SRDP

Science Ready Data Products

The Science Ready Data Products (SRDP) Initiative

The SRDP Initiative aims to improve the user experience for radio interferometry data from the VLA and ALMA by providing users with science quality data and tools for data processing and discovery through the NRAO archive.

Quick Access to SRDP Features: Visit the NRAO Archive https://data.nrao.edu

 Download calibrated Measurement Sets for VLA or ALMA:

  1. Go to https://data.nrao.edu
  2. Search for some data (e.g., project code, target name, position/radius)
  3. Click the '+' to see more detail about the project
  4. For ALMA - Click the blue 'Download Restored MS' button for the desired data
  5. For VLA - Click the 'Select for Download icon' and click 'Download'

Run ALMA User-Defined Imaging (AUDI):

  1. Follow steps 1-3 from above
  2. Click the blue 'Re-imaging' button for the desired data
  3. Fill out the dialog box for a frequency-based or velocity-based cube
    • A valid setting for the frequency-based cube is filled by default for the selected spectral window

 See the tutorial video for AUDI for more detail.

 

SRDP Features At a Glance

SRDP features will be released approximately yearly, with subsequent releases adding new features and enhancing existing features. SRDP began pilot operations in June 2019  with the following features:

  • Quality Assured calibration and continuum imaging for selected VLA projects
    • To qualify for SRDP calibration and imaging the following conditions must be met:
      • Observations should be in C, X, Ku, K, Ka, or Q bands (may include multi-band datasets that do not use any other bands).
      • The SRDP pipeline is optimized for continuum science. Observations should have wide (~1 GHz or wider) bandwidths (i.e. be focussed on continuum science, not on narrow spectral lines).
      • Scheduling blocks need to follow the recommended calibration strategy for the band, with standard intents.
      • Phase calibrators should not be significantly resolved (<5%).
      • Observations should use one of the two standard flux calibrators that has not varied recently (3C286 or 3C147). Observations using 3C48 or 3C138 as calibrators are currently excluded.
    • Continuum imaging is performed on the calibrated data on a per-target, per execution block basis.
    • Polarimetric (cross-hand phase and leakage) calibration is not currently included, though Stokes I SRDP calibration will be performed on polarimetric datasets that satisfy the conditions above.
  • ALMA Calibrated Measurement set download
    • Cycle 5 data and beyond
    • only available for data calibrated by pipeline (no manual reductions)
  • VLA Calibrated Measurement set download
    • only available for data for which calibration pipeline run was successful
  • Updated NRAO archive interface (data.nrao.edu)
  • ALMA User-Defined Imaging
    • Generate datacube with a custom spectral axis from a pipeline-reduced dataset
    • User-defined spectral width of cube
    • Velocity or frequency definitions supported
    • Channel averaging
    • Angular resolution modification (higher or lower resolution). This is limited by what data will allow, one may not exactly get their requested resolution.
    • Attempt self-calibration based on continuum data and apply to lines if successful (new June 2023!)
      • Both non-self-calibrated and self-calibrated images will be provided to users
    • Continuum (aggregate and per-spectral window) produced as ancillary product
    • Quality assurance to check that the datacube is of good quality, with no obvious artifacts, and has the RMS and beam size expected given the data it was constructed from. (Note this is distinct from the ALMA QA process, and is designed only to catch problems with the images.)

Pre-requisites:

The SRDP system features are publicly available; any user from any country or ALMA region may utilize the SRDP system. Logins are only required if a user wishes to access proprietary data or local delivery of data to the NRAO Lustre file systems. Accounts can be created at my.nrao.edu.

Account Linking

Users were previously able to link their NRAO and ALMA accounts via the ALMA Science portal, which enabled users to use their NRAO account to access both proprietary VLA/VLBA and ALMA data. However, this capability was disabled by the ALMA project. Thus, users who did not previously link their accounts will likely need to login with their ALMA account to access proprietary ALMA data and their NRAO account to access proprietary NRAO data.

Help with SRDP products:

Please visit the NRAO helpdesk and submit a ticket under the ‘Data Products’ Topic.

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