Progress Report on Modeling CTE in ACS/WFC TIPS May 19, 2011 Jay Anderson

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%

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…

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

Life is never easy… 1000s DARK * 33/ s DARK 5000 e  in deep

CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500

CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500

CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500

CLOSE TO READOUT FAR FROM READOUT 33s DARK100s DARK339s DARK J~1000 J~1500

FIXED… 33s DARK100s DARK339s DARK

The Trails HIGH WP LOW WP

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

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

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

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…

Column-by-Column dependency PHYSICAL PRE-SCAN MAGIC SQUARE OVER-SCAN DEEPLY EXPOSED FLAT

ACS OVER TIME P1WP

ACS OVER TIME P1WP JULY 2006 TEMP CHG BEFORE:  77  C AFTER:  81  C

ACS OVER TIME P1WP

FAR FROM; UNCORR

FAR FROM AMP; CORR

NEAR AMP; CORR