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

• 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