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Offered VLA Capabilities during the Next Semester

by Stephan W. Witz last modified Jun 26, 2017 by Emmanuel Momjian

The Call for Proposals

The most recent Call for Proposals summarizes the General Observing (GO) capabilities being offered for the Karl G. Jansky Very Large Array (VLA).

In addition to these general capabilities, NRAO continues to offer shared risk observing options for those who would like to push the capabilities of the VLA beyond those offered for general use. These are the Shared Risk Observing (SRO) and Resident Shared Risk Observing (RSRO) programs.

Details about what is being offered for each program is given below. If you have any questions or problems with any link or tool, please submit a ticket through the NRAO Helpdesk.

Considering the lack of future hybrid configurations after semester 2016A, guidelines on how to substitute such configurations with the use of principal array configurations are presented in the Array Configurations section of the Guide to Proposing for the VLA.


General Observing (GO) and Shared-Risk Observing (SRO)

Summary of Capabilities

As described in the Call for Proposals, the VLA offers continuous frequency coverage from 1–50 GHz in the following observing bands: 1–2 GHz (L-band); 2–4 GHz (S-band); 4–8 GHz (C-band); 8–12 GHz (X-band); 12–18 GHz (Ku-band); 18–26.5 GHz (K-band); 26.5–40 GHz (Ka-band); and 40–50 GHz (Q-band). Both single pointing and mosaics with discrete, multiple field centers will be supported under General Observing (GO). P-band (230–470 MHz) Stokes I continuum observations are also offered under GO; see the Low Frequency Observing section below for more details. Data rates of up to 60 MB/s (216 GB/hour) will be available to all users, combined with correlator integration time limits per band and per configuration, as described in the Time Resolution and Data Rates section. However, data rates in excess of 25 MB/s (90 GB/hour) require additional justification. Limitations on frequency settings and tuning ranges are described in the Frequency Bands and Tunability section.

The GO capabilities being offered are:

Capability Description
8-bit samplers
  • Standard default setups for:
    • 2 GHz bandwidth continuum observations at S/C/X/Ku/K/Ka/Q bands (16 × 128 MHz subbands)
    • 1 GHz bandwidth continuum observations at L band (16 × 64 MHz subbands)
    • 256 MHz bandwidth continuum observations at P band (16 × 16 MHz subbands)
  • Flexible setups for spectroscopy using two, independently tunable, 1 GHz baseband pairs, each of which can be split into up to 16, flexibly tunable, subbands
  • Single, dual, and full polarization products
  • Number of channels summed over all polarization products up to 16384 (no recirculation) or up to 1,048,576 (with recirculation; subject to the data rate limits and the chosen subband bandwidth)
3-bit samplers
  • Standard default setups for:
    • 8 GHz bandwidth continuum observations at K/Ka/Q bands
    • 6 GHz bandwidth at Ku band
    • 4 GHz bandwidth at C/X bands
  • Flexible setups for spectroscopy using four, independently tunable, 2 GHz baseband pairs, each of which can be split into up to 16, flexibly tunable, subbands
  • Single, dual, and full polarization products
  • Number of channels summed over all polarization products up to 16384 (no recirculation) or up to 1,048,576 (with recirculation; subject to the data rate limits and the chosen subband bandwidth)
Mixed 3-bit and 8-bit samplers
  • Allows more flexibility for simultaneous continuum and high-resolution spectral line observing

Subarrays

  • Up to 3 independent subarrays using standard 8-bit continuum setups
Phased-array for VLBI
  • VLA Phased Array (Y27) for VLBI (see the VLBA call for proposals and the VLBA Observational Status Summary for a detailed description of the VLA Phased Array capabilities being offered)


SRO capabilities can be set up via the Observing Preparation Tool (OPT) and run through the dynamic scheduler without intervention, but are not as well tested as GO capabilities. A summary of the SRO capabilities being offered are:

  • On-the-Fly (OTF) mosaicing
  • Up to 32 subbands per baseband with the 8-bit samplers

‡Note: OTF mosaic observations have certain limitations on the length and number of scans. Contact the VLA staff through the NRAO Helpdesk to check if the OTF mosaic observations to be proposed are technically feasible ahead of submitting a proposal.

We expect that most SRO programs will have no or only minor problems that can be corrected quickly. If an SRO program fails, however, and it becomes clear that detailed testing with additional expertise is needed, then the project must make an experienced member from their team available to help troubleshoot the problem. In some cases, this may require the presence of that experienced member in Socorro. If adequate support from the project is not given, then the time on the telescope will be forfeited. The additional effort is to be determined based on discussions with the NRAO staff and management and the project team.

The guidelines for General and Shared Risk observing proposals, along with information about tools and other advice, can be found in the VLA Proposal Submission Guidelines.

Resident Shared Risk Observing (RSRO)

Summary of Capabilities

The RSRO program provides access to extended capabilities of the VLA that require additional testing in exchange for a period of residence to help commission those capabilities. Capabilities that would fall under the RSRO program include:

  • correlator dump times shorter than 50 msec, including integration times as short as 5 msec for transient detection;
  • pulsar observations;
  • data rates above 60 MB/s;
  • recirculation beyond a factor of 64 in the correlator;
  • P-band system (230–470 MHz) polarimetry and spectroscopy;
  • 4-band system (54–86 MHz, see the Low Frequency Observing section below);
  • more than 3 subarrays or subarrays with the 3-bit system;
  • complex phased array observations (e.g., pulsar and complex VLBI observing modes), and;
  • frequency averaging in the correlator: a new capability for averaging to wider frequency channels in the correlator has been developed that will reduce the data volume for all continuum subbands

 

The guidelines for Resident Shared Risk Observing proposing, along with requirements and considerations, can be found in the VLA Proposal Submission Guidelines.

 

Low Frequency Observing (P-band and 4-band)

The new, low frequency receiver system, developed in collaboration with the Naval Research Laboratory, will be available for Stokes I continuum observations at P-band (230–470 MHz) through the GO program. Use of the P-band system for polarimetry and/or spectroscopy will be through the RSRO program as noted above. The new receivers also work at 4-band (54–86 MHz), and new feeds are expected to be available on seventeen VLA antennas. Both 4-band and P-band can be observed simultaneously, but access to the 4-band system is only available through the RSRO program.

 

Commensal Observing Systems at the VLA

There are two commensal systems on the VLA that may take data at the same time as your proposed observation.  The first is the VLITE system, which will take data at P-band during regular observations that use bands other than P-band. The VLITE system will be deployed on fifteen VLA antennas by the 2018A semester. Observers wishing to gain access to the commensal VLITE data taken during their VLA observations should follow the instructions on the VLITE web page for doing so.  The second is the realfastsystem, which takes data at very fast dump rates in an effort to detect Fast Radio Bursts (FRBs).  This system is still in development, but may be observing during the 2018A semester.

 

To report errors or problems encountered in any link or while using any NRAO tool listed here, please submit a ticket through the NRAO Helpdesk.