Doc:
Issue
Date
Page
VLT-MAN-ESO-14650-4942
P96
24.06.2015
19 of 161
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
2.2.1 The Backbone
2.2.1.1 The Instrument Shutter and The calibration unit
In the converging beam coming from the telescope, the first element is the telescope
entrance shutter.
Then follows the Calibration Unit that allows to select a choice of flat-fielding and wavelength
calibration lamps. This unit consists of a mechanical structure with calibration lamps, an
integrating sphere, relay optics that simulate the f/13.6 telescope beam, and a mirror slide
with 3 positions that can be inserted in the telescope beam:
one free position for a direct feed from the telescope,
one mirror which reflects the light from the integrating sphere equipped with:
o
Wavelength calibration Ar, Hg, Ne and Xe Penray lamps operating
simultaneously
o
three flat-field halogen lamps equipped with different balancing filters to
optimize the spectral energy distribution for each arm
one mirror which reflects light from:
o
a wavelength calibration hollow cathode Th-Ar lamp
o
a D
2
lamp for flat-fielding the bluest part of the UV-Blue spectral range
A more detailed description of the functionalities of the calibration system is given in Sect. 6.
Figure 3: 3D view of a cut through the backbone.
