'MOHAWK' : a 4000-fiber positioner for DESpec

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.Comment: 10 pages, to appear in Proc. SPIE 844

'MOHAWK': A 4000-fiber positioner for DESpec

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 compara

The Maunakea Spectroscopic Explorer Book 2018

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.Comment: 5 chapters, 160 pages, 107 figure

Echidna: the engineering challenges

The Anglo-Australian Observatory’s (AAO’s) FMOS-Echidna project is for the Fiber Multi-Object Spectroscopy system for the Subaru Telescope. It includes three parts: the 400-fiber positioning system, the focal plane imager (FPI) and the prime focus corrector. The Echidna positioner concept and the role of the AAO in the FMOS project have been described in previous SPIE proceedings. The many components for the system are now being manufactured, after prototype tests have demonstrated that the required performance will be achieved. In this paper, the techniques developed to overcome key mechanical and electronic engineering challenges for the positioner and the FPI are described. The major performance requirement is that all 400 science fiber cores and up to 14 guide fiber bundles are to be re-positioned to an accuracy of 10µm within 10 minutes. With the fast prime focus focal ratio, a close tolerance on the axial position of the fiber tips must also be held so efficiency does not suffer from de-focus. Positioning accuracy is controlled with the help of the FPI, which measures the positions of the fiber tips to an accuracy of a few µm and allows iterative positioning. Maintaining fiber tips sufficiently co-planar requires accurate control in the assembly of the several components that contribute to such errors. Assembly jigs have been developed and proven adequate for this purpose. Attaining high reliability in an assembly with many small components of disparate materials bonded together, including piezo ceramics, carbon fiber reinforced plastic, hardened steel, and electrical circuit boards, has entailed careful selection and application of cements and tightly controlled soldering for electrical connections