Kavli Affiliate: Stuart Marshall
| First 5 Authors: Alex Broughton, Yousuke Utsumi, Andrés Plazas Malagón, Christopher Waters, Craig Lage
| Summary:
Thick, fully depleted charge-coupled devices (CCDs) are known to exhibit
non-linear behavior at high signal levels due to the dynamic behavior of
charges collecting in the potential wells of pixels, called the brighter-fatter
effect (BFE). This particularly impacts bright calibration stars, which appear
larger than their intrinsic shape, creating a flux-dependent point-spread
function (PSF) that if left unmitigated, could make up a large fraction of the
error budget in Stage IV weak-lensing (WL) surveys such as the Legacy Survey of
Space and Time (LSST). In this paper, we analyze image measurements of flat
fields and artificial stars taken at different illumination levels with the
LSST Camera (LSSTCam) at SLAC National Accelerator Laboratory in order to
quantify this effect in the LSST Camera before and after a previously
introduced correction technique. We observe that the BFE evolves
anisotropically as a function of flux due to higher-order BFEs, which violates
the fundamental assumption of this correction method. We then introduce a new
sampling method based on a physically motivated model to account these
higher-order terms in the correction, and then we test the modified correction
on both datasets. We find that the new method corrects the effect in flat
fields better than it corrects the effect in artificial stars which we conclude
is the result of a unmodeled curl component of the deflection field by the
correction. We use these results to define a new metric for the full-well
capacity of our sensors and advise image processing strategies to further limit
the impact of the effect on LSST WL science pathways.
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