FUSE (Far Ultraviolet Spectroscopic Explorer) was a NASA ultraviolet astronomy satellite. A MIDEX (medium-class Explorer) mission, it carries four 0.35-m far ultraviolet (UV) telescopes each with an ultraviolet high resolution spectrograph. The detectors covered the far ultraviolet band from the hydrogen ionization edge at 91 to 119 nanometers (nm), just short of the Lyman alpha line at 122 nm. These far UV spectra were used to measure the abundance of deuterium in the universe, as well as study helium absorption in the intergalactic medium, hot gas in the galactic halo, and cold gas in molecular clouds from molecular hydrogen lines.

 

The last operational reaction wheel on FUSE stopped workingon 12 July 2007. Attempts to restart any of the reaction wheels were unsuccessful. Although the telescope itself remained in excellent condition, the satellite was incapable thereafter of the fine pointing control required to acquire useful science data and the mission was terminated.

 

launch date	Jun 24, 1999
launch vehicle	Delta 7925
launch site	Cape Canaveral
mass	1,400 kg
orbit	753 × 769 km × 25.0°