A prototype cryogenic pick-off arm for multi-IFU spectrometers

A prototype cryogenic 'pick-off' arm for selecting a small field from the focal plane of a large telescope has been built and tested against a set of scientific requirements representative of those for proposed multi-integral-field spectrographs. In this paper, we present the design of the arm and the results of the cryogenic testing. Since the proposed instruments will require tens of arms, perhaps hundreds, we have also considered the industrialisation of the manufacture and assembly of the arms. We briefly discuss this aspect of the design and the possibilities for future instrumentation on Extremely Large Telescopes.