M U S E - Feeding And Mounting Twenty-Four Spectrographs

The Multi Unit Spectroscopic Explorer MUSE is an integral field device containing 24 spectrographs at the Nasmyth focus of the VLT unit telescope. The total field size of 1'x1' needs to be split and separated into 24 sub-fields which are relayed along a central structure into the entrance aperture of the individual spectrographs. The realization of the optics for field splitting and separation as well as the relay optics to direct the light of the individual fields to the spectrographs is described here. A very tight link exists between the relay optics system layout and the mechanical arrangement of the spectrographs in the common central structure. A compact mounting is essential due to the restricted space for such a large instrument even on the VLT Nasmyth platform. A suitable arrangement of vertical and horizontal stacking of the spectrographs was found enabling their feeding from the unobstructed front side of the instrumental structure. The central instrument mount was designed as a stiff structure absorbing print-through effects due to thermal mismatch with the telescope platform but rigid enough to withstand earthquakes.