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Register a new userMOHAWK : a 4000-fiber positioner for DESpec
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We present a concept for a 4000-fibre positioner for DESpec, based on the Echidna tilting spine technology. The DESpec focal plane is 450mm across and curved, and the required pitch is ~6.75mm. The size, number of fibers and curvature are all comparable with various concept studies for similar instruments already undertaken at the AAO, but present new challenges in combination. A simple, low-cost, and highly modular design is presented, consisting of identical modules populated by identical spines. No show-stopping issues in accommodating either the curvature or the smaller pitch have been identified, and the actuators consist largely of off-the-shelf components. The actuators have been prototyped at AAO, and allow reconfiguration times of ~15s to reach position errors 7 microns or less. Straightforward designs for metrology, acquisition, and guiding are also proposed. The throughput losses of the entire positioner system are estimated to be ~15%, of which 6.3% is attributable to the tilting-spine technology.
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In this paper we present the Australian Astronomical Observatorys concept design for Sphinx - a fiber positioned with 4332 spines on a 7.77mm pitch for CFHTs Mauna Kea Spectroscopic Explorer (MSE) Telescope. Based on the Echidna technology used with FMOS (on Subaru) and 4MOST (on VISTA), the next evolution of the tilting spine design delivers improved performance and superior allocation efficiency. Several prototypes have been constructed that demonstrate the suitability of the new design for MSE. Results of prototype testing are presented, along with an analysis of the impact of tilting spines on the overall survey efficiency. The Sphinx fiber positioned utilizes a novel metrology system for spine position feedback. The metrology design and the careful considerations required to achieve reliable, high accuracy measurements of all fibres in a realistic telescope environment are also presented.
The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We will describe the production and manufacturing processes developed for the 5000 fiber positioner robots mounted on the focal plane of the Mayall telescope.
The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. To achieve this goal, it is crucial to guarantee that fiber positioners work properly under the extremes of potential operating conditions, including the full range of temperatures, high speed wind disturbance etc. Thermal testing provides valuable insight into the functionality of the fiber positioners that can be used to help mitigate poor performance at extreme temperatures and wind disturbance test provide guidance to design of ventilation system. Here, we describe the thermal and wind disturbance tests for DESI fiber positioners and how the test results helped improve the robustness of the positioners.
We describe an initiative to build and use the Dark Energy Spectrometer (DESpec), a wide-field spectroscopic survey instrument for the Blanco 4 meter telescope at Cerro Tololo InterAmerican Observatory (CTIO) in Chile. A new system with about 4000 robotically positioned optical fibers will be interchangeable with the CCD imager of the existing Dark Energy Camera (DECam), accessing a field of view of 3.8 square degrees in a single exposure. The proposed instrument will be operated by CTIO and available for use by the astronomy community. Our collaboration proposes to use DESpec to conduct a wide, deep spectroscopic survey to study Dark Energy. In a survey of about 350 nights, the DESpec collaboration proposes to obtain spectroscopic redshifts for about 8 million galaxies over 5000 square degrees selected from the Dark Energy Survey (DES). This Dark Energy Spectroscopic Survey will advance our knowledge of cosmic expansion and structure growth significantly beyond that obtainable with imaging-only surveys. Since it adds a spectroscopic third dimension to the same sky as DES, DESpec will enable increasingly precise techniques to discriminate among alternative explanations of cosmic acceleration, such as Dark Energy and Modified Gravity.
WEAVE is the new wide-field spectroscopy facility for the prime focus of the William Herschel Telescope at La Palma, Spain. Its fibre positioner is essential for the accurate placement of the spectrographs 960 fibre multiplex. We provide an overview of the final assembly and metrology of the fibre positioner, and results of lab commissioning of its robot gantries. A completely new z-gantry for each positioner robot was acquired, with measurements showing a marked improvement in positioning repeatability. We also present the first results of the configuration software testing, and discuss the metrology procedures that must be repeated after the positioners arrival at the observatory.
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