ORFEUS deployment. The ORFEUS free-flying astronomy satellite, seen shortly after retrieval by Shuttle Discovery on the second day of Mission STS-51. The long object at far right is the Shuttle's Remote Manipulator System (RMS) arm. The Orbiting & Retrievable Far & Extreme UV Spectrometer (ORFEUS) was a joint German/US research project. Its main areas of study were hot galactic objects and absorption by the interstellar medium. ORFEUS was mounted on a Shuttle Pallet Satellite (SPAS). It was retrieved six days later, and returned to Earth by the Shuttle at the end of the mission. Mission STS-51 flew on 12-22 September 1993.