Uniformity and Stability of the LSST Focal Plane

Abstract: The LSST focal plane consists of 21 autonomous modules ("Raft Tower Modules", RTM), each of which contains nine thick, fully-depleted 4K x 4K CCDs with associated control and readout electronics. To enable LSST's repetitive short-exposure cadence while maintaining high duty factor and low read noise, the readout is highly parallelized into 3024 independent video channels (16 per CCD, 144 per RTM). Two vendors supplied the LSST sensors; the devices have compatible mechanical and electrical interfaces and meet the same electro-optic specifications, but each RTM is constructed with sensors from a single supplier. The full complement of rafts were assembled at Brookhaven National Laboratory during January 2017 - March 2019. Each unit underwent extensive electro-optic and metrology characterization at operating temperature, the results of which are presented here along with a discussion of uniformity and stability.