Novel metrology for tilting spine multi-fiber positioners

A few telescope projects plan to feed spectrographs through thousands of fibres, needing metrology accuracy for feedback of just a few μm. This generally requires accuracy at the metrology camera better than 0.1 arcsec, which can be frustrated by local seeing. With fiducials situated with the array of science fibres, seeing displacements can be calibrated, with accuracy depending on the fiducial spacing. Fiducials within the field usually require sacrificing science fibres but AAO’s positioner for MSE will take advantage of its tilting spines and a special but simple metrology camera to provide a multitude of fiducials within the field with no such sacrifice.