VASAO: visible all sky adaptive optics: a new adaptive optics concept for CFHT

Abstract

International audienceVASAO is an ambitious project that explores new conceptual direction in the field of astronomical adaptive optics. In the era of 8 meter and larger telescopes, and their instrument costs and telescope time pressure, there is a natural niche for such ground-breaking conceptual development in the 4 meter class telescope. The aim of VASAO is to provide diffraction limited imaging in the visible with 100% sky coverage; the challenge (but potential rewards) arises from the simultaneity of these requirements. To this end, CFHT is conducting a feasibility study based on the polychromatic guide star concept (Foy et al., 1995 [4]) coupled with a high order curvature AO system, presented in this paper. A number of experiments have been started (or carried out) to study the challenges and limits of the techniques involved in an operational setting; these include the FlyEyes detector, and a polychromatic tip-tilt test on natural stars. Because such a project straddles such a fine line between facility instrument and experimental facility, careful thought has to be given to the balance between modes of operations and potential astrophysical targets

Pulsed frequency-shifted feedback laser for laser guide stars: intracavity preamplifier

“…In section 4 we discuss the experimental and theoretical results. This work corresponds to the first stage of the all-optical FSF laser channel that we are developing for CFHT-Lsp_On-sky Experiment (CLOE) project [18]. It will be followed by a single amplifier stage.…”

Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars

“…Nevertheless for sub-pupils located far away from the laser axis, the vertical structure of the sodium layer should be considered to account for the elongation of the LGS spot. Moreover, the effect of the evolution of the beam size and shape along the 10 km sodium layer should also be considered [6].…”