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  1. Data Management
  2. DM-26582

Add spline fit to ISR linearizers

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    Details

    • Type: Improvement
    • Status: Invalid
    • Resolution: Done
    • Fix Version/s: None
    • Component/s: cp_pipe, ip_isr
    • Labels:
      None
    • Team:
      Data Release Production

      Description

      It has become clear that, as discussed in Astier, et.al., we need to correct the non-linearity of the ASPIC amplifiers.  I created a linearizer with the current cubic polynomial fit using measurePhotonTransferCurve.py, then applied it using the ISR and re-ran measurePhotonTransferCurve.py.  It did not correct the "bump" around 50,000 ADU, as shown in the attached NonLinearity_R22S11_C04_25Aug20.png.  Astier, et.al. recommend using a spline fit to better capture the nature of the bump.  I implemented this in a notebook at NCSA at:

      /project/cslage/BOT_lspdev/notebooks/Linearity_Study_Sat_02Sep20.ipynb

      and also uploaded it to git hub at:

      https://github.com/craiglagegit/ScratchStuff/blob/master/notebooks/Linearity_Study_Sat_02Sep20.ipynb

      It does a much better job at correcting the bump, although not as good as in Pierre's paper. You can see the improved correction in the attached NonLinearity_Correction_R22S11_C04_02Sep20.png.  Both of these plots are analogous to Figure 3 in Astier, et.al.  

      Note that the expTime data in this notebook was generated by applying the MONDIODE correction.  In order to do this, I modified ptc.py with the following lines.  While I added "fudge factors" for three of the neutral density filters, I think this is not that critical since I ended up not using the low flux points in the spline fit.  Please contact me if any of this is not clear.  I think the next step is to implement the spline correction, which I think Chris Waters may already be working on.  Then we can try correcting the flux in the ISR using the spline fit and re-do the PTC curves.  

      # Lage - 24Aug20 changes below to include mondiode                                                                                                                                                                                 
      md1 = exp1.getMetadata()
      md2 = exp2.getMetadata()
      filter2 = md1['FILTER2'].split('D')[2]
      mondiodeNormalizer = 3.0E-9 # This puts the exptime back in the normal range                                                                                                                                                       
      try:
          mondiode = (md1['MONDIODE'] +  md2['MONDIODE']) / 2.0 / mondiodeNormalizer
      except:
          continue
      useMondiode = True
      if useMondiode:
          if filter2 == '1.0':
              fudgeFactor = 0.98 # Empirically determined fudge factor to compensate for ND filter error                                                                                                                                 
              mondiode *= fudgeFactor
          if filter2 == '0.5':
              fudgeFactor = 0.9876 # Empirically determined fudge factor to compensate for ND filter error                                                                                                                               
              mondiode *= fudgeFactor
          if filter2 == '0.3':
              fudgeFactor = 0.9961 # Empirically determined fudge factor to compensate for ND filter error                                                                                                                               
              mondiode *= fudgeFactor
          expTime = expTime * mondiode
      

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            czw Christopher Waters added a comment -

            Useful information that I'll link to the other ticket to save time.

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            czw Christopher Waters added a comment - Useful information that I'll link to the other ticket to save time.

              People

              Assignee:
              czw Christopher Waters
              Reporter:
              cslage Craig Lage
              Reviewers:
              Andrés Alejandro Plazas Malagón, Merlin Fisher-Levine
              Watchers:
              Christopher Waters, Craig Lage
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              Watchers:
              2 Start watching this issue

                Dates

                Created:
                Updated:
                Resolved: