MATISSE: Warm Optics Integration and Performance in Laboratory

MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the spectro-interferometer of the European Southern Observatory VLT operating in the spectral bands L, M and N, and, combining four beams from the unit or auxiliary telescopes. The concept constitutes an evolution of the two-beam interferometric instrument MIDI operating on the VLTI. It will give access to the mapping and the distribution of the material, the gas and essentially the dust, in the circumstellar environments and will provide aperture synthesis images in the mid-infrared spectral regime. The Warm OPtics (WOP) of the instrument provides the functions of spectral band separation, optical path equalization and modulation, pupil positioning, beam anamorphosis, beam positioning, and beam commutation. It also allows the alignment function of the beams with the Cold Optics contained in two separate cryostats. This sub-system is presently aligned and tested at the Observatoire de la Côte d'Azur in Nice, France, to validate accuracy and stability. The present paper gives the results of the Warm OPtics laboratory tests.