VLT-MAN-ESO-14650-4942
P96
24.06.2015
18 of 161
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
2.1 Overview of the opto-mechanical design
Figure 2 shows a schematic view of the layout of the instrument. It consists of four main
components:
The backbone which is directly mounted on the Cassegrain derotator of the
telescope. It contains all pre-slit optics: the calibration unit, a slide with the 3-
positions mirror and the IFU, the acquisition and guiding camera, the dichroic box
which splits the light between the three arms, one piezo tip-tilt mirror for each arm to
allow active compensation of backbone flexures, atmospheric dispersion
compensators (ADCs) in the UVB and VIS arms and a warm optical box in the NIR
arm.
The three arms are fixed format cross-dispersed échelle spectrographs that operate
in parallel. Each one has its own slit selection device.
o The UV-Blue spectrograph covers the 300 – 550 nm wavelength range with a
resolving power of 5100 (for a 1” slit)
o The Visible spectrograph covers the range 550 - 1000 nm with a resolving
power of 7500 (0.9” slit).
o The near-IR spectrograph: this arm covers the range 1000 - 2500 nm with a
resolving power of 5300 (0.9” slit). It is fully cryogenic.
2.2 Description of the instrument sub-systems
This section describes the different sub-systems of X-shooter in the order they are
encountered along the optical path going from the telescope to the detectors (see
Figure 2). The functionalities of the different sub-units are explained and reference is made
to their measured performance.
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