MOONS is the Multi-Object Optical and Near-IR Spectrograph for ESO’s Very Large Telescope. The instrument will use ∼1000 optical fibres which can be individually aligned to on-sky targets across a field of view of 500 square arcmin. Each fibre is positioned using a dual arm theta-phi fibre positioning unit (FPU). The MOONS metrology system must be able to simultaneously measure the position of each fibre to a high accuracy (∼15 micrometres) as well as measuring the orientation of the FPU arms. In this paper, we present a description of photogrammetry-based metrology system design and its implementation in the instrument. We also report on the integration, testing, and performance of the system within the instrument.
KEYWORDS: Control systems, Advanced distributed simulations, Telescopes, Antennas, Design and modelling, Observatories, Computer hardware, Microcontrollers, Control software, Windows
The ALMA Observatory was inaugurated in 2013; after the first 8 years of successful operation, obsolescence emerged in different areas. One of the most critical areas is the control bus of the hardware devices located in antennas, which is based on a customized protocol built on top of the controller area network bus. Similarly, other observatories are facing the same problem. In collaboration with the Universidad de la Frontera, initial studies were performed to explore alternatives to provide state-of-the-art solutions for the next decades, and one of the candidate solutions can be based on the EtherCAT technology. Our study takes the ALMA control system as an example; it compares the current architecture with the new design that is not only compatible with the existing hardware devices of ALMA but also provides the foundation for the new subsystems associated with ALMA 2030 initiatives. The progress of a proof of concept is reported, which explores the possibility of embedding the existing ALMA monitor and control data structure into EtherCAT frames, using EtherCAT as the primary communication protocol to monitor and control hardware devices of ALMA telescope subsystems.
MOONS is the Multi-Object Optical and Near-IR Spectrograph to be mounted at a Nasmyth focus at the Very Large Telescope. The instrument is equipped with 1000 fibres configured over a field of view of ~500 square arcmin using theta-phi fibre positioning units (FPUs). The MOONS metrology system must accurately determine the position of the fibres in the focal plate, providing fast feedback to the instrument control software during operations. The returned fibre positions can be used for calibrations of the FPUs or fast system recovery after a power loss. If required, the system can also be used for calculating fine adjustments of the fibre positions during acquisition. In this paper, a description of the system design, implementation, and testing in the MOONS focal plate are provided. The presented system has high potential for adaptation to a variety of astronomical instrument applications during integration, testing, and operation stages.
The ALMA Observatory was inaugurated in 2013; after almost ten years of successful operation, obsolescence emerged in different areas. One of the most critical areas is the real-time controller, there are around 80 of this kind of controller distributed across the observatory. They monitor and control hardware devices through a customized protocol built on top of the CAN bus. Similarly, other observatories are facing the obsolescence problem in this area. In collaboration with Universidad de la Frontera, initial studies were performed to explore alternatives to provide state-of-the-art solutions for the next decades. One of the candidate solutions explored is based on the EtherCAT technology. This project takes the ALMA control system as a challenge, and evaluated a new design that is not only compatible with the existing hardware devices framework of ALMA but also provides the foundation for the new subsystems associated with ALMA 2030 initiatives. In this paper, the progress of a proof of concept is reported, which explores the possibility of embedding the existing ALMA monitor and control data structure into EtherCAT frames and using EtherCAT as the primary communication protocol to monitor and control hardware devices of ALMA telescope subsystems.
The Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument is the next generation multi-object spectrograph for the Very Large Telescope (VLT). The instrument combines the high multiplexing capability offered by 1000 optical fibres deployed by individual robotic positioners with a novel spectrograph able to provide both low- and high-resolution spectroscopy simultaneously across the wavelength range 0.64μm - 1.8μm. Powered by the collecting area of the 8-m VLT, MOONS will provide the astronomical community with a world-leading facility able to serve a wide range of Galactic, Extragalactic and Cosmological studies. This paper provides an updated overview of the instrument and its construction progress, reporting on the ongoing integration phase.
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