N'DIAYE , M.

Context. Segmented aperture telescopes require an alignment procedure with successive steps from coarse alignment to monitoring process in order to provide very high optical quality images for stringent science operations such as exoplanet imaging. The final step, referred to as fine phasing, calls for a high sensitivity wavefront sensing and...

Direct imaging of exoplanets is very attractive but challenging and specific instruments like Sphere (VLT) or GPI (Gemini) are required to provide contrasts up to 16-17 magnitudes at a fraction of arcsec. To reach higher contrasts and detect fainter exoplanets, more-achromatic coronagraphs and a more-accurate wavefront control are needed. We...

Circumstellar environments are now routinely observed by dedicated high-contrast imagers on large, ground-based observatories. These facilities combine extreme adaptive optics and coronagraphy to achieve unprecedented sensitivities for exoplanet detection and spectral characterization. However, non-common path aberrations (NCPA) in these...