Offered VLA Capabilities during the Next Semester

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 are 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 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). In addition to these, all VLA antennas are equipped with 224–480 MHz (P-band) and 54–86 MHz (4-band) receivers near the prime focus. Data rates of up to 60 MB/s (216 GB/hour) will be available to all users as GO, combined with correlator integration time limits per band and per configuration, as described in the Time Resolution and Data Rates section. 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 full polarization 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) 12 MHz bandwidth Stokes I continuum observations only* at 4-band (3 x 4 MHz subbands) Dual 4/P-band for Stokes I continuum observations only* Flexible setups for spectroscopy using two independently tunable, 1 GHz baseband pairs, each of which can be split into up to 32 flexibly tunable subbands Single, dual, and full polarization products for non-default setups *Note: 4-band and dual 4/P-band observations are offered for Stokes I continuum only using standard full polarization default setups. Polarization, spectral-line, or the use of non-standard setups, should be submitted as a RSRO proposal.
3-bit samplers	Standard full polarization 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 for non-default setups
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, with only one 8-bit setup per subarray.
Y27 or Y1 for VLBI	VLA Phased Array (Y27) or single VLA antenna (Y1) for VLBI: see the VLBA call for proposals and the VLBA Observational Status Summary for a detailed description of the VLA capabilities being offered for VLBI.
Solar observing	All solar observing except the L-band reverse-coupled system*
On-The-Fly Mosaicking (OTF)‡	P-, L-, S-, and C-bands only, using linear interpolations in Equatorial Coordinates; no subarrays
Pulsar	Phase-binned and coherent-dedispersion (YUPPI) pulsar observing, except 4-band YUPPI and combining YUPPI mode with VLBI recording, which are Resident Shared Risk Observing (RSRO) capabilities.

*Note: The VLA L-band (1-2 GHz) has a special signal path (the "reverse coupler" path) that allows coherent radio bursts to be observed without saturating the system, as the brightest of these solar bursts can exceed 10⁵ solar flux units, or 10⁹ Jy. This signal path has not yet been fully commissioned and is therefore not yet available under GO.

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. Data rates higher than 60 MB/s (216 GB/hour) and up to 100 MB/s (360 GB/hour) are considered SRO. A summary of the SRO capabilities being offered are:

• Up to 3 independent subbarrays using standard 3-bit continuum setups, or a mix of standard 3-bit and standard 8-bit continuum setups, and up to 3 independent subarrays with changing standard continuum setups in a given subarray (e.g., to perform reference pointing at X-band for high frequency observations).
• On-the-Fly (OTF) mosaicking for X-, Ku-, K-, Ka-, and Q-bands (used when each pointing on the sky is on the order of several seconds or less), but not using subarrays.
• Wideband VLA for VLBI: Enables recording of VLA WIDAR continuum-mode correlations during VLA phased array (Y27) VLBI observations. Currently, this only supports standard VLA 8-bit continuum modes with a 2-GHz bandwidth. See the VLBA Call for Proposals for more details.
• eLWA: Joint LWA and VLA 4-band observations using a single 8 MHz subband centered at 76 MHz, and 4-bit VDIF output. Note: During semesters 2024A and B, LWA1 is undergoing infrastructure upgrades and will likely not be available for this observing mode, which will leave only LWA-SV to join VLA observations. For 2025 and after, three LWA stations in New Mexico are expected to be available in this observing mode.

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 VLBA Resident Shared Risk Observing (RSRO) program provides users with early access to new capabilities in exchange for a period of residency in Socorro to help commission those capabilities.

RSRO proposals should be submitted using the NRAO Proposal Submission Tool in response to a regular proposal call. The proposal should include a scientific justification, as for normal proposals, which will be peer reviewed as part of NRAO's time allocation process. Selecting "VLA RSRO" from the "Observing Mode" menu on the Resources page makes an "RSRO Comments" text-entry facility available for describing the technical resources required. A description of the personnel who will be involved in the effort along with their expertise and availability should also be included in the technical justification.

We emphasize the "shared risk" nature of the RSRO program. Since observers will be attempting to use capabilities under development and in the process of being commissioned, NRAO can make no guarantee of the success of any observations made under this program, and no additional commitment is made beyond granting the hours actually assigned by the peer review process.

Proposals for any area of user interest bit offered under GO or SRO are welcome. Here, we provide some examples of capabilities that are being utilized in recent RSRO proposals.

• Correlator dump times shorter than 50 msec, including integration times as short as 5 msec for transient detection, or data rates above 100 MB/s. In order to reduce the data rate, frequency averaging in the correlator may be utilized in RSRO proposals;
• YUPPI pulsar mode combined with VLBI recording;
• Subarray observations with setups other than the default continuum setups, or observations with more than 3 subarrays;
• Currently, OTF observing is implemented as linear interpolations in Equatorial Coordinates (i.e., RA/Dec). This can be expanded to allow using stripes linear in Galactic coordinates (l,b), as well as more complex patterns other than linear in RA and Dec, such as Rosetta or Spiral patterns. Note that these must still adhere to the restrictions of the OTF mode under General Observing, i.e., using the full array below 8 GHz (up to C-band), and no subarrays.

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

 

Commensal Observing Systems at the VLA

There are three 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. Hence, VLITE is turned off by default during P-band or dual 4/P-band observations. The VLITE system is deployed on up to eighteen VLA antennas. 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 realfast system, which takes data at very fast dump rates in an effort to detect Fast Radio Bursts (FRBs). This system is fully commissioned for observing at L- through X-bands, in parallel with standard continuum correlator configurations. The third commensal system, COSMIC SETI, enables the search for extraterrestrial intelligence (SETI) using the VLA, and collects data during unconflicted PI science observations. For information about commensal observing see the Commensal Observing with NRAO Telescopes page.

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.