[an error occurred while processing this directive] Expanded Very Large Array (EVLA) [an error occurred while processing this directive]
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The Open Shared Risk Observing Program

The Open Shared Risk Observing (OSRO) program continues with new capabilities for the next configuration cycle (Sep 2011 - Dec 2012). For OSRO this cycle, we will offer up to 2 GHz bandwidth with full polarization. This will be configured as It provides early access to a number of WIDAR capabilities and observing modes for the general user community that represent a significant improvement over the capabilities of the old VLA correlator. At the same time as the telescope has transitioned from the VLA correlator to WIDAR the direction of the configuration cycles has also changed, from A→B→C→D→A… to D→C→B→A→D…, to facilitate correlator commissioning and to limit data rates during Early Science. The VLA is therefore spending two trimesters in D configuration, one with the VLA correlator (October 2009 - January 2010) and one with WIDAR. The second of these was initially used for commissioning the OSRO observing modes with the full array. Astronomical observations with WIDAR began in March 2010.

Expected EVLA capabilities

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New receiver bands will be offered for general use when the performance of at least five antennas has been verified by EVLA commissioning staff.

WIDAR correlator

Initially we are providing options for configuring WIDAR for OSRO in the following ways:

  1. "OSRO: Full polarization": Four polarization products. This configuration will comprise full polarization for each sub-band each of which will have 128 MHz bandwidth with 64 channels, with the possibility of smoothing in frequency to reduce dataset sizes or to improve spectral response offline. In this configuration it is also possible to decrease the bandwidth by powers of two, keeping the same number of channels, to provide the capabilities in Table 1.

    Table 1: Correlator capabilities per sub-band for full-polarization

    Sub-band BW (MHz) Number of channels/poln product Channel width (kHz) Channel width (km/s at 1 GHz) Total velocity coverage per sub-band (km/s at 1 GHz)
    128 64 2000 600/ν(GHz) 38,400/ν(GHz)
    64 64 1000 300 19,200
    32 64 500 150 9,600
    16 64 250 75 4,800
    8 64 125 37.5 2,400
    4 64 62.5 19 1,200
    2 64 31.25 9.4 600
    1 64 15.625 4.7 300
    0.5 64 7.813 2.3 150
    0.25 64 3.906 1.2 75
    0.125 64 1.953 0.59 37.5
    0.0625 64 0.977 0.29 18.75
    0.03125 64 0.488 0.15 9.375

  2. "OSRO: Dual polarization": Two polarization products. The possibility exists of smoothing in frequency offline to reduce dataset sizes or to improve spectral response offline.

    Table 2: Correlator capabilities per sub-band for dual polarization

    Sub-band BW (MHz) Number of channels/poln product Channel width (kHz) Channel width (km/s at 1 GHz) Total velocity coverage (km/s at 1 GHz)
    128 128 1000 300/ν(GHz) 38,400/ν(GHz)
    64 128 500 150 19,200
    32 128 250 75 9,600
    16 128 125 37.5 4,800
    8 128 62.5 19 2,400
    4 128 31.25 9.4 1,200
    2 128 15.625 4.7 600
    1 128 7.813 2.3 300
    0.5 128 3.906 1.2 150
    0.25 128 1.953 0.59 75
    0.125 128 0.977 0.29 37.5
    0.0625 128 0.488 0.15 18.75
    0.03125 128 0.244 0.073 9.375

  • "OSRO: Single polarization": A single polarization product. The possibility exists of smoothing in frequency offline to reduce dataset sizes or to improve spectral response offline.

    Table 3: Correlator capabilities per sub-band for single polarization

    Sub-band BW (MHz) Number of channels/poln product Channel width (kHz) Channel width (km/s at 1 GHz) Total velocity coverage (km/s at 1 GHz)
    128 256 500 150/ν(GHz) 38,400/ν(GHz)
    64 256 250 75 19,200
    32 256 125 37.5 9,600
    16 256 62.5 19 4,800
    8 256 31.25 9.4 2,400
    4 256 15.625 4.7 1,200
    2 256 7.813 2.3 600
    1 256 3.906 1.2 300
    0.5 256 1.953 0.59 150
    0.25 256 0.977 0.29 75
    0.125 256 0.488 0.15 37.5
    0.0625 256 0.244 0.073 18.75
    0.03125 256 0.122 0.037 9.375

    • These capabilities will be provided with integration times no shorter than 1 second (for A configuration). For B, C, and D configurations, 3 seconds integration time will be the default. Doppler tracking will not be available, but Doppler setting will be available with these correlator configurations. Please consult the Current OSRO Restrictions web page for the most up-to-date information on current OSRO capabilities. The capabilities available to the OSRO program will be expanded as soon as they can be supported for general use. These OSRO programs will run from September 2011 through the end of the EVLA construction phase. Access to the OSRO program will be via the existing time allocation process and regular calls for proposals.

    It will be possible to reduce simple OSRO datasets using AIPS, although users are encouraged to use CASA, which will also be available.

    It should be recognized that the EVLA will be undergoing commissioning throughout the duration of the Early Science programs, and that the quality of data taken during this time cannot be fully guaranteed. Nevertheless, NRAO will make every effort to ensure projects awarded time under the OSRO program do obtain data, subject to the availability of our resources.

    Latest update: November 2, 2010

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