Twelve years of planning and scheduling the Hubble Space Telescope: process improvements and the related observing efficiency gains

Over the last twelve years, the Space Telescope Science Institute (STScI) planning and scheduling teams have reduced the lead time to schedule the Hubble Space Telescope (HST) five-fold while doubling the overall observing efficiency. After the launch of HST, a one-week flight calendar took 56 days to prepare, schedule, and convert to flight products; the process now begins 11 days before execution. Early observing efficiency was in the 25% range; it is now typically 50%. In this paper, the process improvements that allowed these advancements are summarized. We also discuss the most recent scheduling advancement, which allows interruption of an executing flight calendar for fast-turnaround science observations or telescope anomaly resolution within 24 hours of activation.