On-sky results of the Leiden EXoplanet Instrument (LEXI)


The Leiden EXoplanet Instrument (LEXI) is a bench-mounted high-contrast spectrograph (HCS) and high- contrast imager(HCI). Both science instruments are mounted behind a common adaptive optics (AO) system. The AO can be controlled by several new wavefront sensors for which we will show the first on-sky results. There is a new pupil-plane wavefront sensors; the Generalized Optical Differentiation Wavefront sensor(g-ODWFS). LEXI can switch between two observing modes, the HCI mode or the HD-IFS mode. The spectrograph is very compact because it is fed by single- mode fiber. The HD-IFS is an IFS that covers the spectral range of 600 800 nm with a constant spectral resolving power of 96000. The 2kx3k detector makes it possible to deliver diffraction limited spectra of up to 20 input fibers. The high-dispersion spectra of the HD-IFS allow for robust post-processing technique to remove residual stellar speckles and allows for direct characterization of the faint stellar environment. We will show the first sucesful on-sky results of the injection into a single-mode fiber with LEXI. In HCI mode an Apodizing Phase Plate (APP) is used to create a dark region around the star with an average design contrast of 1E-4. The APP is multiplexed with holographic modes to create the Coronagraphic Modal Wavefront sensor (cMWS) for non-common path error (NCPE) correction. The cMWS creates holographic copies in the focal plane that react linearly to aberrations. The holographic copies are measured simultaneously with the science target. There is no downtime for NCPE correction. We will show the first on-sky closed-loop correction of (NCPEs) with the cMWS.