Laboratory Measurements of Instrumental Signatures of the LSST Camera Focal Plane

TL;DR

This paper details the electro-optical testing of the LSST Camera focal plane using custom optical projectors to measure instrumental signatures like crosstalk, astrometric shifts, and the brighter-fatter effect, aiding in calibration and correction algorithms.

Contribution

It introduces the design and application of optical projectors for detailed instrumental signature measurements of the LSST Camera focal plane.

Findings

Successful measurement of crosstalk, linearity, and full well.

Identification of instrumental signatures such as deferred charge distortions.

Improved algorithms for instrumental signature removal.

Abstract

Electro-optical testing and characterization of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Camera focal plane, consisting of 205 charge-coupled devices (CCDs) arranged into 21 stand-alone Raft Tower Modules (RTMs) and 4 Corner Raft Tower Modules (CRTMs), is currently being performed at the SLAC National Accelerator Laboratory. Testing of the camera sensors is performed using a set of custom-built optical projectors, designed to illuminate the full focal plane or specific regions of the focal plane with a series of light illumination patterns: the crosstalk projector, the flat illuminator projector, and the spot grid projector. In addition to measurements of crosstalk, linearity and full well, the ability to project realistically-sized sources, using the spot grid projector, makes possible unique measurements of instrumental signatures such as deferred charge distortions, astrometric shifts due to sensor effects, and the brighter-fatter effect, prior to camera first light. Here we present the optical projector designs and usage, the electro-optical measurements and how these results have been used in testing and improving the LSST Camera instrumental signature removal algorithms.