Astro-1 was the first space shuttle mission dedicated exclusively to astronomical observations since the start of shuttle flights in 1981. When the development of the Astro telescopes was proposed in the late 1970s, many astronomers hoped that the space shuttle would provide relatively easy and vastly expanded access to space for small and moderate-sized telescopes, such as those that were being launched on sounding rockets. Such vehicles typically provide an experimenter with only 5 min to collect data at high altitudes, enough to get a brief measurement of 1 or 2 bright objects. The prospect of a week or more in orbit (actually, up to 28 days were then contemplated by NASA officials), collecting data on hundreds of celestial objects 24 hours per day, was more than enough of an incentive to overcome the concern that working in the shuttle world (as it came to be known at NASA) might not be so easy for academic scientists.
An additional attraction offered by the shuttle-attached-payload program was the promise of multiple flights of an individual instrument. This approach allows for repairs, modifications, and calibrations to be performed between missions. It was also supposed to make space science more like laboratory experimentation and provide opportunities to train graduate students and young scientists in the development of space hardware. Finally, the new approach was expected to reduce the need for extremely high-level quality assurance, and its associated costs, because occasional instrument failures could be tolerated in a program of this type.
More than one decade after they were conceived, the telescopes of the Astro-1 mission were finally launched aboard the space shuttle Columbia. During the mission, both of the shuttle computer terminals used by the crew to control the Astro-1 instruments overheated and had to be shut down. We recovered from these events by devising a new operating procedure in which the crew pointed the UV telescopes at the objects of interest with a joy-stick control (similar to that on a simple video game) while the ground-support team controlled the telescopes by up-linking commands directly to the computers in the telescopes, bypassing the malfunctioning terminals on the shuttle.
Averaged over the 7-day portion of the mission devoted to scientific operations, HUT achieved a net observing efficiency (on-target time divided by total clock time) of 25%, while the three other Astro telescopes simultaneously gathered data. Comparison with other missions reveals that this is an excellent level of efficiency for a complex astronomical satellite in low-Earth orbit, especially considering that only 24 hours were used for all the preparations before the observations began. During the Astro-1 mission, HUT obtained observations of 77 different objects, with multiple observations made of some of them, totaling nearly 40 hours. Although only a portion of the data has now been analyzed in detail, it is already clear that HUT and the other Astro telescopes are providing important new insights in many branches of astronomy. Because of this success, NASA officials have decided to conduct a second mission, dubbed Astro-2, currently scheduled for launch in 1994.