Pioneering exoplanet reflected-light spectroscopy with RISTRETTO: a pathfinder for ANDES and PCS

RISTRETTO is a proposed visitor instrument for the VLT which will combine high contrast and high spectral resolution at the diffraction limit of the telescope to probe exoplanets in reflected light. It will be able to characterize our nearest neighbour Proxima b, a temperate rocky world. It will also explore super-Earths, Neptunes and cold Jupiters around nearby stars. Moreover, RISTRETTO will address accreting protoplanets through their H-alpha emission and the kinematics of protoplanetary disks through Doppler shift measurements in scattered light. It will also offer new capabilities in the field of stellar physics. In this contribution I will discuss the science cases and present the current status of the instrument. The spectrograph is in the integration phase, and first laboratory results will be presented. I will also show innovative concepts for the adaptive optics front-end which have been successfully demonstrated: a coronagraphic integral-field unit and an infrared, 3-sided unmodulated Pyramid wavefront sensor. I will present the RISTRETTO end-to-end simulator, which shows that molecular absorption in the atmosphere of Proxima b can be detected in about 85 hours of observing time for an Earth-like composition. Finally, I will discuss how RISTRETTO can be used as a pathfinder for the SCAO mode of ANDES and the future PCS instrument at the ELT.