Reflective engineered diffusers on the Roman Space Telescope Wide Field Instrument

Abstract

NASA’s Roman Space Telescope’s Wide Field Instrument mosaic detector array of 18 H4RG-10 chips requires regular and uncommonly accurate calibrations to meet its science objectives. In addition to the quasi-Lambertian diffuser used for detector flat-fielding, a novel engineered diffuser is incorporated as part of seven cold stop masks on the science bandpass filters. These engineered diffusers are used to illuminate the focal plane concurrently with an exposure from the observatory, enabling signal-dependent nonlinearity corrections. This presentation demonstrates via experimental data how these diffusers can produce a spatially uniform and smooth illumination profile with increased flux compared to a Lambertian diffuser.