Coronagraphy robust to segmented aberrations: low-wind effect mitigation on Subaru/SCExAO

Low-wind effect is a strong limitation to direct imaging of exoplanets from ground-based telescopes, such as the Subaru telescope, the Very Large Telescope and probably the future extremely large telescopes. To mitigate it, we propose to design coronagraphs passively robust to low-wind effect. The Redundant Apodized Pupils (RAPs) are built so each pupil petal independently contributes to the contrast and therefore petal-level errors do not impact the final coronagraphic image, up to the loss of coherence in the star i m age. In this paper, w e present the first experimental validation of the RAP concept, which is now applied on the Subaru/SCExAO instrument. We have designed three RAPs: two for the infrared channel (CHARIS) and one for the visible instrument (VAMPIRES). After these designs having been set up on the instrument in September 2023, we conducted internal source tests and obtained a contrast robustness up to a few radians. After this first e x perimental a p plication, t h e RAP technology will be adapted, at higher contrasts (10⁻⁸-10⁻⁹), to segment-level errors, one of the main limitations for space segmented telescopes like the Habitable Worlds Observatory.