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; 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.
eLWA: Joint LWA and VLA 4-band observations using a single 8 MHz subband centered at 76 MHz, and 4-bit VDIF output.

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 residency in Socorro to help commission those capabilities. Due to the ongoing pandemic, the RSRO program participants may choose to contribute remotely to help with the commissioning of these 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;
Data rates above 100 MB/s;
Recirculation beyond a factor of 64 in the correlator;
4-band (54–86 MHz) polarization or spectral line;
4-band (54-86 MHz) coherent-dedispersion (YUPPI) pulsar observing;
YUPPI pulsar mode combined with VLBI recording;
subarray observations with setups other than the default continuum setups, or observations with more than 3 subarrays;
Complex phased array observations (e.g., pulsar and complex VLBI observing modes);
Frequency averaging in the correlator or any frequency averaging in setups with mixed subband bandwidths, e.g., for spectral line+continuum with the averaging used in subbands designated for continuum (while frequency averaging by a factor of 2 or 4 was offered as GO in the past, our operational experience suggests that it is best offered as RSRO at this time);
Rapid response capability: Automatically scheduling VLA observations in response to a trigger on timescales shorter than 1 day and/or requiring interruption of running observations;
eLWA: Joint LWA and VLA 4-band observations and correlations using options other than offered under SRO (e.g., a different center frequency, 16 MHz bandwidth, and/or 8-bit VDIF output for a higher dynamic range), and
WIDAR real-time RFI blanking: Such RFI blanking can remove intermittent, impulsive forms of interference on nanosecond to microsecond timescales, which in turn avoids corrupting integrated measurements over longer timescales (1-5 seconds of correlator integration time). Test results show that this blanking is particularly effective at removing pulsed RFI at L-band (e.g., below 1200 MHz for redshifted HI 21 cm and OH 18 cm science), and limited pulsed RFI at S and X-bands.
Currently, OTF observing using stripes linear in Galactic coordinates (l,b) is being implemented, but OTF in more complex patterns other than linear in α,δ (J2000) or l,b such as Rosetta or Spiral patterns can be proposed for as RSRO. Note that this must be in General Observing OTF mode, i.e., at the time of writing, using the full array below 8 GHz (up to C-band, not using 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. A third commensal system, COSMIC SETI, is expected to become operational at the start of the 2023A semester. This system enables the search for extraterrestrial intelligence (SETI) using the VLA, and will collect 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.