While the technical and performance considerations of an observatory's azimuth rotation system (ORS) are fundamentally distinct from those of a telescope's azimuth rotation system (TRS), their impact on the capital cost, maintenance cost, and overall telescope uptime and reliability metrics can be equally impactful. Furthermore, due to its inherently larger scale, higher loads, extreme stiffnesses, and exposure to a larger variety of environmental forces, the design and construction of an ORS poses unique technical challenges that merit an appropriately unique approach. In particular, construction imperfections can have an unexpectedly outsized impact on ORS mechanisms loads, leading to underestimated design loads and premature component failures. In response, this study proposes a methodology of analysis, design, and construction of an ORS that is fundamentally distinct from that of a typical TRS. The need for extremely tight tolerances and high precision is deemphasized, in exchange for a more rigorous analytical approach that ensures that all performance and reliability objectives can be achieved while following tolerance schemes more typical of the commercial built environment. To do so, the proposed methodology derives mechanism and structural loads by pairing typical building codes with a Monte Carlo analysis; the presented techniques can be used to derive loads for various general arrangements of ORS mechanisms, including a variety of restraint schemes, structural and mechanism compliances, and tolerance envelopes. Representative simulation results generated with SAP2000 are presented along with general design guidelines for detailing an observatory rotation system with economical tolerances, reduced maintenance demands, and high long-term reliability.

The Giant Magellan Telescope (GMT), one of three next-generation extremely large telescopes (ELTs), will have a 25.4meter diameter effective aperture, and will be located on the summit of Cerro Las Campanas in Chile. Developing a new observatory for cutting-edge science operations and a 50-year lifespan poses challenges that have resulted in competing design concepts. This paper discusses the concepts that have been adopted in the GMT site master plan, including designs for the site infrastructure, telescope enclosure, and facilities. The GMTO site has been in active construction since 2015, and in the past two years has completed important steps in site development including completion of residential and office facilities, road improvements, and other necessary infrastructure to support upcoming work. This paper concludes with an overview on managing design and construction simultaneously.

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.

(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 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.

Performance of the GMT azimuth drive system is vital for the operation of the telescope and, as such, all components subject to wear at the drive interface merit a high level of scrutiny for achieving a proper balance between capital costs, maintenance costs, and the risk for downtime during planned and unplanned maintenance or replacement procedures. Of particular importance is the interface between the azimuth wheels and rail, as usage frequency is high, the full weight of the enclosure must be transferred through small patches of contact, and replacement of the rail would pose a greater logistical challenge than the replacement of smaller components such as bearings and gearmotors. This study investigates tradeoffs between various wheel-rail and roller-track interfaces, including performance, complexity, and anticipated wear considerations. First, a survey of railway and overhead crane industry literature is performed and general detailing recommendations are made to minimize wear and the risk of rolling contact fatigue. Second, Adams/VI-Rail is used to simulate lifetime wear of four specific configurations under consideration for the GMT azimuth wheel-rail interface; all studied configurations are shown to be viable, and their relative merits are discussed.

The Giant Magellan Telescope (GMT), one of several next generation Extremely Large Telescopes (ELTs), is a 25.4 meter diameter altitude over azimuth design set to be built at the summit of Cerro Campánas at the Las Campánas Observatory in Chile. This paper describes the current status of the GMT enclosure structure and mechanisms design as it evolves in the current preliminary design phase.

The Advanced Technology Solar Telescope (ATST) will be the largest solar telescope in the world with a 4m aperture primary mirror. The off axis nature of the telescope optical layout, has the proportions of an 8 metre class telescope. Accordingly the instrumentation for solar observations a 16m diameter co-rotating laboratory (Coude Rotator) is also located within the telescope pier.The pier has a lower cylindrical profile with an upper conical section to support both the telescope mount with a 9m bearing diameter and contain the 16m diameter Coude rotator.The performance of this pier cannot be considered in isolation but must account for ancillary equipment, access and initial installation. The Coude rotator structure and bearing system are of similar size to the telescope base structure and therefore this is the proverbial 'ship in a bottle' problem.This paper documents the competing requirements on the pier design and the balancing of these as the design progresses. Also summarized is the evolution of the design from a conceptual traditional reinforced concrete pier to a composite concrete and steel framed design. The stiffness requirements of the steel frame was a unique challenge for both the theoretical performance and overall design strategy considering constructability. The development of design acceptance criteria for the pier is discussed along with interfacing of the A&E firm responsible for the pier design and the telescope designer responsible for the telescope performance.