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Laboratory and on-sky experience suggests that the integration of big astronomical instruments, specially of a
complex interferometric system, is a challenging process. LINC-NIRVANA is the Fizeau interferometric imager
for the Large Binocular Telescope (LBT). Simulating the final operating environment of every system component
has shown how critical is the presence of flexures, vibrations and thermal expansion. Assembling and aligning
the opto-mechanical sub-systems will require an absolute reference which is not affected by static displacements
or positioning errors.
A multi-purpose calibration unit has been designed to ensure the quality of the alignment of optics and
detectors and the reliability of the mechanical setup. This new compact and light-weighted unit is characterized
by sophisticated kinematics, simple mechanical design and composite materials. In addition, the reduced number
of motorized axis improves the stiffness and lowers the angular displacements due to moving parts. The modular
concept integrates several light sources to provide the proper calibration reference for the different sub-systems
of LINC-NIRVANA. For the standard alignment of the optics an absolute reference fiber will be used. For flatfielding
of the detectors the unit provides an integrating sphere, and a special rotating multi-fiber plate (infrared
and visible) is used to calibrate the advanced adaptive optics and the fringe-tracking systems. A module to
control non-common path aberrations (Flattening of Deformable Mirrors) is also provided.
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