A step towards joint operations began with the launch of Shuttle mission STS-63 on 3 February 1995, which was to rendezvous with Mir. If the launch missed the five-minute slot, the additional propellant that it would need to complete the rendezvous would jeopardise the deployment and retrieval of a satellite, in which case Discovery was to proceed with its primary mission. Based on prior experience, it had a one-in-three chance of making it. Nevertheless, the launch took place at the opening of the window. Immediately on attaining orbit, two of Discovery’s reaction control system thrusters developed a leak. This led to concern that the nitrogen tetroxide might coat instrumentation mounted on the Mir complex. It was decided that if the leaks could not be stemmed, Discovery would not be allowed to approach within 125 metres of the complex. The problem was solved during the three days of manoeuvres leading up to the final approach, and permission was granted to close in to 10 metres of the androgynous port at the end of the Kristall module. Flown by Jim Wetherbee and Eileen Collins, Discovery approached from below, then, with its nose high and its payload bay facing back, stationed itself directly in Mir’s path. Mir was oriented to align Kristall’s axis along the velocity vector, in order to aim its docking port at the newcomer. On Discovery, Vladimir Titov was responsible for communications with the Mir crew, and had been talking by VHF radio virtually continuously since they established line-of-sight contact. Discovery paused at 300 metres for permission to proceed. From this point, the upward-firing thrusters were not to be used, in order not to blast Mir with efflux.
KeywordsBase Block International Space Station European Space Agency Solar Panel Microgravity Experiment
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