Resources

by Gustaaf Van Moorsel last modified Jun 28, 2017 by Dana Balser

The Resources section is used to specify the telescope setups to be used for the proposed observations. There is one such section per telescope. Each observing setup is called a resource; each resource is defined by the receiver, back end, spectral mode, configuration, etc. to be employed.

 

What is a Resource?

A resource consists of an array configuration (for the VLA) or a combination of stations (for the VLBA/HSA and GMVA), a front end receiver, a back end processor, and the technical details of how they are to be used together. A resource is given a name which can be any unique character string. It is used to identify a specific experimental setup, e.g., 'setup1','Cont_43GHz', 'mapping_with_SP', 'Bconf-Xband', 'B14a', 'SiO_30kms'.

When defining an observing session you will combine a source group with one or more resources to specify what and how to observe. A single observing session may employ multiple resources, with some restrictions (e.g., only a single VLA array configuration may be used in a given session).

The Resource Page is different for the four telescopes - VLA, GBT, VLBA/HSA, GMVA - (although the VLBA/HSA and GMVA instruments are very similar). For the GBT there are resource groups that work the same way as source groups. One or more resources are selected within a given resource group that are later associated with a source group within a Session. For the VLA, the VLBA/HSA, and GMVA there are no resource groups but a list of resources that can be combined later within a given Session.

 

GBT Resources section

The GBT Resource section is where you select the back ends that you wish to use during the proposed observations. You are also asked to provide information such as rest frequencies, desired bandwidths, desired spectral resolution, desired time resolution, etc. Click on New Resource Group'' to add a resource group. Once a resource group exists click on the Add'' button to add a resource.

You are then asked to fill in the following information:

  • Resource Name: A unique name for the resource.
  • Receiver: The GBT receiver that you wish to use for this resource. A pull-down list of the receivers is available.
  • Back End: The back end/observing mode combination that you wish to use for your observing. Depending on which back end was selected you may have to provide more details for the resource. For additional details consult the GBT Proposer's Guide: GBT Proposer's Guide. This information includes:
    • Digital Continuum Receiver (DCR)
      • Rest Frequencies: A comma separated list of rest frequencies.
      • Instantaneous bandwidth: The desired bandwidth.
      • Desired time Resolution: The minimum dump time requested.
    • Radar Back End
      • Rest Frequencies: A comma separated list of rest frequencies.
      • Desired Frequency Resolution: The frequency resolution needed to perform the requested science.
      • Time Resolution: The minimum dump time requested.
      • No GBT staff support provided: Check this box to acknowledge that you understand how to use this back end, and that the GBT staff will not provide any support for such use.
    • JPL Radar Back End
      • Rest Frequencies: A comma separated list of rest frequencies.
      • Desired Frequency Resolution: The frequency resolution needed to perform the requested science.
      • Time Resolution: The minimum dump time requested.
    • VErsatile GBT Astronomical Spectrometer (VEGAS): VEGAS consist of 8 independent spectrometers. First select the observing type, the number of beams, and the number of spectrometers before specifying the details for each spectrometer. For observing type Continuum only mode 1 is currently available. For observing type Spectral Line'' modes 1-29 are available where up to 8 spectrometers can be used. For each spectrometer the following information is specified:
      • Mode: The desired mode. See the proposer's guide for details about each mode.
      • Bandwidth: The desired bandwidth which depends on the mode and cannot be edited.
      • Rest Frequencies: A comma separated list of rest frequencies. The number of rest frequencies must equal the number of spectral windows.
      • Spectral Resolution: The spectral resolution which depends on the mode and cannot be edited.
      • Integration Time: The integration time. The value must be between a specified range (listed in the proposer's guide). Currently the integration time must be the same for all spectrometers.
      • Date Rate per Spectrometer: Based on the mode and integration time, the data rate is calculated and displayed.
    • Caltech Continuum Back End (CCB): The CCB is a sensitive, wide-band detector with 14 GHz of instantaneous bandwidth that cover 26-40 GHz. The CCB may only be used with the Ka-band receiver.
    • Mustang 2: A 223-feedhorn bolometer camera that is both a frontend and backend operating at W-band.  You must have permission from the instrument team to use this camera.
    • Breakthrough Listen: A non-standard backend developed for the Breakthrough Listen project.  You must have permission from the observatory director to use this backend.
    • Vegas Pulsar
      • Bandwidth: the desired bandwidth from the menu.
      • Observing Mode: the pulsar observing mode (timing or search).
      • Polarizations: the polarizations (full stokes or total intensity).
      • Channels: the number of spectral channels.
      • Dedispersion: coherent or incoherent dedispersion.
    • Other
      • Rest Frequencies: A comma separated list of rest frequencies.
      • Name of the special back end: Short descriptive name.
      • Comments: Any comments about this back end.

    The GBT Resource section is where you select the back ends that you wish to use during the proposed observations. You are also asked to provide information such as rest frequencies, desired bandwidths, desired spectral resolution, desired time resolution, etc. Click on New Resource Group'' to add a resource group. Once a resource group exists click on the Add'' button to add a resource.

    Additional GBT Information

    Please consult the GBT Proposer's Guide for more information.

    VLA Resources section

    The VLA Resources section allows you to create, edit, and remove resources appropriate to the VLA, specifying such information as the array configuration, observing frequency, frequency resolution, and number of channels. You must create a separate resource for every different combination of these attributes. Click on the Add'' button to add a resource. Details about how to make these choices may be found in the VLA Observational Status Summary:  VLA Observational Status Summary An VLA resource is defined by the following information:

    • Resource Name: A unique name for the resource.
    • Configuration: The array configuration.
    • Receiver: The VLA receiver that you wish to use. This specifies the range of frequencies within which you will be observing. The pull-down menu shows the available receivers.
    • Back End: The back end you wish to use. Currently there are 3 backends'' which are essentially different elements of the WIDAR correlator that are available. General and Shared Risk Observing - Wideband are those modes within the correlator that are set up for wideband observing; General and Shared Risk Observing - Spectral line are those modes within the correlator that are set up for Spectroscopic (or mixed Spectroscopic and Wideband) observing; finally there is the RSRO -- Resident Shared Risk Observing and VLA Commissioning Staff Observing programs which provides access to the extended capabilities of the VLA. For descriptions of these different observing capabilities, see the Call for Proposals. The choice of back end brings up further information and tools to assist in selecting the proper choices to set up the correlator:
      • General and Shared Risk Observing - Wideband: The Wideband part of General and Shared Risk Observing is now incorporated into the PST itself (spectroscopic or mixed wideband/spectroscopic modes still use an independent too - see below). One may select 8-bit or 3-bit sampling for the basebands, the frequencies of the baseband centers, number of polarization products, and the dump time. Some combinations are General Observing, some are Shared Risk, and some are Resident Shared Risk (RSRO). The PST will report these different Shared Risk and Resident Shared Risk when trying to save a Resource. One cannot save a RSRO configuration under this Backend''.
      • General and Shared Risk Observing - Spectral Line:
        • General Observing Set-up Tool (GOST) This stand-alone tool has been modified to only help set up the WIDAR correlator configurations for spectral line (or mixed spectroscopic/wideband modes) for the PST. Since it is a stand-alone tool, the information provided by GOST is moved to the PST via a screen-shot (a screen-shot may be taken by using the Save button at the bottom of the GOST display). GOST has its own Help button (which drives a browser to a useful web page), and the screen-shot is uploaded to the PST at the bottom of the General and Shared Risk Observing - Spectral Line screen. A list of rest frequencies may also be entered; units should be attached to the frequencies. GOST can be found at the following link: General Observing Setup Tool (GOST)
        • Receiver Finally, GOST and the PST are independent tools, so the correct Receiver should still be selected by the proposer in the PST resource.
      • WIDAR RSRO This is the backend'' one should select for the highly successful Resident Shared Risk Observing program and NRAO commissioning staff to help NRAO accelerate commissioning of the VLA's full scientific capabilities. RSRO participants obtain early access to the VLA's growing capabilities, in exchange for a period of residence in Socorro to assist with commissioning. Information about the RSRO program can be obtained at VLA RSRO program

    VLBA/HSA Resources section

    The VLBA/HSA Resources section allows you to create, edit, and remove resources appropriate to the VLBA and HSA, specifying such information as the stations (antennas) requested, observing frequency, number of baseband channels, polarization, sample rate, and other observing-time setup information. In addition, this section allows you to select a processor (correlator) and correlator set-up information, such as the requested polarization products, number of spectral channels, number of correlation passes, and the averaging time.

    You must create a separate resource for every different combination of these attributes. Click on the Add'' button to add a resource. Details about how to make these choices may be found in the VLBA Observational Status Summary.  A VLBA/HSA resource is defined by the following information:

      • Resource Name: A unique name for the resource.
      • Stations: The requested stations. Checking VLBA'' selects all VLBA stations. Checking HSA'' selects all of Ar, Ef, GBT, and Y27 (the phased VLA). In both cases individual stations may be unchecked, once selected. VLA-Y1 selects a single antenna of the VLA to be in the VLB array. Y1 and Y27 may not both be selected. Currently, VLA-Y1 may be selected as commissioning of that modes for the VLA has not yet been completed. Codes for geodetic stations may be entered in the box marked Geodetic''. For the HSA, the stations that may be selected depends upon the Observing System selected, as some stations may not have the needed hardware or software installed. The discussion of which stations may be selected depending upon Observing System will be discussed under Observing System''. Beginning with the 2013B semester (1 February 2013 deadline) the GBT will no longer provide setup and overhead time prior to the beginning of the VLBI observations. All VLBI proposals requesting the GBT should include any needed setup and overhead time in the time request of their proposals.
      • Wavelength: The wavelength at which you wish to observe. The pull-down menu shows the available VLBA receivers. There is no checking whether other antennas (besides the VLBA) are actually equipped with a selected receiver. The Tool will happily allow you to select an array including Ar at 1.3 cm, even though Ar does not have such a receiver.
      • Processor: The processor (or correlator) you wish to have the data sent to and correlated. Possible selections are Socorro (the VLBA software correlator DiFX), Bonn (in Effelsberg), JIVE, and Washington (USNO). For most VLBA/HSA experiments, the correlator will be Socorro.
      • Observing Mode: New from the 1 August 2014 proposal deadline the Observing Mode'' drop-down menu, has two new entries: Standard/Shared Risk'' and VLBA RSRO''. Some modes, especially for the HSA, are considered Shared Risk. The proposer is notified of Shared Risk status in VLBA Resources as pop-up comments. The VLBA RSRO (Resident Shared Risk Observing) mode is modeled after the successful VLA program of the same name. Details of this program can be found at VLBA RSRO program Selection of VLBA RSRO under Observing Mode'' brings up a RSRO Comments'' text box to describe the resources required. Selecting this mode also allows two extra pages in the Scientific Justification. For both Observing Mode Standard/Shared Risk'' and VLBA RSRO'' the following items can be managed:
        • Observing Parameters: Under Observing Parameters'' the following parameters which are specific to observing are listed. The parameters that you wish to set at observe time; these include the Observing System, the Bandwidth per baseband channel. the number of Baseband Channels, and the Polarization. The Aggregate Bit Rate is calculated, based on the other selections.
          • Observing System: The Observing System'' allows two different sets of firmware in the RDBE hardware at the VLBA/HSA stations to be selected. Currently, both systems are not necessarily available or ready at all HSA stations. The Observing Systems'' that are now supported are: 1) the Polyphase Filter Bank (PFB) personality of the RDBE FPGA, and 2) the Digital Down Converter (DDC) personality of the FPGA. If the PFB System'' is selected, Bandwidth'' and Baseband Channels'' are filled in by the Tool, and cannot be modified. Further details of these systems can be found at the Call for Proposals (CfP) under VLBA Observing Capabilities'' and the VLBA Observational Status Summary (OSS). The CfP can be found at: Call for Proposals and the OSS can be found at VLBA Observational Status Summary
            Bandwidth: A pull-down menu lets you select the recorded bandwidth per subband (or baseband channel), in factor of 2 steps from 1 MHz to 128 MHz. If spectral selection'' is to be used (Socorro correlator, or other DiFX installations by special arrangement), the bandwidths specified here are for the recorded bands only -- specifications for the zoom'' band should be communicated directly to the correlator.
            Baseband Channels: A pull-down menu lets you select the number of BBCs, in factor of 2 steps from 1 to 8.
            Polarization: One can observe with right circular polarization, left circular polarization, or both (dual) using the VLBA. In the hardware, each BBC selects either RCP or LCP.
            Aggregate Bit Rate: This is calculated by the tool, by the product of number of Baseband Channels, Sample Rate, and Bits / Sample. Sample Rate and Bits/Sample are no longer selectable by the proposer. They are assumed to be Nyquist sampling and 2 bits/sample.
        • Correlation Parameters: The parameters that you wish to set at correlation time; number of Correlator Passes, Integration Period, number of Spectral Points per BBC, and No. of Phase Centers per Pointing. Correlator resources are as valuable as Observing resources, so proposers are asked to justify the correlator resources as well as the observing resources. There are some interactions among correlation parameters as well as among correlator and observing parameters. Most of these interactions are not currently checked in the Tool.
          • Number of Correlator Passes: The number of correlator passes required (default one). Note that 2 passes are no longer required for 512 Mbps data at the Socorro correlator. More than one pass may be necessary for correlating at two different positions, or to allow different correlator setups for the same time range of date. Note that multiple positions can be correlated in a single pass with the Socorro correlator (and may be possible at other DiFX installations), and this is recommended if more than 2 positions are required (see the number of fields'' section below). If the multiple field/single pass correlation is used, the number of correlator passes'' field should remain at 1 unless multiple passes are also required for different correlator setups. If more than one correlator pass is required, a brief justification should be written in the Technical Justification Section.
          • Integration Period: The averaging time, in seconds, in the correlator (default 2 seconds). The shorter the averaging time, the larger the (rate) field of view. One must balance the output rate of the correlator with the required field of view. While there is no hard upper limit on output data rates, rates above 10 MB/s require specific justification in the Science Justification.
          • Spectral Points / BBC: For continuum observations, the default number of spectral points is to have each point represent 0.5 MHz of bandwidth (for example a 32 MHz BBC bandwidth has a default number of spectral points of 64). For spectroscopy, the number of spectral points is 16. For spectroscopy, the number of spectral points depends upon the required velocity resolution. As with averaging time, there is no hard upper limit to the number of spectral points per subband, but requests for more than 4096 points per subband, or values that would lead to a data rate ≥10 MB/s, require specific justification. The output data rate is calculated in the PST and a warning pop-up is given when it is greater than 10 MB/s.
          • Number of Phase Centers per Pointing: The maximum number of phase centers to be correlated simultaneously in a single correlator pass (only available with the Socorro correlator, or other DiFX installations by special arrangement). The default is 1. If this feature is used, the source positions entered using this tool for pointings with multiple fields should be the pointing centers (i.e. it is not necessary to list every target source). However, the Scientific Justification should make it clear what the selection criteria for sources to be correlated will be. Use of this feature consumes additional correlator resources (although the increase is nearly constant at 2.5-3x normal'' correlation, regardless of the number of sources generated) and thus usage of this feature should be justified in the Scientific Justification. Due to this increase in required resources, for 2 phase centers it is more efficient to request two correlator passes (in which case number of fields should be set to 1). Thus, this feature should only be used for 3 or more target sources within a single primary beam. In principle there is no upper limit to the number of phase centers, but values which would cause the output data rate to exceed 10 MB/s must be specifically justified.
        • Special Features: These are special features in the correlator that may be needed, including Full Polarization, Pulsar Gate, and Output Format Conversion to Mark4.
          • Full Polarization: If checked, the correlation of all polarization cross-products are requested, for each baseline: RR, RL, LR, and LL. If unchecked, only the correlation of parallel-hand products are requested: RR, LL, or RR and LL, depending on what was observed. Obviously, Full Polarization cannot be requested if only one polarization is observed; the Tool does check this.
          • Pulsar Gate: The correlator can gate based on a pulsar ephemeris; i.e., do the correlation only at times when the pulse is on (or off for that matter). If this item is checked, further input to the correlator will be required -- see the Pulsar Gate Observer's Guide:  VLBA Pulsar Gate Observers' Guide
          • Output Format Conversion to Mark4: Conversion of DiFX correlator output to the Haystack Mark 4 format is available, and can be selected via the checkbox here.

     

    GMVA Resources section

    The GMVA Resources section allows you to create, edit, and remove resources appropriate to the GMVA, specifying such information as the stations (antennas) requested, observing frequency, etc. Currently, the only possible observing setup is that of the RDBE PFB (polyphase filter bank) personality; tests have been made using European and VLBA stations to realize that this is a viable observing mode. Thus the number of baseband channels, polarization, sample rate, and other observing-time setup information is essentially fixed. In addition, this section allows correlator set-up information, such as the requested polarization products, number of spectral channels, number of correlation passes, and the averaging time. The DiFX correlator at Bonn is the only selectable processor (correlator) for GMVA observations.

    You must create a separate resource for every different combination of these attributes. Click on the Add'' button to add a resource. Details about how to make these choices may be found at the GMVA Home Page.

    A GMVA resource is defined by the following information:

    • Resource Name: A unique name for the resource.
    • Stations: The requested stations. Checking US'' selects all VLBA stations with a 3mm receiver and the GBT. Checking European'' selects all of the standard European stations for the GMVA. In both cases individual stations may be unchecked, once selected. In addition there is an Other'' box, which may be used to add stations which are not a part of the standard GMVA'', for example the GBT. Beginning with the 2013B semester (1 February 2013 deadline) the GBT will no longer provide setup and overhead time prior to the beginning of the VLBI observations. All VLBI proposals requesting the GBT should include any needed setup and overhead time in the time request of their proposals.
    • Wavelength: The wavelength at which you wish to observe. The pull-down menu allows both 3 and 7mm, as pointing (especially at the VLBA stations) may be done at 7mm.
    • Processor: The processor (or correlator) you wish to have the data sent to and correlated. The only possible selection for the GMVA is the Bonn (DiFX) processor. Observing parameters are listed for the RDBE PFB: 16 baseband channels, 32 MHz bandwith, dual polarization. The only one of these that can be changed is the polarization. With dual polarization the aggregate bit rate is 2048 Mbps. Correlation parameters can be selected:
    • Correlation Parameters: The parameters that you wish to set at correlation time; number of Correlator Passes, Integration Period, number of Spectral Points per BBC, and No. of Phase Centers per Pointing. Correlator resources are as valuable as Observing resources, so proposers are asked to justify the correlator resources as well as the observing resources. There are some interactions among correlation parameters as well as among correlator and observing parameters. Most of these interactions are not currently checked in the Tool.
      • Number of Correlator Passes: The number of correlator passes required (default one). Note that multiple positions can be correlated in a single pass with the Socorro correlator (and may be possible at other DiFX installations), and this is recommended if more than 2 positions are required (see the number of fields'' section below). If the multiple field/single pass correlation is used, the number of correlator passes'' field should remain at 1 unless multiple passes are also required for different correlator setups. If more than one correlator pass is required, a brief justification should be written in the Technical Justification Section.
      • Integration Period: The averaging time, in seconds, for the GMVA, in the Bonn correlator, defaults to 1 second. The shorter the averaging time, the larger the (rate) field of view. One must balance the output rate of the correlator with the required field of view.
      • Spectral Points / BBC: For continuum observations, the default number of spectral points is to have each point represent 0.5 MHz of bandwidth (for example a 32 MHz BBC bandwidth has a default number of spectral points of 64). For spectroscopy, the number of spectral points depends upon the required velocity resolution. As with averaging time, there is no hard upper limit to the number of spectral points per subband, but requests for more than 4096 points per subband, or values that would lead to a data rate ≥ 10 MB/s, require specific justification.
      • Number of Phase Centers per Pointing: The maximum number of phase centers to be correlated simultaneously in a single correlator pass (only available with the Socorro correlator, or other DiFX installations by special arrangement). The default is 1. If this feature is used, the source positions entered using this tool for pointings with multiple fields should be the pointing centers (i.e. it is not necessary to list every target source). However, the Scientific Justification should make it clear what the selection criteria for sources to be correlated will be. Use of this feature consumes additional correlator resources (although the increase is nearly constant at 2.5-3x normal'' correlation, regardless of the number of sources generated) and thus usage of this feature should be justified in the Scientific Justification. Due to this increase in required resources, for 2 phase centers it is more efficient to request two correlator passes (in which case number of fields should be set to 1). Thus, this feature should only be used for 3 or more target sources within a single primary beam. In principle there is no upper limit to the number of phase centers, but values which would cause the output data rate to exceed 10 MB/s must be specifically justified.
    • Special Features: These are special features in the correlator that may be needed. For the GMVA, Full Polarization is the only one selectable.
      • Full Polarization: If checked, the correlation of all polarization cross-products are requested, for each baseline: RR, RL, LR, and LL. If unchecked, only the correlation of parallel-hand products are requested: RR, LL, or RR and LL, depending on what was observed. Obviously, Full Polarization cannot be requested if only one polarization is observed; the Tool does check this.