International Ultraviolet Explorer

Explorer 57, IUE

Mission Profile

International Ultraviolet Explorer (IUE, Explorer 57) was a joint NASA/ESA/UK science satellite launched on 26 January 1978 aboard a Thor-Delta 2914, operating as a UV observatory for nearly 19 years — far exceeding its planned 3-year lifetime. Positioned in a geosynchronous orbit for continuous observational access, IUE functioned essentially as a space-based spectroscopic telescope available to visiting astronomers for time-allocated observing runs, similar to a ground-based observatory. It conducted UV spectroscopy of stars, galaxies, nebulae, comets, and solar system objects, accumulating over 100,000 spectra in archives still actively used today. IUE's discovery highlights include the first UV light curve of a Type II supernova (SN 1987A) and detailed studies of stellar chromospheres and mass loss from hot stars.