A Guide to VLBA Dynamic Scheduling

A Guide to VLBA Dynamic Scheduling

Proposal Eligibility

Available Dynamic Time

Dynamic Queue Activity

Preparing Observe Files for Dynamic Time

Example Observe File for Dynamic Time

Tactical Considerations

Submitting Observe Files for Dynamic Time

Proposal Eligibility

To be eligible for VLBA dynamic scheduling, you must have a regular or large VLBA proposal which has been approved for dynamic scheduling or approved for triggering on a known transient. Alternatively, you must have an exploratory or target-of-opportunity proposal that was approved for dynamic scheduling.

A valid regular or large VLBA 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, high priority
Approved for dynamic scheduling, second priority
Approved for dynamic scheduling, low priority

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

Available Dynamic Time

The VLBA schedule for the current month shows the available open time. To fill the open time, the most appropriate proposal from the observe files available in the dynamic scheduling queue will be selected. This selection may occur only hours in advance of actual observing, 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.

Dynamic Queue Activity

Lists are posted giving titles of all proposals currently in the queue, proposals from the queue recently observed, and an approximate ordering of the top proposals in the queue. The latter list is generated by actually running the dynamic scheduling program, and reporting the priorities things would have if scheduled in the next few days. Occasionally, operations schedules things enough ahead of time that your project cannot be scheduled around what they have committed to in the next three or four days. In that case, your project will not appear in this list.

Preparing Observe Files for Dynamic Time

Generic information is available about preparing a keyin file for the NRAO program SCHED. The following points highlight information specific to the dynamic queue.

You must prepare a SCHED keyin file in sidereal time rather than UT; that is, your keyin file should contain the command LST=VLBA_PT The time allocated for your proposal is based in Pie Town LST, with the caveat that the VLBA is scheduled with half-hour granularity, so the actual LST range may differ by up to 30 minutes.

For some proposals, a range in the number of hours to be scheduled is given. When the observation is scheduled, the minimum duration will be allocated, and then will be extended on either end to the extent permitted by neighboring projects or by media availability. Your SCHED keyin file should cover the entire maximum range. The LST observation times in your file will not be changed, only the date. Late starts will be handled by activating the file when the array is ready and then skipping forward to the observation scheduled for that time. You must ensure that any essential calibration observations (e.g., fringe finders) occur within the minimum duration.

Please submit your preferred dynamic constraints with your SCHED keyin file, by editing the form for Preferred Dynamic Constraints as desired and inserting it at the top of your keyin file (the "!" symbol in the form indicates to SCHED that these are comment lines). Please note:
- We cannot guarantee that all your preferred constraints, especially those related to weather, will be satisfied when your project is observed.
- It is rare to have 9 stations with weather appropriate for 1cm or 7mm. So specifying this combination in your preferences will make scheduling difficult, especially for proposals queued at medium or low priority.
Please ensure that the correlation parameters you submit with your SCHED keyin file are correct. Once your program has been observed and is being prepared for correlation, we will use the correlation parameters from your SCHED keyin file.

For some proposals, a local technical contact person has been assigned. If you have questions about preparing your SCHED keyin file, then please seek advice from that technical contact person.

Example Observe File for Dynamic Time

A continuum example is available.

Tactical Considerations

You can improve your chances of being scheduled by accepting the defaults indicated in the form for Preferred Dynamic Constraints. You can improve your chances even more by requesting even milder constraints, such as a minimum of 8 stations for observations at 6cm. If your preferences change after you submit your keyin file, then please E-mail a revised form for Preferred Dynamic Constraints to schedsoc@nrao.edu.

Submitting Observe Files for Dynamic Time

There is no deadline for the receipt of SCHED keyin files for dynamic time. E-mail your SCHED keyin file to vlbiobs@nrao.edu. The data analysts will verify that your keyin file can be used by SCHED to produce the VLBA station control files. Verified keyin files will be inserted into the queue to await scheduling.

For programs involving monitoring segments, in which you want to use the same SCHED keyin file (including its dynamic constraints) for every segment, you may submit a generic keyin file and the analysts will insert segment codes as you instruct.

Some programs request closely-spaced and multi-epoch segments, with different observing frequencies per segment. We recommend that you start with the highest frequency first and assign it segment code A, then descend across the epochs with the lowest frequency last.

Modified on Thursday, 19-Nov-2009 13:59:46 MST by schedsoc.