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Published byAngela Welch Modified over 8 years ago
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Progress Report on Modeling CTE in ACS/WFC TIPS May 19, 2011 Jay Anderson
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CTE in ACS/WFC Brief review Many many ISRs… –Riess, Mack, Chiaberge… Massey et al paper in 2010 –Modeled WPs in COSMOS images –50e- background ; assumed mini-channel Anderson/Bedin 2010 correction –Modeled WPs in darks Two parameters: – (q) - the density of traps at electron level – (j;q)-the trail profile for electron level –V low background; no mini-channel –Implemented into CAL/ACS in Fall. –Good job, but… 25% 15% 10%
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Limitations to the Implemented Algorithm 1)1000s Darks are only so dark Could not probe below 30 e ACS team took shorter darks: 33s, 100s, 339s <30 e WPs more sparse “truth”-type constraints on the model improved model… 2)Mild deconvolution Necessarily amplifies noise Readnoise in particular causes problems 3)Pathological cases When are more than 50% of e lost? 90%? No remedy, but insight…
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Updated Model Improvements –Constrain low e traps better Both the trap density ( ) and release profiles ( ) –Do the charge transfer iteratively Old: 2048 transfers in one step New: 2048 transfers in N (~5) steps Optimization –Fit model to long and short darks
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Life is never easy… 1000s DARK * 33/1000 33s DARK 5000 e in deep
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CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500
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CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500
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CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500
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CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500
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FIXED… 33s DARK100s DARK339s DARK
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The Trails HIGH WP LOW WP
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New Model (q) trap density –below 10e : >99% chance of loss! (j;q) trail profile for electron level –a surprise… –Lower e - traps have steeper trails “Low” trap trails go out to only 19 pixels “High” trap trails go out to 60 pixels
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New Model (q) trap density –below 10e : >99% chance of loss! (j;q) trail profile for electron level –a surprise… –Lower e - traps have steeper trails “Low” trap trails go out to only 19 pixels “High” trap trails go out to 60 pixels
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New Model (q) trap density –below 10e : >99% chance of loss! (j;q) trail profile for electron level –a surprise… –Lower e - traps have steeper trails “Low” trap trails go out to only 19 pixels “High” trap trails go out to 60 pixels
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ACS Team Plans 1) Port to Python / IRAFX 2) How to modify the error array? 3) How best to mitigate readnoise? 4) Column by column fine-tuning? 5) How does CTE impact S/N? (When pathological?) 6) Integrate into pipeline (darks, new products) 7) x-CTE and bias-shift effect de-striping, too… 8) Time dependency 9) UDF/HDF comparisons 10) Validation against standard tests: recommendations 11) Optimization within Multi-drizzle… NEXT: UVIS…
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Column-by-Column dependency PHYSICAL PRE-SCAN MAGIC SQUARE OVER-SCAN DEEPLY EXPOSED FLAT
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ACS OVER TIME P1WP
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ACS OVER TIME P1WP JULY 2006 TEMP CHG BEFORE: 77 C AFTER: 81 C
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ACS OVER TIME P1WP
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FAR FROM; UNCORR
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FAR FROM AMP; CORR
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NEAR AMP; CORR
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