LSST optical beam simulator

TL;DR

This paper presents a sophisticated optical beam simulator for LSST that enables realistic testing of CCD performance and systematics under conditions mimicking actual observations, aiding in the development of better astronomical imaging sensors.

Contribution

The paper introduces a novel LSST beam simulator capable of illuminating large fields with realistic scenes, facilitating detailed CCD characterization and systematics analysis.

Findings

Optical quality meets design specifications with 50% energy within 5 microns.

The simulator effectively reproduces LSST observing conditions for CCD testing.

It enables analysis of charge transport effects in thick, fully depleted CCDs.

Abstract

We describe a camera beam simulator for the LSST which is capable of illuminating a 60mm field at f/1.2 with realistic astronomical scenes, enabling studies of CCD astrometric and photometric performance. The goal is to fully simulate LSST observing, in order to characterize charge transport and other features in the thick fully depleted CCDs and to probe low level systematics under realistic conditions. The automated system simulates the centrally obscured LSST beam and sky scenes, including the spectral shape of the night sky. The doubly telecentric design uses a nearly unit magnification design consisting of a spherical mirror, three BK7 lenses, and one beam-splitter window. To achieve the relatively large field the beam-splitter window is used twice. The motivation for this LSST beam test facility was driven by the need to fully characterize a new generation of thick fully-depleted CCDs, and assess their suitability for the broad range of science which is planned for LSST. Due to the fast beam illumination and the thick silicon design [each pixel is 10 microns wide and over 100 microns deep] at long wavelengths there can be effects of photon transport and charge transport in the high purity silicon. The focal surface covers a field more than sufficient for a 40x40 mm LSST CCD. Delivered optical quality meets design goals, with 50% energy within a 5 micron circle. The tests of CCD performance are briefly described.