Fig. 1
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Modifications made to the VLTI switchyard in December 2021 to implement the first phase of GRAVITY Wide. Located in the VLTI laboratory underneath the VLTI platform, the switchyard receives the light from the main VLTI delay lines and directs the light to the various downstream instruments such as GRAVITY, MATISSE, and PIONIER. Typically, the light first enters the beam compressors to convert the beam diameters from 80 mm down to 18 mm. To allow for simultaneous observations of FT targets separated by more than 2 arcsec from the SC we enabled the use of the B beams from the VLTI. We added a four-fold periscope consisting of eight flat fold mirrors to merge the A (black) and B (blue) beams with a 2 arcsec separation. For this it was also necessary to rearrange four of the eight main switchyard mirrors, and reactivated the original PRIMA differential delay lines.
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