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Description of Driving Event:

One of the first United States Microgravity Laboratory (USML-1) pre-mission timeline constraints addressed the number of hours that a crew member could be scheduled for payload operations. For the first four shifts of the missions, crew members could only be scheduled for 70% of the available time. For the remaining shifts of the mission, 90% of their time was available for experiment operations. The crew's comments indicated that this constraint was very valuable in preventing fatigue and supported the period of time during which space adaptation was occurring. However, because of the learning delay, experiments were unable to achieve science objectives during initial runs. As a result of this mission, it was recommended to continue the use of the timeline constraint for crew utilization and include more time early in the mission for a learning curve for the crew's Zero-G skills.