RCT 2.0 TTA Tester Tutorial

The following is a tutorial for the TTA group on how to setup the basics of a spectral line or spectral scan resource, as a proposer, in the new RCT 2.0. It is intended to show the ease of use creating the majority of the anticipated spectral line/scan resources.

It may be that the proposer is directed to this tool (as is now done with GOST) and uploads a png of the validation page (as is done for P- and 4-band), or that the proposer just provides lines (or uploads a file with lines) in the PST that triggers this algorithm and returns values to the PST. The TTA group should then decide how these return values are displayed in the PST, for example resemble the GOST table with a header with basic parameters and tables splitting out each subband in a baseband.

Please use webtest RCT 2.0 (on a Firefox web browser) for testing, using your my.nrao.edu login credentials. Note that there is also some more information, including known issues, available in the beta-tester information page (this page has not yet been updated to reflect the latest changes (2023June06 HM)).

 

Create a New Resource

For continuum observations it is assumed that the current resource creation in the PST will be sufficient and continued. For creating a spectral line/scan resource, as a potential replacement for GOST, here is a possible implementation that uses the RCT. For writing a proposal, the creation of a catalog probably would be suppressed, and the entire RCT interface may be omitted.

  • So we may more easily access your test resources, please select the shared resource catalog named "TTA testers".
  • To create a new resource, select  File → Create New → Instrument Configuration. 
  • You will now be presented with a "New Resource Wizard" pop-up box. (Any feedback on the terminology and wording to make this step more clear is very much appreciated.)
    • Spectral Line option will allow you to create or import lines and make use of the new automated system or if you prefer, use the manual setup option to generate the lines in their respective basebands. For this type of resource to validate, the Doppler setting is required.
    • Spectral Scan option will allow you to create or import lines as a visual aid for their location within the frequency range. This utilizes manual setup only and the Doppler setting is optional (i.e., not required to validate the resource).

Important Note: When creating a new Spectral Line resource, the default view of the graphical display at the top will always appear to be using the K-band resource. This is a default view built into the RCT. Once you have selected the "Automate" button or manually select the observing band in the Basebands tab, the graphical display will then show the requested frequency range.

 

Basics

If you are familiar with the original RCT, you will notice the Basics tab is no longer a tab. Instead, it is a box near the upper right. This is where the name of the resource and the correlator integration time are defined; default integration times per receiver band and array configuration are listed in the OSS.

 

Doppler Position Tab

This is unique to the Spectral Line setup option since this requires the use of the Doppler settings. Here you will enter in a source position. For testing purposes, any random position will do.

 

Lines Tab

In the Lines tab, you may either enter in the line information one-at-a-time or import a text file containing a list of lines to observe. If you chose to setup a Spectral Scan resource, the lines entered in the lines tab are only there as a visual aid and will not be generated as a subband. Below are options specific to a Spectral Line resource.

  • A few example text files in order of difficulty for setting up a Spectral Line resource are provided below. You may use your own lines if you prefer.
  • If you do not wish to use all of the lines uploaded in the "Lines" tab, you may deselect them in the column labeled "Use Line in Automated Setup" (for the Spectral Line option only).
  • You may also make any adjustments to the lines.

 

Basebands Tab

This is the part where the smarts of the new RCT are deployed (for the Spectral Line option only), where a single button will provide the user with a first suggestion of a possible setup to cover the requested lines or issue a warning if this is not feasible. The solution to the latter generally is to remove/deselect lines to be covered (in the "Lines" tab) and start anew.

  • Start Automated Setup  This will automatically generate the line coverage in their respective subbands and properly center the basebands. Only one receiver band will be activated when your lines are spread over frequencies spanning more than one band.
      • If all your lines fall below 4 GHz, i.e., up to the S-band frequency range, you will only be permitted to use the 8-bit system.
      • If all your lines fall within the 4-50 GHz frequency range, the RCT will select the system which best covers all of the lines. It will default to using the more line-sensitive 8-bit samplers, but in cases where necessary to cover all lines with the desired velocity coverage, it will use the 3-bit system.
      • You may manually make adjustments if you do not like what the RCT has selected. However, this may result in missing some lines if you choose the 8-bit system. Keep in mind, the hybrid 3/8-bit system may also be selected.
  • Start Manual Setup  This is essentially the same implementation as the original RCT and will require you to select the desired system (if applicable), set the baseband centers and generate each line/subband one-at-a-time. To see the table of lines and their respective Generate button, scroll down in the "Basebands" tab.
  • Shifting the baseband center frequencies can be done in two ways:
      • Use the '+' or '-' buttons next to the displayed baseband center frequency.  This will shift the baseband center frequency by multiples of +/- 128 MHz without changing the relative location of the subbands between the 128 MHz boundaries, or
      • Manually enter the desired center frequency, with the caveat of undoing the optimization for placing the subbands away from the 128 MHz boundaries.
      • If you shift the baseband center frequency or change the system after using the automated setup, you will need to manually generate a line if it resides in a different baseband.
      • Be aware of subbands that "hug" a 128 MHz boundary, which is a common symptom that may indicate an unwanted (and generally unnoticed) subband shift due to changing the baseband center. Unless using the Automated Setup and possibly the +/- buttons, if a subband and 128 MHz boundary "touch" after manually shifting the subband, that subband should be regenerated manually and subsequently may issue new warning messages.
  • Redo Automated Setup  If you do not like the changes you made after the automated setup, you may select "Redo Automated Setup" and it will remove all manual edits to the resource. Basically, starting over with the automated setup. 
  • If you wish to start over with the manual setup, then you will need to manually remove all subbands and lines from the Subbands tab.  The same as you would with the original RCT; note that this can be done in bulk.

 

Subbands Tab

Now you may add continuum subbands or make any adjustments to the lines, i.e., bandwidth (BW), polarization, Bl.BPs (baseline board pair stacking), and Recirculation.

  • If subbands overlap or are very close to each other, it may be beneficial to merge the subbands into one with a new subband center frequency and a wider bandwidth that covers the frequency ranges of the overlapping subbands — note that this typically requires to also change the recirculation factor and/or the number of baseline board pairs to keep the channel separation the same as in the original subbands.
  • You may also shift the baseband center frequency by +/- 128MHz from within the Subbands tab. (Again, you may need to manually generate a line if it resides in a new baseband.)
  • 3-bit limitation:   3-bit basebands cannot exceed the standard 16 subbands per baseband
  • 8-bit restriction:  8-bit basebands are a little more flexible
      • The standard is 8x 128MHz wide subbands per baseband to cover the entire continuum.
      • When observing in spectral line mode, 8-bit basebands can have up to 32 subbands. Exceeding 16 subbands per baseband will trigger a special mode requiring the use of data path 1. For simplicity, if you have many lines in a baseband and have filled the baseband with continuum subbands, toggle all of the continuum subbands on the left-hand side so the SBP number turns purple. More details and how to use more than 16 subbands per baseband, can be found in the OPT manual (32 subbands per 8-bit baseband).
      • Note that using overlapping coverage between the subbands/basebands does not physically yield any improvement to sensitivity.
  • Additional restrictions you many encounter for K, Ka, and Q-band are described in the OPT manual.
  • To avoid confusion during the proposal submission process, observers could avoid adding continuum subbands to their line resources and simply state they will add continuum later; we can create a button for this ("Yes, will use unused correlator resources for additional continuum coverage if possible.") but with the note that if continuum is part of the science, a full continuum sensitivity calculation and complete correlator setup should be provided in the proposal.

 

Doppler Settings Tab

This part goes into the details of the actual observing and would be skipped during the proposal submission process. That is, at this time the Doppler tracking position and line frequency to calculate the actual observing frequencies are irrelevant - they may change up to a few MHz from what is generated above, and will shift the entire basebands with up to that amount, keeping the relative subband/baseband structure intact.

  • For a Spectral Line setup, the Doppler setting must be utilized in order for it to pass through the validation algorithm. During the proposal submission process, this would ideally not be enforced.
  • For a Spectral Scan setup, the Doppler setting option is not required for the validation algorithm.

 

Special Modes Tab

Similarly to the Doppler settings, this can be ignored for now.

 

Comments Tab

For personal notes/reminders regarding the setup.

 

Validation Tab

Check that the resource validates.

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