FALCO simulations of high-contrast polarimetry with the Nancy Grace Roman Space Telescope coronagraph instrument

Abstract

The Coronagraph Instrument of the Nancy Grace Roman Space Telescope (Roman Coronagraph) will be capable of both total intensity and polarization measurements of circumstellar disks. The polarimetric performance is impacted by polarization effects introduced by all mirrors before the Wollaston prisms. In this paper, we aim to characterize these effects for the Roman Coronagraph in bands 1 and 4 using the FALCO and PROPER packages. We simulate the effect of polarization aberrations that impact the polarimetric contrast and the instrumental polarization effects to study the polarimetric accuracy. We include spacecraft rolls, but leave out systematic camera noise. We find that polarimetric differential imaging (PDI) improves the contrast by a factor of six. The PDI contrast of ∼ 8 × 10 −11 is limited by polarized speckles from instrumental polarization effects and polarization aberrations. By injecting polarized companions with at various contrast levels and demodulating their polarimetric signal, we recover their source Stokes vector within 2%.

Simulation of High-contrast Polarimetric Observations of Debris Disks with the Roman Coronagraph Instrument

“…The instrumental polarization, 0.92%, and polarization rotation 0.99 × 10 −6 obtained from the instrument Mueller matrix are within the expected measurement error and can be easily calibrated. The Lu-Chipman decomposition of the Mueller matrices in Doelman et al (2023) shows that the negative Q out is obtained due to a mirror and a retarder in the optical path.…”