CFHT's FlyEyes: Assessing On-sky Performance of the New MIT/LL CCID-35 CCD Curvature Wavefront Sensor
Résumé
Due to strict requirements of a very short integration time and very low readout noise, Avalanche Photodiodes (APDs) are the only detectors that have been used for curvature wavefront sensors in astronomy thus far. In 1999, Beletic et al. [1] presented a new CCD design that achieves the same performance as APDs, but with higher reliability and lower cost. In addition, this CCD has a higher quantum efficiency than APD modules and a larger dynamic range, eliminating the need for neutral density filters when viewing bright objects. In close collaboration with ESO and IfA, MIT Lincoln Laboratory designed and fabricated the device, the CCID-35. R. Dorn [2] tested the CCD in the laboratory at ESO extensively and proved that it achieves the predicted performance. CFHT is currently implementing this CCD on the PUEO Adaptive Optics system, to assess its performance on the sky for the first time, and for a direct comparison with the current 19 APD detector system. In this overview we present the current implementation scheme and discuss the upgrade we foresee for PUEO NUI, a 104 element high-order curvature AO system envisaged to replace the current AO system at CFHT [3,4].