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The Gran Telescopio Canarias Adaptive Optics (GTCAO) will measure the wavefront with a Shack-Hartmann sensor. This wavefront sensor (WFS) is based on the CCD220, an electron-multiplying CCD (EMCCD) that achieves sub-electron readout noise, increasing the signal to noise ratio when weak natural guide stars (NGS) are used as reference. GTCAO will start its operation in telescope with NGS, using only one wavefront sensor, and later it will incorporate a Laser Guide Star (LGS) and consequently a second WFS, also based on an EMCCD. Both EMCCDs and a third one used as spare, have been characterized and compared including the system gain, electron- multiplication gain, readout noise vs gain, excess noise and linearity. The EM gain calibration is important to keep all EMCCD channels in the linear regime and the camera manufacturer carries it out, but it is reported that the multiplication gain may suffer ageing and degradation even if the camera is not in use. This suggests the need to monitor this ageing. In this paper it is proposed and tested a procedure for predictive maintenance that re-characterize the system gain, electron- multiplication gain and linearity periodically in order to predict the eventual ageing of the EMCCD multiplying registers. This procedure can be carried out quickly while the detector is installed in the WFS and in operational status. In order to provide the required illumination, the GTCAO calibration system is used.

The Sun is an ideal object for the development of Multi-Conjugate Adaptive Optics (MCAO) since solar structure provides multiple “guide stars” in any desired configuration. Current MCAO systems imply a number of wavefront sensors, each of them sensing an area of the Sun. The plenoptic camera is a novel concept for wavefront sensing, capable of measuring the tomography of the atmospheric turbulence. By using it, the possibility of a MCAO system with a single sensor becomes a reality. This paper describes the functionality of the plenoptic camera as a tomographic wavefront sensor after implementing it into the OOMAO simulator. Simulation results demonstrate the potential of this sensor to reconstruct atmospheric turbulence in different layers by using a synthetic solar image as a reference.

The Uplink Wavefront Corrector System (UWCS) has been conceived by following the premises from simulation outcomes as a pathfinder instrument to demonstrate Adaptive Optics uplink correction in both applications: Free-Space Optical Communications and self-propagating path of Laser Guide Stars. Preliminary design and expected performance have been analysed via simulations in previous studies. Current activities focus on the turbulence measurement on the launch axis itself by using pulsed or modulated lasers and a pulse-synchronized Shack-Hartmann as wavefront sensor. Present paper describes the test bench it has been built in the Instituto de Astrofisica de Canarias (IAC) to experimentally demonstrate the uplink correction and its advantages.