MOONS – Multi Object spectroscopy for the VLT: Design and testing of the MOONS metrology system

Abstract

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MOONS – multi object spectroscopy for the VLT: overview and instrument integration update

“…These are briefly described in the subsequent subsections together with an update on their integration procedure. A detailed description of all MOONS components can be found in [1] and in dedicated papers for the different subsystems [2], [3], [4], [5], [6], [7], [8], [9]. The MOONS RFE is mounted to the telescope and contains the focal plate and fibre positioning system used to align the optical fibres to their desired on-sky locations.…”

“…The final integration of the metrology system is done once the focal plate is installed in the RFE and the endto-end system can be fully verified. Further details on the MOONS metrology system can be found in [8].…”

MOONS fibre positioner control and path planning software

“…MOONS has a camera-based metrology system capable of providing feedback on the location of the fibre positioners, which is described in [3]. The metrology system must be capable of detecting all the fibre positioners and determining their locations and orientations unambiguously to within the same positioning tolerance as the positioners themselves.…”

“…If nothing has changed since they were parked, the flow will pass through the upper part of the "Initialise FP" box of Figure 13; and initialisation consists of finding the datum reference point. A metrology measurement [3] can be used to determine the locations of the fibre positioners after a fault. The "Recover FPUs" box in Figure 13 shows the procedure needed to bring fibre positioners back to a SAFE state after a fault.…”

“…The MOONS metrology camera [3] can't be used to measure synchronisation because it cannot achieve the required time resolution, even if the camera is operated in video mode. The time measurement requirements were achieved by using a 16-channel logic analyser to view and measure the relative synchronisation timings between the initial stepper motor electrical movement pulses across up to 16 FPUs at once.…”