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MUSE (Multi Unit Spectroscopic Explorer) is a second generation Very Large Telescope (VLT) integral field
spectrograph developed for the European Southern Observatory (ESO). It combines a 1’ x 1’ field of view sampled at 0.2
arcsec for its Wide Field Mode (WFM) and a 7.5"x7.5" field of view for its Narrow Field Mode (NFM). Both modes will
operate with the improved spatial resolution provided by GALACSI (Ground Atmospheric Layer Adaptive Optics for
Spectroscopic Imaging), that will use the VLT deformable secondary mirror and 4 Laser Guide Stars (LGS) foreseen in
2015. MUSE operates in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently
commissioning MUSE in the Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September,
2014.
MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates
and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units
(IFU), that are mounted within a large monolithic instrument mechanical structure. Each IFU incorporates an image
slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and
cryogenic system. During 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at
Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile
where it was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transferred in monolithic
way onto VLT telescope where the first light was achieved.
This paper describes the MUSE main optical component: the Field Splitter Unit. It splits the VLT image into 24
subfields and provides the first separation of the beam for the 24 Integral Field Units. This talk depicts its manufacturing
at Winlight Optics and its alignment into MUSE instrument. The success of the MUSE alignment is demonstrated by the
excellent results obtained onto MUSE positioning, image quality and throughput onto the sky. MUSE commissioning at
the VLT is planned for September, 2014.
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