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.

中文翻译：

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使用人造星在 LSST 相机焦平面中进行光度测量、质心和点扩散函数测量


Vera C. Rubin 天文台的 LSST 相机 (LSSTCam) 像素响应已使用人造恒星网格的实验室测量进行了表征。我们量化了 LSSTCam CCD 中的小异常对光度、质心、点扩散函数大小和形状测量误差的影响。这些异常的主要来源是放大器分段边界和“年轮”（硅掺杂浓度的圆形变化）引起的量子效率变化和像素面积变化。这项使用投射在传感器上的人造星进行的实验室研究显示，总体影响很小。对点扩散函数（PSF）大小和形状的残余效应低于0.1%，满足十年LSST调查科学要求。然而，CCD 中线存在失真，可能对 PSF 测量产生中等影响。可以通过屏蔽受影响的区域来避免此功能。在人造星的质心和 PSF 上观察到树木年轮的影响，并且通过平场响应的研究证实了该影响的性质。然而，利用恒星数据对全焦平面进行进一步研究应该更全面地探测变化，并可能揭示新的特征，例如波长相关效应。本研究结果可为LSSTCam的在空运行提供指导。