GRAVITY belongs to the 2nd generation of the Very Large Telescope Interferometer (VLTI) and will operate inK-band on 6 baselines using all 4 Unit Telescopes of the VLT. With an unprecedented astrometrical accuracy of l0μas it will be, amongst others, capable of detecting the highly relativistic motion of the photocenter of a flare surrounding the supermassive black hole at the Galactic Centre, and thus probe General Relativity. The contribution of the University of Cologne within the international GRAVITY-Consortium is the design, manufacturing, qualification and assembly of the Fringe Tracking Spectrometer and the Science Spectrometer in the Beam Combiner Instrument (BCI). The BCI will be located in the interferometric lab of the VLTI. The spectrometers will be operated at 85K in a 200K environment in the BCI. We present the design and qualification of a linear displacement mechanism, which will be used at the focus stages of the detectors in both spectrometers and at the zoom stage in the Fringe Tracking Spectrometer. The mechanism consists of 4 double-hinged compliant joints which support the stage and provide a linear motion along the optical axis. The stage characterization at room and cryogenic conditions are presented.
[1]
Frank Eisenhauer,et al.
The GRAVITY spectrometers: optical design
,
2012,
Other Conferences.
[2]
Vianak Naranjo,et al.
GRAVITY: observing the universe in motion
,
2011
.
[3]
K. Perraut,et al.
The GRAVITY spectrometers: system design
,
2012,
Other Conferences.
[4]
C. Straubmeier,et al.
Beating the confusion limit: the necessity of high angular resolution for probing the physics of Sagittarius A* and its environment: opportunities for LINC-NIRVANA (LBT), GRAVITY (VLTI) and and METIS (E-ELT)
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2012,
Other Conferences.