The mission of the Large Synoptic Survey Telescope (LSST) is to meet a broad range of science goals with a single 10-year, time-domain survey. Over the course of the survey, LSST will deliver a more than 800-frame movie of 18,000 square degrees of the sky in six optical bandpasses. LSST’s observing strategy will invest ~90% of its time in this wide-fast-deep survey, with a typical single visit depth of r = 24.7 mag. The remaining ~10% of the observing time will be used to obtain improved coverage of parameter space through Deep Drilling Fields or observations of “special” regions such as the ecliptic, Galactic plane, and the Large and Small Magellanic Clouds. LSST was designed around four key science pillars: taking an inventory of our Solar System, exploring the transient and variable optical sky, mapping the Milky Way and its neighborhood, and delving into the nature of dark matter and dark energy. LSST will be a super discovery machine for an enormous number and diversity of objects across these fields (including Near Earth Objects, distant supernovae, and ultra-faint galaxies) - discoveries that will transform our view of the universe for decades to come. I will give an overview of the LSST Project and science goals, give updates on the construction progress towards first-light, and highlight ways for the scientific community to get involved now.

This PDF file contains the front matter associated with SPIE Proceedings Volume 10700, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The LSST Coating Plant consists of a Coating Chamber for high reflective optical coatings deposition and a Cleaning and Stripping Station for the M1M3 and M2 mirrors. The Coating Chamber sputtering process will be capable of depositing bare and protected Silver/Aluminum coating recipes. The Cleaning and Stripping Station consists of a rotating washing/drying boom, perimeter platforms, and an effluent handling system within the M1/M3 mirror cell. This paper describes the status of the Coating Plant construction effort at the Von Ardenne and MAN facilities. Progress on factory testing, review of the design features and reflective/coating requirements, and results are presented.

After gathering spectrophotometer data from the 6.5m primary mirror at the MMT Observatory (MMT) for over ten years, the MMT has developed a soap and water wash procedure that effectively removes contaminates from the surface of the mirror without damaging the bare aluminum coating. While the in-situ soap and water wash requires a small amount of telescope downtime, these washes are still scheduled to take place every six months. The frequency of the washing was selected to keep the mirror performance as close to a fresh coating as possible throughout the year and to extend the recoating interval without allowing the reflectivity degrading more than 3% from a fresh coating. After being in service for almost two years, the spectrophotometer measurements indicate the 2016 primary mirror coating is on-track to maintain the specified reflectance for five years. This paper outlines the soap and water wash procedure developed for the MMT primary mirror and presents spectrophotometer data throughout the life of the 2005 and the 2016 mirror coatings.

The SALT Building Management System (BMS) was designed to control sub-system cooling and environmental control in the telescope chamber as part of ensuring optimal science data quality. With over 400 inputs and output points for monitoring and control, this required an effective system when performing maintenance in the event of any failure or degradation of the system. The BMS lacked this effectiveness due to an unstructured design and a lack of documentation, causing time-consuming root cause analysis and excessive downtime. In this paper, we describe the research and development of an effective Building Management System.

M3 Engineering and Technology Corp. (M3) a full discipline architectural, engineering and construction management firm designed the site, infrastructure, enclosure and support facilities for the Space Surveillance Telescope Australia (SSTA) to site specific design requirements, Australian codes and standards, stringent Australia Department of Defense security stipulations and capable of sustaining cyclonic wind loads. This paper presents the design and construction challenges of the of this uniquely situated telescope observatory in the most active Australian cyclonic region. The SSTA is a joint project between the Australian Department of Defense and the United States Defense Advanced Research Projects Agency (DARPA). This project is part of the Space Surveillance Network, a worldwide network of 29 military radar and optical telescopes that observe and catalogue space objects to identify potential collisions. The telescope after going through an initial trial period at White Sands Missile Range, New Mexico is now at its permanent home in the furthest western point of Australia awaiting the completion of the observatory and support facilities. SSTA’s relocation to Harold E. Hold Naval Communication Station (HEH) near the Shire of Exmouth, Western Australia will allow the telescope to relay information quickly to the United States. It will be looking into the southern hemisphere from its strategic location, an area of the sky that according to DARPA is “sparsely observed.”1 Although the location is strategic for viewing and tracking purposes, it places the telescope in a cyclonic region, making the enclosure that protects the telescope very challenging to design and construct. Typically, astronomical observatories are designed to sustain survival wind speeds of 54 to 78-meters per second. However, given the extreme weather conditions in Exmouth, the SSTA observatory must survive 94-meters per second wind speeds and be operationally ready after the cyclonic event. The basis of design for the SSTA is the enclosure and support facility that M3 designed at White Sands Missile Range, New Mexico. The project site in New Mexico is a more traditional astronomical observatory site with normal survival wind loads and cooler temperatures. Temperatures in Exmouth typically vary from 12°C to 37°C and is rarely below 9°C or above 42°C. Exmouth also experiences extreme seasonal variation in the perceived humidity. Due to HEH’s site remoteness, two critical operational challenges in comparison to the base line New Mexico design influenced major changes to the SSTA observatory design. The unavailability of a mirror aluminizing facility within Australia and the risk of handling the primary and secondary mirrors with external cranes required the SSTA observatory to increase the enclosure diameter by 5.0 meters allowing the implementation of an overhead bridge crane and enough space to handle the mirrors internally within the observatory. The SSTA site is designed for a future aluminizing facility on site. These design requirements heavily influenced the architectural, structural and mechanism designs. The SSTA enclosure larger diameter and therefore heavier rotating enclosure along with the cyclonic wind loads and high angular dome rotational requirements required additional mechanisms compared to the New Mexico design. The azimuth bogie wheel diameter increased, and the quantity doubled to 16 total. The (8) azimuth drives units changed from 9.3kW to 56kW and the lateral and uplift restraint system implemented an additional 16 external lateral restraint arms to keep the enclosure from shifting during a cyclonic event. The relocation of the US based telescope and components designed to operate at 60Hz power frequency added complexity because the power at the SSTA site is 50Hz. M3 designed a stand-alone primary and backup power plant to Australian standard frequency of 50Hz. To minimize operational risks to the telescope, M3 implemented a frequency converter providing 60Hz power to the US designed telescope and components and 50Hz to the rest of the facilities. This allowed the observatory to comply with Australian codes and standards and the use of standard Australian 50Hz equipment for the facilities electrical and HVAC systems.

The Large Synoptic Survey Telescope (LSST) is a large (8.4 meter), wide-field (3.5 degree) survey telescope, undergoing assembly on the summit of Cerro Pachón, in Chile¹ . In May 2015 EIE Ground Technologies Srl - Company of EIE GROUP with headquarters in Venice-Mestre, Italy – signed the contract with AURA Inc. The Design Phase of the rotating enclosure system (Dome) was completed in February 2016. All the structures, mechanisms, electronics, software, etc. are approaching completion. On-site activities started in the spring of 2017, and are scheduled to finish testing in early 2019, in time to begin the installation of the telescope. The Dome’s steel structure supports the two Slit Doors, a moving Permeable Windscreen, a Light Baffled Louver System, numerous platforms and the exterior cladding. The Dome structures are shielded by insulated sandwich panels which provide protection from the exterior environment. The Dome is equipped with a series of Louvers, with associated hinged light baffles, which simultaneously provide exceptional Dome flushing and stray light attenuation. The Windscreen also functions as a light screen, and helps define the optical aperture of the Telescope. The Dome’s azimuth rotation is enabled by trolleys acting on tracks, fixed to the cylindrical, concrete Dome Pier. The rotational torque is provided by the Azimuth Drives fixed directly on the Dome Pier. This simplifies the glycol/water cooling and eliminates the need for a utility cable wrap. During the day, internal temperature control is provided by an Air Duct System interfacing with the facility thermal control system. These ducts align when the Dome is in its parked position. Furthermore, the Dome is equipped with electrical systems, a safety and interlock System, and an overhead bridge crane. A series of ladders, stairs and platforms allow inspections, maintenance and repair of all of the Dome installations. In this paper, we present the status of the manufacturing activities, erection processes, and testing.

The Dome and the telescope Main Structure of the ELT are being procured by ESO as an integrated unit, which includes also the technical buildings needed to host the various system plants and the primary mirror maintenance facilities. At conclusion of a Call for Tender, ESO has signed in May 2016 a contract with the Italian Consortium ACe for the design, manufacture, transport and construction at Cerro Armazones in Chile of the Dome and Telescope Structure (DMS) of the ELT. The Consortium is constituted by Astaldi S.p.A. and Cimolai S.p.A. The first step of the design phase, namely the Preliminary Design Review (PDR) of both Dome and Main Structure has been completed, and rapid progress is being achieved toward the completion of the detail design. For some long lead items, the procurement via Critical Design Reviews (CDRs) is taking place in parallel to the detail design phase. The Contractor was given access to the Armazones site, including the levelled ELT platform in June 2017, and he has prepared at the base of the Armazones peak a large construction camp with dormitories and construction facilities. At the top of the mountain the excavation for the ELT foundations are completed, and foundation construction is starting. The overall status of the procurement of the DMS and some key aspects of the design will be described herein.

The Giant Magellan Telescope (GMT), one of three next-generation extremely large telescopes (ELTs), will have a 25.4- meter 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.

Many radio telescopes, radar antennas, and enclosures for optical telescopes use wheel-on-track systems for their azimuth rotations. Design of such systems requires properly understanding of the contact behavior between the wheel and the azimuth track as the wheel rolls forward. Unless the azimuth track has a continuous running surface, one needs to understand how the track joints will affect the contact stress. In the case of multi-layer track systems where the track segments consist of wear plates mounted on base plates, finite element analyses are needed to capture friction and slip, and opening and closing of gaps at the interfaces between the wheel, wear plate, and the base plate. The paper presents lessons learned from the design, analysis, and rehabilitation of a few wheel-on-track systems. The paper discusses (1) how geometry of the wheel, geometry of the track, stiffness of the wheel bogie, and alignment will affect the contact stress, (2) how to evaluate possible impact load at track joints, (3) what design criteria should be used for strength and fatigue at the wheel/track contact, and (4) how wear between wear plate and base plate can be evaluated.

The Large Millimeter Telescope (LMT) Alfonso Serrano is a bi-national (Mexico and USA) telescope facility operated by the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) and the University of Massachusetts. The LMT is designed as a 50-m diameter single-dish millimeter-wavelength telescope that is optimized to conduct scientific observations at frequencies between ~70 and 350 GHz. The LMT is constructed on the summit of Sierra Negra at an altitude of 4600m in the Mexican state of Puebla. The site offers excellent mm-wavelength atmospheric transparency all-year round, and the opportunity to conduct submillimeter wavelength observations during the winter months. Following first-light observations in mid-2011, the LMT began regular scientific operations in 2014 with a shared-risk Early Science observing program using the inner 32-m diameter of the primary reflector with an active surface control system. The LMT has already performed successful VLBI observations at 3mm with the High Sensitivity Array and also at 1.3mm as part of the Event Horizon Telescope. Since early 2018 the LMT has begun full scientific operations as a 50-m diameter telescope, making the LMT 50-m the world´s largest single-dish telescope operating at 1.1mm. I will describe the current status of the telescope project, including the early scientific results from the LMT 50-m, as well the instrumentation development program, the plan to improve the overall performance of the telescope, and the on-going transition towards the formation of the LMT Observatory to support the scientific community in their use of the LMT to study the formation and evolution of structure at all cosmic epochs.

The Javalambre Survey Telescope (JST/T250) is a wide-field 2.6 m telescope ideal for carrying out large sky photometric surveys from the Javalambre Astrophysical Observatory in Teruel, Spain. The most immediate goal of JST is to perform J-PAS, a survey of several thousands square degrees of the Northern sky in 59 optical bands, 54 of them narrow (∼ 145 Å FWHM) and contiguous. J-PAS will provide a low resolution photo-spectrum for every pixel of the sky, hence promising crucial breakthroughs in Cosmology and Astrophysics. J-PAS will be conducted with JPCam, a camera with a mosaic of 14 CCDs of 9.2k × 9.2k pix, more than 1200 Mpix and an effective FoV of 4.3 deg² . Before JPCam is on telescope, the project will work in 2018 with an interim camera, JPAS-Pathfinder, with a reduced FoV of ∼ 0.6 × 0.6 deg² to perform commissioning and the first JST science. This paper presents the current status and performance of the JST telescope, describing the commissioning and first science of the JPAS-Pathfinder at JST.

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project between NASA and the German Aerospace Center DLR to provide infrared and sub-millimeter observing capabilities to the worldwide astronomical community. With a wide range of instruments that cover both imaging and spectroscopy, SOFIA has produced unique scientific results that could not be obtained with a ground-based facility. In the coming decade, SOFIA will be a critical complement to the other major facilities for astronomical research, the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA) by filling in the otherwise unobservable wavelength range of 30–300 μm. SOFIA provides a wide range of instrumentation, and this paper will describe some of the new capabilities in heterodyne spectroscopy, direct detection spectroscopy, and polarimetry.

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter far-infrared (30-100 μm) double-Fourier Michelson interferometer designed to fly on a high altitude scientific balloon. The project began in 2011, and the payload was declared ready for flight in September 2016. Due to bad weather, the first flight was postponed until June 2017; BETTII was successfully launched on June 8, 2017 for an engineering flight. Over the course of the one night flight, BETTII acquired a large amount of technical data that we are using to characterize the payload. Unfortunately, the flight ended with an anomaly that resulted in destruction of the payload. In this paper, we will discuss the path to BETTII flight, the results of the first flight, and some of the plans for the future.

The Greenland Telescope Project (GLT) has successfully commissioned its 12-m sub-millimeter. In January 2018, the fringes were detected between the GLT and the Atacama Large Millimeter Array (ALMA) during a very-long-baseline interferometry (VLBI) exercise. In April 2018, the telescope participated in global VLBI science observations at Thule Air Base (TAB). The telescope has been completely rebuilt, with many new components, from the ALMA NA (North America) Prototype antenna and equipped with a new set of sub-millimeter receivers operating at 86, 230, and 345 GHz, as well as a complete set of instruments and VLBI backends. This paper describes our progress and status of the project and its plan for the coming decade.

We analyze the principal sources of thermal self-emission (TSE) in the European Southern Telescope (ELT) as they will be seen by the instruments observing in the infrared. Expected TSE levels for different mirror contamination levels and instrument cold stop types are provided.

Since the CTIO 4m Blanco Telescope was successfully upgraded, commissioned, and integrated with the DECam Instrument in Sept 2012, the performance of the telescope mount tracking has been excellent, with a median tracking jitter of 0.025”, and 0.06”rms, for the declination, and right ascension axes respectively. Any occasional increase in mount tracking jitter, has been associated with wind induced torque disturbances, affecting both axes simultaneously, especially during high speed wind conditions, combined with dome, and wind direction alignment.

In order to investigate the response to the telescope mount servo control, to wind induced disturbances, we have instrumented the 4m Blanco Telescope mount, upper secondary ring, with a novel 2-axis direct wind force sensor, sampled at 200 Hz, using inexpensive pocket digital scale type load cells, this combined with a small surface area of 0.00375 m², we have obtained wind pressure noise values of 0.4 Pa-rms.

Our investigation will compare the Power Spectral Density (PSD) of the wind disturbance forces, with the expected Kolgomorov model, and explore the correlation between wind disturbance forces, and mount tracking jitter.

Also we will establish under what dome, wind direction, and wind speed conditions the increased mount tracking jitter, could affect science image results, and cause an increase in image ellipticity, and FWHM. This information should help observers, in taking appropriate measures, to minimize the wind induced image degradation in the future.

The telescope structure of the Stratospheric Observatory for Infrared Astronomy (SOFIA) is subject to vibration excitation due to aircraft motions and turbulence from the airflow coming into the telescope cavity. A proper understanding of the dynamical behavior of the telescope structure under operational loads is crucial for pointing control and measures against higher order optical aberrations. During design and construction a Finite Element model of the telescope assembly has been created in order to assess the structural integrity and the early performance. This legacy model used conservative assumptions and had a coarse approach on the approximation of some structural features. We present an updated Finite Element model of the SOFIA Primary Mirror Assembly, which represents support members as well as the primary mirror itself in greater detail, in order to support ongoing development for performance optimization. An iterative approach employing structural optimization was used to tune the model in order to fit modal parameters of the Primary Mirror Assembly which were measured in a test campaign prior to integration into the full telescope structure. The updated and tuned model is used to calculate deformations due to gravity, thermal loads and dynamic excitation. These deformations serve as input for ray-tracing analyses to investigate alterations in the light path in order to evaluate pointing errors and higher order optical aberrations.

The Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, providing a significant increase in the resolution of solar data available to the scientific community. In large ground-based telescopes, vibration of telescope optics caused by the telescope subsystems is typically the limiting factor of image resolution.¹ The impact of vibration increases with the resolution of the telescope and is therefore a much greater problem in long focal-length telescopes, such as the DKIST. In addition, vibration is a consumer of the adaptive optics image-quality error budget limiting the correction available for atmospheric seeing. In some cases, the adaptive optics might even amplify the vibration at higher frequencies. For all of these reasons, a vibration error budget is a critical component in any large telescope project, and a plan for active vibration management and mitigation is critical to the success of a large telescope project. In the design of a large telescope, finite element analysis is employed and this is historically the only effort put into understanding vibration issues. However, after the telescope mount is constructed and the instruments and ancillary equipment are more clearly defined, there are many opportunities to perform path analyses by directly measuring the low-frequency single- input-single-output (SISO) frequency response function (FRF) between vibration source locations and image motion on the focal plane. These measurements are carried out using inertial-mass shakers along with seismic accelerometers providing an accurate measurement of the image degradation that will be caused by vibration sources in various locations. This allows the designers to determine an appropriate vibration mitigation plan (if needed) long before the vibration source is attached to the telescope. These measurements have proven sensitive enough that they can be performed for equipment not mounted on the telescope structure but located in the telescope building or even in nearby buildings. In a previous paper, techniques were described for measuring vibration which is particularly challenging at frequencies below 10 Hz where accurate measurement requires several noise reduction techniques, including high-performance windows, noise-averaging, tracking filters, and spectral estimation. In this follow-up paper, the development of the DKIST vibration budget detailing the advantages of the shaker measurement technique is described, along with examples of testing performed on the DKIST structures currently under construction at the Haleakala High-Altitude Observatories site in Maui, HI.

The Keck telescope segments were manufactured by stressed mirror polishing of large circular pieces of Zerodur that were then cut into hexagons and finished by Ion Beam Figuring (IBF). It has long been believed that this process results in segments with little or no edge effects. As a result, this same general approach is planned for segment manufacturing for the Thirty Meter Telescope (TMT) and the European Extremely Large Telescope (E-ELT). However, recent measurements at the Keck telescope suggest that at least some of the Keck segments have significant aberrations within 60 mm of the edge. These aberrations impact the telescope phasing and the overall telescope image quality. We present interferometric measurements of multiple Keck segments, characterizing the surface errors near the edges over spatial periods from ~5 cm down to ~1 mm. We show that the largest phasing and image quality effects are due to plateaus of unremoved material, left behind after IBF as a result of obscuration by the IBF supports. Apart from these plateaus, the edge quality is relatively good, though not as good as in the segment interiors. Some residual phasing and image quality effects remain, and these are not currently understood.

The 25.4m Giant Magellan Telescope (GMT) consists of seven 8.4 m primary mirror (M1) segments with matching segmentation of the Gregorian secondary mirror (M2). When operating the GMT in the diffraction-limited Adaptive Optics (AO) modes, using the Adaptive Secondary Mirror (ASM), the M1-M2 pairs of segments must be phased to a small fraction of the observing wavelength. To achieve this level of correction across the scientific field of view (<90” in diameter), the phasing system relies on multiple (up to four) natural guide-star probes deployed across the field of view (from 6’ to 10’ from the center of the field) measuring at slow rates (~0.033 Hz) segment phase piston in the infrared and low-order field-dependent phase aberrations in the visible. This paper describes the overall phasing strategy and requirements when operating in the Natural Guide-star AO (NGAO) and the Laser Tomography AO (LTAO) modes. We will also present a first evaluation of segment piston error induced by wind buffeting on the telescope structure. Wind loads have been computed for different observatory configurations using Computational Fluid Dynamics (CFD) simulations. This analysis showcases the GMT Dynamic Optical Simulation (DOS) environment which integrates the optical and structural dynamic models of the GMT with the Fourier optics models of AO and phasing sensors.

The W. M. Keck Observatory Segment Repair Project is repairing stress-induced cracks at the support points in all of the 84 primary mirror segments. The repair process for each segment involves disassembling hardware, removing bonded attachments, grinding out the damaged glass, etching, bonding new attachments, reassembling , and testing on sky. This also presents an opportunity to inspect and thoroughly clean the supports and segments after almost 25 years of service. The production phase of the project will reach the halfway point of the repairs during the summer of 2018. This paper summarizes some of the issues encountered and anomalies discovered during the repair process and presents on-sky results of the performance of the repaired segments. An update on the project status, schedule, and budget is also presented. Details of the project development to the production phase, and step by step descriptions and photos of the repair process are included.

The Hobby-Eberly Telescope (HET) is an innovative large telescope with 10 meter aperture, located in West Texas at the McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker, which moves the fourmirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. We have completed a major multi-year upgrade of the HET that has substantially increased the field of view to 22 arcminutes by replacing the optical corrector, tracker, and prime focus instrument package and by developing a new telescope control system. The upgrade has replaced all hardware and systems except for the structure, enclosure, and primary mirror. The new, reinvented wide-field HET feeds the revolutionary Visible Integral-field Replicable Unit Spectrograph (VIRUS‡), fed by 35,000 fibers, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX§), a new low resolution spectrograph (LRS2), the Habitable Zone Planet Finder (HPF), and the upgraded high resolution spectrograph (HRS2). The HET Wide Field Upgrade has now been commissioned and has been in science operations since mid 2016 and in full science operations from mid 2018. This paper reviews and summarizes the upgrade, lessons learned, and the operational performance of the new HET.

Optical distortions arising from inhomogeneous air in the telescope dome can be a non-negligible contributor to the delivered image quality (DIQ). Optimization of the dome environment is particularly important for first-class wide-angle imagers, such as the DECAM on the 4-m Blanco telescope, Omegacam at CFHT and, in the future, LSST. However, the standard method of comparing the DIQ with the site seeing does not single out the effect of the dome, being affected by contributions from other sources and by biases. We developed the dome seeing monitor for the Blanco telescope. It propagates the collimated 4-cm beam from the mirror cell to the top ring and back, parallel to the main beam. The angle-of-arrival fluctuations on this 10 m long path gives a quantitative estimate of the dome seeing. We describe the instrument and its software. The results for the Blanco telescope are presented. The median dome seeing is around 0.2 00. It shows the expected dependence on the temperature difference with the outside air and on the speed and direction of the wind.

The Northern Extended Millimeter Array (NOEMA) is a facility which will focus on large surveys but at the same time generate together with ALMA all sky coverage in the millimeter range with similar sensitivities. NOEMA consists of twelve 15-meter antennas equipped with ultra-low noise SIS receivers covering the frequency range from 70 to 375 GHz. With a surface accuracy of 35 micrometer, the NOEMA antennas offer excellent efficiency for the wavebands in operation. The NOEMA receivers deliver dual linear polarization signals in separated side bands of 8GHz bandwidth each. The resulting total IF bandwidth of 32 GHz is processed in an advanced FX-correlator using high speed samplers and FPGA technology. The correlator offers simultaneously high efficiency for continuum and high resolution spectroscopy without any need for trade-offs. The final baseline length will be 1.7 km enabling resolutions down to 0.1". The key technologies used for NOEMA including the antenna technology are summarized and an overview on the actual status of the project and first science results will be given. Further upgrades such as a dual band extension for the coming years are already in preparation. The related technological developments including the path for efficient short spacing measurements with the IRAM 30m telescope are shortly outlined.

The MeerKAT radio telescope array, the Large Synoptic Survey Telescope (LSST), and eventually the Square Kilometer Array (SKA) will usher in a remarkable new era in astronomy, with thousands of transients being discovered and transmitted to the astronomical community in near-real-time each night. Immediate spectroscopic follow-up will be critical to understanding their early-time physics – a task to which the Southern African Large Telescope (SALT) is uniquely suited, given its southerly latitude and the 14-degree-diameter uncorrected field (patrol area) of its 10-m spherical primary mirror. A new telescope configuration is envisioned, incorporating multiple “mini-trackers” that range around a much larger patrol area of 35 degrees in diameter. Each mini-tracker is equipped with a small spherical aberration corrector feeding an efficient, low resolution spectrograph to perform contemporaneous follow-up observations.

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 extensive preparations of the Mayall telescope and its environs for DESI, and will report on progress-to-date of the installation of DESI itself.

The Large Synoptic Survey Telescope (LSST) Project is a public-private partnership now half way through the 8- year construction period. LSST construction was initiated in 2014 by the US National Science Foundation to build the observing system within a $473M budget and in time to start the survey in October 2022. The US Department of Energy also participates by funding the camera fabrication with a budget of $168M. LSST will construct the system to conduct a wide fast deep survey of the entire visible sky and to process and serve the data to the US, Chilean, and international contributors without any proprietary period. The designs have matured around the 3-mirror wide field optical system; an 8.4 meter primary, 3.4 meter secondary, and 5 meter tertiary mirror that feed three refractive elements and a 64 cm 3.2 gigapixel focal plane camera. The data management system will reduce, transport, alert, archive roughly 15 terabytes of data produced nightly, and will serve raw and catalog data on daily and annual timescales throughout the 10-year survey. Additional access portals and tools will extend the scientific reach to education and public outreach efforts for students and non-professionals. LSST has completed key elements of the system with hardware being sent to the observing site on Cerro Pachón, Chile, factory integration efforts underway, and the focal plane assembly process started. Software development continues as an open-source project and completed demonstrations of key algorithm performance on existing data sets. LSST continues to plan an on-time and on-budget completion.

Construction of the Daniel K. Inouye Solar Telescope (DKIST) is well underway on the Haleakalā summit on the Hawaiian island of Maui. Featuring a 4-m aperture and an off-axis Gregorian configuration, the DKIST will be the world’s largest solar telescope. It is designed to make high-precision measurements of fundamental astrophysical processes and produce large amounts of spectropolarimetric and imaging data. These data will support research on solar magnetism and its influence on solar wind, flares, coronal mass ejections, and solar irradiance variability. Because of its large aperture, the DKIST will be able to sense the corona’s magnetic field—a goal that has previously eluded scientists—enabling observations that will provide answers about the heating of stellar coronae and the origins of space weather and exo-weather. The telescope will cover a broad wavelength range (0.35 to 28 microns) and operate as a coronagraph at infrared (IR) wavelengths. Achieving the diffraction limit of the 4-m aperture, even at visible wavelengths, is paramount to these science goals. The DKIST’s state-of-the-art adaptive optics systems will provide diffraction-limited imaging, resolving features that are approximately 20 km in size on the Sun.

At the start of operations, five instruments will be deployed: a visible broadband imager (VTF), a visible spectropolarimeter (ViSP), a visible tunable filter (VTF), a diffraction-limited near-IR spectropolarimeter (DLNIRSP), and a cryogenic near-IR spectropolarimeter (cryo-NIRSP). At the end of 2017, the project finished its fifth year of construction and eighth year overall. Major milestones included delivery of the commissioning blank, the completed primary mirror (M1), and its cell. Commissioning and testing of the coudé rotator is complete and the installation of the coudé cleanroom is underway; likewise, commissioning of the telescope mount assembly (TMA) has also begun. Various other systems and equipment are also being installed and tested. Finally, the observatory integration, testing, and commissioning (IT&C) activities have begun, including the first coating of the M1 commissioning blank and its integration within its cell assembly. Science mirror coating and initial on-sky activities are both anticipated in 2018.

The University of Tokyo Atacama Observatory Project is to construct and operate a 6.5m infrared telescope at the summit of Co. Chajnantor (5640m altitude) in northern Chile, promoted by the Institute of Astronomy of the University of Tokyo. Thanks to the dry climate (PWV~0.5mm) and the high altitude, excellent observation condition in the NIR to MIR wavelengths is achieved. The telescope has two Nasmyth foci where two facility instruments, SWIMS for the near-infrared and MIMIZUKU for the mid-infrared, are installed and two folded- Cassegrain foci for carry-in instruments. All these four foci can be switched by rotating a tertiary mirror. The final focal ratio is 12.2 and the foci have large field-of-view of 25 arcmin in diameter.

We adopted a 6.5-m F/1.25 light-weighted borosilicate honeycomb primary mirror and its support system that are developed by Steward Observatory Richard F. Caris Mirror Lab. An enclosure has the shape of carousel, and large ventilation windows with shutters control the wind to flush heat inside the enclosure. A support building with a control room, a mirror coating system and maintenance facilities is located at the side of the enclosure. The mirror coating system consists of a large aluminizing chamber and a mirror washing facility. The operation of the telescope will be remotely carried out from a base facility at San Pedro de Atacama, 50km away from the summit. Development of the two facility instruments has already been completed and they are transported to Hilo, Hawaii in 2017. We are going to carry out engineering observations of those instruments on the Subaru telescope for clearing up technical issues and verifying their performance. The existing summit access road from the ALMA concession area was laid in 2006, however, it is too narrow to carry large components of the telescope and the ancillary facilities such as the primary mirror, its cell, and the aluminizing chamber. The road is being expanded so that it has the width of <5m for straight portion and <7m for curved portion.. The telescope mount and the enclosure are being pre-assembled for functional and performance tests in Japan. All telescope system will be assembled at the summit and see the engineering first light early 2019.

The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very high energies. With more than 100 telescopes at two sites, CTA will be the world’s largest and most sensitive high-energy gamma-ray observatory covering the full sky with a northern array located at the Roque de los Muchachos astronomical observatory on the island of La Palma (Spain) and a southern array near the European Southern Observatory site at Paranal (Chile). Three classes of telescope types spread over a large area are required to cover the full CTA very-high energy range from 20 GeV to 300 TeV.

Building on the technology of current generation ground-based gamma-ray detectors (H.E.S.S., VERITAS and MAGIC), CTA will be 5 to 20 times more sensitive, depending on gamma-ray energy, and have unprecedented accuracy in its detection of high-energy gamma rays. Current gamma-ray telescope arrays host up to five individual telescopes, but CTA is designed to detect gamma rays over a larger area and a wider field of view.

Prototypes for the major CTA subsystems including the various size telescopes and cameras have been developed and built at different places. CTA is currently preparing for the full construction phase, both technically and organizationally, with the goal to achieve first light by the year 2022 and completion by 2024/25.

CTA will be the first ground-based gamma-ray observatory open to the worldwide astronomical and particle physics communities as a resource for data from unique, high-energy astronomical observations.

This paper will describe the progress of the SKA-1 Telescope during the period from Preliminary Design Review to Critical Design Review. In addition to this, it will provide information on the management of the project with respect to managing cost and scope whilst working within a fixed cost cap. The paper will consider the balance between the technical choices made with the risk of delivering a large, distributed observatory across several continents. In addition, it will consider the challenges of carrying this out whilst developing the organisation towards an Inter-Governmental Organisation. It will consider, briefly, the key management tools used and the lessons learned.

The Telescopio San Pedro Martir project intends to construct a 6.5m telescope to be installed at the Observatorio Astron´omico Nacional in the Sierra San Pedro M´artir in northern Baja California, Mexico. The project is an association of Mexican institutions, lead by the Instituto Nacional de Astrofısica, Optica y Electronica and UNAM’s Instituto de Astronomia, in partnership with the Smithsonian Astrophysical Observatory and the University of Arizona’s Department of Astronomy and Steward Observatory. The project is advancing through the design stage, having completed five design reviews of different subsystems in 2016 and 2017 (enclosure and services: PDR, CDR; optical design: PDR; optics: progress review; telescope: PDR). Once completed, the partners plan to operate the MMT and TSPM as a binational astrophysical observatory.

The Gamma-ray Cherenkov Telescope (GCT) is one of the telescopes proposed for the Small Sized Telescope (SST) section of CTA. Based on a dual-mirror Schwarzschild-Couder design, which allows for more compact telescopes and cameras than the usual single-mirror designs, it will be equipped with a Compact High-Energy Camera (CHEC) based on silicon photomultipliers (SiPM). In 2015, the GCT prototype was the first dual-mirror telescope constructed in the prospect of CTA to record Cherenkov light on the night sky. Further tests and observations have been performed since then. This report describes the current status of the GCT, the results of tests performed to demonstrate its compliance with CTA requirements, and the optimisation of the design for mass production. The GCT collaboration, including teams from Australia, France, Germany, Japan, the Netherlands and the United Kingdom, plans to install the first telescopes on site in Chile for 2019-2020 as part of the CTA pre-production phase.

The Giant Magellan Telescope project is proceeding with design, fabrication, and site construction. The first of the seven required 8.4-m primary mirror segments is completed and in storage, three segments are in various stages of grinding and polishing, and the fifth segment has been cast. Industry contracts are underway to complete the design of the telescope structure. Residence buildings and other facilities needed to support construction at the Las Campanas site in Chile are complete. Hard rock excavation is imminent in preparation for the pouring of concrete for the telescope pier and other foundations. Computational fluid dynamics analysis is informing the design of the telescope enclosure, and further construction work packages are being readied for tender. Seismic design considerations have resulted in the incorporation of a seismic isolation system into the telescope pier, as well as modifications to the primary mirror support system. Designs for the fast-steering and adaptive secondary mirrors, science instruments, and other subsystems are maturing. Prototyping is underway in various aspects, including on-sky testing of wavefront sensing and control elements, and the telescope metrology system. Our fabrication and construction schedule calls for engineering first light with a subset of primary mirror segments in late 2023, with buildout to the full configuration occurring in stages, paced by the availability of primary mirror segments and other components.

The Thirty Meter Telescope (TMT) is an extremely large optical-infrared telescope with diffraction-limited performance that will shape the landscape of astronomy for the next 50 years from its vantage point in the northern hemisphere. The TMT International Observatory, LLC is formed as a public-private-international partnership to fund and manage the design, development, construction and operation of the observatory. The partnership represents a truly global collaboration of the scientific, instrumentation and industrial communities of India, Canada, China, Japan and the USA. This paper will describe the latest status on telescope site preparation, communications and management, requirements flow down and interface definition, telescope and instrument performance, hardware and software development, education and public outreach.

Over the last few years, the ESO’s ELT has made tremendous progress in defining and procuring the many components of one of the future world largest optical-infrared telescopes. More than two dozen large scale contracts have been placed to industry to design and manufacture several items, among them the dome, the telescope structure, the mirrors and their supports, the control system, the infrastructure, and more. In addition, four agreements were signed with consortia of astronomical research institutes to develop the first suite of scientific instruments. As of today, this represents a financial commitment of more than 90% of the total ESO material budget for the ELT.

Currently planned massively segmented telescopes like the European Extremely Large Telescope (EELT)1 or the Thirty Meter Telescope (TMT)2, use “Keck-era” optics. Their mirror subapertures create a dynamically rigid primary optical surface from 100’s of 1m-scale few-cm thick mirrors. We suggest that a dedicated telescope for distinguishing reflected exoplanet light from its host star may not follow these design principles. To reduce moving mass and telescope-scattered light, a post-Keck era large telescope could use new technologies that replace this opto-mechanical stiffness with massively parallel active electro-optics and interferometric concepts. This opens the intriguing possibility of building a dedicated ground-based exoplanet telescope with an aperture of 20m at a cost-scale of $100M. This is a compelling reason for exploring what we call “synthetic aperture” or “hybrid optical telescopes.” Even larger apertures that could be an order of magnitude less costly per square meter than comparable Keck-like optics are possible. Here we consider an optical system built from a relatively “floppy” optical structure and scalable interferometrically phased, moderate size (5m diameter), subapertures. This ExoLife Finder (ELF) telescope is sensitive to optical biomarker signals and has the power to map the surfaces of nearby M-dwarf exoplanets on subcontinental scales.

In September 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) initiated the era of gravitational wave astronomy, a new window on the universe. In its first 4 months of operation, the Advanced LIGO instrument made the first, two direct detections of gravitational waves (ripples in the fabric of space-time). Each of these events were the result of merger of a pair of black holes into a single larger black hole. The first detected system consisted of two black holes of about 30 solar masses each which merged at a distance of 400 mega-parsecs or 1.4 billion years ago, revealing a new population of black holes. As of October 2017 five black hole mergers have been announced. In August 2017, after some further improvements and commissioning, the LIGO and VIRGO collaborations announced the first direct detection of gravitational waves associated with a gamma ray burst and the electromagnetic emission (visible, infrared, radio) of the afterglow of a kilonova -- the spectacular collision of two neutron stars at a distance of 40 mega-parsecs. This marks the beginning of multi-messenger astronomy. The discovery was made using the U.S.-based LIGO; the Europe-based Virgo detector; and some 70 ground- and space-based observatories. The Advanced LIGO gravitational wave detectors are second generation instruments designed and built for the two LIGO observatories in Hanford, WA and Livingston, LA. These two identically designed instruments employ coupled optical cavities in a specialized version of a Michelson interferometer with 4 kilometer long arms. Fabry-Perot cavities are used in the arms to increase the interaction time with a gravitational wave, power recycling is used to increase the effective laser power and signal recycling is used to improve the frequency response. In the most sensitive frequency region around 100 Hz, the displacement sensitivity is 10-22 meters rms, or about 10 million times smaller than a proton. In order to achieve this unsurpassed measurement sensitivity Advanced LIGO employs a wide range of cutting-edge, high performance technologies, including a ultra-high vacuum system; an extremely stable laser source; multiple stages of active vibration isolation; super-polished and ion milled, ultra-low loss, fused silica optics with high performance multi-layer dielectric coatings; wavefront sensing; active thermal compensation; very low noise analog and digital electronics; complex, nonlinear multi-input, multi-output control systems; and a custom, scalable and easily re-configurable data acquisition and state control system.

Virgo is the French-Italian interferometric gravitational wave detector located near Pisa, Italy. Virgo has undergone a several year upgrade period to the second generation, and has come online recently as Advanced Virgo for participating in a common observation run with the American LIGO detectors. After its first successful observation of gravitational waves, the detector is now undergoing further commissioning and upgrades for preparing it for a longer common observation run scheduled for next year with improved sensitivity.

This paper explains the setup of the Virgo detector and the main technical choices, leading to the Advanced Virgo upgrade program for enhancing the sensitivity. The status of the detector and the ongoing upgrades for achieving the second-generation design sensitivity are presented, together with the mid-term plans for going beyond the limits of the Advanced Virgo configuration while retaining the current infrastructure.

The ELT is a project led by the European Southern Observatory (ESO) for a 40-m class optical, near- and mid-infrared, ground-based telescope. When it will enter into operation, the ESO ELT will be the largest and most powerful optical telescope ever built. It will not only offer unrivalled light collecting power, but also exceedingly sharp images, thanks to its ability to compensate for the adverse effect of atmospheric turbulence on image sharpness. The basic optical solution for the ESO ELT is a folded three-mirror anastigmat, using a 39-m segmented primary mirror (M1), a 4-m convex secondary mirror (M2), and a 4-m concave tertiary mirror (M3), all active. Folding is provided by two additional flat mirrors sending the beams to either Nasmyth foci along the elevation axis of the telescope. The folding arrangement (flat M4 and M5 mirrors) is conceived to provide conveniently located flat surfaces for an adaptive shell (M4) and field stabilization (M5). This paper provides an update of the specifications, design, and manufacturing of the ESO ELT optical systems

The Large Synoptic Survey Telescope (LSST) large field of view is achieved through a three-lens camera system and a three-mirror optical system comprised of a unique 8.4-meter diameter monolithic primary/tertiary mirror (M1M3) and a 3.4-meter diameter secondary mirror (M2)¹. The M2 is a 100mm thick meniscus convex asphere. The M2 Assembly includes a welded steel cell and a support system comprised of 72 axial and 6 tangential electromechanical actuators to control the mirror figure. The M2 Assembly (including optical polishing and integrated optical testing) is being fabricated by Harris Corporation in Rochester, NY. The summary status of this system and results are presented.

To cater the need of growing astronomical community of India, there is a proposal to install 10-12m size optical-NIR telescope, equipped with state of the art back-end instruments . A telescope of this size is possible only, when primary mirror is made of smaller mirror segments. In order to get acquainted with segmented mirror telescope technology, at Indian Institute of Astrophysics Bangalore, we have initiated a project to develop a small prototype telescope made of small mirror segments. The proposed prototype telescope will use seven hexagonal mirrors, which will be supported by simple mirror support assembly and driven by indigenously developed voice coil based actuators. We also plan to make use of in-house developed inexpensive inductive edge sensor, which can precisely sense inter-segment relative displacement. The telescope mount is supposed to be Alt-Az and secondary mirror will be supported by trusses made of steel. The primary axes like elevation, azimuth and field de-rotator will be driven by direct drive motors. Though the primary objective of this telescope is to demonstrate the segmented mirror technology, however, we have designed the telescope in such way that it can also be used to a few dedicated science cases. The telescope is planned to be installed at Hanle, Ladakh India which is also a potential site for India's large telescope project. In this paper, we will present the progress made in opto-mechanical design as well development of other sub-systems required for the PSMT. The prototyping effort is one step toward realization of a large telescope in India and it is expected to be completed in two years period.

The Prefocal Station (PFS) is the last opto-mechanical unit before the telescope focal plane in the Extremely Large Telescope (ELT) optical train. The PFS distributes the telescope optical beam to the Nasmyth and Coudé instrument focal stations and it contains all of the sky metrology (imaging and wavefront sensing) that will be used by the active optics of the telescope and to support operations such as phasing the primary mirror (phasing and diagnostic station). It also hosts local metrology that will be used for coarse alignment and maintenance. We present the main results of a concept design study for the Nasmyth A prefocal station.

An observational and modeling technique to look for possible systematic bias in the phasing of the segments of a large aperture optical telescope is presented. The technique uses on-sky images from adaptive optics (AO) science instruments in conjunction with detailed AO modeling to make predictions on possible periodic residual segment piston errors. The technique is demonstrated on the sky using the Keck II telescope to cancel two bright speckles seen in the NIRC2 science images by applying appropriate piston corrections to the telescope segments. Follow-up observations are planned for this summer to validate another model prediction, using this technique on low order aberrations to improve the image quality of AO science observations. The significance of the technique for AO observations with the existing and future extremely large segmented telescopes is discussed.

The narrowband segment phasing algorithm that was originally developed at Keck was replaced many years ago by a broadband algorithm that, although slower and less accurate than the former, has proved to be much more robust. A thorough investigation into the lack of robustness of the narrowband algorithm has now shown that this results from systematic errors (∼ 20 nm on average) that are wavelength-dependent. We show that the seemingly continuous distribution of these chromatic errors in fact results from (at least) two independent causes. The largest and most problematic effects are due to “plateaus” of unremoved material that were covered by supports during the ion beam figuring of three of the segments, but other smaller chromatic effects are also shown to be present and these are not yet understood. If the purely chromatic effects can be eliminated, we show that the intrinsic accuracy of the narrowband algorithm is about 6 nm (surface).

One of the most complex systems of the Stratospheric Observatory for Infrared Astronomy (SOFIA) is the Secondary Mirror Assembly (SMA) providing fast mirror steering capability for image stabilization and infrared square wave chopping. Since its integration in 2002 the performance of the SMM is limited by a strong structural resonance caused by the deformation of a ring-shaped reaction mass. Constraining this resonance would not only lead to a wider actuation bandwidth and therefore a faster transition between the chop positions but also reduce the image jitter introduced by external disturbances acting on the active mechanism itself. Concepts have been developed to attenuate this resonance by structural modifications on the hardware level. To predict the later in-flight performance of these concepts an end-to-end simulation has been setup. The design changes are implemented into a finite element model of the SMA to compute the open loop system response of the mechanism. Subsequently the new dynamic system behavior is implemented into a controller model to simulate the closed loop controlled SMA. Next to the new steering bandwidth, the disturbance rejection capability is analyzed by applying a white noise excitation simulating wind loads and process noise. Moreover, the transition time between the chop positions is determined by applying a square wave input signal to the simulation.

Alignment and Phasing system (APS) is one of essential device for any segmented mirror telescope. It helps to align and phase mirror segments, so that all together they works like a monolithic surface. Over last two years we have been exploring a possibility of using pyramid based wave-front sensor in the APS of a Prototype Segmented Mirror Telescope (PSMT), being developed in India. As a first step, we have derived the basic mathematical formulations required for the pyramid sensor and then after simulated the functional aspects of the pyramid sensor in the MATLAB. In order to carry out experimentation on pyramid sensor, we have also designed an optical setup using the ZEMAX. Since manufacturing of a high quality pyramid is a challenge, therefore, we have come up with a simple scheme in which the PSF is divided into multiple pupils using a rotating mask. In this paper, we briefly present the mathematical formulation, the technique of wave-front reconstruction, various simulations using the MATLAB and the ZEMAX as well as results obtained through a preliminary experimentation.

Several classes of planetary science observations require high spatial resolution in UV and visible wavelengths. Key examples include (a) the detection of satellites and characterization of their orbits, (b) the discovery of faint and small objects among the NEO, asteroid, Kuiper belt or Sedna-like populations and (c) cloud or trace gas observations in planetary atmospheres. Hubble Space Telescope (HST) observations have been very productive in these areas: consider the recent discovery of Makemake's satellite (Parker et al., 2016), the discovery of 2014 MU69 (now the flyby target of the New Horizons spacecraft) or the OPAL (Outer Planet Atmospheres Legacy) program. Like HST, large-aperture ground-based telescopes with adaptive optics can also achieve spatial resolutions of 50 mas, but normally at wavelengths longer than ~1 μm. Projects like MagAO-2K are working on improving image quality at visible wavelengths, but while the core PSF (Point Spread Function) width might be narrow (projected to be 15 mas at the Magellan telescope), the Strehl ratio drops steeply with wavelength (Males et al., 2016). Not all science goals suffer equally from low Strehl ratios, however: cloud tracking on Venus is more tolerant of a low Strehl ratio than searching for a close satellite of Makemake. A telescope on a NASA super-pressure balloon would float above 99.3% of the atmosphere, where the inner Fried parameter is thought to be two meters or more. While atmospheric turbulence is not expected to impact image quality, there are other sources of wavefront error (WFE), such as mirror figuring, misalignment of the OTA (Optical Telescope Assembly) or asymmetric heating from the Sun or Earth. We reference recent work that estimates balloon telescope WFEs from different sources to generate a suite of plausible PSFs. We apply these PSFs to the UV and visible wavelength science cases outlined in the GHAPS/SIDT report (Gondola for High Altitude Planetary Science/Science Instrument Definition Team). We quantify the impact that WFE has on achieving the planetary observations outlined in the SIDT report.

We present here SPECULOOS, a new exoplanet transit search based on a network of 1m-class robotic telescopes targeting the ~1200 ultracool (spectral type M7 and later) dwarfs bright enough in the infrared (K-mag ≤ 12.5) to possibly enable the atmospheric characterization of temperate terrestrial planets with next-generation facilities like the James Webb Space Telescope. The ultimate goals of the project are to reveal the frequency of temperate terrestrial planets around the lowest-mass stars and brown dwarfs, to probe the diversity of their bulk compositions, atmospheres and surface conditions, and to assess their potential habitability.

The BlackGEM Phase 1 array for optical synoptic surveys consists of three wide-field telescopes providing an 8.1 square degrees field-of-view sampled at 0.56". It will be installed at the ESO La Silla Observatory. Each unit telescope consists of a modified Dall-Kirkham (Wynne-Harmer) configuration with a 65cm parabolic primary mirror, a 23cm spherical secondary and a triplet corrector lens. The third lens in the triplet is motorized to double as an Atmospheric Dispersion Corrector. The 10cm x 10cm flat, achromatic focal plane contains a single STA1600 10.5k x 10.5k chip with 9 micron pixels, providing a 2.7 square degree field-of-view sampled at 0.56"/pix. The telescope is equipped with a 6 slot (u,g,q,r,i,z) filter wheel. Limiting magnitude (5 sigma) in dark conditions is q=23 in 300s integration in 1" seeing. The telescope structure is made from carbon-fibre for maximum stability. The secondary mirror is mounted on a piezo-stage for active control. Each telescope is mounted on the Fornax 200 mount. On La Silla each telescope will be housed in a clamshell dome, and be located on a 7m high double-walled cylinder to lift it above the ground-layer seeing. The outer cylinder will carry the dome and the inner cylinder the telescope. The scientific program of BlackGEM is centered on optical afterglows of gravitational wave mergers, reacting to Advanced LIGO/Virgo triggers. The array will also perform a full southern sky survey (BG-SASS), covering 30000 square degrees (Dec < +30d) down to 22nd magnitude in all six filters at 1" resolution; a fast synoptic survey at 1 minute cadence for characterization of fast transients; bi-weekly all-sky q-band scan; and a twilight survey of the local universe. The BlackGEM consortium consists of the Netherlands Research School for Astronomy (NOVA), Radboud University and KU Leuven as founding members and the University of Manchester, UC Davis, Tel Aviv University, the Weizmann Institute, the University of Canterbury and the Hebrew University Jerusalem as partners. BlackGEM data will be processed on-line for transients and a full-source database using optimal photometry and the ZOGY image subtraction techniques. BlackGEM transients will be announced publically upon detection. All BlackGEM data will be cloud-based, including the 150Tb live database of the full source photometry. BlackGEM Phase 1 is scheduled for installation on La Silla in Q2-Q3 2018 and start of operations of in Q4 2018. In Phase 2 (2019-2022) the array is to be expanded to 15 unit telescopes, providing a 40.5 square degree instantaneous field-of-view. An overview of the array, first results of the prototype and an update of the installation will be given. www.blackgem.org

Solar activity and related space weather phenomena can have a potential impact on the space environment and affect critical infrastructures and systems like, for instance, communication networks, power grids, aviation systems. It is therefore of fundamental importance to forecast these events enough in advance (several hours) to put in place mitigation strategies that can reduce the associated risks. The forecasting of solar activity is only possible by monitoring the complex magnetic structures in the Suns atmosphere that can give birth to sudden explosive events. SAMM, the solar activity MOF monitor, is an undergoing project at INAF-OAR in cooperation with a SME industry (DS Group srl - Avalon Instruments) and funded by the Italian Ministry for economic development (MiSE), for the realization of a robotic telescope, based upon magneto-optical filters, for the continuous monitoring of the magnetic field topology and the Doppler velocity of the plasma, at multiple heights in the solar atmosphere. The first channel of SAMM is currently under on-sky tests and system evaluation.

The site testing shows that Antarctic Dome A is one of the best site on earth for astronomical observations, for wavelength ranging from visible to infrared and sub-millimeter. Continuous observation for nearly four months in polar nights makes Dome A quite suitable for time domain astronomy. In the past decade CCAA already led a series of Antarctic astronomy activities and telescope projects which will be introduced in this paper. The first generation telescope is Chinese Small Telescope Array known as CSTAR, which was composed of four identical telescopes with 145mm entrance pupil, 20 square degrees FOV and different filters, all pointing to the celestial South Point, mainly used for variable stars detection and site testing. The telescope was deployed in Dome A in Jan. 2008, and followed by automatic observations for four consecutive winters. Three Antarctic Survey Telescopes (AST3) is the second generation telescope capable of pointing and tracking in very low temperature, with 500mm entrance pupil, 8.5 square degree FOV. AST3-1 and AST3-2 were respectively mounted on Dome A in Jan. 2012 and 2015, fully remotely controlled for supernovae survey and exoplanets searching. In Aug. 2017, AST3-2 successfully detected the optical counterpart of LIGO Source GW 170817. Now AST3-3 is under development for both optical and near infrared sky survey by matching different cameras. Based on the experience of the above smaller sized optical telescopes, the 2.5m Kunlun Dark Universe Survey Telescope (KDUST) was proposed for high resolution imaging over wide field of view. Currently the KDUST proposal was submitted to the government and waiting for project review.

We present the detailed science case, and brief descriptions of the telescope design, site, and first light instrument plans for a new ultra-wide field submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m elevation site on Cerro Chajnantor in northern Chile. Our science goals are to study star and galaxy formation from the epoch of reionization to the present, investigate the growth of structure in the Universe, improve the precision of B-mode CMB measurements, and investigate the interstellar medium and star formation in the Galaxy and nearby galaxies through spectroscopic, polarimetric, and broadband surveys at wavelengths from 200 m to 2 mm. These goals are realized with our two first light instruments, a large field-of-view (FoV) bolometer-based imager called Prime-Cam (that has both camera and an imaging spectrometer modules), and a multi-beam submillimeter heterodyne spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very low system emissivity, so that combined with its wide FoV at the unsurpassed CCAT site our telescope/instrumentation combination is ideally suited to pursue this science. The CCAT-prime telescope is being designed and built by Vertex Antennentechnik GmbH. We expect to achieve first light in the spring of 2021.

The Maunakea Spectroscopic Explorer (MSE) project has completed its Conceptual Design Phase. This paper is a status report of the MSE project regarding its technical and programmatic progress. The technical status includes its conceptual design and system performance, and highlights findings and recommendations from the System and various subsystems design reviews. The programmatic status includes the project organization and management plan for the Preliminary Design Phase. In addition, this paper provides the latest information related to the permitting process for Maunakea construction.

The next-generation Very Large Array (ngVLA) is an astronomical observatory planned to operate at centimeter wavelengths (25 to 0.26 centimeters, corresponding to a frequency range extending from 1.2 GHz to 116 GHz). The observatory will be a synthesis radio telescope constituted of approximately 214 reflector antennas each of 18 meters diameter, operating in a phased or interferometric mode.

We provide an overview of the current system design of the ngVLA. The concepts for major system elements such as the antenna, receiving electronics, and central signal processing are presented. We also describe the major development activities that are presently underway to advance the design.

Except for the spectroscopic survey telescope LAMOST, there are only two 2m class general purpose telescopes for precision observation in China (2.16m in Xinglong and 2.4m in Lijiang). Chinese astronomical community unanimously agrees that a 10m class large diameter general purpose optical/infrared telescope is urgently needed in China for a wide range of scientific research. The configuration for LOT with primary aperture 12m has been selected by Chinese government for the Thirteen-five-years plan in July, 2016. The concept design introduced here has been approved by Chinese astronomical community and Chinese Academy of Sciences in Dec. 2017, and submitted into the formal funding procedure of Chinese government. For quite a long time, China will very likely have only one 10m class telescope, therefore LOT should be a general-purpose telescope including multi-foci. The Nasmyth focus, prime focus, Cassegrain focus and coudé focus have been considered or reserved. Also, LOT will closely combine with the development of new technologies, such as AO, GLAO, fiber and instrument related new technologies, to make it has powerful capability for the frontier sciences. The four-mirror Nasmyth system, optimized according to the GLAO requirements, has a f-ratio about 14 and field of view 14 arecmin with excellent image quality. Some off-axis four-mirror Nasmyth optical systems are also presented in this paper. The primary focus system has a f-ratio 2 and 1.5degree field of view with 80% light energy encircled in 0.5 arecsec, which will let LOT complementary with the coming 30m-class telescopes. A double–layer Nasmyth platforms are proposed to accommodate more instruments, such as the wide field imaging spectrograph, broad band medium resolution spectrograph, high resolution spectrograph and multi-object fiber spectrographs and so on. Not all optical systems will be constructed in the same time, which will be in stages depending on the science and funding situation.

Recently, China is planning to construct a new large optical-infrared telescope (LOT), in which the aperture of the primary mirror is as large as 12m. China’s LOT is a general-purpose telescope, which is aimed to work with multiple scientific instruments such as spectrographs. Based on the requirements of LOT telescope, we have compared the performance of Ritchey–Chrétien (RC) design and Aplanatic-Gregorian (AG) design from the perspective of scientific performance and construction cost. By taking the primary focal ratio, Nasmyth focal ratio, and telescope’s site condition into consideration, we finally recommend a RC f/1.6 design configuration for LOT’s Nasmyth telescope system. Unlike the general identical configuration, we choose a non-identical configuration for the telescope system which has a shorter Cassegrain focal ratio compared to the designed Nasmyth focal ratio. The non-identical design can allow for a shorter back focal distance and therefore a shorter telescope fork to guarantee the gravitational stability of the whole telescope structure, as well as relatively lower construction cost. Detailed analysis for the feasibility of our recommended design is provided in this paper.

The Daniel K. Inouye Solar Telescope (DKIST) is a 4-meter aperture, off-axis, Gregorian configuration, solar telescope currently under construction on the top of Haleakela on the island of Maui, Hawaii¹. When completed, DKIST will be the world’s largest solar telescope.

The optical performance of the telescope will depend on the accurate alignment of its mirrors. During Integration Testing and Commissioning (IT&C), mirrors will be installed and aligned sequentially. The alignment will be verified by measuring the wavefront progressively at different focus locations using starlight at night with a custom-designed wavefront measurement system (WMS) that consists of a Shack-Hartmann wavefront sensor. In this paper, we will present the optical design of the WMS. We will discuss the testing and calibration process of the as-built WMS in the lab and demonstrate the final in-lab performance.

The Giant Magellan Telescope (GMT)¹ is a 25 m telescope composed of seven 8.4 m “unit telescopes”, on a common mount. Each primary and conjugated secondary mirror segment will feed a common instrument interface, their focal planes co-aligned and co-phased. During telescope operation, the alignment of the optical components will deflect due to variations in thermal environment and gravity induced structural flexure of the mount. The ultimate co-alignment and co-phasing of the telescope is achieved by a combination of the Acquisition Guiding and Wavefront Sensing system (AGWS) and two segment-edge-sensing systems². An analysis of the capture range of the AGWS indicates that it is unlikely that that system will operate efficiently or reliably with initial mirror positions provided by open-loop corrections alone³.

Since 2016 GMT have been developing a telescope metrology system, that is intended to close the gap between openloop modelling and AGWS operations. A prototyping campaign was initiated soon after receipt of laser metrology hardware in 2017. This campaign is being conducted in collaboration with the Large Binocular Telescope Observatory (LBTO), and hardware was first deployed on the LBT in August 2017. Since that time the system had been run and developed over some hundreds of hours on-sky. It has been shown to be capable of reliably measuring the relative positions of the main optics over ~ 10 m to a repeatability of ~ 1-2 microns RMS. This paper will describe the prototyping campaign to date, the basic design of the system, lessons learned and results achieved. It will conclude with a discussion of future prototyping efforts.

The Acquisition Guiding and Wavefront Sensing System (AGWS) is responsible for making the measurements required to keep the optics of the seven-segment GMT coaligned, phased, pointing in the correct direction, and conforming to the correct mirror shape. The AGWS consists of four identical probes that patrol the outer parts of the GMT field of view. Each probe is comprised of two channels. The visible channel contains optics that can provide high-speed full aperture guiding, segment guiding, or Shack-Hartmann wavefront sensing feeding an EMCCD camera. In natural seeing operations, these probes feed the GMT active optics system. In ground layer AO mode, they are the primary wavefront sensors. The second channel, used for phasing the seven segments in diffraction limited operation, contains J-band dispersed fringe sensor optics feeding a SAPHIRA IR e-APD array. We present the system architecture, and an overview of requirements, optical, mechanical and electrical designs.

The Cherenkov Telescope Array (CTA) will be the next-generation ground-based detector for gamma rays with very high energies. Telescopes will be located at one site each in both the northern and southern hemisphere. The arrays will comprise, in total, more than 100 telescopes of different sizes and designs. The sensitivity of CTA in its central energy range, i.e. between approximately 100 GeV and 1 TeV, will be driven by the performance of the Medium-Sized Telescopes (MSTs). This performance crucially depends on an exact alignment of the facets of the tessellated mirror surface of each telescope. In this contribution, an automated mirror alignment procedure for MSTs is presented. This procedure consists of two steps. First a rough mirror alignment is achieved with the socalled Bokeh method, which is based on the non-focused imaging of an artificial light source onto the Cherenkov camera plane. Afterwards, an optimal mirror alignment is achieved with an alignment procedure based on the focused imaging of stars. Here, the Bokeh method will be described in detail, including the hardware and software setups, devised technologies and pattern recognition with classical and neural network-based methods. Also results from star alignment procedures are given and compared to results from the Bokeh method. The performance of the presented approach is demonstrated with results obtained from measurements at the MST prototype installation in Berlin, Germany.

Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in the world.

Being the most sensitive single dish radio telescope. It was completed and put into use in September 2016. Its innovative engineering concept and design pave a new road to realize a huge single dish in the most effective way. The idea of sitting a large spherical dish in a karst depression is rooted in Arecibo telescope. FAST is an Arecibo-type antenna with three outstanding aspects: the karst depression used as the site, which is large to host the 500-meter telescope and deep to allow a zenith angle of 40 degrees; the active main reflector correcting for spherical aberration on the ground to achieve a full polarization and a wide band without involving complex feed systems; and the light-weight feed cabin driven by cables and servomechanism plus a parallel robot as a secondary adjustable system to move with high precision. The common feature of the latter two innovations is the transformation of large scale rigid structures into large scale flexible structures. To realize precise real-time control, the challenge of measurement and control technology is very challenging. This review intends to introduce the implementation methods, the recent progress, results, problems and future development of FAST measurement and control.

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.

On June 9th, 2014, the design/build contract for the Large Synoptic Survey Telescope (LSST) Mount Assembly (TMA) system was awarded to GHESA Ingeniería y Tecnología, S.A. and Asturfeito, S.A. This paper describes the current status of the fabrication, assembly, and verification, along with the logistic plans to ship the mount and equipment to Cerro Pachón in Chile. The design of the mount successfully passed the final design review on January 29, 2016, and is currently under full-scale construction at Asturfeito’s factory in Avilés, Spain. A detailed description the critical design, fabrication challenges, and the state of testing is presented for the following subsystems: Azimuth track assembly: The 16-m diameter azimuth track which was fabricated in four large sectors provides the mounting surfaces for the axial and radial hydrostatic bearings. This high precision surface has been machined to high flatness and circularity to meet the high pointing repeatability requirements. Azimuth structure: The azimuth structure consists of 20 large weldments. These large heat-treated weldments were designed to minimize pointing hysteresis and yet be small enough to be transported by truck. Elevation structure: The elevation structure consists of a large central ring structure that supports both the M1M3 mirror cell and the optical support for the M2 and camera. Azimuth mechanicals: The azimuth structure uses 16 linear motors designed and fabricated by Phase Motion Control. All motors, motion control, and capacitor banks have been delivered to the factory and are being prepared for installation Hydrostatic bearings: All hydrostatic bearings have been designed and fabricated by SKF. The oil supply system was designed by SKF and HYDX hydraulic solutions. The azimuth bearings have been installed and tested using the azimuth platform. Mount control system hardware and software: The hardware, engineering interface and the software that connects to the telescope control system was designed, assembled, and tested by iK4 Tekniker. This system has been tested using the camera cable wrap and the M1M3 mirror covers at Tekniker. The system is now being installed the factory to begin testing on the assembled mount. Camera cable wrap: The top end of the telescope requires a complex cable wrap for all of the cameras services and utilities. This wrap successfully passed verification testing and is now installed on the telescope top end. M1M3 mirror cover: This unique four-fan design was developed and tested at ik4 Tekniker. After verification at Tekniker it was shipped to the factory and is now assembled on the azimuth ring assembly. Utility distribution: Fluid distribution system includes a large network of coolants, refrigerants, air, fibers optics, and data communication lines. The unique challenges to routing throughout the telescope all of these services required coordinated design and implementation and four cable wraps. The azimuth cable wrap is a motorized drape design designed by Empresarios Agrupados and Tekniker. The two elevation drapes were designed by Empresarios Agrupados and Kabbleschlepp. An overview of the logistics required for shipping, ground transportation, and cranes will be described.

AMOS with EIE as a main subcontractor, was awarded a contract in November 2014 for the design, manufacturing and installation of a 4m-class telescope for the Turkish Eastern Anatolia Observatory (DAG) situated at 3170 m above the sea level in Palandöken mountains. The telescope is based on a Ritchey-Chretien configuration with two folded Nasmyth focal planes and a focal length of 56m.

Diffraction-limited performances will be reached thanks to the combination of the active optics system and the adaptive optics system that will be implemented on one of the Nasmyth ports. The active optics system aims at controlling the shape of the primary mirror by means of 66 axial force actuators and positioning actively the secondary and tertiary mirrors by means of hexapods.

More than 30 years of experience in testing instruments and telescopes, including optical testing, alignment, metrology, mechanical static and dynamic measurements, system identification, etc. allow to implement an adequate verification strategy combining component level verifications with factory and site test in the most efficient and reliable manner.

As a main contractor, AMOS is in charge of the overall project management, the system engineering, the optical design and the active optics development. As a main sub-contractor and partner of AMOS, EIE is in charge of the development of the mount. The factory test therefore takes place in EIE premises.

In this paper is shortly presented the overall design of the telescope with a review of the specification, the optical design and a description of the major sub-systems, including the optics. The assembly, integration et test plan is outlined. The assembly sequence and the tests of the active optics and the mount are discussed. Finally, the site integration and tests are explained. The process to assess the image quality of the telescope and the verification instrument developed for this purpose by AMOS are presented.

The Next Generation Very Large Array (ngVLA) project to replace the VLA telescope in New Mexico is just beginning. As a part of the initial Community Studies phase, we have contributed the concept design of a 15m feed-low wheel and track design. This telescope, the Next Generation Dish Verification Antenna 15m (ngDVA-15) follows on from the DVA-1 and DVA-2 antennas developed at the Dominion Radio Astrophysical Observatory (DRAO) between 2012 and the present day. This paper will concentrate on the design and optimization process for the ngDVA-15 back-up structure. Topology and free-size optimization were used to develop the initial design concepts. Both methods helped to steer the back-up structure in the initial design phase, but ultimately engineering intuition also played a role. Topology optimization can lead directly to useful solutions in some cases but hardware and software limitations still limit the physical size of the model. Also, topological routines cannot yet correctly model truss-type networks with no moment transfer at the joints, and optimizing structures with only gravitational loads proved to be challenging for the current generation of optimization routines. Size optimization was also used once the design was sufficiently refined. The initial stage of design involved minimization of reflector surface deflections under gravitational loads only. FEA modelling of surface deflections together with in-house developed fitting algorithms were used to determine primary surface accuracy. Surface accuracies of better than 80 microns RMS were achieved which met the initial design goal for telescope operation at 120GHz.

The ELT, Extremely Large Telescope, a 40m class optical, near and mid-infrared telescope that will be installed on Cerro Armazones, on the Chilean Andes, will be characterized by a an alt-azimuthal steel structure mounting weighting about 3700 tons. The telescope design consists of a highly optimized, space-frame structure, whose deflection characteristics have been carefully tuned to facilitate the performance of the oil film associated with the hydrostatic bearing system and the performance of the rotation associated with the drive and encoder systems. The Altitude structure design incorporates the M1 Mirror cell and hosts all the telescope optics. The major challenges in the design are the need to keep the primary mirror segments within a reasonable range from the prescribed locations and the need to minimize the static and dynamic deflections of the secondary mirror. The telescope rotates on tracks fixed to a concrete pier with a diameter of about 52m, completely isolated from the ground by means of special seismic devices. Power, data, control cables and fluid hoses follow the azimuth range of 550 degrees by means of the 18m diameter cable wrap, and the altitude range of 96 degrees with two lateral cable drapes. The rotation of the Azimuth and Altitude axes are possible thanks to the Direct Drive System and kept in place by high precision incremental tape encoders. The telescope is equipped with a very performing Control System that implements state of the art automation technologies, such as isochronous real time fieldbus, communication protocols, absolute time synchronization and safety, state of the art software engineering methods, such as object oriented design and iterative AGILE software development methodology.

The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter mapping experiment planned for a 28 day long-duration balloon (LDB) flight from McMurdo Station, Antarctica during the 2018-2019 season. BLAST-TNG will detect submillimeter polarized interstellar dust emission, tracing magnetic fields in galactic molecular clouds. BLAST-TNG will be the first polarimeter with the sensitivity and resolution to probe the ∼0.1 parsec-scale features that are critical to understanding the origin of structures in the interstellar medium. With three detector arrays operating at 250, 350, and 500 μm (1200, 857, and 600 GHz), BLAST-TNG will obtain diffraction-limited resolution at each waveband of 30, 41, and 59 arcseconds respectively. To achieve the submillimeter resolution necessary for its science goals, the BLAST-TNG telescope features a 2.5 m aperture carbon fiber composite primary mirror, one of the largest mirrors flown on a balloon platform. Successful performance of such a large telescope on a balloon-borne platform requires stiff, lightweight optical components and mounting structures. Through a combination of optical metrology and finite element modeling of thermal and mechanical stresses on both the telescope optics and mounting structures, we expect diffractionlimited resolution at all our wavebands. We expect pointing errors due to deformation of the telescope mount to be negligible. We have developed a detailed thermal model of the sun shielding, gondola, and optical components to optimize our observing strategy and increase the stability of the telescope over the flight. We present preflight characterization of the telescope and its platform.

The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very high energies in the range from 20 GeV to 300 TeV.¹ In order to cover the entire sky an observatory with two telescope arrays is planned, one in the southern hemisphere and one in the northern hemisphere. Each site will combine imaging air Cherenkov telescopes of different sizes and designs to cover the very wide energy range. These sites will complement each other, providing full-sky coverage for galactic and extra-galactic sources. At least three telescope types are required to cover the full CTA energy range in a cost-effective way. The sensitivity in the core energy range between 150 GeV and 5 TeV will be dominated by up to 40 Medium Size Telescopes (MSTs) distributed over both observatory sites. It is intended to equip the MSTs with FlashCam and NectarCAM cameras. This document describes the aspects of the MST design and the status of commissioning and performance validation of the individual assemblies.

More and more astronomical instruments have been installed in Antarctica because of good seeing. Due to adverse circumstances, remote location and unattended, a high fault rate was found in these astronomical instruments in Antarctica. To ensure the reliable operation of these instruments is one of critical technology problems. This paper presents an experimental platform with semi-physical simulation technique for Antarctic Telescopes. The platform helps the research for fault detection, fault diagnosis method, fault handling and so on. It consists of fault simulation system and fault diagnosis and self-recovery system. Furthermore, the platform can be used as fault diagnosis unit for Antarctic telescope directly.

This paper describes the integration of a LSST Technical Writing process, project planning, tools, and the software SOLIDWORKS Composer, as well as the review process and storage. LSST creates highly effective visual work instructions with SOLIDWORKS Composer directly from existing 3D CAD models, with content that can be updated automatically if the design & development changes. We are able to create quickly any kind of interactive images and animations for the technical documentation which helps clearly present even the most complex data without the ambiguity that may occur with traditional 2D static images.

By creating clear and easily understandable visual technical documentation, LSST minimizes both, technical and personnel risks by ensuring workers fully understand all aspects of the required task. By illustrating what tools to use and where to use them, LSST protects the health and safety of their workers and equipment, while streamlining the construction process. These documents also facilitate educating new employees on best practices.

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) mission launched from Palestine, Texas in June 2017. After an exciting launch and successful cruise, the BETTII gondola suffered an anomalous event at termination. BETTII separated from its parachute and free-fell 136,000 feet into the west Texas desert. This event was classified as a “close-call” and investigated as such. We present here the recovery effort required to find the payload and extract the payload from its impact site. We also present lessons learned from the event and results from the investigation, the design for the next BETTII gondola, and a path forward for return to flight.

The Greenland Telescope completed its construction, so the commissioning phase has been started since December 2017. Single-dish commissioning has started from the optical pointing which produced the first pointing model, followed by the radio pointing and focusing using the Moon for both the 86 GHz and the 230 GHz receivers. After Venus started to rise from the horizon, the focus positions has been improved for both receivers. Once we started the line pointing using the SiO(2-1) maser line and the CO(2-1) line for the 86 GHz and the 230 GHz receivers, respectively, the pointing accuracy also improved, and the final pointing accuracy turned to be around 3" - 5" for both receivers. In parallel, VLBI commissioning has been performed, with checking the frequency accuracy and the phase stability for all the components that would be used for the VLBI observations. After all the checks, we successfully joined the dress rehearsals and actual observations of the 86 GHz and 230 GHz VLBI observations, The first dress rehearsal data between GLT and ALMA were correlated, and successfully detected the first fringe, which confirmed that the GLT commissioning was successfully performed.

Since the large scale use of paralleled controllable fiber positioner in LAMOST, the newly designed spectral survey telescope project generally uses the fiber position unit which similar to LAMOST to obtain the target spectrum. The positioning accuracy of the fiber positioner is directly related to the performance of the telescope. In order to further improve the positioning accuracy of positioners system, it is an important way to improve the accuracy by measuring the position of the optical fiber end on the positioners by using the visual metrology system. This paper mainly introduces the research design of LAMOST closed-loop metrology system, and the closed-loop system was established in different positions within the telescope to acquire best results. The metrology system will improve the fiber positioner system operation accuracy and reliability after the completion of the entire system in the future.

The Hobby-Eberly Telescope is an innovative 10-meter telescope, located at the McDonald Observatory. We have completed a major multi-year upgrade of the HET that has substantially increased the field of view to 22 arcminutes by replacing the optical corrector, tracker, and prime focus instrument package and by developing a new telescope control and metrology systems. The metrology systems include four independent optical sensors to provide fully redundant alignment and pointing information to keep the telescope aligned to within a few microns and a few arc seconds. We detail the design, implementation, on-sky performance, and lessons learned.

As the LMT/GTM has moved to final completion as a 50 m diameter telescope, the scientific and instrumentation teams have requested information concerning the actual motions between the reinforced M3 platform of the telescope and the receiver cabin floor. To provide some bounding information on these effects, the LMT/GTM engineering and metrology teams developed a test program to measure these effects by means of a laser tracker. Two sets of tests were performed. The first focused on the relative motions between the M3 platform, the M4 mirror, and the receiver cabin floor. The second was directed at measuring the effective stiffness of the floor under load.

In the first tests, a laser tracker was employed to measure groups of targets on the M3 platform, the M4 mirror, and the receiver cabin floor. The baseline distances were then compared continuously for several hours. In this test, the M4, which is supported directly from the M3 platform, was found to be more stable than the receiver cabin floor. In most cases, the errors were consistent with thermal variations in the structure. The most dramatic change was observed near sunset, with position drift rates of about 300 μm/hr. Later at night, the M4 position stabilized, but the receiver cabin still sometimes showed position variations of over 100 μm/hr. These results put a bound on the maximum allowable time between checking the pointing and focus of the telescope.

The second tests measured the stiffness of the receiver cabin floor by measuring the underside of the platform from the floor below while weights were placed at different locations in the testing area of the floor above. As expected, the largest deflections were measured when the load was placed at the center of the floor grating between the mid-span of the smallest floor structure I-beams, with a stiffness of 14 N/μm. The stiffness was about 10% higher (just under 16 N/μm) directly at the smaller I-beams near their mid-span. A more dramatic difference was measured for loads near a main structural cross beam. In that case, targets that connected to the beam itself were found to have a stiffness of nearly 34 N/μm, more than twice the mid-span stiffness. However, in that location, the stiffness for loads in the middle of the floor grating increased only to 17 N/μm, because the flexibility is dominated by the floor grating itself. Comparison of the unloaded condition of the structure after each test showed slow drifts of the relative positions of the platforms, consistent with the thermal drift hypothesis supported by the first tests.

This paper presents the tests and analysis, together with the detailed results of the receiver room motion and floor stiffness.

The Fast Steering Secondary Mirror (FSM) for the Giant Magellan Telescope (GMT) will have seven 1.05 m diameter circular segments and rapid tip-tilt capability to stabilize images under wind loading. In this paper, we report on the assembly, integration, and test (AIT) plan for this complex opto-mechanical system. Each fast-steering mirror segment has optical, mechanical, and electrical components that support tip-tilt capability for fine coalignment and fast guiding to attenuate wind shake and jitter. The components include polished and lightweighted mirror, lateral support, axial support assembly, seismic restraints, and mirror cell. All components will be assembled, integrated and tested to the required mechanical and optical tolerances following a concrete plan. Prior to assembly, fiducial references on all components and subassemblies will be located by three-dimensional coordinate measurement machines to assist with assembly and initial alignment. All electronics components are also installed at designed locations. We will integrate subassemblies within the required tolerances using precision tooling and jigs. Performance tests of both static and dynamic properties will be conducted in different orientations, including facing down, horizontal pointing, and intermediate angles using custom tools. In addition, the FSM must be capable of being easily and safely removed from the top-end assemble and recoated during maintenance. In this paper, we describe preliminary AIT plan including our test approach, equipment list, and test configuration for the FSM segments.

The Nanshan radio telescope (NSRT) is a fully steerable radio telescope with a diameter of 26 meters, located in Urumqi, Xinjiang, China. The NSRT currently operate in the frequency range from 1.4 GHz to 22.4 GHz。In order to reduce effect of gravity-induced structural deformations on antenna efficiency and pointing accuracy, the subreflector adjustment system has been used to adjust subreflector position in 6 degree-of-freedom to correct subreflector defocusing and reflectors misalignment. The Stewart platform is used as the adjustment mechanism to perform translation -50/+50 mm (along x, y, z axis) and rotation -5/+5 degree (with respect to x, y axis) with repeated positioning accuracies of 0.07 mm (translation) and 0.01 degree (rotation). The paper will mainly introduce an overview of the NSRT subreflector adjustment system, including Stewart platform and control system, performance testing, and position adjustment of subreflector.

As the most important feedback source of the FAST telescope control system, the measurement system directly determines the overall performance and observing efficiency of FAST. High-precision total station measurement equipment is used in real-time measurement of the FAST reflector and the feed cabin. Because the measurement accuracy of total station is easily influenced by the atmospheric environment, in this paper, we established the distribution model of temperature, humidity and pressure through the meteorological information collected by the weather stations evenly distributed in the reflector. We analyzed the changes of atmospheric environment caused by FAST topography and calculated the real-time atmospheric correction at each location within the coverage of the weather station based on the formula. Finally, according to the variation of the atmospheric correction value in the measurement path, the optimal atmospheric correction parameter of the path is obtained, so as to improve the measurement accuracy of the FAST reflector.

The Large Synoptic Survey Telescope (LSST) Project¹ received its construction authorization from the National Science Foundation in August 2014. The LSST Telescope and Site (T and S) group has achieved significant progress in the development and delivery of an integrated telescope system solution to meet the LSST science mission requirements. The summit facility construction has been completed on Cerro Pachón in Chile, construction of the base facility and data center continues in La Serena, and many major vendor subsystem integration and verification efforts are currently in progress. This paper summarizes the status of the T and S group, which is responsible to provide the summit and base facilities and infrastructure necessary to support the wide, fast, deep LSST survey mission. The major elements of the telescope system are well into factory assembly and testing, in anticipation of shipping, integration and final acceptance testing and verification on the summit. Progress continues on the dome system assembly atop the lower enclosure of the summit facility. The M1M3 primary/tertiary and M2 secondary mirror assembly systems are undergoing integrated system testing prior to shipment to Chile. Factory testing has been achieved on the telescope mount assembly, hexapod and rotator systems, coating plant, and the auxiliary calibration telescope. Other in-house efforts including software for observatory supervisory functions, scheduling of the survey, and active optics control has also advanced. The summary status of these subsystems and future integration and verification plans are presented.

East Anatolia Observatory (DAG) is the new observatory of Turkey with the optical (VIS) and near-infrared (NIR) largest telescope (4 m mirror) and its robust observing site infrastructure. This national project consists of three phases with DAG (telescope, enclosure, building, infrastructure), FPI (Focal Plane Instruments and Adaptive Optics) and MCP (Mirror Coating Plant) and is supported by the Ministry of Development of Turkey. Almost all infrastructure (roads, geological and atmospheric surveys, electricity, fiber optics, water, generator, etc.) of DAG site (Erzurum/Turkey, 3170 m altitude) have been completed. The recent developments (telescope, enclosure, mirror, focal plane instruments, building, atmospheric studies, etc.) of DAG and its site in 2017 and 2018 were presented for the future possible collaborations for various astronomical instruments and telescopes which can be set up in DAG site.

The MROI – Magdalena Ridge Observatory is a project that comprises an array of 10 1.4m diameter mirror telescopes, arranged in a “Y” configuration. Each of these telescopes will be housed inside a Unit Telescope Enclosure (UTE) that is relocatable onto any of 28 stations.

EIE Group Srl, based in Venice – Italy, was awarded the contract for the design, construction and erection on site of the MROI UTE by New Mexico Institute of Mining and Technology.

The close-pack array of the MROI – including all 10 telescopes, several of which are at a relative distance of less than 8 meters center to center from each other – necessitated an original design for the UTE.

February 2018 saw a series of Factory Acceptance Tests to verify that everything is working in a proper way, to guarantee the restricted performances in the sky.

These performances will be respected only thanks to a detailed engineering design and special materials.

The first enclosure is now on-site, in order to be assembled with the telescope, before its final positioning in the array.

Telescope enclosure azimuth rotation systems have traditionally been supported by custom bogies with steel wheels and steel rails, with mixed results in terms of long-term reliability and performance. Because the enclosure azimuth rotation mechanisms are vital for the operational success of all telescopes, and because the scale of the Giant Magellan Telescope (GMT) enclosure will exceed that of all enclosures now in existence, the GMT project team has explored alternative solutions for enclosure rotation in search of cost, reliability, and maintainability benefits. Four concepts are studied: railway bogies, ring crane bogies, segmented slewing bearings, and THK curved linear bearings. All four concepts are highly developed systems engineered to meet specific design objectives and performance requirements, some objectives of which overlap those of the GMT enclosure azimuth rotation system; however, in all four instances, significant customization or development of an altogether new product would be required for fulfilment of the GMT performance requirements.

The ELT Dome has been conceived for protecting the 39m ELT telescope, with its 86m base diameter and its almost 80m height. The rotating Dome is spherical to enhance the aerodynamic behavior; it weights about 6000 tons and it is provided with a 42m wide slit, to allow the telescope observation.

The bearing structure of the Dome is a truss structure made of steel, having a base ring and a series of arch girders as its main elements.

The Dome Rotation is performed by 36 trolleys, which are fixed to the top of the reinforced concrete Dome Base. Safety against seismic events is guaranteed by a dedicated Isolation and Damping System at the Dome Pier.

The Dome is covered by a custom Cladding System, that has been tailored in order to provide the required thermal insulation and withstand the harsh Environmental Conditions of the ELT Site.

With the aim of controlling the airflow around the Telescope, the ELT Dome is provided with a series of 89 Louvers, which are distributed among the rotating and the fixed structures. Besides, a Windscreen made of four permeable aluminum panels protects the Telescope; each panel spans over the 42m slit and is 10m high. The Windscreen is able to track with the Telescope on a 20 to 70deg range of the altitude angle.

The Auxiliary Building is a ring surrounding the Dome Pier and houses the Dome Technical Rooms, thus guaranteeing a radial distribution of all the Services. Among the Dome Supplies, a custom HVAC System is able to control the Telescope Chamber temperature with a ±2°C precision. The ELT Dome is provided with specific Plants so to supply Power to all the relevant loads and to the Electrical Equipment, as well as with a custom Global Control System and a series of Safety Systems.

The Instituto de Astronomía of the Universidad Nacional Autónoma de México (UNAM) along with Instituto Nacional de Astrofísica, Óptica y Electrónica, the University of Arizona and the Smithsonian Astrophysical Observatory are developing the Telescopio San Pedro Mártir (TSPM) project, a 6.5m diameter optical telescope. M3 Engineering and Technology Corp. (M3) is the design and construction administration firm responsible for all site infrastructure, enclosure and support facilities. The Telescopio San Pedro Mártir project (TSPM) will be located within the San Pedro Mártir National Park in Baja California, Mexico at 2,830 m. above sea level, approximately 65 km. east of the Pacific Ocean, 55km west of the Sea of Cortes (Gulf of California) and 180km south of the United States and México border. The aim of this paper is to provide an update of SPIE paper 9906-84 to identify the changes associated with final design for the site infrastructure, enclosure and support facilities to date and share the design and construction approach.

Following the magnitude 7.1 earthquake in central Mexico on 19 September 2017, personnel from the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT/GTM) performed a visual inspection of the foundation and structure of the LMT/GTM. Though no damage was found, the project also conducted a measurement of the system using the precision tiltmeters that are permanently installed at the elevation axis. Fortunately, a series of baseline tests had been run in 2013 after the installation of the first tiltmeter, including a comparison to the original survey results. To match the fastest of these tests, the site crew ran the telescope through ±360° of azimuth rotation at moderate slew speeds in each direction.

The most important result is that there have been no statistically significant changes in the tilt variation of the alidade since either the original track surveys during initial construction or the tiltmeter tests in 2013. This conclusion is based on comparisons of tilt results averaged over 2 degree bins in the data. The result confirms that there was no apparent change to system performance.

The Giant Magellan Telescope (GMT) uses four glycol-based cooling fluids as well as a refrigerant to provide cooling for telescope heat sources. The refrigerant’s evaporative characteristic has the benefit of mitigating the risk of catastrophic leaks inherent in using glycol-based fluids. It is valuable to study the benefits and disadvantages of expanding refrigerant use towards a large-scale implementation that could potentially replace all telescope glycol-based cooling. GMTO is working with M3 Engineering to complete a refrigerant trade study to determine if consolidation of cooling resources is feasible, and if a practical limit exists to expanding the use of refrigerant to cool more telescope heat sources.

Nanshan 26 m Radio Telescope (NSRT) constructed in Nanshan Urumqi, Xinjiang, China, it is a fully steerable radio telescope, the observing frequency up to 43GHz. The telescope was refurbishment in 2015 after 20 years operation. A rapid feed switching mechanism was designed and installed on antenna sub-reflector. The mechanism including a “hexapod” structure which used to adjustment the sub-reflector supporting legs deformation at difference elevation angles, and a turret used to changing the position of light source focus to meet the different feeds requirement. All the feeds distributed on the circle of Cassegrain focal plane. An overview of the mechanism design, FE (finite element) analysis and kinematics simulation will be show in this paper.

The MMT Observatory, a joint venture of the Smithsonian Institution and the University of Arizona, will soon celebrate the 40th anniversary of the dedication of its innovative Multiple Mirror Telescope. The original 4.5-m telescope, consisting of six 1.8-m mirrors on a common mount, operated productively for nearly 20 years until it was decommissioned to install a new telescope. The new MMT, which was dedicated in 2000, is equipped with a monolithic 6.5-m borosilicate primary mirror. The new telescope will soon surpass the operating lifetime of the original telescope. Coincident with this transition, the MMT will enter a new era of scientific discovery with the addition of new instrumentation and improved capabilities. This paper provides an overview of the current telescope and instrument configurations and then highlights recent and forthcoming developments, including new and upgraded instrumentation, that will usher in this new era. For example, a new high throughput wide-field multi-object imaging spectrograph with a long-slit mode, Binospec, was recently commissioned at the MMT. This powerful new instrument will very likely become a highly productive workhorse instrument in dark and grey time. Another major advancement that is underway at the MMT is a full redesign and refurbishment of the world’s first adaptive secondary mirror. This effort, dubbed the MMT Adaptive Optics exoPlanet characterization System (MAPS), will result in a cutting edge AO system with a performance that greatly exceeds the original, now 20-year old, system. This system, together with the NIR spectrograph ARIES and the imaging- and spectropolarimeter MMTPol, provides some unique and powerful capabilities.

CFHT currently removes heat from the Closed-Cycle Cold Heads of the telescope prime focus instruments, MegaPrime (Wide-Field Optical Imager) and WIRCam (Wide-Field Infrared Camera) by using water-cooled Helium Compressors which provide gas transfer characteristics allowing the dewars to achieve Cryogenic Temperatures. In addition, CFHT uses air-cooled Compressor Units to provide Closed-Cycle cooling for their telescope Cassegrain instrument, SITELLE (Optical imaging Fourier transform spectrometer). With the addition of a new instrument at the end of 2017, SPIRou (near-infrared spectropolarimeter); an upgrade to the Closed-Cycle cooling system was required to remove the extra 10 kW of heat. Therefore the decision to design and develop a more efficient and less complicated cooling system was pursued. The initial concepts were incorporated from Chas Cavedoni of the GEMINI Observatory, the master mind behind their ambient air cooling system. The cool ambient temperatures experienced year round on Mauna Kea (+4° C to +21° C), coupled with the relatively warm (+10° C to +32° C) cooling water required by the Helium Compressor Units; lends itself to a much simpler and less expensive Fluid-Cooling system which essentially utilizes a glorified Radiator (Heat Exchanger). This paper shall describe the Design Considerations, System Design, and System Performance of this new cooling method and share the lessons learned from this innovative concept. This new design will not only provide cooling for the additional 10 kW introduced by SPIRou, but also handle the existing 10 kW (MegaPrime and WIRCam) currently being removed by stand-alone Refrigeration Chillers. An additional 10kW capacity has been incorporated into the new system to provide cooling for future expansion, which ultimately results in a Fluid Cooling System capable of removing a 30 kW heat load.

Nanshan Radio Telescope (NSRT) constructed in Nanshan Urumqi, Xinjiang, China, it is a fully steerable radio telescope. It contribution not only the Chinese astronomy community but also an important member of international VLBI net. After more than 20 years operation the telescope was refurbishment in 2015. In this paper an overview of the refurbishment project will be introduction, actually except the alidade all the antenna structures and systems were rebuilt. Now the observing frequency is up to 43GHz, the accuracy of reflector surface is 0.3mm (r.m.s) at the best adjustment angle, the pointing accuracy is 10 arcs, after 2 years operation the antenna reached a good condition, more details will be shown in this paper.

In 2015 the Institute of Physics and Astronomy of the Universidad de Valparaiso in Chile received as a donation the Bochum 0.61-meter telescope. Here we preset the ongoing project to convert this senior member of La Silla Observatory to modern standards aiming at performing state-of-art science, as well as teaching and outreach. Firstly, the site characterization was performed in order to verify the observing conditions. The preliminary results were auspicious in relation to the nights available for observation. In early 2016 began the transfer work form La Silla Observatory to the new site of operations. The actual status of the telescope was analyzed and an upgrade plan was proposed to make it usable remotely using a web-based telescope control system developed in Chile by ObsTech SpA. Future upgrade and scientific collaboration will be discussed based on the site characterization and technical studies regarding the potential for new instrumentation.

ALMA has been demonstrating its exceptional capabilities with unprecedented scientific results achieved over the past six years of operation. To keep ALMA as a leading-edge telescope, it is essential to continue technical upgrades and development of new potential. While our future development programs have already achieved remarkable technological breakthroughs at the level of front-end receivers, we are discussing the upgrades of the analog and digital backend and the correlator. We report the required concept design of the interferometric system focused on these sub-systems to realize new science use cases.

The United Kingdom Infrared Telescope (UKIRT) observatory has been transferred to the ownership of the University of Hawaii (UH) and is now being managed by UH. We have established partnerships with several organizations to utilize the UKIRT for science projects and to support its operation. Our main partners are the U.S. Naval Observatory (USNO), the East Asian Observatory (EAO), and the UKIRT microlensing team (JPL/IPAC/OSU/Vanderbilt). The USNO is working on deep northern hemisphere surveys in the H and K bands and the UKIRT microlensing team is running a monitoring campaign of the Galactic bulge. EAO, UH, and USNO have individual P.I. research programs. Most of the observations are using the Wide Field Camera (WFCAM), but the older suite of cassegrain instruments are still fully operational. Data processing and archiving continue to be done CASU and WSA in the UK. We are working on a concept to upgrade the WFCAM with new larger infrared detector arrays for substantially improved survey efficiency.

When an alt-azimuth telescope is tracking at a specific field, it is necessary to use a de-rotator system to compensate the Earth’s rotation of the field of view. In order, to keep the telescope tracking the field of view selected, the instrument will need to a rotation system for compensating it [1]. The new WEAVE [2] two degrees field of view requires a new field de-rotator on the top-end of the telescope. The rotator system has been designed with a direct drive motor which eliminates the need for mechanical transmission elements such as gearboxes, speed reducers, and worm gear drives. This design is a huge advantage for the system performance and lifetime because it eliminates undesirable characteristics such as long-time drift, elasticity, and backlash. The hardware control system has been developed with a Rockwell servo-drive and controller. The rotator has to be controlled by the high-level software which is also responsible for the telescope control. This paper summarizes the model developed for simulating and the software which will be used to accept the rotator system. A performance study is also carried out to test the CIP (Common Industrial Protocol) for communications between the high-level software and the rotator hardware.

The GMT active optics (AcO) control problem is unique because the primary and secondary mirrors are both segmented. This paper describes the AcO control algorithms and assesses their performance for the Natural Seeing observing modes of the GMT. In this case, there are wavefront sensors in four off-axis probes, which are used to control the position and rotation of each of the seven primary and seven secondary mirror segments, as well as the bending modes of the primary mirror. The segmentation of both mirrors leads to a number of unsensed modes (e.g., segment piston and a rotation of the segment around the telescope optical axis) and poorly sensed modes (e.g., M1 segment translations compensated with the corresponding M2 segment translation). Uncertainties in the location of the probes and guide star coordinates also lead to blind modes. In this paper, we first introduce the GMT optical design in the context of the AcO system. The modes of the telescope controlled by the AcO system, and their counterparts in the wavefront sensing space, are presented next, including field-dependent and blind modes. The control architecture is then outlined along with a description of the singular modes of the system. Finally, performance results are provided with respect to various error terms.

The Large Synoptic Survey Telescope (LSST) primary/tertiary (M1M3) mirror cell is a 25-ton, 9-meter x 9-meter x 2- meter steel weldment that supports the 19-ton borosilicate M1M3 monolith mirror on the telescope and acts as the lower vessel of the coating chamber when optically coating the mirror surfaces. The M1M3 telescope mirror cell contract was awarded to CAID Industries, Inc., of Tucson, Arizona in October 2015. After the mirror cell final acceptance in October 2017, the integration of the mirror support system started. The M1M3 cell assembly with the surrogate mirror will take place in a dedicated controlled-environment area at CAID Industries. All components of the mirror support system that were developed and tested by the LSST Telescope and Site M1M3 team at the NOAO offices in Tucson have been moved to CAID premises and have been integrated into the cell by a team of LSST, CAID and Richard F. Caris Mirror lab personnel. After completion of the cell integration and its assembly with the surrogate, a test phase that includes zenith and offzenith testing for the mirror support system will be carried by the LSST team. These tests aim to verify that the active support system components, mirror control, and software are performing as expected and the mirror support system is safe for the next step, the M1M3 cell to borosilicate glass assembly and tests at the RFC Mirror Lab of the University of Arizona.

This paper describes the design, status, and test program for the Giant Magellan Telescope (GMT) Primary Mirror Subsystem (M1). It consists of the mirror cells, positioning system, support systems, and thermal control system. The seven 8.4m mirror segments are excluded from this paper because they are considered a separate subsystem of the M1 System.

The M1 Subsystem leverages heritage design of similar telescope systems; for example, the Magellan telescopes and the Large Binocular Telescope. The M1 Subsystem incorporates pneumatic force actuators, hardpoints, and a thermal control ventilation system.

Design developments have been introduced to address the challenging levels of performance and unique requirements needed by the GMT telescope. Imaging goals necessitate an increase in mirror support performance, figure control, and higher-levels of thermal control. Additionally, there are challenges associated with matching and tracking the relative position of the seven mirror segments for mirror phasing. The design of the static support system needs to protect the mirrors from loads transmitted through the structure during an earthquake. Finally, the telescope design with interchangeable off-axis mirror cells necessitate mirror cells and support components that function under any range of gravitational vector orientations

. A full-scale Test Cell prototype is being constructed including production versions of mirror cell components to test and validate the M1 subsystem design. A Mirror Simulator will be used with the Test Cell to validate the M1 Control System. Later, a primary mirror segment will be used with the Test Cell to perform optical tests at the University of Arizona.

The Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) team is developing Giant Steerable Science Mirror (GSSM) for Thirty Meter Telescope (TMT) which has got into the preliminary design phase in 2017. To develop the passive support structure system for the largest elliptic-plane flat mirror and a smoothest tracking mechanism for the gravity-variant condition, CIOMP had developed a 1/4 scale, functionally accurate version of the GSSM prototype as the pre-construction of GSSM. The prototype incorporates the same optical-mechanical system and servo control system as GSSM. The size of the prototype mirror is 898.5mm×634mm×12.5 mm with elliptic-plane figure and is supported by 18 points whiffletree on axial and 12 points whiffletree on lateral. The main objective of the preconstruction includes validate the conceptual design of GSSM and increase more confidence when meet the challenge during the development of GSSM. The assembling, integration and verification of the prototype have been completed based on the test results. CIOMP has got the sufficient test results during the pre-construction phase and got into the preliminary design for GSSM.

The Large Synoptic Survey Telescope (LSST) is a large (8.4 meter) wide-field (3.5 degree) survey telescope, which will be located on the Cerro Pachón summit in Chile. Both the Secondary Mirror (M2) Cell Assembly and Camera utilize hexapods to facilitate optical positioning relative to the Primary/Tertiary (M1M3) Mirror. A rotator resides between the Camera and its hexapod to facilitate tracking. The hexapods and rotator have been designed, fabricated, assembled, and are currently being tested by Moog CSA. An update on these activities is provided along with a detailed discussion of the testing approach and results ranging from proof load and life testing to positioning performance. Particular emphasis is given to testing of the positioning accuracy, repeatability, and resolution of the hexapods and tracking accuracy and runout of the rotator. Verification of power off braking, heat dissipation, settling time, range of motion, and velocity requirements are also presented.

A new prime focus corrector for the WEAVE project for the William Herschel Telescope is being produced. The corrector consists of six lens elements, the largest being 1.1 m in diameter. It also incorporates an Atmospheric Dispersion Corrector. Testing procedures for the WEAVE prime focus corrector lens elements are described here. Critical issues encountered in practice, including the influence of the lens size, wedge and weight on the testing procedure are discussed. Due to large lens dimensions, a dedicated test tower and lens support system has been developed to measure the optical surface form errors of the concave surfaces and the transmitted wavefront of each lens. For some of the lens elements, sub-aperture measurements have been performed using an off-axis Hindle sphere and the resultant OPD maps have been stitched together. The challenge of testing a wedged lens with a combination of a long radius convex surface and a short radius concave surface has been resolved by using another lens from the system as an auxiliary lens. The practice of testing convex surfaces via internal reflection/transmission through the lens element has been avoided entirely in this case and some discussion justifying the choices of metrology approach taken is given. The fabrication and acceptance testing of the lens elements has been completed within the expected time and budget, and all elements have been shown to meet requirements.

The Astronomical Imaging System of a 1.2-meter-aperture Telescope is a multi-band imaging system with red and blue channels. The mass and structure of AGN central black hole are studied by observing the change of AGN spectral line. We designed an optical system with dual channels, changing the focal length ratio of telescope from f/8.429 to f/5 through the lens, and divide the optical path into red and blue channels through the beam splitter. The red waveband is 650nm1000nm and the blue waveband is 400nm-650nm. Each channel has a CCD camera. We set up focusing lens before the camera of blue channel to compensate the difference focusing length between red and blue channel after the red channel being focused by adjusting the telescope. For the realization of three groups of broadband photometry and twenty-four groups of narrowband photometry, an automatic filter wheel system is designed to switch the filter. At the same time, in order to reduce the influence of temperature drift of the filter, a constant temperature adjusting system for filter wheel box is carried out. In order to overcome the issue that the telescope itself does not have enough tracking accuracy, a guiding system for the imaging system is designed and implemented. Finally, we designed and implemented a multi-level software control system so that the users can remotely control the telescope.

The Large Synoptic Survey Telescope (LSST) Commissioning Camera (ComCam) is a smaller, simpler version of the full LSST camera (LSSTCam). It uses a single raft of 9 (instead of twenty-one rafts of 9) 4K x 4K LSST Science CCDs, has the same plate scale, and uses the same interfaces to the greatest extent possible. ComCam will be used during the Project’s 6-month Early Integration and Test period beginning in 2020. Its purpose is to facilitate testing and verification of system interfaces, initial on-sky testing of the telescope, and testing and validation of Data Management data transfer, infrastructure and algorithms prior to the delivery of the full science camera.

The Simons Observatory will consist of a single large (6 m diameter) telescope and a number of smaller (∼0.5 m diameter) refracting telescopes designed to measure the polarization of the Cosmic Microwave Background to unprecedented accuracy. The large aperture telescope is the same design as the CCAT-prime telescope, a modified Crossed Dragone design with a field-of-view of over 7.8 degrees diameter at 90 GHz. This paper presents an overview of the cold reimaging optics for this telescope and what drove our choice of 350–400 mm diameter silicon lenses in a 2.4 m cryostat over other possibilities. We will also consider the future expandability of this design to CMB Stage-4 and beyond.

We present an optomechanical test bench setup (MELT) for testing and validating key functionalities to be used on the Extremely Large Telescope (ELT) during the periods of system verification, wavefront control commissioning, through the handover to science, up to regular diagnostic, monitoring, and validation tasks during operations.

The main objectives of MELT are to deploy and validate the telescope control system, to deploy and validate wavefront control algorithms for commissioning and operations, as well as to produce and validate key requirements for the phasing and diagnostic station (PDS) of the ELT.

The purpose of MELT is to deploy optomechanical key components such as a segmented primary mirror, a secondary mirror on a hexapod, an adaptive fourth mirror, and a fast tip/tilt mirror together with their control interfaces that emulate the real telescope optomechanical conditions. The telescope control system, deployed on MELT can test control schemes with the active mounts emulating the real ELT optomechanical control interfaces.

The presented optomechanical setup uses the Active Segmented Mirror (ASM) with its piezo-driven 61 segments and a diameter of 15 cm. It was designed, built, and used on sky during the Active Phasing Experiment (APE).

Several beam paths after the telescope optical train on MELT are conditioned and guided to wavefront sensors and cameras, sensitive to wavelength bands in the visible and infrared to emulate wavefront commissioning and phasing tasks. This optical path resembles part of the phasing and diagnostics station (PDS) of the ELT, which is used to acquire the first star photons through the ELT and to learn the usage and control of all the ELT optomechanics. The PDS will be developed, designed, and built in-house at ESO. MELT helps its design by providing a detailed test setup for defining and deploying system engineering tasks, such as detailed functional analysis, definition of tasks to be carried out, and technical requirements, as well as operational commissioning aspects.

The bench test facility MELT will in the end help us to be as much as possible prepared when the telescope sends the first star light through the optical train to be able to tackle the unforeseeable problems and not be caught up with the foreseeable ones.

The Large Synoptic Survey Telescope is an 8.4m telescope now in construction on Cerro Pachón, in Chile. This telescope is designed to conduct a 10-year survey of the southern sky in which it will map the entire night sky every few nights. In order to achieve this goal, the telescope mount has been designed to achieve high accelerations that will allow the system to change the observing field in just 2 seconds. These rapid slews will subject the M1M3 mirror to high inertial and changing gravitational forces that has to be actively compensated for in order to keep the mirror safe, aligned, and properly figured during operations. The LSST M1M3 active support system is composed of six “hard point” actuators and 156 pneumatic actuators. The hard points define the mirror position in the mirror cell (with little or no applied force) and hold that position while observing in order to maintain the alignment of the telescope optics. The pneumatic actuators provide the force-distributed mirror support plus a known (static) figure correction as well as dynamic optical figure optimizations coming from other components of the Active Optics System. Optimizing this mirror support system required the introduction of innovative control concepts in the control loops (Inner and Outer). The Inner Loop involves an extensive pressure control loop to ensure precise force feedback for each pneumatic actuator while the Outer Loop includes telescope motion sensors to provide the real-time feedback to compensate for the changing external inertial and gravitational forces. These optimizations allow the mirror support system to maximize the hard point force-offloading while keeping the glass safe when slewing and during seismic events.

The preparations for the design and construction of the Extremely Large Telescope (ELT) are in full swing. One of the most critical components of this enormous telescope is its segmented primary mirror (M1), for which Netherlands Organisation for Applied Scientific Research (TNO), in collaboration with VDL, has designed the mechanical segment support (M1SS) in the period 2015-2016.¹ This new M1SS design is based on the previous M1SS prototypes developed in 2009-2010,² but includes several enhancements to further improve its performance. Specific design drivers were, among others, the serviceability of the M1SS, the introduced surface form error at the segment, and the increased target values for the structural eigenfrequencies. The latter defines the dynamic performance of the structure (including the ~178 kg segment), which needed to be validated experimentally.

From the latest M1SS design one engineering model (EM) and six qualification models (QMs) have been manufactured recently, which have tested intensively to verify their performance. This work will present the test procedure employed to validate the dynamic behavior, describe these dynamic tests and present their results in detail. During these tests a QM, including a dummy segment, has been placed on a heavy rigid structure and three accelerometers have been mounted across the assembly. The structure has then been excited on several strategic locations using a roving hammer technique,³ resulting in a large collection of frequency responses. From these, the eigenfrequencies and accompanying mode shapes have been estimated, resulting in accurate determination of the clocking, lateral, piston and tip/tilt modes of the structure. This allows for correct assessment of the dynamic performance and comparison to the design objectives and finite element model (FEM) predictions.

This procedure has been applied to two different QMs, but since each M1SS consists of a fixed frame (FF) and a removable segment assembly (SA), four different configurations have been tested. The results demonstrate compliance with the challenging design objectives for all QMs, and they show only small variations among the configurations, demonstrating that the dynamic performance of the M1SS design is very reproducible.

We present in this article some of the techniques applied at the Instituto de Astronomía of the Universidad Nacional Autónoma de México (IA-UNAM) to the mechanical structural design for astronomical instruments. With this purpose we use two recent projects developed by the Instrumentation Department. The goal of this work is to give guidelines about support structures design for achieving a faster and accurate astronomical instruments design. The main guidelines that lead all the design stages for instrument subsystems are the high-level requirements and the overall specifications. From these, each subsystem needs to get its own requirements, specifications, modes of operation, relative position, tip/tilt angles, and general tolerances. Normally these values are stated in the error budget of the instrument. Nevertheless, the error budget is dynamic, it is changing constantly. Depending on the manufacturing accuracy achieved, the error budget is again distributed. That is why having guidelines for structural design helps to know some of the limits of tolerances in manufacture and assembly. The error budget becomes then a quantified way for the interaction between groups; it is the key for teamwork.

The work that is presented is in its early stage. The intention of this document is to present the conceptual proposal of the design of the cell for Nasmyth-f/5 secondary mirror (TSPM-M2-f/5-Nasmyth), its support system and the mirror of this configuration for the “Telescopio San Pedro Mártir” (TSPM) project. In order to obtain more precise input data for the requirements of the telescope in terms of its: weight, center of gravity, interfaces with the telescope spider assembly and manufacturing viability. The goal of providing accurate data for the mechanical studies of the telescope was fulfilled. With this we ensure more realistic results in the opto-mechanics performance analysis of the whole telescope´s. The telescope´s requirements are the input data for the Opto - mechanics performance and survival analyses, both studies done by CIDESI. For this, it is necessary to have for this telescope configuration a conceptual proposal design of TSPMM2- f/5-Nasmyth. We present the TSPM-f/5 Nasmyth support system proposal, which include the M2 cell, mirror and interface. Finite Elements Analyses (FEA) results of the support system and the mirror are presented too. In the conclusion we present some evidence of the pending future work for this study.

The design of the instrument support system for the Daniel K. Inouye Solar Telescope (DKIST), located at the Haleakala Observatory on Maui, presented several challenges. These challenges included the need to be able to reconfigure instruments in the future, a highly complex opto-mechanical layout that did not conveniently align with the underlying structure, seismically driven mechanical resonance requirements, and formidable site handling and transport logistics. These challenges were overcome using a modular design that combines 0.5-inch steel plates, W6X25 support beams, and a flexible clamping system to fasten the system to the underlying structure. This design relied largely on an iterative, finiteelement structural analysis that guided modifications and provided the fast turnaround times needed to meet tight project deadlines. The analysis revealed a need to increase the size of the instrument support beams and reinforce them with weldments to increase torsional rigidity. Creating a stiffer, more uniform support structure with larger, reinforced beams not only resulted in a structurally sound architecture but it also simplified the installation process. This paper summarizes the requirements, design, development, analysis, fabrication, and installation of the DKIST’s instrument support structure, known as the “coudé rotator interface–mechanical,” or “CRIM.” The design effort began in September 2016 and the installation of the CRIM was completed in late February 2018, ahead of schedule and with greaterthan-expected accuracy.

Future extremely large telescopes, equipped with high-contrast instruments targeting very small Inner Working Angle, will provide the requisite resolution for detecting exoplanets in the habitable zone around M-stars. However, the ELT segmented pupil shape is unfavourable to high-contrast imaging. In this context, the SPEED project aims to develop and test solutions for high contrast with unfriendly apertures. SPEED will combine a PIAACMC coronagraph and two deformable mirrors for the wavefront shaping. In this paper, we describe an end-to-end model of SPEED, including the Fresnel wavefront propagation, the PIAACMC implementation and the dark hole algorithm, and present a statistical analysis of the predicted performance.

The Giant Magellan Telescope (GMT) will be equipped with two Gregorian secondary mirrors: a fast-steering mirror (FSM) system for seeing-limited operations and an adaptive secondary mirror (ASM) for adaptive optics observing modes. The FSM has an effective diameter of 3.2 m and is comprised of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment has a tip-tilt capability for fast guiding to attenuate telescope wind shake and jitter. To verify the tip-tilt performance at various orientations, we performed tiptilt tests using a conceptual prototype of the FSM (FSMP) which was developed at KASI for R&D of key technologies for FSM. In this paper, we present configuration, methodology, results, and lessons from the FSMP test which will be considered in the development of FSM.

The National Astronomical Research Institute of Thailand (NARIT) is currently developing a five lenses prime focus camera in order to enlarge the field of view of the 2.3 m Thai National Telescope to a one degree diameter circle. The instrument shall operate in the spectral bands B, V, R and I of the Johnson-Cousins photometric system with an angular resolution better than 2 arcsecond. In this paper, we describe the camera design, we estimate the theoretical performance in the V-band and we show that the theoretical angular resolution after tolerancing is better that 1.3 arcsecond. Then, we present the results of the stray light analysis and we show that the system is free of critical ghost images.

The thickness of the thin shell used in the large aperture adaptive mirrors is usually less than 2mm, in contrast the shell’s diameter could be larger than several hundred millimeters, so that the shell’s stiffness could be low enough to adapt the high frequency deformation. However the shell could very easily be out of shape during the process when the pads were glued onto the mirror, some analysis based on the experiment would be presented in this paper, and force introduced by the glue process could be extracted by the method, so the result could be used during the polishing process to eliminate the influence of the bonding process on the shell

The Large Synoptic Survey Telescope (LSST) primary/tertiary mirror is an 8.4-meter cast borosilicate monolith. The hardpoints form a hexapod that is used to define the location of the M1M3 relative to the mirror cell, as the pneumatic figure actuators, which support the mass of the M1M3 during operation, are unable to define position. The hardpoints must have high stiffness, precise displacement control, and features to limit loads in all six degrees of freedom in order to protect the mirror. Assembly of the hardpoints and verification of the hardpoints and their requirements was undertaken in the summer and fall of 2017.

We present the optical design, the error budget, the differential distortion budget and the baffle design of the Telescopio San Pedro Mártir f/5 Nasmyth configuration. The TSPM in its Cassegrain configuration will be assembled around a closed design (converted MMT/Magellan telescope) with most of its optical parts already manufactured. To anticipate for future possible upgrades, the project includes the design of an extreme f/5 Nasmyth configuration. Our optical design demonstrates the feasibility of the configuration, closes the interfaces to the telescope, provides a full picture of the expected performance, and identifies the critical points involved in the configuration.

A so-called Semi-Active Support (SAS) system was proposed for the primary mirror of the YNAO 2-m Ring Solar Telescope (2-m RST of Yunnan Astronomical Observatory, China), whose primary mirror is distinctively figured in a ring with an outer diameter of 2.02 m and a ring width of 0.35 m. This paper reports the design and tests of the prototype of the pneumatic-based semi-active axial support system of the 2-m RST. The dummy mirror was a solid circular plate glass of 700 mm in diameter and 20 mm in thickness, which was support by nine Pneumatic Force Actuators (PFAs) organized in three groups, each group was regulated by one proportional regulating solenoid valve. Besides, three Displacement Actuators (DAs) were used to actively define the three Degrees Of Freedom (DOFs) of piston and tip/tilt of the dummy mirror. The pneumatic force actuators were to be actively pumped and regulated, meanwhile, the displacement actuators to actively define the primary’s position, according to the variation of the elevation pointing of the telescope. The PFA was build with a metal bellow as its cylinder, and a pressing load cell of 200 N capacity with 5 mN resolution was integrated on its output tip. The DA was a step-motor based design with a travel range of 4 mm and a theoretical resolution of 50 nm. Basic technical requirements for the PFAs and DAs were reviewed first. General consideration and configuration of the prototype was elaborated, followed by detailed designs and comprehensive tests of the either type standalone actuator. The prototype was finally tested on a systematic level as well. This prototype study has paved a reasonable way for critical design of the axial support system of the 2-m RST primary mirror.

The Large Synoptic Survey Telescope¹ (LSST) is an altitude-azimuth mounted three mirror telescope and camera. The primary (M1) and tertiary (M3) mirrors are integrated into a single, monolithic borosilicate substrate 8.42 m diameter. The annular secondary (M2) mirror is located above the M1M3 mirror and the camera is nested inside the M2. The M1M3 mirror is supported on a mirror cell by two independent systems: one system is for Active Mode and the other for Static Mode.

During observing, or Active Mode², the M1M3 mirror is supported by an array of 156 support and figure control actuators consisting of 268 pneumatic cylinders that react to gravity and inertial loads and provide figure error correction. Load cells on the actuators measure forces that are communicated to the M1M3 control system. However, the figure actuators do not define the mirror position. This is defined with six axially stiff linear actuators called hardpoints³ arranged in a hexapod pattern to restrain rigid body motion of the mirror in a kinematic fashion. By adjusting the length of each hardpoint, the mirror can be adjusted in all six degrees of freedom with respect to the cell. Displacement sensors and load cells on the hardpoints communicate displacements and forces to the control system, which processes the telemetry and issues force corrections to the figure actuators to zero out any loads and moments on the hardpoints.

In Static Mode, the M1M3 mirror is no longer supported by figure actuators and the position sensing of the hard point hexapod is inactive. A second support system consisting of 288 wire rope isolators called Static Supports come into play. The static supports mechanically capture the mirror whether in Active or Static Mode and in the event the mirror experiences motion beyond the active motion range in any direction. The static supports also safely support the mirror during seismic events for all elevation angles. In active mode, the static supports do not contact the mirror and thus, do not affect the mirror positioning or figure.

This paper focuses on the detailed design, development, testing, integration, and current status of the M1M3 pneumatic figure actuators.

The field rotation effect can be described as observing the gyration of an object with the pupil of the Eastern Anatolian Observatory (DAG) telescope around the optical axis under the influence of the latitude of the observatory while the telescope is following that astronomical object. This is possible as a result of the alt-azimuthal mount of the telescope. (the orientation of the astronomical observed object, the parallactic angle, is defined as “q”)

Since the CCD has a low signal on noise ratio, it necessitates long integration time that can vary from a few minutes to hours. It is essential to correct and compensate the rotation of the optical field caused by the earth’s rotation during the monitoring of the astronomical object.

A (field) derotator is a class of devices that is used to correct the optical field rotation. In a telescope of a Ritchey- Chretien, Nasmyth configuration, the device must be integrated between the scientific instruments and the M3 mirror. The anastigmatic and the anachromatic features of this type of derotator is the main reason that it is chosen. These characteristics are provided by the K-Mirror design.

The aim of this study is to evaluate the possibility to integrate the derotator in the central hole of the telescope fork and to evaluate the mechanical/optical features of the model.

In the era of high-angular resolution astronomical instrumentation, where long and very long baseline interferometers (constituted by many, ∼20 or more, telescopes) are expected to work not only in the millimeter and submillimeter domain, but also at near and mid infrared wavelengths (experiments such as the Planet Formation Imager, PFI, see Monnier et al. 2018 for an update on its design); any promising strategy to alleviate the costs of the individual telescopes involved needs to be explored. In a recent collaboration between engineers, experimental physicists and astronomers in Valparaiso, Chile, we are gaining expertise in the production of light carbon fiber polymer reinforced mirrors. The working principle consists in replicating a glass, or other substrate, mandrel surface with the mirrored adequate curvature, surface characteristics and general shape. Once the carbon fiber base has hardened, previous studies have shown that it can be coated (aluminum) using standard coating processes/techniques designed for glass-based mirrors. The resulting surface quality is highly dependent on the temperature and humidity control among other variables. Current efforts are focused on improving the smoothness of the resulting surfaces to meet near/mid infrared specifications, overcoming, among others, possible deteriorations derived from the replication process. In a second step, at the validation and quality control stage, the mirrors are characterized using simple/traditional tools like spherometers (down to micron precision), but also an optical bench with a Shack-Hartman wavefront sensor. This research line is developed in parallel with a more classical glass-based approach, and in both cases we are prototyping at the small scale of few tens of cms. We here present our progress on these two approaches.

We have completed a major Wide Field Upgrade (WFU) of the Hobby-Eberly Telescope (HET) and reentered scheduled queue science operations in mid-2016. This paper assesses the performance of the various mechanical systems which were upgraded, or added to HET, including the Telescope Structure, the star Tracker (aka, WFU Tracker), Prime Focus Instrument Package (PFIP), and VIRUS Support Structure (VSS). The upgrades were required to increase the field of view of HET, from 4 arc-minutes, to 22 arc-minutes, increasing the observed area of sky by 30 times the original FoV. In the process, the total weight of the system increased from 100 tons, to 153 tons, requiring a complete overhaul of most of the mechanical, servo, and control systems. The new 13-axis Tracker and control system was tested extensively prior to shipping and installation, and followed up with laser tracker measurements, which brought the tracking system to within 1 arc-minute RMS pointing, and followed up with on-sky derived mount-models, which has improved the pointing and guiding to within 12 arc-seconds RMS, and 0.1 arc-seconds, respectively. A completely new structural support system was implemented to house and connect a total of 156 VIRUS spectrographs, plus 4 new Low-Resolution Spectrographs (LRS2). The VIRUS units are arrayed in two large enclosures mounted to either side of the telescope. Each enclosure is approximately 1.3m deep x 6.7m wide x 6.2m tall and weighs 38 tons fully loaded. This structure is attached to HET in a way that allows it to be positioned by, but stand independent of, the HET during observation. As commissioning has transitioned to phased-science/engineering operations, and subsequently, to science operation, the tracking software and mechanical performance of the Tracker and VSS have been improved to meet specification. Performance data and lessons learned are provided.

The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Research telescope since 2014. It was designed and built in collaboration between the University of North Carolina at Chapel Hill, and Cerro Tololo Inter-American Observatory. The device is installed in the elevation axis before the instruments mounted at the optical Nasmyth focus. It consists of two 300mm diameter sol-gel coated fused silica prisms, trombone mounted, which can be folded in or out of the beam. It is important for long slit spectroscopy, and essential for Multi-Object Slit spectroscopy. We present optical and mechanical designs, electronics and software control, and on-sky performance.

A common optical design for a coma-corrected, 6-meter aperture, crossed-Dragone telescope has been adopted for the CCAT-prime telescope of CCAT Observatory, Inc., and for the Large Aperture Telescope of the Simons Observatory. Both are to be built in the high altitude Atacama Desert in Chile for submillimeter and millimeter wavelength observations, respectively. The design delivers a high throughput, relatively flat focal plane, with a field of view 7.8 degrees in diameter for 3 mm wavelengths, and the ability to illuminate >100k diffraction-limited beams for < 1 mm wavelengths. The optics consist of offset reflecting primary and secondary surfaces arranged in such a way as to satisfy the Mizuguchi-Dragone criterion, suppressing first-order astigmatism and maintaining high polarization purity. The surface shapes are perturbed from their standard conic forms in order to correct coma aberrations. We discuss the optical design, performance, and tolerancing sensitivity. More information about CCAT-prime can be found at ccatobservatory.org and about Simons Observatory at simonsobservatory.org.

The preliminary design for the f/5 Nasmyth tertiary mirror opto-mechanical configuration for the 6.5m Telescopio San Pedro Mártir (TSPM), to be installed at the Observatorio Astronómico Nacional (OAN) in the Sierra San Pedro Mártir in Baja California is presented. The proposed system consists of support and alignment of the honeycomb mirror within the cell, the correction of the optical surface deformation, both tasks by means of an active push-pull pneumatic system and the correction of the displacements and rotations transferred by the Tube support structure to the configuration by means of electro-mechanical actuators. This optical configuration and four folded Cassegrain stations will be fully defined after first light of the f/5 Cassegrain configuration, so the requirements and considerations of these positions also need to be taken into account.

In the last years the ELT Program has entered construction phase. For the large 39 meter segmented primary mirror unit with thousands of components this means that the start of the series production is getting closer, where the final hardware will be built. The M1 Unit has been broken down in products and a procurement strategy has been developed. Most of the major design decisions have been frozen and component specifications have been settled. Most of the suppliers have already been selected and contracts have been kicked off. This paper describes the ELT M1 Unit product breakdown and the procurement baseline for each product and its status. The production contracts would not have been possible without intense prototyping and verification strategies independent of the component contracts. Therefore, the paper also takes a look back at the prototypes and de-risking strategies, which had been put in place to prepare for construction phase. Ramping up the construction contracts involves finishing design details for some products while setting up production lines for others. This requires controlling interfaces and cross-contract dependencies, a challenge described in this paper. For continuous de-risking similar verification strategies than during the design phase are planned in parallel with the production until telescope assembly, integration and verification. These measures will increase confidence in the design choices, allow early discovery of remaining design flaws and provide training means for assembly and integration long time before all components of the ELT M1 are complete and being installed on Cerro Armazones in Chile. The paper will also give an outlook on these running and planned activities.

The Giant Magellan Telescope (GMT) will be equipped with two Gregorian secondary mirrors; a fast-steering secondary mirror (FSM) for seeing-limited operations and an adaptive secondary mirror (ASM) for adaptive optics observing modes. The FSM has an effective diameter of 3.2 m and is comprised of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary mirror. Each FSM segment has a tip-tilt capability for fast guiding to attenuate telescope wind shake and jitter. The FSM is mounted on a two-stage positioning system; a macro-cell that positions the entire FSM segments as an assembly and seven hexapod actuators that position and drive the individual FSM segments. In this paper, we present a technical overview of the FSM development status. More details in each area of development will be presented in other papers by the FSM team.

A 4-layer protected silver coating was chosen for the Gemini telescopes due to its high reflectivity in visible and infrared wavelengths. Due to the reflective and absorptive properties of silver, the Gemini 4-layer coating suffers from poor reflectivity in wavelengths shorter than 400 nm. By utilizing different dielectric materials for protective layers it is possible to enhance the reflectance of silver to 350 nm, without compromising infrared performance or coating durability. Several different recipes were found that achieve a goal reflectivity of 80% at 350 nm and 90% at 400 nm. Five recipes were chosen for testing based on their modeled UV enhancement, the protective properties of their materials, and their simplicity. These recipes consist of variations of aluminum oxide, as well as silicon dioxide or silicon nitride. The aluminum oxide replaces the nickel chromium interlayer in the current Gemini coating and provides a receptive surface for the other protective layers. These materials were chosen because they can be produced in the Gemini coating facility without requiring significant and costly upgrades of the sputtering cathodes.

The MMT Observatory (MMTO) initiated a series of coating process improvement projects after an issue with the coating system in 2010 resulted in blemishes on the 6.5m primary mirror coating. Formally started in 2013, these projects focused on four major tasks: 1) development of a software-based system to control the tungsten filament power sources, 2) characterization of an integrally wound tungsten and aluminum filament, 3) prevent stray molten aluminum droplets from contacting the isolation membrane separating the high and rough vacuum sections of the system, and 4) assemble a coating facility capable of performing full-scale system testing. The completion of these projects was realized with the successful re-aluminization of the MMTO primary mirror in 2016. With a focus on the implementation of the process improvements, the present state of the MMTO coating system is described along with data from the 2016 realuminization.

Currently, there is a discussion about constructing a new large optical-infrared telescope, in which the diameter of the primary mirror is 12m (Su et al., 2016). Su et al. (2016) propose an innovative design (SYZ design) which consists of three mirrors with non-zero power, including a relay mirror below the primary mirror. This design yields a good imaging quality and a relatively flatten field curvature at Nasmyth focus. To evaluate the science compatibility of this three-mirror telescope, we compare the system performance of SYZ design with conventional two-mirror telescope designs such as Ritchey–Chrétien (RC) design and Aplanatic Gregorian (AG) design available in the world in this report. We found that SYZ telescope yield a superb imaging quality. Nevertheless, RC and AG designs has a higher total throughput which translate to smaller equivalent-noise-area (ENA).

The observations of the solar system Jovian planets performed by ground-based medium size telescopes can provide an efficient support to the space missions by performing observations of the planet atmospheres. In particular, ground-based medium size telescopes are able to provide high resolution images close to the diffraction limit of giant planets while observing through the Earth atmosphere by using some Lucky Imaging processing. These observations of the Jovian planet atmospheres ideally require i) an instrument with a high angular resolution close to the diffraction limit and ii) a high contrast, especially for the low and medium spatial frequencies that corresponds to the turbulence areas inside the atmosphere clouds bands. We thus decided to design one telescope that shall provide diffraction limited images (without the contribution of the atmosphere) over a circular Field of View (FOV) of diameter equal to 2 arcminutes. This, over the photometric spectral band V, R and I of the Johnson-Cousin photometric. In this paper, we present the design and the performance of a Ritchey-Chretien telescope dedicated to solar system planet imagery with a linear central obscuration lower than 0.15 and an active system to correct the low frequency distortions of the wavefront before each observation. First, we describe the optical design, then we establish the image quality budget. Finally we show that the stray light signal induced by the moon light scattering is negligible during the observations of Jupiter.

The exponential growth in exoplanets studies and related science such as detecting life and even civilizations on Earth-like planets requires high angular resolution and high-contrast observations. Such appealing sciences cases are a powerful reason for developing a dedicated high contrast telescope concept – The ExoLife Finder (ELF) Telescope. Here we describe the ELF overall optical concept, its preliminary Adaptive Optics concept and a novel and revolutionary technology to produce mirrors making use of force-sensor-actuator elements that are 3D-printed onto very thin slumped glass-sandwich elements of fire-polished glass – a very precise aspherical optical surface dedicated to high contrast measurements.