Gary Welter, Jim Legg and Glenn Cammarata
The Next Generation Space Telescope (NGST), planned for launch in 2007, poses a number of interesting engineering challenges. This article addresses one such challenge, specifically that of maximizing observatory efficiency through an appropriate balance between non-real-time construction of the near-term observing schedule and onboard adaptation to real-time conditions during actual observation execution. The appeal of onboard adaptive scheduling is particularly strong for NGST because of its expected placement near the second Earth/Sun Lagrange point, a comparatively benign location vis-a-vis scheduling constraints. This is expected to make event-driven, in contrast to time-tagged, execution the norm for most observations. However, experience with previous missions has demonstrated to science operations teams that it is very useful for the team to be able to have substantial control of schedule construction, particularly when the mission is yet young and the team is first learning how to effectively use the satellite and science instruments. In this article, we explore a hybrid scheme designed to provide the advantages of real-time adaptive response under most circumstances, while at the same time giving the operations team the level of control perceived as appropriate for current mission conditions.