Scheduling Strategy to Minimize Instrumentation Changes

Although quick instrument changes are often a design goal, it is quite common for there to be significant operational costs in going from one telescope/instrument configuration to another. In constructing a long-term scheduler for ESO telescopes, Johnston, Chavan and Albrecht (1995) employed a cost function for installation of the IRSPEC since a one day instrument change time is needed in this case. Since the scheduler minimizes the amount of unused time and maximizes the number of observations scheduled, this cost function drives the schedule towards a minimum number of instrument changes. In the case of CFHT, certain instrument changes require a telescope upper-end change (e.g. from cassegrain to coude). It is desirable to minimize the number of upper-end changes to the degree consistent with other constraints and there is also a firm limit of 11 upper-end changes in a semester. Unlike ESO case, there is no observing time lost due to a change so a different technique was employed. The scheduling strategy was modified to select observations on the basis of the upper-end and instrument being used.

paragraph41em 1ex plus .5ex minus .5ex-1em. Mark Johnston (STScI) developed the core extensions to Spike for ground-based scheduling and Johnston and Maurizio Chavan (ESO) developed the most recent extensions which were used for this work. John Glaspey (CFHT) provided the scheduling data and constraints for CFHT along with substantial encouragement.