VLA/GBT/VLBA Resource Changes

NRAO Interactive Services Modification Request 1C409, Oct 2009

1. Introduction

Resources naturally change with each trimester.

2. EVLA WIDAR Background

Observations using the EVLA will only be possible with the new WIDAR correlator, beginning in the 2010 A trimester. The VLA correlator will be turned off nominally on Jan 11, 2010. We expect that there will be no VLA/EVLA observing, with either correlator, approximately from Jan 11 to Feb 28, 2010.

The WIDAR correlator will be very flexible, and the number of different modes it will eventually be able to support is large.

At the beginning of WIDAR commissioning, beginning in 2010 trimester A, we will support only two "general" modes for most EVLA users. These are known by the term OSRO (Open Shared Risk Observing). The two modes are OSRO I and OSRO II. We will also support Resident Shared Risk Observing (RSRO), in which experts from the community will be resident in Socorro to help commission different modes of the correlator/EVLA system, and EVLA Commissioning Staff Observing (ECSO), in which NRAO commissioning staff may submit proposals for using the system beyond OSRO.

OSRO I: This is a mode for continuum applications and broad-band spectro-polarimetry, which comprises 2 independently tunable subbands, full polarization, and each of which has 128 MHz bandwidth (or less) and 64 spectral channels, with options for smoothing in frequency to reduce dataset sizes or to improve spectral response (snr). In this mode it will also be possible to decrease the bandwidth, by powers of two (keeping the same number of spectral channels). See Table 1 at http://www.aoc.nrao.edu/evla/astro/osro.shtml. The two subbands may placed anywhere within the receiver band, though they may not be separated by more than 10 GHz (this only affects the Ka band).

OSRO II: This is a higher resolution mode for spectral line observations, It comprises one tunable sub-band, dual polarization, with 128 MHz bandwidth (or less) and 256 spectral channels, again with options for smoothing in frequency to reduce dataset sizes or to improve spectral response. In this mode it will also be possible to decrease the bandwidth by powers of two, keeping the same number of channels. See Table 2 at http://www.aoc.nrao.edu/evla/astro/osro.shtml.

3. EVLA WIDAR Requirements

a. VLA Resources

i. Back End

For the PST, we need to add the following capabilities to the VLA Resources. For the Back End, we need to add WIDAR OSRO I, WIDAR OSRO II, WIDAR RSRO, and WIDAR ECSO in the list of the pull-down menu. When either of the OSRO modes are selected, then a "Correlator Setup" table, similar to the current implementation for VLA Correlator - Spectral Line, should be displayed. The table for each of OSRO I or OSRO II should be taken from the tables at the above website. Only the first four columns of each table need be displayed. As is done currently, each row should be selectable for the EVLA resource (however, there are not different IF modes for different bandwidths as are now currently available for the VLA correlator). (While we're at it, please remove the High Time Resolution Processor entry from the Back End pull-down menu.)

At the top of the current page when VLA Correlator - Spectral Line is selected is a box which is labeled Frequencies and a "Enter Rest Frequencies" or "Select Standard Spectral Transition". Radio buttons are used to select between these. There are also Hanning Smoothing radio buttons (yes no). Both the frequency part and the smoothing part can be used for the new OSRO modes. The tables referenced above get selected for Hanning smoothing "No" (which should be the default). If Hanning smoothing "Yes" is selected then the tables are modified by dividing the "Number of Channels per Polarization Product" by two, and multiplying the "Channel Width (kHz)" by 2. For OSRO I two frequencies may be entered (corresponding to the two independently tunable subbands), but they may not be more than 10 GHz apart (only possible at Ka band). For OSRO II, only one frequency (since there is only one available subband) may be entered.

For WIDAR RSRO or ECSO, a text box in which proposers can write a paragraph about what resources they need is sufficient.

ii. Receivers

Under Receiver, on the Resources page, we require that the lines for 4 Band, P Band, and U Band be "grayed out", i.e., not selectable, for this cycle (not removed).

b. Connections to Scientific Justification Page Limits

For WIDAR RSRO, we require that the scientific justification be allowed an additional four pages over the standard (depending on Regular, Large, or Rapid Response) in order that proposers may outline their proposed commissioning plans, residency plans, budget, and present a "use case" for their proposed observations. For WIDAR ECSO, we require that the scientific justification be allowed an additional two pages over the standard, so that proposers may also submit a "use case" with their scientific justification. After further discussion WIDAR ECSO will not be allowed any additional pages. Therefore, only WIDAR RSRO will be allowed additional pages (4) over the standard amount.

c. Time Lines

From now (when these changes to the PST are available) until January 11, 2010 (nominal turn-off date for the VLA correlator), when Resources are selected for the VLA Correlator, there should be a warning message displayed, and the selection disallowed, if the proposal type is anything but Rapid Response. Only Rapid Response proposals should be allowed for the VLA Correlator back ends. During this same time period, proposals with Resources selecting WIDAR Back Ends may only be used in Regular or Large proposals.

After January 11, 2010, the Resources should be changed so that the VLA Correlator Back Ends are no longer available. The plan is that VLA will not be observing at all between January 11, 2010, and February 28, 2010, but proposals will be accepted at the February 1, 2010 deadline for the 2010 B trimester. Thus proposers may use the PST between January 11 and February 28, 2010, but only to submit OSRO, RSRO, or ECSO Regular or Large proposals (i.e. no Rapid-Response proposals).

After February 28, 2010, all types of proposals (Regular, Large, or Rapid-Response) may again be submitted.

4. Other Requirements

  • VLBA DiFX correlator:

We need what's there now under Socorro-FXCORR, and add Socorro-DiFX. The Stations and Observing Parameters under Socorro-DiFX would look exactly the same as Socorro-FXCORR. The difference would come under Correlation Parameters. We would like to add to the pull-down menu for Spectral Points/BBC more possibilities, multiplying up by factors of two through 32768. That is, in addition to what's there for FXCORR, we would add 2048, 4096, etc... up to 32768. Actually, everything else could remain the same. But we would like to be able to disable the Socorro-DiFX Processor, i.e. make it not selectable, in case the people working on this decide at the last minute that it won't be available. I don't think they'll do this, but it's possible.

  • GBT Resources:
    1. Remove "GBT Spectrometer Spigot System" from the list of GBT back-ends.
    2. Guppi
      • Remove 400 MHz BW mode.
      • Add "Polarization:" with a selectable menu list of "Full Stokes" and "Total Intensity". The default should be "Full Stokes".
      • Add "Channels:" with a selectable menu list of 64, 128, 256, 512, 1024, 2048, and 4096. The default should be 64.

5. Design

Technical lead should provide a brief description of how this will be implemented in the code.

6. Deployment Checklist

Documentation? Systems/hardware/networking things needed for deployment?

7. Test Plan

7.1 Internal Testing

7.2 Sponsor Testing

7.3 Integration/Regression Tests


APPROVED: I acknowledge that my request is fully contained in this MR, and if the Open Sky (or other NIS or PST developers) deliver exactly what I specified, I will be happy.

ACCEPTED: I acknowledge that I have validated the completed code according to the acceptance tests, and I am happy with the results.

Written - - - - -
Checked - - - - -
Approved by Scientific Sponsor - - - - -
Accepted/Delivered by Sponsor - - - - -

  • Use %X% if MR is not complete (will display ALERT!)
  • Use %Y% if MR iscomplete (will display DONE)

Discussion Area

-- DanaBalser - 2009-06-11
Topic revision: r7 - 2009-08-28, DanaBalser
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