a sounding rocket payload flown in the 1990s by Professor of the Smithsonian Astrophysical Observatory, to prototype normal-incidence (conventional) optical designs in extreme ultraviolet (EUV) solar imaging. In the EUV, the surface of the Sun appears dark, and hot structures in the solar corona appear bright; this allows study of the structure and dynamics of the solar corona near the surface of the Sun, which is not possible using visible light. A successor program to NIXT, was the TXI (Tunable XUV Imager) sounding rocket program