Investigation of the Scratched Tape Scattered Light Artifact at Rubin Observatory

Abstract

The “scratched tape” stray light feature is the most prominent and prevalent stray light artifact identified during the commissioning of the Vera C. Rubin Observatory. The scratched tape feature originates when light from large off-axis angles (∼20 deg) passes between the mid-level and center-section light baffles, reflects off of the primary mirror (M1), and illuminates the LSST Camera focal plane. This scenario represented an unobstructed light path to the sky during Rubin commissioning due to delays in the integration of the dome slit light–wind screen. This document describes the identification, modeling, characterization, and proposed stop-gap mitigation strategy for the scratched tape stray light artifact.