Observation Preparation

Observing with NRAO Telescopes

All observations on NRAO telescopes are executed using the concept of  Scheduling Blocks, although the blocks may not be specifically called Scheduling Blocks (see, for example, the VLBA). An accepted proposal might require tens or hundreds of Scheduling Blocks to gather the data necessary for exploring that project's objectives. The following sections describe the tools and techniques needed to create Scheduling Blocks for each telescopes.

VLA Observing

After the shutdown of the old VLA correlator and the deployment of the new WIDAR correlator observers will have to use the Observation Preparation Tool (OPT) in order to create, validate, and submit VLA observing scripts. Submitting observe files (e.g., prepared using Jobserve) is no longer possible.

GBT Observing

Scheduling Blocks for the GBT are prepared using the Astronomer's Integrated Desktop (Astrid), or alternatively, your favorite text editor. Before your observations you need to prepare for your observations. You will be assigned a scientific contact person. They will help you develop an appropriate observing strategy for your proposal. They will also help you with any technical questions, e.g. dealing with RFI. At this time you should develop your Scheduling Blocks.

You will travel to Green Bank for your observations or if you are an experienced GBT observer you can observe remotely. You should arrive in Green Bank at least one business day before your observations. This will allow you to meet with the contact scientist and also with the scientific staff person who will be "on call" during your observations (these might be different people).

Shortly before your observations begin you should go to the GBT control room. You can log into one of the computers and bring up any programs that you need so that you are prepared when you observation time begins. If you are observing remotely you should contact the GBT operator (304-456-2341 or 304-456-2346) about 30 minutes before your observations. You should give the operator your contact information (phone numbers, emails) so that they can contact you during the observations if necessary. You will also need to let the operator know what computer you will be using during your observations. At this time you will begin to open a Virtual Network Computer (VNC) session that you will use for the remote observations. Starting this early will allow for any problems encountered while preparing to observe remotely to be solved before the observations are to begin. You can find information about GBT remote observing policies and you can find information about opening a VNC session. The operator on duty will handle several tasks for you at the beginning of your observations. They will "put you in the gateway" (give you security access) so that you can control the GBT. They will also get the correct receiver into the focus position of the GBT, get the antenna motor drives ready for movement, place the correct pointing models into the system, and set the GBT's AS into the proper state. The operator is there to take care of all safety issues concerning the GBT.

Now you are ready to observe. You will use Astrid to perform your observations by submitting your Scheduling Blocks and monitoring progress.

VLBA Observing

All VLBA observations begin with the program SCHED. The full User Manual and installation instructions are available at this link.

As described in the user manual, SCHED is a program for "planning and scheduling Very Long Baseline Array (VLBA), High Sensitivity Array (HSA), Global Very Long Baseline Interferometry (Global VLBI), European VLBI Network (EVN), Long Baseline Array (LBA; Australia), Korean VLBI Network (KVN), VLBI on the Karl G. Jansky Very Large Array (VLA) and other VLBI observations."

Observers will need to create an input file for SCHED with a text editor. SCHED uses that input file to create various output files, including a VEX file. VEX files are the most common way to distribute observation schedules to VLBI telescopes and correlators.

When a satisfactory SCHED input file has been achieved, observers will email that input file to [email protected]. Including any of the SCHED output files is not necessary.  NRAO Data Analysts will always rerun SCHED using the provided input file.