Polarization aberrations in next-generation Giant Segmented Mirror Telescopes (GSMTs)

Context . Direct exo-earth imaging is a key science goal for astronomy in the next decade. This ambitious task imposes a target contrast of ≈10 −7 at wavelengths from I to J -band. In our prior study, we determined that polarization aberrations can limit the achievable contrast to 10 −5 to 10 −6 in the infrared. However, these results assumed a perfect coronagraph coupled to a telescope with an ideal coating on each of the mirrors. Aims . In this study we seek to understand the influence of polarization aberrations from segment-to-segment coating variations on coronagraphy and polarimetry. Methods . We use the Poke open-source polarization ray tracing package to compute the Jones pupil of each GSMT with spatially- varying coatings applied to the segments. The influence of the resultant polarization aberrations is simulated by propagating the Jones pupil through physical optics models of coronagraphs using HCIPy. Results . After applying wavefront control from an ideal adaptive optics system, we determine that the segment-to-segment variations applied limit the performance of coronagraphy to a raw contrast of approximately 10 −8 in I -band, which is 2–3 orders of magnitude lower the target performance for high-contrast imaging systems on the ground. This is a negligible addition to the nominal polarization aberrations for ground-based systems. We further observe negligible degradation in polarimetric imaging of debris disks from segment-to-segment aberrations above and beyond the impact of nominal polarization aberration.