ALMA Single Dish Pipeline Meeting

  • Jul 28-30 2014
  • Socorro New Mexico

Attendance
  • Jeff Kern
  • Cat Vlahakis
  • Hiroko Shinnaga
  • George Kosugi
  • Bunyo Hatsukade
  • Takeshi Nakazato
  • Kana Sugimoto

Day 1: July 28

  • Note: Single Dish Observing Mode will change at start of cycle 3
    • Will include more efficient calibrations, including overheads.
    • Better and more flexibility in spatial sampling (5 X Beam along row, 3 X Beam perp)
    • How often are off's taken and where
  • Linearity Correction:
    • In early science apply constant correction factor (fix comes in Feb 2015)
    • Scripted Pipeline apply factor of (1.2)
    • Need to understand exactly what happens here. Cat to give a summary tomorrow.
    • PROTO-DECISION: Based on understanding that this is an imaging only correction will apply as part of Scan Table to MS translation.
    • Perhaps better to only apply to the image (AI: Cat to clarify)
  • Single Dish Pipeline Overview:
    • Calibration
      • Using SDCal2
      • T_sys solutions are the same derived from SDCAL2
      • Both versions are using the same code
    • Baseline
      • Selection of channels is done manually in the script
      • ACTION: Automated pipeline stage needs commissioning
    • To Do: Add Edge channel flagging
      • We should actually Flag data
      • Adding Channel Flagger to Pipeline (Heuristic contact Eric V.)
    • Inspect Data:
      • DECISION: Compare get TP Sampling to detail plots in the inspect Data method.
        • What is the definition of the "off"
        • Relative offsets
        • TP Sampling plot to go in weblog on the MS Splash Page (talk to Todd about the code, should we rewrite this or just use what they have.)
    • SD Imaging:
      • What gridding function should we be using in the imaging.
      • To Do: Commission the GJINK gridding function
      • Decision:
        • SD Pipeline will for now use Prolate Sepheroidal
        • Cell size to be beam size / 9.0
        • convsupport = 6 (size of kernel) * Decision: Transition to making I image as output * To Do: Jansky to Kelvin Discussion *
    • Amplitude Calibrator:
      • DECISION: Increase number of edge points used as offs to 35%
      • QUESTION: What happens if the calibrator does not have the required 6 beams on edge? QA0 Fail!
    • Flagging:
      • Automated Flags: Edge Channels
      • Add Deterministic flagging stage
      • May need to flag atmospheric features.
    • PlotBandpass
      • Only in the Tsys plots
      • QUESTION: When should we make the transition to plot bandpass
      • (would need to create interferometric Tsys Cal table)

Day 2: July 29

Topics for further Discussion:
  • Linearity Correction:
    • The factor of 1.2 will be applied in a special step in the pipeline to facilitate direct comparison with the scripted pipeline in Dec.
    • DECISION: To be implemented in single dish pipeline
    • DECISION: PI's must be warned that their data has the Nonlinearity correction issue and will not be processed via. standard pipeline.
    • DECISION: Official Pipeline will only handle the data that is taken after Feb.

  • Upcoming changes
    • Changes to the "OFFs":
      • Multiple Offs:
        • An off and an off for the off
      • Not clear who has responsibility
    • Testing of the OFFs can we use the pipeline to help? Sounds like they have a script in place for now.
    • Future of Amp Cal:
      • Likely will ditch this ASAP (Cycle 3 is going to be the same)
      • May ditch Amp Cal altogether and just use a lookup table
        • Would require an Astro Holography run
    • Scanning in Az / El and other coordinate systems
    • Absolute Coordinates for off position
    • Calibration Efficiency (mitigation of overheads)
      • Would allow more Tsys at high frequency
    • Changes in scan length
    • Gridding functions
    • Identification of subscan / rasters
      • DECISION: Heuristic based on time gaps and position gaps
    • Fast Scanning Modes?
    • True basket weaving (CSV-239)
      • Needed for Fast Scanning modes
      • Probably a cycle 5 target
      • Implementation Schedule
  • Tsys Cal: What to do?
    • Can we take the interferometric Tsys cal and generate the SD:TsysCal from it
    • DECISION: To use interferometric Tsys table for flagging etc, then cross fill that to the SD:CalTable (including flags)
      • May not make it for 4.3, but perhaps for a November patch (?)
  • Reduction Issues
    • Determine Beamsize:
      • getFWHM2: Find half power (subtract and then do a root find) in a azimuthal average
      • Alternatively use a theoretical value:
        • Values in CASA repository are voltage, in AU they use the squares (complex2Square)
  • Kelvin to Jansky Conversion
    • Jy/K is coming from Amplitude calibrator
    • AI: Cat to define if the Jy/K is done before or after imaging.
  • Position of antenna is off in 4.2.2
    • Correct version is in 4.3
  • RECOMMENDATION: Only use PM antenna's on the ACA pad.
  • Open Issues
    • Jy/K issues:
      • 1.2 vs. 1.3 for the linearity correction
    • Antenna Positions
    • Brogan:
      • Average value of Tsys rather than spectral side <- Done by Bunyo
      • Use of weights in the imaging

-- JeffKern - 2014-07-28
Topic revision: r6 - 2014-07-30, JeffKern
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