STS-51

The Advanced Communications Technology Satellite was deployed on flight day 1. This satellite served as a test bed for advanced experimental communications satellite concepts and technology. Its Transfer Orbit Stage (TOS) upper stage fired on time 45 minutes after deployment and boosted the satellite to geosynchronous altitude on the first day of the mission. Another payload on this mission was the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer (ORFEUS) telescope mounted on the Shuttle Pallet Satellite (SPAS) payload carrier. ORFEUS was designed to provide information on how stars are born and how they die, while studying gaseous interstellar clouds. Also in the cargo bay was the Limited Duration Space Environment Candidate Materials Exposure (LDCE) experiment.