Discovery flew a dual-deployment mission in September 1993, releasing an advanced communications technology satellite meant to test new high-frequency broadcasting methods, along with a German-American platform carrying ultraviolet and X-ray telescopes to study hot stars and the space between them.
The free-flying telescope platform was later retrieved, and the crew of five carried out a spacewalk to evaluate tools and techniques for the upcoming Hubble servicing mission, then only months away. Repeatedly delayed by technical scrubs, including a pad abort earlier that summer, STS-51 finally flew a productive flight that combined satellite deployment, astronomy and hands-on preparation for one of the programme's defining challenges.
Discovery deployed the Advanced Communications Technology Satellite in September 1993, an experimental spacecraft built to prove technologies that now underpin most satellite communications: steerable spot beams that concentrate bandwidth where it is needed, on-board switching, and operation in the higher-frequency bands that allow much smaller ground terminals.
The flight also carried a German ultraviolet telescope on a free-flying platform, released for six days of astronomy and then recaptured, and a spacewalk by James Newman and Carl Walz to rehearse tools and techniques for the Hubble repair mission that was then three months away and carrying the weight of the agency's reputation.
Getting off the ground took four attempts across two months, with scrubs for a faulty igniter, a suspect sensor and weather — a reminder of how far the Shuttle was from the airline-like operation once advertised. The technologies proven by the satellite it carried are, however, in every satellite broadband terminal sold today.
