Performance and results of the NAOS visible wavefront sensor

Philippe Feautrier, Gerard Rousset, Reinhold J. Dorn, Cyril Cavadore, Julien Charton, Claudio Cumani, Thierry Fusco, Norbert N. Hubin, Pierre Y. Kern, Jean-Luis Lizon, Yves Magnard, Pascal Puget (+5 others)
2003 Adaptive Optical System Technologies II  
The NAOS adaptive optics system was installed in December 2001 on the Nasmyth focus of the ESO VLT. It includes two wavefront sensors: one is working at IR wavelengths, the other at visible wavelengths. This paper describes the NAOS Visible Wave Front Sensor based on a Shack-Hartmann principle. This wavefront sensor unit includes: 1) a continuous flow liquid nitrogen cryostat and a low noise fast readout CCD camera controlled by the ESO new generation CCD system FIERA using a fast frame rate
more » ... /Marconi CCD-50. This 128 x 128 pixels split frame transfer device has a readout noise of 3 e-at 50 kilopixel/sec/port. FIERA provides remotely controlled readout modes with optional binning, windowing and flexible integration time. 2) two remotely exchangeable micro-lens arrays (14x14 and 7x7 micro-lenses) cooled to the CCD temperature ( -100 ˚C). The CCD array is directly located in the micro lenses focal plane, only a few millimeters apart without any relay optics. Additional opto-mechanical functions are also provided (atmospheric dispersion compensator, flux level control, field of view limitation). On sky performances of the wavefront sensor are presented. Adaptive Optics corrections was obtained with a reference star as faint as visible magnitude 17. The maximum achievable band-path is 35 Hz at 0 dB for the open loop transfer function.
doi:10.1117/12.458945 fatcat:ktc7v2tljzhjlkxgqo6nxz7fki