An MCAO test bench for NFIRAOS

At NRC Herzberg - Astronomy we are developing a closed-loop multi-conjugate adaptive optics bench to simulate a scaled-down version of NFIRAOS, the first light MCAO system on the Thirty Meter Telescope. The current bench consists of four laser guide stars, an evenly spaced array of natural guide stars, two magnetic deformable mirrors, a Shack-Hartmann wavefront sensor and a science camera at the focal plane for the evaluation of the performance and the tip-tilt measurements. Three phase screens conjugated at different altitudes simulate the atmospheric perturbation over the telescope. We can recreate the spot elongation on the SHWFS by defocusing the ground DM and at the same time modulating the intensity of the LGS spots in order to simulate the time-varying density profile of the sodium layer. The goals of this experiment are to compare the experimental performance on the bench with the predicted results of NFIRAOS models and to test the robustness of the tomographic reconstruction under conditions including the use of faint guide stars, non-uniform density profiles of the sodium layer and known non-common path aberrations. In this paper we present an update on the status of the bench and some first results.