The Palomar Kernel Phase Experiment: Testing Kernel Phase Interferometry for Ground-based Astronomical Observations

摘要

At present, the principal limitation on the resolution and contrast ofastronomical imaging instruments comes from aberrations in the optical path,which may be imposed by the Earth's turbulent atmosphere or by variations inthe alignment and shape of the telescope optics. These errors can be correctedphysically, with active and adaptive optics, and in post-processing of theresulting image. A recently-developed adaptive optics post-processingtechnique, called kernel phase interferometry, uses linear combinations ofphases that are self-calibrating with respect to small errors, with the goal ofconstructing observables that are robust against the residual opticalaberrations in otherwise well-corrected imaging systems. Here we present adirect comparison between kernel phase and the more established competingtechniques, aperture masking interferometry, point spread function (PSF)fitting and bispectral analysis. We resolve the alpha Ophiuchi binary systemnear periastron, using the Palomar 200-Inch Telescope. This is the first casein which kernel phase has been used with a full aperture to resolve a systemclose to the diffraction limit with ground-based extreme adaptive opticsobservations. Excellent agreement in astrometric quantities is found betweenkernel phase and masking, and kernel phase significantly outperforms PSFfitting and bispectral analysis, demonstrating its viability as an alternativeto conventional non-redundant masking under appropriate conditions.