WEAVE is a new wide-field multi-object spectroscopy (MOS) facility proposed for the prime focus of the 4.2m William Herschel Telescope. The facility comprises a new 2-degree field-of-view Prime Focus Corrector (PFC) with a 1000-multiplex fibre positioner, a small number of individually deployable integral field units, and a large single integral field unit (IFU). The IFUs and the MOS fibres can be used to feed a dual-beam spectrograph that will provide full coverage of the majority of the visible spectrum in a single exposure at a spectral resolution of ~5000 or modest wavelength coverage in both arms at a resolution ~20000. In order to compensate the field rotation, the Prime Focus Rotator (PFR) is assembled in between the WEAVE Fiber Positioner (system that positions the fibers in the focal plane) and with the Central Can (contains the Prime Focus corrector optics) on the William Herschel Telescope (WHT). The Prime Focus Rotator must provide a rotation degree of freedom for the Fibre Positioner with a high bending stiffness (causing a deflection smaller than 0.008° between interface flanges) adding the minimum mass possible to the system (less than 700kg). This is easily identified as the main design driver to be considered. The Prime Focus Rotator positions the Fibre Positioner to an accuracy of 5 arcsec when tracking and guides all the fibres and other power and control lines through a cable wrap, for which the available space is limited. IDOM proposal to comply with these coupled requirements consists of an optimized structural system with a slightly preloaded cross roller bearing providing the highest possible stiffness to weight ratio. The rotation is driven by means of a direct drive motor powered by a servo drive. For the Cable Wrap, a compact design based on a concept previously developed by IDOM for the Folded Cassegrain Sets the GTC was proposed.
The Canada France Hawaii Telescope Corporation (CFHT) plans to repurpose its observatory on the summit of Maunakea and operate a new wide field spectroscopic survey telescope, the Maunakea Spectroscopic Explorer (MSE). MSE will upgrade the observatory with a larger 11.25m aperture telescope and equip it with dedicated instrumentation to capitalize on the site, which has some of the best seeing in the northern hemisphere, and offer its user’s community the ability to do transformative science. The knowledge and experience of the current CFHT staff will contribute greatly to the engineering of this new facility.
MSE will reuse the same building and telescope pier as CFHT. However, it will be necessary to upgrade the support pier to accommodate a bigger telescope and replace the current dome since a wider slit opening of 12.5 meters in diameter is needed. Once the project is completed the new facility will be almost indistinguishable on the outside from the current CFHT observatory. MSE will build upon CFHT’s pioneering work in remote operations, with no staff at the observatory during the night, and use modern technologies to reduce daytime maintenance work.
This paper describes the design approach for redeveloping the CFHT facility for MSE including the infrastructure and equipment considerations required to support and facilitate nighttime observations. The building will be designed so existing equipment and infrastructure can be reused wherever possible while meeting new requirement demands. Past experience and lessons learned will be used to create a modern, optimized, and logical layout of the facility. The purpose of this paper is to provide information to readers involved in the MSE project or organizations involved with the redevelopment of an existing observatory facility for a new mission.
KEYWORDS: Telescopes, Control systems, Space telescopes, Spectrographs, Spectroscopy, Mirrors, Optical instrument design, Computer programming, Structured optical fibers, Chemical elements
The Maunakea Spectroscopic Explorer (MSE) project aims to build a 10-meter class telescope that will be fully dedicated to spectroscopic exploration of the universe. With an ability to simultaneously measure thousands of objects with a spectral resolution range spanning from 2,500 to 40,000, this one-of-a-kind facility will offer unique scientific opportunities to the astrophysics community in the study of the chemistry and dynamics of the Cosmos.
Maunakea is one of the best sites in the world for astronomy and, at the same time, a culturally and environmentally sensitive area. The location of the current 3.6m Canada France Hawaii Telescope (CFHT) is arguably one of the best observation points in Maunakea, and thus, it was resolved to minimize impact on the site by redeveloping the 3.6 meter CFHT Telescope and using their former facility building and telescope pier to build and host a larger 10-meter class telescope for the MSE Project.
The MSE – CFHT Corporation entrusted IDOM with the Conceptual Design of the MSE Telescope. The telescope design developed by IDOM features a novel architecture that combines well-proven and robust technologies, integrated in a telescope assembly that delivers optomechanic and mechatronic performances exceeding the 10-meter class telescopes currently in operation.
The developed solution offers a very high stiffness-to-mass ratio that leads to optimal seeing performance. It also incorporates a high efficiency seismic protection system and other remarkable features.
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