Kavli Affiliate: Aaron Roodman
| First 5 Authors: Johnny H. Esteves, Yousuke Utsumi, Adam Snyder, Theo Schutt, Alex Broughton
| Summary:
The Vera C. Rubin Observatory’s LSST Camera (LSSTCam) pixel response has been
characterized using laboratory measurements with a grid of artificial stars. We
quantify the contributions to photometry, centroid, point-spread function size,
and shape measurement errors due to small anomalies in the LSSTCam CCDs. The
main sources of those anomalies are quantum efficiency variations and pixel
area variations induced by the amplifier segmentation boundaries and
"tree-rings" – circular variations in silicon doping concentration. This
laboratory study using artificial stars projected on the sensors shows overall
small effects. The residual effects on point-spread function (PSF) size and
shape are below $0.1%$, meeting the ten-year LSST survey science requirements.
However, the CCD mid-line presents distortions that can have a moderate impact
on PSF measurements. This feature can be avoided by masking the affected
regions. Effects of tree-rings are observed on centroids and PSFs of the
artificial stars and the nature of the effect is confirmed by a study of the
flat-field response. Nevertheless, further studies of the full-focal plane with
stellar data should more completely probe variations and might reveal new
features, e.g. wavelength-dependent effects. The results of this study can be
used as a guide for the on-sky operation of LSSTCam.
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