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Paper: Recent Improvements to HST Parallel Scheduling
Volume: 172, Astronomical Data Analysis Software and Systems VIII
Page: 81
Authors: Henry, Ronald; Butschky, Mike
Abstract: The Hubble Space Telescope (HST) has several scientific instruments (SIs) that may be used at any given time. Most primary visits submitted by HST observers only use one SI, leaving the other SIs free to be requested by ``pure parallel'' observing programs. In order to accomplish this, separate scheduling units (SUs) for each parallel SI must be created and then scheduled by the Science Planning and Scheduling System (SPSS), taking into account numerous orbital and scientific constraints. The Parallel Observation Matching System (POMS) has the task of matching parallel visits to primary observations and ``crafting'' appropriate parallel SUs at each opportunity, taking scientific criteria and orbital constraints into account. The process for planning and scheduling parallel observations is thus quite different from the process for primary science. In the past, custom crafting rules for each parallel program were necessary, requiring full-time support from a software developer. In addition, because POMS ran as a standalone system, its ability to model how long parallel SUs would take was limited, especially with the flexible buffer-management schemes used for the second-generation SIs. A new version of POMS was developed in 1997. This version uses a formal proposal syntax (the same used for primary observations) for parallels, so that different proposals can be handled uniformly and without the need for customized ``crafting rules.'' In addition, POMS is integrated with the Transformation (TRANS) planning system in order to give it full knowledge of overheads within an SU, eliminating the need for ad hoc modeling. The power and versatility of this approach has paid off in improved utilization of parallel opportunities, greatly reduced maintenance costs, and an ability to gracefully handle new parallel proposals and new SIs with minimal software effort. This paper discusses the requirements, design, and operational results of the new POMS.
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