Introduction to Dynamic Scheduling

Most scheduling blocks (SBs) are observed dynamically, based on factors that NRAO controls and on factors that the observer controls. Such dynamic scheduling enhances science data quality and the array's ability to discharge time-sensitive science. On rare occasions, an SB that requires coordinated observations with other telescopes will be scheduled on a fixed sidereal date.

NRAO staff use the Observation Scheduling Tool (OST) to examine the current observing conditions and the queue of SBs submitted for the current array configuration. The observing conditions are quantified by the RMS phase measured with the Atmospheric Phase Interferometer (API), the wind speed, and the sunrise/sunset time. The OST then applies heuristics to create a schedule, which is just a time series of optimal SBs. The first optimal SB in the series is then sent off for execution by the monitor and control system. Just before that execution completes, the OST again applies heuristics to create a new schedule.

The heuristics used by the OST include the scheduling priority (A, B, or C) assigned by the Time Allocation Committee and the linear-rank score assigned by the Science Review Panel. The heuristics also include SB attributes under observer control, specifically its duration, weather constraints (API and wind limits), observing bands, range of LST start times and, optionally, an earliest start date and a request to avoid sunrise/sunset. The observer can also convey comments to the operator, for example to instruct the operator not to execute the SB for some reason if it has been selected from the queue.

Dynamic scheduling obviously means that the observer does not know when the observations will occur. This must be kept in mind when preparing an SB. In particular, the observer should check that none of the possible LST start times create problems with antenna wraps and the scans of the flux density scale calibrator. These topics are discussed in more detail below.