Scheduling Procedures for NRAO Telescopes

NRAO is steadily moving towards being able to dynamically schedule all of its observations. Dynamic scheduling is currently in place for the VLA, and a limited form of dynamic scheduling has been available at the GBT. This summer, the GBT will explore a more comprehensive, advanced system for dynamic scheduling that is projected to significantly improve the observers' ability to complete high-frequency observing projects. VLA dynamic scheduling is done at the Scheduling Block (observe file) level, whereas GBT dynamic scheduling is done with respect to observing sessions. An observer whose session is dynamically scheduled on the GBT still has the freedom to choose which Scheduling Blocks from his or her project to execute, and in which order.

VLA 90cm Image of Inner Galactic Plane

VLA Scheduling

Dynamic scheduling is performed for some VLA projects. To be eligible for VLA dynamic scheduling, you must have a regular VLA proposal which was submitted at the deadline for the current configuration, or approved for triggering on a known transient during the current configuration, or pre-approved at an earlier deadline for the current configuration. Alternatively, you must have an exploratory or target-of-opportunity proposal that was approved for the current VLA configuration. A VLBA proposal that requests a small amount of prepatory VLA time may also be eligible for VLA dynamic scheduling.

A valid regular VLA proposal will have one of the following statues assigned by the VLA/VLBA Proposal Selection Committee, and listed in decreasing order of the relative probability of actually being scheduled:

• Target of opportunity, waiting for occurence.
• Approved for ToO triggering, this trimester only.
• Approved for dynamic scheduling, priority A
• Approved for dynamic scheduling, priority B
• Approved for dynamic scheduling, priority C
• Approved for dynamic scheduling, priority D
• Dynamic scheduling, lowest priority. Unlikely to accomplish goals.
• Time scheduled this config; will not be considered further.
• Time allocated for this configuration and subsequent one(s)

An approved VLA exploratory proposal will usually have a relative priority below that of any regular VLA proposal.

The VLA schedule for the current month shows the available "dynamic" time. To fill the dynamic time, the most appropriate proposal from the observe files (scheduling blocks) available in the dynamic scheduling queue will be selected. This selection typically occurs a few hours before the dynamic time begins, and is based on the proposals' referee ratings and the statuses assigned by the VLA/VLBA Proposal Selection Committee, as well as on the state of the array, including the weather conditions.

GBT Scheduling

The GBT spans a larger range of frequencies than other comparable centimeter/millimeter single-dish telescopes, and is located in a continental, mid-latitude region where weather is dominated by water vapor and small-scale effects. As a result, the observing efficiency of the GBT can be enhanced significantly by dynamically scheduling observations best matched to weather conditions.

During the period between June 1 - September 30, 2008 we are testing a prototype Dynamic Scheduling System (DSS). The goal of the DSS is to maximize the observing efficiency of the telescope while ensuring that none of the flexibility and ease of use of the GBT is harmed and the data quality of observations is not adversely affected. After September 30, the telescope will revert back to its previous scheduling system until the full release of the DSS (currently planned for summer, 2009). The previous scheduling system was an intermediate step between generating a classical (fixed) schedule and full dynamic scheduling. Effectively two schedules are generated, one for high frequency observing and one for low frequency. See Schedular Procedures for Dynamic Observing for details on this system.