SCHED
Creating VLBA Schedules
The program observers will use to create VLBA schedules is called SCHED. Anyone who observes with the VLBA is required to submit their schedules as SCHED .key files. SCHED is also very useful for creating VLBA proposals. Proposers can use SCHED to determine when a source is visible at the various VLBA stations, and also create dummy schedules to estimate the total observing time needed for a project.
The instructions for installing SCHED can be found on the SCHED installation page. Users who require additional assistance with the installation can submit a helpdesk ticket. Once logged into the NRAO helpdesk, use the radio buttons to select “VLBA”, and then “VLBA Observing” (and be sure to specify that it is a SCHED issue in the subject line).
To determine when a source is visible to the VLBA stations, proposers can use the extremely simplified scheduling file uvcov.key. Proposers should change the sources in the file to their target sources. To get a summary of the times when each station can see each target, run SCHED on the .key file by typing
sched < uvcov.key
and SCHED will create a file called "uvcov.sum" in the current working directory with details about as when each source is visible to each VLBA station.
To see plots of the uv coverage, times above a minimum elevation, and elevation vs. time for the targets, type
sched
plot sch=uvcov.key
and SCHED will bring up a plotting GUI that will allow the user to create various figures. See the plotting section of the SCHED User Manual for more details on producing these plots.
Proposers are encouraged to create dummy .key files for their observations in order to determine their total observing time for their projects. If you are proposing for triggered Target of Opportunity (ToO) observations and do not know your target’s position, you can still create a dummy .key file with reasonable (or even worst-case) target coordinates just to estimate the total observing time for your project. SCHED comes packaged with a variety of example .key files to help new (and experienced) users get started. For a dummy schedule, it is not extremely important to have the exact setup you will use for your observations. What is important at the proposal stage is determining the amount of time your science targets are observable and estimating the total observation duration for each epoch. This is covered in more detail in the Exposure and Overhead chapter.
Once you have created your dummy .key, run SCHED by typing
sched < dummy.key
where “dummy.key” is the name of your dummy schedule file. This will generate several new files in your current working directory. The most important one at this point is the summary (.sum) file. The summary file contains a great deal of information about your schedule, including the total time on source for each target, the total run time of the observation, and when each antenna is on source.
4 Gbps Setups
The 4 Gbps observing mode on the VLBA is now operational. For more information on creating setups, including several examples of 4 Gbps setups, see Linford & Brisken (2020) and the "Building a Scheduling File in SCHED" chapter of the Guide to Observing with the VLBA. Some users who wish to create schedules using the 4 Gbps mode may need to contact NRAO staff to obtain assistance with creating the frequency setups in SCHED.
