Correcting sensor based PSF ellipticity Tony Tyson
Steps • Characterization of CCD based shear systematics • Systematics suppression via ISR and observing strategy • Validation via simulations • Dither schemes and ComCam validation
SRD goals for shear systematics reduction
Brighter-fatter xy assymetry Craig Lage 2018
Serial register deferred charge In some ITL segments Craig Lage 2018
Serial register deferred charge In some ITL segments Andrew Bradshaw 2018
CCD B-F & serial anisotropies Don’t average down like root 1/N_fields. Suppress by factor of 30 via two steps: • Pixel pipeline processing correction • Camera rotation dithering
ISR and residuals Application of ISR kernel correction Andrew Bradshaw 2018
Shear systematic imprinted on sky 100 rotation dithers James Jee + TT 2015 WL Workshop
Science-Driven Optimization of the LSST Observing Strategy Shear systematic imprinted on sky 1708.04058 Ch9 Josh Meyers & TT
Residual systematics suppression • Need uniform distribution of PSF ellipticity over all visits to a field • Requires camera rotator span -90 to +90 deg • But not uniformly! Weather, seeing variations. • Sets Observatory Scheduler requirements • Validate dithering scheme early with ComCam deep drilling tests
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