ASSIST development of a test-infrastructure for the VLT AO facility

ASSIST - The Adaptive Secondary Setup and Instrument STimulator is a test setup to verify the operation of three elements of the VLT Adaptive Optics Facility, namely the Deformable Secondary Mirror (DSM) and the two AO systems using this DSM, the AO system for the visible light integral field spectrograph MUSE (GALACSI) and the AO system for the IR wide field imager HAWK-I (GRAAL). To support the testing of these elements, ASSIST will provide both an interferometry setup for testing the DSM as well as a full atmospheric turbulence simulator and star simulator to mimic the conditions at the telescope. To test the instruments using the DSM, the output beam is matched the output beam of the VLT telescope, including the correct exit-pupil and high-quality imaging and a similar hardware interface is provided. Since one of the modes to be verified is nearly diffraction limited, also the thermal and vibrational stability are very important, with strong constraints on both the mechanical as well as the optical design. ASSIST is finalizing its preliminary design phase and in this paper we present the current optical and mechanical design of ASSIST and the projected performance of the test bench for both the testing and calibration of the DSM as well as for the two AO systems under test.