MOONS (Multi-Object Optical and Near-infrared Spectrograph) is a third-generation visible and near-infrared spectrograph for the ESO Very Large Telescope, currently nearing the end of the assembly phase. The three channel spectrograph is fed via a fibre positioning module (FPM) which configures the location of 1001 fibres. The robotic fibre positioning units (FPUs) have been jointly developed by the UK Astronomy Technology Centre (UKATC) and MPS Microsystems (MPS) and provide a high-performance multiplexed focal plane with excellent transmission characteristics. An overview of the as-built mechanisms and supporting infrastructure is presented, with details on the extensive calibration process carried out. The integration process to date will be described, including a discussion of key lessons learned.
The MOONS multi-object spectrograph relies on an array of 1000 fibre positioners to acquire targets in the focal plane. The fibre positioners have a larger overlap than similar instruments because MOONS can observe in the infrared. The large overlap gives MOONS the ability to acquire close pairs of object and sky targets, but it makes moving positioners to their targets without a collision even more technically challenging. We describe how the MOONS fibre positioner control system overcomes those challenges with custom electronics to manage the synchronisation between the positioners, a collision protection system, and a grid driver software system which manages the control of the fibre positioners. We also describe our experiments with different path planning algorithms and present the latest results from MOONS testing.
MOONS (Multi-Object Optical and Near-infrared Spectrograph) is a third-generation visible and near-infrared spectrograph for the ESO Very Large Telescope currently under construction. The instrument’s spectroscopic capabilities are multiplexed via a fibre positioning module (FPM) which configures the location of 1001 fibres. The fibre positioning units (FPUs) have been jointly developed by the UK Astronomy Technology Centre (UKATC) and MPS Microsystems (MPS) to optimise instrument efficiency by providing excellent transmission and an open-loop positioning strategy, allowing a tightly packed focal plane to be rapidly reconfigured. The mechanism geometry enables all positions in the focal plane to be observed in conjunction with a companion sky fibre at close separation. A description of the as manufactured design and production process of the FPUs is presented, along with a discussion of the performance proven to date, including achievement of the critical pupil alignment and positional repeatability requirements. An overview of the custom testing rig built to automate the characterisation and calibration process is also presented.
After completion of its final-design review last year, it is full steam ahead for the construction of the MOONS instrument - the next generation multi-object spectrograph for the VLT. This remarkable instrument will combine for the first time: the 8 m collecting power of the VLT, 1000 optical fibres with individual robotic positioners and both medium- and high-resolution spectral coverage acreoss the wavelength range 0.65μm - 1.8 μm. Such a facility will allow a veritable host of Galactic, Extragalactic and Cosmological questions to be addressed. In this paper we will report on the current status of the instrument, details of the early testing of key components and the major milestones towards its delivery to the telescope.
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