The Fourth Decade: 1991–2000

Abstract

Atlantis left the pad almost on time with low-level clouds causing the only delay, of four minutes. Atlantis now carried newly upgraded general purpose computers. The primary payload, the Gamma Ray Observatory, was deployed during FD 3 (7 April), but its high-gain antenna failed to deploy on command. Ross (EV1) and Apt (EV2) performed an unscheduled EVA, the first since April 1985 (STS 51-D) to manually deploy the antenna, permitting the observatory to be successfully released into orbit. The two EVA astronauts had been preparing to exit the Shuttle in the event of something going wrong with the deployment, and as the GRO was lifted out of the payload bay by the RMS, they were checking out their suits. The solar panels of the GRO were opened to their full span of 21 m, although the high-gain antenna it unlatched did not deploy its 5-metre boom. As the procedures for the contingency EVA were faxed up to the crew, Ross and Apt donned their suits and prepared to exit the vehicle. Meanwhile, the crew fired the thrusters on the Shuttle to try to shake the boom loose, but without success. During the 4 hour 26 minute EVA, Ross tried to push the boom free. When that did not work, they set up a work platform to proceed with the manual deployment sequence they had practised four times in the Weightless Environment Training Facility, or WETF, during training. Finding adequate hand holds was a problem, especially during the night time pass of the orbit. While Apt checked to ensure they were not damaging the boom, Ross removed a locking pin and pulled the antenna boom to its deployment position, then used a wrench to lock it into position. While they were outside, they also took the opportunity to perform some of the planned EVA Development Flight Experiment activities by evaluating hand rails, measuring the forces imparted on the foot restraints during the performance of simple tasks, and performing translation exercises. When the GRO was ready for deployment they returned to the airlock, but did not re-pressurise it in case they were needed again. They watched the deployment from the vantage point of the airlock hatch.