This PDF file contains the front matter associated with SPIE Proceedings Volume 12182 including the Title Page, Copyright information, and Table of Contents.

Laser trackers and autostigmatic microscopes/telescopes both represent the "best-in-class” instruments for the types of measurement that they are designed for. While laser trackers allow the very precise determination of objects locations and orientations, laser trackers cannot easily measure general optical properties of optical elements and systems. Alignment telescopes can easily measure various properties of optical surfaces such as surface tilts, centre of curvature locations, optical axes etc., but it is difficult to refer these measurements to mechanical data. By determining the optical axis of an alignment telescope with a laser tracker measurement, it is possible to link the capabilities of these two metrology systems. This allows types of measurement that neither a laser tracker nor an alignment telescope are capable of independently of each other. This paper describes results of experiments that test the accuracy with which a laser tracker can capture the optical axis of an alignment telescope. It is found that accuracies of < 1 arcseconds optical axis recovery with a laser tracker are achievable.

The Sardinia Radio Telescope, a 64-metre diameter fully steerable radio telescope operated by INAF, will be upgraded in order to extend its current operating frequency range 0.3-26.5 GHz up to 116 GHz, thanks to a National Operational Program (PON) funding assigned to INAF by the Italian Ministry of University and Research. The PON project is organized in nine Work Packages, one of which is dedicated to the accomplishment of a sophisticated metrology system designed to monitor the cause of the pointing errors and the reflector surface deformations. The entire antenna structure will therefore be equipped with a network of sensors, like thermal sensors, inclinometers, accelerometers, collimators, anemometers, strain gauges and others, to study environmental stresses and how they affect the SRT performances. This work is devoted to the investigation of the thermal stress effects produced by solar radiation. In particular, two analyses are carried out to confirm the relevance of a thorough temperature monitoring system, both conducted using Finite Element Analysis. First, a possible approach for the simulation of realistic thermal scenarios due to insolation is proposed and the effects on the pointing accuracy are analysed. Second, a feasible method to study the impacts that a differential heating of the Back Up Structure (BUS) produces on the radio telescope main reflector surface is presented. Finally, these effects are analysed as optical aberrations and modelled in terms of Zernike polynomials.

The upcoming balloon-borne imaging telescope, GigaBIT, is a three-mirror anastigmat (TMA) system with a 1.35-m primary mirror designed to perform wide-field imaging with diffraction limited resolutions in the near ultraviolet (NUV) over a 0.8-deg field of view. An in-flight alignment procedure is being developed that incorporates many techniques novel to ballooning. First, coarse rigid-body adjustments are accomplished through feedback of combined laser rangefinder and retroreflector measurements between the three mirrors. Next, rigid-body adjustments are accomplished using the field-distortion estimated misalignment of each mirror. Lastly, any residual wavefront error of the entire system is compensated by a deformable primary with a set of force actuators. As every step of the procedure will be automated, significant time reduction can be achieved from hours to mere minutes, saving precious time for scientific observations. This paper details the models and simulation results involved in the steps of the procedure.

The ELT M1 Local Coherencer is a non-contact metrology system aimed to simultaneously measure the relative pistons on the six sides of a target M1 segment with respect to neighboring ones (reference segments) with an accuracy below 300nm in a range of ±250μm. This measurement shall be performed while the Local Coherencer is supported by the M1 Segment Manipulator hanging from the M1 Segment Crane. IDOM has developed for the M1 Local Coherencer a lean, compact and robust solution featuring: - Six lightweight and compact Sensing Modules whose main system is a partially coherent light interferometer for the piston measurements that hugely simplifies image processing and avoids any ambiguity in the measurements. - Comprehensive and robust alignment detection and alignment compensation systems that ensure proper positioning and prevent apparent (bias) piston measurement errors. - A lean embodiment in which all the subsystems, including control and safety elements, are mounted on a single support structure and enclosed in the specified design volume, with no need to use the space reserved in the M1 Segment Manipulator - A solution largely based on small COTS and simple electronics, which account for ease of use, high reliability, easy replaceability and high durability of the system. This paper describes the proposed design as presented in the Preliminary Design Review (PDR) of the system held in May 2022.

The Giant Magellan Telescope will be a 25.4-m visible and infrared telescope at Las Campanas Observatory. The optical design consists of 7 8.4-m primary mirror segments that reflect light to 7 secondary mirror segments in a doubly segmented direct Gregorian configuration. GMT is developing a Telescope Metrology System (TMS) to decrease the complexity of alignment and increase observatory efficiency. The TMS has been developed to Preliminary Design Review level. A prototyping, modelling, and analysis effort has been completed. All components of the system were matured, and the edge-sensing strategy was significantly revised. This paper describes the current TMS design.

The Wide Field Phasing Testbed will be used to test phasing and active optics systems planned for the doubly segmented Giant Magellan Telescope. The testbed consists of a set of optical relays in which are located segmented and deformable mirrors that represent the GMT M1 and M2 mirrors. The testbed output beam has the GMT’s f/8.16 focal ratio and has a back focal distance large enough to allow using a full-scale prototype of one unit of the Acquisition Guiding and Wavefront Sensing System. The testbed will reproduce the telescope field dependent aberrations that result from misalignment of M1 and M2. Over its 20mm diameter field of view, the testbed will generate aberrations corresponding to the 20′ field of the GMT. A rotating turbulence screen and zero-deviation prisms in the testbed will generate seeing limited images that correspond to typical atmospheric seeing and dispersion conditions expected at the GMT. The software for the testbed is designed to allow connection of the testbed wavefront sensing analysis components to simulations of the testbed optical system, as well as to conform to the planned software interfaces of the GMT’s telescope control system.

The success of the Keck telescopes’ segmented mirror technology provided a basis for the development of other large and extremely large telescopes. We investigate ways to optimize the performance of the segmented mirror telescope further to (1) take on the challenges of high contrast imaging to characterize habitable zone exoplanets, (2) enable visible adaptive optics (AO), and (3) fully benefit from recent extreme AO developments. The current status of Keck telescope phasing using the phasing camera system (PCS) is briefly presented. A phase retrieval technique is presented that uses AO science instrument images to improve the phasing of the telescope primary mirror. The technique was tested on the Keck telescopes, and the first experimental results are presented along with the limitations of this approach. The static, semi-static, and dynamic nature of the residual segment piston errors are discussed, along with possible elevation-dependent residual segment piston errors. We propose that the technique be periodically used at Keck observatory to monitor and improve telescope phasing. We discuss the significance of the technique for AO observations with the existing and future large aperture optical telescopes. The ultimate goal is to push large aperture ground-based telescopes to their performance limits and make them competitive with space telescopes in terms of PSF stability to enable breakthrough science.

The Active Optics System (AOS) of the Iranian National Observatory 3.4 m telescope (INO340) is designed to support and deform the M1 and to adjust the position of the M2 with the purpose of optical aberrations’ compensation. Sixty active axial pneumatic actuators and 32 passive lateral actuators support M1 axially and laterally, respectively. The arrangement and force vectors of the lateral actuators are optimized in such a way that minimum deformation on M1 occurs. There are 3 axial and 3 lateral fixed-points as positioning detectors for M1, and an accurate hexapod keeps M2 in the appropriate position. M1 surface shape and M2 positions are actively controlled by AOS during telescope operations using either a look-up table in open-loop control or the wavefront error in closed-loop control to achieve the best image quality. There are three levels of the control loop in AOS: 1- A proportional controller for a single actuator, 2- Inner-loop control to equilibrate M1 within the bandwidth of 1 [Hz], 3- Outer-loop control to remove optical aberrations within the bandwidth of 0.01 [Hz]. A test setup for the axial actuator and an Alt-simulator setup are provided to design and optimize a proportional controller for a single actuator and to test the inner-loop control. In this paper, the mechanical, control, and software designs for INO340 AOS are presented.

The preliminary concept development phase of the Southern African Large Telescope (SALT) mini-tracker (MT) project was completed. The addition of up to four MTs to the telescope would in effect create multiple four-to-six-meter class telescopes using SALT’s 10-m diameter primary mirror. Each MT would be able to provide spectroscopic follow up for current and future large astronomical surveys (e.g. MeerKAT, eROSITA, Gaia, LSST, SKA, etc.). This phase included development of a novel optical design for the spherical aberration corrector, preliminary mechanical design for the telescope interface and the MTs themselves, and simulation tools to calculate the effective illumination of each MT for a selected target. A detailed project management plan and documentation framework were also created, including a prototype development path, a project cost estimate, and a schedule to completion. Following a review of the project near the end of this concept development phase, the decision was taken to put the project on hold. Although the MTs were deemed to be technically feasible, a more detailed science case was required in order to proceed with the project. In addition, several personnel-intensive projects to improve the performance and reliability of the telescope, either now underway or soon to be started, would need to be completed prior to beginning a project of this magnitude and complexity. However, a number of valuable tools and results that will benefit SALT emerged from this concept development phase, and are outlined here.

LBTO, in partnership with GMTO, has been developing a laser-truss-based metrology system for the active alignment of telescope main optical components. Positive initial results convinced LBTO to commence to develop a "pathfinder" integrated operational active-optics system at prime focus, utilizing this technological approach. The prime-focus active-optics system benefits LBTO directly in improved system performance and is also very useful for GMTO in developing and gaining experience with a critical technical component of the GMT Telescope Metrology System. This paper describes the current system, which is now commissioned and operates in support of regular scientific observing. Technical aspects unique to direct laser truss metrology, such as system stability, the effects of correlated and uncorrelated noise, and the benefits of channel redundancy, will be discussed. Commissioning results and general system performance will also be reported. The paper will conclude with a section discussing some of the unexpected insights and improvements that the TMS has brought about at LBT by enabling the measurement of “clean” aberration data for aberrations arising from shape change on the borosilicate primary mirrors.

We describe the details into the design and development of a low-cost yet efficient telescope control system (TCS) and observatory control software (OCS) for the 50cm telescope at the Indian Astronomical Observatory. The TCS and OCS facilitate precise pointing and tracking of the main axes, handle peripheral sub systems such as the secondary focuser and the filter wheel, conduct observation, monitor weather and incorporate safety interlocks, aimed to run the telescope in a robotic manner. The TCS comprises a computer, control hardware components and an efficient programmable system on chip (PSoC) based motion controller. A distributed control architecture on the controller area network (CAN) bus allows for controlling many subsystems in a modular fashion. The control algorithm comprises the close loop proportional integral derivative (PID) controller and the motion profiler, which ensure very precise pointing and tracking performances. After optimum tuning of the PID gains, we could achieve performance that otherwise one can expect only in large telescopes. The control level pointing accuracy is 3 arc-seconds and unguided sidereal tracking accuracy of 2 arc-seconds over 10 minutes is achieved. The TCS related high-level calculations such as topo-centric and geocentric corrections and the pointing model etc. are carried out in a dedicated computer system, whereas the low-level control program runs in the PSoC. The pointing model software developed is automated and computes the coefficients by image processing using the plate solve method. The OCS which is the top most layer in the control architecture, handles the filter wheel, the detector, the enclosure, the weather station as well as many safety mechanisms. The OCS combined with the scheduler tool and client-server architecture facilitates the un-manned operation of the telescope.

In this article, we present a model describing the mechanical error stack-up and pointing analysis for primary focus radio arrays and summarize our metrology and simulation results. The mathematical framework of the error model is especially formulated for the Deep Dish Development Array 6-m (D3A6) which is a small interferometric radio telescope being deployed at the Dominion Radio Astrophysical Observatory (DRAO) site. The 3-element D3A6 will serve as a test bed for the upcoming Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) project which will survey the northern sky to measure baryon acoustic oscillations (BAO) observing the 21 cm hyper-fine transition of neutral hydrogen. CHORD will complete similar surveys done by Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) in the southern hemisphere. All the mechanical error modelling and metrology steps presented here will similarly be used and beneficial for the upcoming CHORD array. Using a Monte Carlo analysis pipeline based on this error propagation model, we study if our mechanical requirements should be tighten or relaxed and how the assembly and alignment of the D3A6 should be adjusted. The dishes are made out of fiber glass composites with metal reflectors embedded in them. Vacuum infusion process is used to fabricate the dishes from a precision mold. The mean mold RMS is measured as 0.54 mm RMS. The dish surface mean RMS error is 0.68 mm with a precision of 0.09 mm obtained from the 3 dishes. The mean boresight error is 21.72 arcmin with a precision of 5.44 arcmin. The study presents the metrology methods and errors obtained from the dish fabrication, assembly of the telescope components, alignment of the dishes. The study provides an insight on the errors and their specified requirement towards the development of CHORD array.

The small ExoLife Finder (sELF) telescope is a 3.4m diameter fixed pupil tracking Fizeau interferometer. Its design relies on several new technologies the ELF-PLANETS consortium has championed that will enable large narrow-field optical coronagraphic direct imaging. These distinguish it from other segmented aperture telescopes by its light weight, low cost, and its capability to create a coronagraphic point spread function with the telescope pupil, ahead of the secondary optics. This diffractive control emphasizes high dynamic range imaging in the presence of a bright central star in a narrow field-of-view. Its optomechanical design uses elements of tensegrity combined with thin (2mm thick by 0.5m diameter) off-axis parabola segments to decrease both the optical payload and mechanical structural mass. The sELF optomechanical design has been completed and contracts for construction in the Canary Islands will be tendered during the 1st quarter of 2023

Mezzocielo (or "half of the sky") is a concept for a single large monocentric optical system composed by a tessellated spherical container filled with low refractive index liquid characterized by an extremely high transparency. This system allows for a continuous monitoring of the whole sky with a large number of mass produced correcting cameras. In comparison with existing projects is characterized by a high efficiency and by a relatively large aperture. The current status of development with the aim of producing a prototype of one meter class size is being reported.

The ASTRI Mini-Array is a gamma-ray experiment led by INAF with the partnership of the Instituto de Astrofisica de Canarias, Fundacion Galileo Galilei, University of Sao Paulo, North-West University S.A., and Observatoire de Geneve. It is being implemented at the Observatorio del Teide Tenerife. The nine (9) Cherenkov dual-mirror aplanatic telescopes of 4 m diameter are positioned at an average distance from each other of 160 m. Thanks to the unprecedented field-of-view (10.5 deg) of the ASTRI telescopes, the MA will allow us to observe the gamma-ray sky from a few up to a few hundred TeVs with competitive flux sensitivity and enhanced angular resolution. The curved focal plane of the camera is covered with SiPM sensors and is equipped with fast front-end electronics. The control SW will allow us to operate the Mini-array remotely, while a dedicated off-site Data Center in Italy will process the scientific products every night. The ASTRI Mini-Array represents a pivotal instrument to perform groundbreaking measurements very soon. In this paper, we will review the implementation plan of the ASTRI Mini-Array and report on the ongoing construction.

The Cherenkov Telescope Array Observatory (CTAO) consists of three types of telescopes: large-sized (LST), mediumsized (MST), and small-sized (SST), distributed in two observing sites (North and South). For the CTA South “Alpha Configuration” the construction and installation of 37 (+5) SST telescopes (a number that could increase up to 70 in future upgrades) are planned. The SSTs are developed by an international consortium of institutes that will provide them as an in-kind contribution to CTAO. The SSTs rely on a Schwarzschild-Couder-like dual-mirror polynomial optical design, with a primary mirror of 4 m diameter, and are equipped with a focal plane camera based on SiPM detectors covering a field of view of ~9°. The current SST concept was validated by developing the prototype dual-mirror ASTRI-Horn Cherenkov telescope and the CHEC-S SiPM focal plane camera. In this contribution, we will present an overview of the SST key technologies, the current status of the SST project, and the planned schedule.

The Cherenkov Telescope Array Observatory (CTAO) will be the world-wide largest and most sensitive ground-based gamma-ray observatory. CTAO consists of three telescope types: Large, Medium, and Small Sized Telescopes (LST, MST, SST). The observatory construction period is expected to commence in 2023 and will last for five years. The Medium-Sized Telescopes (MSTs) of CTA are dominating the sensitivity in the core energy range from 100 GeV to 5 TeV. Covering an about 8 degrees field of view, the modified Davis-Cotton telescopes will have a tiled reflector of 12-m diameter and 16-m focal length. This contribution will detail the construction plans of the MSTs on both observatory sites and present in detail the design and expected performance of the telescopes and cameras.

MARCOT Pathfinder is a precursor for MARCOT (Multi Array of Combined Telescopes) at Calar Alto Observatory (CAHA) in Spain. MARCOT is intended to provide CARMENES, currently fiber-fed from the CAHA 3.5m Telescope, with a 5-15m light collecting area from a battery of several tens of small telescopes that are incoherently fed into the final joint single fiber feed of the spectrograph. The modular concept, based on commercially available telescopes, results in cost estimates that are a fraction of the ones for extremely large telescopes (ELT). As a novel approach, MARCOT will employ Multi-Mode Photonic Lanterns (MM-PL) that are being developed as a variant of classical photonic lanterns, to combine the light from the individual telescopes to a single fiber feed to the instrument. This progress report presents the overall concept of MARCOT, the pathfinder telescope and enclosure that is being commissioned at CAHA, the concept of MM-PL, and the next step of installing the Potsdam Multiplex Raman Spectrograph (MRS). MARCOT Pathfinder will be used to validate the conceptual design and predicted performance of MM-PL on sky with a 7-unit telescope prototype.

The Cherenkov Telescope Array (CTA) is the major ground-based gamma-ray observatory under construction. The CTA South observatory is foreseen to consist of Large-, Medium-, and Small-sized imaging atmospheric Cherenkov telescopes (IACTs). The innovative Schwarzschild-Couder Telescope (SCT) is a candidate IACT and a proposed major U.S. contribution for the Medium-sized, 10m aperture telescopes for CTA. The SCT is designed to simultaneously achieve 8 degrees field of view and high imaging resolution with unprecedented 11,328 pixels camera by implementing novel, aplanatic, segmented dual-mirror optics and compact silicon photomultiplier detectors. This presentation will provide an overview of the SCT program in the U.S. including the construction of a full-scale prototype instrument by an international consortium of scientists with the focus on the alignment of the segmented primary and secondary mirrors and the ongoing upgrade of the camera to full scale.

The National Radio Astronomy Observatory (NRAO) has engaged the broad scientific and technical communities in the design of a next-generation Very Large Array [1] (ngVLA), a large-scale research infrastructure project under development for the National Science Foundation Astronomical Sciences Division (NSF-AST) through a cooperative agreement with Associated Universities, Inc. The ngVLA is envisaged as an interferometric array with ten times greater sensitivity and spatial resolution than the current VLA and ALMA, operating in the frequency range of 1.2 - 116 GHz. Replacing both the VLA and VLBA, the ngVLA will be an open-skies, transformative, multi-disciplinary scientific instrument opening a new window on the Universe through ultra-sensitive imaging of thermal line and continuum emission down to milliarcsecond-scale resolution, as well as unprecedented broad-band continuum polarimetric imaging of non-thermal processes. The ngVLA will be optimized for observations in the spectral region between the superb performance of ALMA at sub-mm wavelengths, and the future Phase I Square Kilometer Array (SKA-1) at decimeter and longer wavelengths, resulting in a transformational instrument for the entire scientific community. In 2019, the ngVLA project completed the public release of the ngVLA Reference Design [2][3] as the technical and cost basis of the ngVLA Astro2020 Decadal Survey proposal [4]. With a strong endorsement of the facility concept by the Decadal Survey [5] and continued support from the National Science Foundation, the project is preparing for a System Conceptual Design Review in the spring of 2022. This paper provides a technical update, noting technical advancements and changes to the design baseline.

The Cherenkov Telescope Array Observatory (CTAO) is the next generation ground-based observatory for gamma-ray astronomy at very high energies. With initially 64 telescopes at two sites, CTAO 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 at the European Southern Observatory Paranal site (Chile). Three classes of telescope types spread over a large area are required to cover the full CTAO 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), CTAO will be one order of magnitude more sensitive, and have unprecedented accuracy in its detection of high-energy gamma rays. Current gamma-ray telescope arrays host up to five individual telescopes, but CTAO is designed to detect gamma rays over a larger area and a wider field of view. Prototypes for the major subsystems including the various size telescopes and cameras have been developed and built at different places. CTAO is currently preparing for the full construction phase, both technically and organizationally, with the goal to achieve completion and enter the operation phase by 2027. CTAO 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.

The Square Kilometre Array (SKA) project will build the largest radio telescope in the world with telescope facilities deployed in Australia and South Africa covering a frequency range from 50 MHz to 15 GHz (initial phase). The approval for the start of construction from its governing Council occurred in June 2021. This paper reviews the key science drivers and the outline observatory organization, design summary and site locations. We note the current progress and status of the SKA construction and projected schedule, noting the challenges within the current global climate.

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will perform precision photometry of resolved and unresolved objects over the visible sky at a 3-day cadence using an 8.4-meter diameter telescope that forms an image of the sky on a 3.2 Gigapixel focal plane array. Meeting and exceeding the photometric precision requirements is a significant challenge and necessitates the calibration and correction of multiple forms of systematic error. This paper describes multiple novel hardware systems that Rubin is developing to measure and compensate for numerous sources of systematic errors, particularly errors impacting photometry measurements.

The NSF's Daniel K. Inouye Solar Telescope (DKIST) is the largest solar telescope in the world, with a 4-m off-axis primary mirror and 16-m rotating coudé laboratory within the telescope pier. Due to its off-axis design, the mount size is equivalent to an on-axis 8-m class telescope. Like other large, complex telescopes, DKIST is affected by vibrations related to its size and several important rotating entities (e.g. enclosure, coudé, telescope mount). However, the DKIST must also disperse a solar heat load of 13kW, using a complex thermal design supplemented by several additional vibration sources. The diffraction limit of the telescope makes the optical error budget very tight, with the allotted budget for vibrations jitter set as low as 70 milli-arcsec. This translates to a few hundred nanometers RMS on certain mirrors, with the impact of jitter on on-sky image motion varying relative to the mirror position in the optical path. The DKIST recently celebrated the end of its construction phase in November 2021, enabling the start of operations and allowing science programs to be started. Vibrations data recording and management has become part of the telescope verification during observing, enabling early detection of new frequency peaks and amplitude increases in known frequencies. Previous vibrations surveys at DKIST were conducted by William McBride who has proposed and presented an allocations budget per location in 2018, implemented and measured various paths analyses, and linked those results to the AO system. As the transition to operations progressed and operations continues, several vibration sources have been activated. Comparisons of current vibration levels to the previous budget is ongoing in order to identify where solutions to improve performance and facilitate AO correction are required. We were notified of two strong frequencies (40 Hz and 80 Hz) contributing significantly to image motion, identified within the High Order Adaptive Optics (HOAO) performance report. Presented herein is the process used to identify the source of that vibration by building a knowledge base of the telescope’s vibration signature, and using data identification of the problematic peaks to find the vibration hardware’s source. An improved design was then engineered, tested and implemented. Finally, by comparing results to prior HOAO measurements, the improvement in performance can be quantified.

The NEID extreme precision radial velocity spectrometer is in operation at the WIYN 3.5-meter telescope located at the Kitt Peak National Observatory, Tucson, Arizona. This newly-commissioned instrument serves both the national exoplanet research community as well as the WIYN consortium partners. In order to meet the stringent 27 cm per second radial velocity precision^[1], and in particular to maximize the efficiency of the 5-year radial velocity survey, it is critical to understand the WIYN telescope vibration environment. In this presentation, we describe the vibration measurement techniques and results used for quantifying the vibration of: the telescope ancillary equipment, the telescope mount, the telescope primary mirror cooling systems, the telescope instruments, wind, and other sources and their effect on the telescope image. Additionally, mitigation methods, current and planned are discussed. This work continues on from a previous paper at this conference^[2], where we presented data gathered from accelerometers on WIYN to begin identifying major features in the vibration spectra and simulate the input to the tip-tilt correction system for the NEID fiber-feed. The WIYN telescope has a well-ventilated and compact dome that ensures excellent seeing, but is also prone to wind-shake. For wind-related vibrations in particular, it is important to model the structural modes to design mitigation strategies and here we discuss possible experimental methods and data analysis techniques to address this. This work will be relevant to upgrade and retrofit efforts as older observatories incorporate low-order wavefront correction to stabilize light to advanced spectrometers and imagers. See Li et al. (this conference).

The Dominion Radio Astrophysical Observatory’s John A. Galt 26 m radio telescope serves multiple roles for the Canadian radio astronomy community. It is currently earmarked to serve as an interferometric reference for the Canadian Hydrogen Intensity Mapping Experiment (CHIME), Canadian Hydrogen Observatory and Radio Transient Detectors (CHORD), and Deep Dish Development Array 6m (D3A6) experiments. The attributes of this telescope make it ideal for spectropolarimetric studies of the interstellar medium, however instrumental conversion of unpolarized radiation into a polarized signal can corrupt the astronomical signal as the telescope undergoes various loading conditions. To characterize these effects, a finite element (FE) model of the telescope was constructed, based on available blue prints and supplemented by manual measurements. Gravity and wind load cases were analyzed for several elevation angles. The FE model will be validated by measuring the first several vibration modes of the actual telescope using the step-release method. This paper will describe the model development and analytical predictions, as well as the experimental approach used to validate these predictions, and will summarize initial results from these tests (if available).

In the last couple of years, the Rubin telescope and site subsystem has made tremendous progress and overcome a few challenges. The insulated cladding on the dome is done and work is now focused on finishing the louvers, weatherproof cladding, interior work, light baffles, and the final fabrications. This has been done concurrently with the installation of the telescope mount, now mostly complete and approaching the beginning of functional testing in September-October, 2022. While work is being done on these two major subsystems, other major components and systems are being integrated and tested in a system spread configuration: M1M3 & M2 mirrors, the camera hexapod/rotator and the control software, including elements of the active optics control and the commissioning camera. Finally, the calibration system - an important contributor to achieving the exquisite photometry required by the Legacy Survey of Space and Time (LSST) - is being finalized.

East Anatolian Observatory’s DAG telescope, with its 4m diameter primary mirror and VIS/IR observation capability, Eastern Anatolian Observatory’s 4m diameter class DAG telescope, with VIS/IR observation capability, will be located on the Konaklı-Karaya summit at an altitude of 3170 m, near the city of Erzurum, Turkey. DAG contains both active optics (aO) and adaptive optics (AO) systems. With the enclosure assembly nearly done, and the dummy mirror integration including the M1 cell integration performed at the end of 2021; DAG telescope's AIV is planned to take place by the end of May/2022 and the Provisional Acceptance by November/2022. DAG is equipped with an in-flange derotator – KORAY (K-mirror Optical RelAY) that will direct the light to the seeing limited Nasmyth platform containing TROIA (TuRkish adaptive Optics system for Infrared Astronomy). The scientific instruments that DAG will receive in 2022, are but not limited to, a stellar coronagraph and a 30" NIR diffraction limited camera. In his paper, a global status update and expected optical performance characteristics will be presented.

Iranian National Observatory (INO) project is approaching completion, with the first light of the flagship 3.4m optical telescope, INO340, planned for 2022. The observatory is located in central Iran on Mt Gargash at 3600m, benefiting from an excellent atmospheric seeing and suitable weather conditions. The observatory comprises the 3.4m optical telescope, the enclosure and auxiliaries, a service building hosting a control room, offices and mirror coating hall, a lens array system for wide-field monitoring, and a site monitoring station equipped with a weather station and an automatic seeing monitor, and essential utilities. The Alt-Az telescope benefits from hydrostatic bearing in the Azimuth, an active optics system to support and deform the primary mirror and a hexapod to position the secondary mirror. This report will provide an overview of the project development, manufacturing and installing the telescope and its enclosure.

The National Science Foundation’s 4m Daniel K. Inouye Solar Telescope (DKIST) on Haleakala, Maui is now the largest solar telescope in the world. DKIST’s superb resolution and polarimetric sensitivity will enable astronomers to unravel many of the mysteries the Sun presents, including the origin of solar magnetism, the mechanisms of coronal heating and drivers of flares and coronal mass ejections. Five instruments, four of which provide highly sensitive measurements of solar magnetic fields, including the illusive magnetic field of the faint solar corona. DKIST operates as a coronagraph at infrared wavelengths where the sky background is low and bright coronal emission lines are available. The high-order, single-conjugate adaptive optics system (AO) provides diffraction limited imaging and the ability to resolve features approximately 20 km on the Sun. A multi-conjugate AO upgrade is in progress. With these unique capabilities DKIST will address basic research aspects of Space Weather and help improve predictive capabilities. DKIST has completed construction and is now in the early phases of operations. Community proposal-based shared-risk observations are conducted by the DKIST operations team.

We report on the CCAT-prime Project, including the science program, the Fred Young Submillimeter Telescope (FYST), its instrumentation, and the schedule. FYST is a 6-m telescope sited at 5600 m elevation near the summit of Cerro Chajnantor in northern Chile. The site, together with its very large field-of-view optics, and high surface accuracy, low-emissivity surface enables pursuit of low surface brightness science over large fields. Our science goals include: tracing the formation and evolution of star forming galaxies from the epoch of reionization to the cosmic peak of star formation activity through wide-field, broad-band [CII] line imaging and dust continuum surveys; constraining thermodynamics and feedback in galaxy clusters through the Sunyaev-Zel’dovich effects on the CMB; improving constraints on primordial gravitational waves through precision removal of polarization foregrounds; and tracing local star formation processes through velocity-resolved spectroscopy at 15” spatial resolution over 110 scales in the Galaxy. These goals are realized through sensitive wide-field surveys. Our main instruments are Prime-Cam, a large FoV direct detection imager and CHAI, a multi-beam submillimeter heterodyne spectrometer. We have also built Mod-Cam which serves as a Prime-Cam test facility and/or first light camera. Prime-Cam has seven instrument modules, four now under construction: three polarimetric cameras (at 280, 350, and 850 GHz) and a 210-420 GHz Fabry-Perot imaging spectrometer, EoR-Spec. CHAI will have 128 pixels covering important lines in the short submillimeter windows. The CCAT-prime team is an international group of universities, led by Cornell University. FYST is being designed and built by CPI Vertex Antennentechnik, GmbH, Germany with first light expected in 2024.

The University of Tokyo Atacama Observatory (TAO) is a project to build and operate an infrared-optimized 6.5m telescope at the summit of Cerro Chajnantor (5640 m.a.s.l). This is promoted by Institute of Astronomy, Graduate School of Science, the University of Tokyo in collaboration with many universities and institutes. The project is now approaching the final phase of the construction. Production of major components are almost completed. The primary mirror fabricated by Steward Observatory Richard F. Caris Mirror Lab in the University of Arizona was temporarily assembled in its support system and confirmed its performance by the optical test in the laboratory. The telescope mount, the enclosure system, and the mirror coating system were fabricated in Japan and already shipped to Chile. They are now stored in an open yard located in the foot area of Cerro Chajanator. The expansion of the summit access road, the summit leveling, the foundation work was completed. Now the construction work of the summit facilities is on-going. TAO will equip three instruments in early science phase. A near-infrared instrument SWIMS is completed, and now used as a PI-type instrument of Subaru telescope. A near-infrared spectrograph NICE which was used on the 1.6m Pirka telescope in Japan is being refurbished for TAO. A mid-infrared instrument MIMIZUKU successfully saw the first light on Subaru telescope and is being prepared for TAO in Japan. We expect to start science operation in FY2023.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) has significant recent scientific accomplishments including water on the moon and magnetic fields in molecular clouds. An airborne platform offers access to the sky at wavelengths where the atmosphere is opaque from the ground. It also has unique challenges that have been met with ingenious engineering solutions. I'll give an up to date report on the observatory at this conference.

The Large Millimeter Telescope (LMT) Alfonso Serrano is a bi-national (Mexico and USA) telescope facility constructed on the summit of Sierra Negra, at an altitude of 4600m, in the Mexican state of Puebla. The LMT is a 50-m diameter single-dish telescope, with an active surface control-system to correct gravitational and thermal deformations of the primary reflector, designed and optimized to conduct scientific observations using heterodyne and continuum receivers, as well as VLBI observations, at frequencies between ~70 and 350 GHz.  We describe the current status and technical performance of the recently commissioned LMT 50-m, the instrumentation development program, and future engineering upgrades that will optimize the optical efficiency of the telescope and increase its scientific productivity.

The Maunakea Spectroscopic Explorer partners' national strategic planning reports were released in late 2021, including the US Astro2020 findings and recommendations. This paper is a two-part summary of the project's response to the reports’ recommendations. The first part incorporates additional considerations due to the State of Hawai’i House Bill 2024 and its new Mauna Kea Stewardship and Oversight Authority, and their effects on the Maunakea Observatories and MSE, specifically. The second part summarizes the national strategic planning recommendations specific to MSE and states our plan to progress MSE as we prepare to enter the next project phase. The stated plan in the second part of this paper describes our programmatic planning within the partnership for public outreach, technology development, and risk mitigation in response to the national strategic planning recommendations including community-based engagement related to the renewal of the Canada, France and Hawai’i Telescope (CFHT) site lease under the new authority. Since the Maunakea Master Lease renewal process is replaced by separate negotiations for individual observatory site leases, the paper also highlights our approach to secure continuous access to Maunakea for MSE.

The European Solar Telescope (EST) aims to become the most ambitious ground-based solar telescope in Europe. Its roots lie in the knowledge and expertise gained from building and running previous infrastructures like, among others, the Vacuum Tower Telescope, Swedish Solar Telescope, or the GREGOR telescope. They are installed in the Canary Islands observatories, the selected EST site. Furthermore, the telescope has a novel optical design, including an adaptive secondary mirror (ASM) that allows reducing the number of optical surfaces to 6 mirrors (plus two lenses) before the instruments’ focal plane. The latter, combined with a configuration of mirrors that are located orthogonally oriented to compensate for the instrumental polarisation induced by each surface, makes EST a reference telescope in terms of throughput and polarimetric accuracy. In its main core design, EST also includes a Multi-Conjugated Adaptive Optics (MCAO) system where the ASM compensates for the ground layer turbulence. The rest of the mirrors on the optical train correct for the atmospheric turbulence at different layers of the atmosphere. The MCAO guarantees that the large theoretical spatial resolution of the 4-metre EST primary mirror is achieved over a circular FOV of 60 arcsec. Those main elements, combined with a set of instruments with capabilities for spectropolarimetry, make EST the next frontier in solar ground-based astronomy. In this contribution, we will cover the main properties and status of all the mentioned sub-systems and the following steps that will lead to the construction phase.

National Astronomical Observatory of Japan (NAOJ) has had the responsibility for the Telescope Structure System (STR) of Thirty Meter Telescope (TMT) and engaged Mitsubishi Electric Corporation (MELCO) to take over the preliminary/final design and pre-production work since 2012. TMT defines that STR shall be designed to withstand earthquakes up to the levels of the 1000-years annual return period as keeping accelerations at the mirror/instrumental interface points below the specified thresholds. In this paper, we present the Seismic Isolation System (SIS) of TMT STR, as focusing on (1) the design to achieve compatibility of two conflicting performances that are the rigid connection to the ground during normal observations and flexible movement during seismic to suppress the seismic energy, (2) prototype results of the seismic isolation system, and (3) compliance status of the seismic requirements which is evaluated by time history analysis using the Finite Element Method (FEM) model of TMT STR.

The Giant Magellan Telescope (GMT) will be a 25 meter optical telescope with a maximum weight of about 2300t, located on Cerro Las Campanas in Chile. The telescope will be equipped with a complex adaptive optical system as well as highly sensitive instrumentation and high performance drive and control components like direct drives and high resolution band encoders. For protection of this sensitive equipment from extreme earthquake excitations, a seismic isolation system implemented at the base of the concrete telescope pier will reduce horizontal accelerations. A second earthquake damping system, currently under development at OHB, will be installed on the GMT Mount to suppress vertical accelerations. In addition to the damping system itself, adaptations need to be made to the drive and control components to allow the damping system movements without having an impact on their functionality. A prototype of the vertical damping system will be built and dynamic testing will be performed. The presentation will provide an overview on the system development status.

Not coincidentally, most of the world’s best astronomical sites are in seismically active areas. As telescopes increase in aperture, they become increasingly sensitive to seismic loads. In this workshop, we want to collect the knowledge, experience, and lessons learned from the previous generations of observatories, to inform the design and construction of future observatories, including the ELTs (ELT, GMT, and TMT). Topics for the workshop include earthquake-induced damage to observatories (telescopes, instruments, enclosures), seismic protection systems and improvements in existing observatories, design of seismic protection systems for new and future observatories, processes and operational procedures for recovery and return to operations following seismic events, and lessons learned that can be applied to the design and operation of future observatories.

Within a difficult and uncertain environment resulting from the COVID-19 pandemic as well as the global geopolitical and economic situation, the ESO’s Extremely Large Telescope (ELT) is progressing on all fronts of design, product and process qualification, manufacturing, subsystem assembly and the two M1 segment coating plants have just been commissioned in the dedicated ELT Technical Facility building at Paranal. The scientific Instruments are now undergoing their final design reviews while series production for the various components constituting the 39 m diameter segmented primary mirror (M1) is well underway. On Cerro Armazones the raft foundations for the dome and for telescope structure are being poured and the piers start to rise above ground. On the programmatic level, all deferred subsystems (so-called phase 2 items) are now funded, and the budget has been moderately increased to account also for infrastructure upgrade needed to fully and optimally integrate the ELT into the Paranal (VLT) Observatory operation scheme. After a year of complete closure of the construction site and other delays in several contracts due to the pandemic and technical difficulties, the programme schedule has been adjusted and Scientific First Light is planned by the end of 2027.

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 (TIO) is a public-private-international partnership that unites the scientific, instrumental and industrial communities of India, Canada, China, Japan and the USA for this endeavor with all partners contributing to the design, development, and scientific operation of the observatory. TMT is now part of the US Extremely Large Telescope Program (US-ELTP), in partnership with the Giant Magellan Telescope in the southern hemisphere and NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab). The National Academies’ latest decadal survey report, Pathways to Discovery in Astronomy and Astrophysics for the 2020s, has ranked the US-ELTP as the highest ground-based priority. This paper will describe recent progress

The Giant Magellan Telescope is proceeding with design, fabrication, and site construction. Of the seven 8.4 m diameter mirror segments required for the primary mirror, two have been completed and placed in storage, a third has been polished to specification, three more have been cast and are in various stages of fabrication, and glass is in hand to cast the final segment. The telescope structure is nearing final design review and the start of fabrication. Residence buildings and other facilities needed to support construction at the Las Campanas site in Chile are complete. Hard rock excavation of the foundations for the enclosure and telescope pier is complete. The enclosure is in final design. The first off-axis adaptive secondary mirror is being fabricated, and a primary mirror cell has been fabricated and is under test. Two adaptive optics and phasing testbeds are being fabricated for risk reduction testing and component qualification. Our fabrication and construction schedule is being revised in response to evolving programmatic factors, including the US-ELT initiative, which received the top ranking in the National Academies’ ASTRO2020 Decadal Survey.

The Cosmic Microwave Background Stage Four Experiment (CMB-S4) is a planned DOE/NSF ground-based experiment, endorsed as a high priority mission in the Astro2020 report, with scientific impacts reaching from transformative measurements of the cosmic microwave background (CMB) to a deep legacy millimeter-wavelength dataset covering a large fraction of the sky. To meet its ambitious goals, CMB-S4 plans to have multiple small-aperture (0.55-meter) and large-aperture (6-meter) telescopes located both in the Chilean Atacama desert (to access a large fraction of the sky) and at the South Pole (for targeted deep-field observations). Over 500,000 superconducting detectors will be distributed across these telescopes, enabling a necessary leap in sensitivity. We present an overview of the project organization, technical design, construction plans, and predicted performance of CMB-S4. We highlight some driving programmatic and technical considerations of the current experimental design.

The segment support system of any segmented mirror telescope is considered to be one of the most critical subsystem. The segment support not only holds the mirror without altering its figure, but also features mechanism which facilitate active alignment of the segments with the help of three linear actuators. We have designed and a developed a segment support system for a proposed prototype segmented mirror telescope (PSMT). The baseline design of the PSMT segment support comprises of nine point axially supporting whiffletree coupled with a moving frame and a central diaphragm for the radial support. Our design uses large number of flexural components including flex pivots which make it friction-less system, requiring no lubrication. In this paper we present the details of our design as well as results of very extensive finite element analysis carried out to explore effect of variable gravity as well as temperature on the performance of the support system. During the course of telescope movement from zenith to horizon, interplay between axial and radial support system has also been studied in great detail. The modal analysis is also carried out to determine different natural frequencies/modes the support system is subjected. Functional and operational aspect of the segment support is also tested by conducting experiments on one fully realized system. The segment support which is primarily designed for 0.5m size PSMT segment can be easily scaled up to 1 m size segment and hence can be used for any large telescopes aimed to utilize segmented primary mirror.

The Giant Magellan Telescope (GMT) is one of three planned ground-based optical/IR Extremely Large Telescopes (ELTs) that will provide a generational leap in ground-based Optical/IR capability. The GMTO Corp. completed in 2019 a multi-stage acquisition process that led to the selection of OHB Digital Connect (formerly MT-Mechatronics or MTM) and Ingersoll Machine Tools (IMT) to supply the final design, fabrication, and installation of the GMT Mount. The ~2000 metric ton GMT Mount comprises the telescope structures, mechanisms, and utilities but does not include the optics and science instruments. This paper provides a general overview of the technical scope of the GMT Mount including the key and driving requirements, systems engineering framework, and planned design development. Due to the GMT site location in Chile, the Mount design must accommodate a challenging seismic environment. Major Mount subsystems are also described including the Hydrostatic Bearing System (HBS), Gregorian Instrument Rotator (GIR), and the Azimuth Track and its interface to the telescope Pier. In addition, a summary is presented of the design path forward to the Final Design Review (FDR) from the point of completing the Preliminary Design Review (PDR) in early 2021, including the current status of critical prototyping efforts. Finally, management processes are outlined that are necessary to execute the Mount design-build contract spanning the next 8-9 years.

The European Solar Telescope (EST) is a next generation large-aperture solar telescope, to be located in the Canary Islands. It will be optimized for studies of the magnetic coupling of the solar atmosphere. This will require diagnostics of the thermal, dynamic and magnetic properties of the plasma over many scale heights, by using multi-wavelength imaging, spectroscopy and spectropolarimetry. The optical design of the EST is based on an aplanatic Gregorian telescope, characterized by a 4.2-metre primary mirror, installed above the elevation axis with the aim of enhancing the natural air flushing. The EST works in open configuration, requiring an active/passive thermal control at telescope level to comply with the maximum temperature gradients of ±2°C. The telescope will be placed on the top of a tower to improve the local seeing conditions. The open configuration exposes the telescope to wind disturbances, higher than in other telescopes. The natural frequency of the global modes affecting the position servosystem bandwidth of the telescope are stablished in 12-15 Hz to ensure pointing and tracking accuracy of 2.3 arcsec and 0.8 arsec during 10 mins, respectively. Sophisticated end-to-end control analysis have been carried out to assess in detail the effects of the wind disturbances, but also the impact of non-linear friction, cogging and torque ripple, among others. CFD analyses and wind tunnel test campaigns have been performed to verify the performance of the telescope in operational conditions. The main axes of the telescope must be in parking position before the closure of the retractable enclosure in order to optimize its size. This requires a robust design, including redundancy in azimuth and elevation mechanisms to ensure the protection of the telescope in case of failure. The detailed maintenance strategy has been also established to ensure that every operation can be performed with the closed enclosure.

The Iranian National Observatory (INO) 3.4 m optical telescope (INO340), has been installed on Mt Gargash peak at an altitude of 3600 m in central Iran. The optical design of the telescope is Ritchey-Chretien Cassegrain type on an altitude-azimuth mount and offers an unvignetted field of view of 20 arcmin and the focal ratio of f/11.25. It has a total mass of 85 tons with a height of 11 m and a maximum diameter of 7.5 m. The telescope design was optimized to achieve 0.2 arcsec tracking accuracy and 3 arcsec blind pointing accuracy. The finite element analyses have been carried out during the design phase to make sure of the functionality and safety of the telescope. This paper presents the mechanical design, analysis and manufacturing of the telescope.

The Fred Young Submillimeter Telescope (FYST) is a 6-meter diameter telescope currently being built by the CCAT-prime project that will observe at millimeter and submillimeter wavelengths. It will deliver a total wavefront error of less than 22 microns at the focal plane. The optics follow a modified crossed-Dragone configuration, yielding a 7.8° field of view across a ~2 meter diameter focal plane. The telescope will be located at 5600 meters on Cerro Chajnantor in the Atacama Desert. The demands of first-generation and future instruments significantly drove the design of the telescope. The telescope layout consists of multiple instrument bays, which provide the capacity to house a total of 11 tons of focal plane instrumentation across 23 square meters of floor space. The Yoke Traverse is divided into telescope servo, instrument electronics, and process spaces, and can support an additional 8 tons of instrument equipment. We discuss the final design and fabrication status of FYST.

The Vera C. Rubin Observatory is the result of a public-private partnership between the USA National Science Foundation (NSF), the lead Federal Agency of the project, the Department of Energy and the Association Of Universities For Research In Astronomy (AURA), and the LSST Corporation. EIE GROUP has developed the Detail Design, the Manufacturing, and the Erection on Site of the giant Rotating Building. In this regard, 2021 was a year full of successes for the development of the project.

The INO340 enclosure design follows recent developments in enclosure and dome design which aims at minimum enclosed air with suitable temperature and humidity control as well as an efficient air flushing to reduce the mirror seeing. The INO340 enclosure performance indicates a quality design and construction which meets the desired specifications. This report will review the design details of INO340 enclosure building architecture and anatomy. It will also describe some back design philosophies that drove design details and construction of the enclosure. We briefly report on the development and installation of the dome.

This work describes the architectural design for the construction of the building for the COLIBRI robotic telescope, which has a 1.3 m primary mirror and forms part of the ground segment of the SVOM (Space Variable Object Monitor) mission dedicated to the detection and study of gamma-ray bursts (GRBs). The building is currently being installed. The building that will house the telescope will have a total height of 10 m including the dome. The center of the building will contain a concrete column with an independent foundation of the building of 2.5 m in diameter and 5.3 meter in height. In addition it will have 2 levels (floors) for the control room and observing room. In this article we share the progress achieved so far, which includes the design for the building structure, installations of the electrical, communication and network systems, air-conditioning systems, special considerations related to the environmental management of the operation site, and the start of construction. We also include the technological challenges and challenges addressed during the design process, in particular we will present our solutions to avoid heat leaks from the control room to the observing room and isolate the telescope from vibrations produced by the dome and the rest of the enclosure.

The New Robotic Telescope (NRT) is a robotic and fully autonomous four-metre-class telescope and the first in its size class to utilise a clamshell enclosure. It will be located at the Roque de los Muchachos Observatory (ORM) on La Palma, Canary Islands, Spain. Fast slew time, robotic functionality, and reduced dome seeing are the main reasons for the clamshell design, however cost is also an important factor. The greatest opportunity for cost reduction is the movable roof structure of the enclosure, but is the most complex to design and the heaviest part in the initial concept considerations. To solve a complex optimisation problem considering all limitations, conditions and assemblies, a combination of generative design approach and machine learning is used. This enables us to overcome two major obstacles: First, we are able to combine multiple models into one optimisation problem that could analyse multiple states simultaneously, such as the closed and semi-open states. Second, the machine learning-based predictive models are able to run much faster, which allows us to explore many more possible design solutions. Structural optimisation results show more than one optimal solution, which is consistent with multi-objective optimisation, since there are certain trade-offs between mass, capacity utilisation, and hydraulic forces. The goal of the structural optimisation was to explore the possible design alternatives before engaging a construction design partner. This allows for more efficient project development, as the design partner could immediately focus on the construction design work without needing to understand the implications for the telescope.

This paper presents an update on the construction, testing, and commissioning of the SDSS-V Local Volume Mapper (LVM) telescope system. LVM is one of three surveys that form the fifth generation of the Sloan Digital Sky Survey, and it will employ a coordinated network of four, 16-cm telescopes feeding three fiber spectrographs at the Las Campanas Observatory. The goal is to spectrally map approximately 2500 square degrees of the Galactic plane with 37” spatial resolution and R~4000 spectral resolution over the wavelength range 360-980 nm. LVM will also target the Magellanic Clouds and other Local Group galaxies. Each of the four LVM telescopes consists of a two-mirror siderostat in alt-alt configuration feeding an optical breadboard. This produces a fixed, stable focal plane for the fiber-based Integral Field Unit (IFU). One telescope hosts the science IFU, while two others observe adjacent fields to calibrate geocoronal emission. The fourth telescope makes rapid observations of bright stars to compensate telluric absorption. The entrance slits of the spectrographs intersperse the fibers from all three types of telescope, producing truly simultaneous science and calibration exposures. We summarize the final design of the telescope system and report on its construction, alignment and testing in the laboratory. We also describe our deployment plan for commissioning at LCO, anticipated for late 2022.

The OPA project, the Original PolyOculus Array, uses the PolyOculus technology to create a large-area-equivalent telescope by using fiber optics to link seven semi-autonomous, small, inexpensive, commercial-off-the-shelf telescopes. OPA will use seven, Celestron 11" telescopes with iOptron central-balanced equatorial (CEM 70) mounts to create a 0.74m equivalent optical telescope for spectroscopic follow up observations. This telescope will include 7 acquisition and guiding systems (one per telescope) to appropriately center objects in the telescopes’ field of view along with an atmospheric dispersion corrector for each unit. That light will then be sent through single optical fibers (one fiber per telescope) and to a photonic lantern where the light from all seven telescopes will be combined then sent to a spectrograph. OPA will be commissioned and operated at Mount Laguna Observatory in southern California.

Cosmic explosions have emerged as a major field of astrophysics over the last years with our increasing capability to monitor large parts of the sky in different wavelengths and with different messengers (photons, neutrinos, and gravitational waves). In this context, gamma-ray bursts (GRBs) play a very specific role, as they are the most energetic explosions in the Universe. The forthcoming Sino-French SVOM mission will make a major contribution to this scientific domain by improving our understanding of the GRB phenomenon and by allowing their use to understand the infancy of the Universe. In order to fulfill all of its scientific objectives, SVOM will be complemented by a fast robotic 1.3 m telescope, COLIBRI, with multiband photometric capabilities (from visible to infrared). This telescope is being jointly developed by France and Mexico. The telescope and one of its instruments are currently being extensively tested at OHP in France and will be installed in Mexico in spring 2023.

The pathfinder Dragonfly Spectral Line Mapper is a mosaic-design telescope based off of the Dragonfly Telephoto Array with additional instrumentation (the Dragonfly “Filter-Tilter”) to enable ultranarrow bandpass imaging. The pathfinder is composed of three redundant optical tube assemblies (OTAs) which are mounted together to form a single field of view imaging telescope (where the effective aperture diameter increases as the square-root of the number of OTAs). The pathfinder has been on sky from March 2020 to October 2021 equipped with narrowband filters to provide proof-of-concept imaging, surface brightness limit measurements, on sky testing, and observing software development in advance of the upcoming full Dragonfly Spectral Line Mapper. Here we describe the pathfinder telescope and the sensitivity limits reached along with observing methods. We outline the current limiting factors for reaching ultra-low surface brightnesses and present a comprehensive comparison of instrument sensitivities to low surface brightness line emission and other methods of observing the ultra-faint line emission from diffuse gas. Finally, we touch on plans for the upcoming 120-OTA Dragonfly Spectral Line Mapper, currently under construction.

The LFAST concept is to use thousands of small telescopes combined by fibers for high resolution (R=150,000) spectroscopy, in a way that will realize large cost savings and lead to an affordable aperture as large as 20,000 m². Such large aperture is needed, for example, to make a comprehensive search for biosignatures in the atmospheres of transiting exoplanets. Each unit telescope of 0.76 m aperture (0.43 m²) will focus the image of a single star onto a small (17 μm core) fiber, subtending 1.32 arcsec. Our telescope design calls for a spherical mirror, with a 4-lens assembly at prime focus that corrects not only for spherical aberration, but also for atmospheric dispersion down to 30° elevation, from 390 nm – 1700 nm, and for rapid image motion caused by seeing or wind jitter. A method for rapid production of such mirrors has been tested, in which a disc of borosilicate float glass is slumped over a high-precision polished mandrel to an accuracy that greatly reduces subsequent optical finishing time. A method for active thermal control of mirror figure using Peltier devices will be incorporated. The projected cost of each unit telescope, when mass produced by the thousand, would then be approximately $8,000. The telescopes will be mounted in the open in groups of 20 located 12 m apart. The mirrors will be arrayed on either side of a central, pedestal-mounted alt-az drive using commercial worm gear bearings. Protection against rain and dust will be provided by automated covers above and below the mirrors, and by pointing the mirrors down (– 20° elevation). The first LFAST array, some 150 m in diameter, will comprise 132 mounts carrying a total of 2,640 mirrors and having 1,200 m² in collecting area. The light from all the fibers is combined at the central spectrographs, with little increase in etendue, by a 5 x 528 array of adjacent hexagonal lenses. A telecentric lens is used to reimage the lens array at the entrance slits of two echelle spectrographs. Together, these two cover simultaneously the full 390 nm – 1700 nm spectral range of the star being observed. The targeted cost for the installed LFAST telescope and fiber array is $60M.

The BlackGEM array Phase I consists of three wide field, optical telescopes, located at the ESO La Silla Observatory, Chile. Each telescope is of a modified Dall-Kirkham design, using an 0.6m primary mirror and a 110 Mpix STA1600 CCD to give a 2.7 square degrees field-of-view sampled at 0.56"/pixel. Preliminary commissioning data shows performance on-par with design specifications. Data obtained with the BlackGEM prototype MeerLICHT highlights the capabilities of the design with a 5-sigma limiting magnitude of m_AB=22.2 in 300s of integration under dark-sky conditions. Extrapolation to the 1" seeing-conditions expected at La Silla shows that the main goal of BlackGEM to probe down to m_AB=23 in 300s can be met. The project suffered a 2-year COVID-19 delay. Commissioning of the array has currently been resumed and science operations are expected to start in Q3/Q4 of 2022. The science programs include the follow-up of gravitational wave alerts from LIGO/Virgo/KAGRA, a six-filter Southern Sky Survey, a Fast Synoptic Survey on selected fields, a Local Universe intra-night monitoring program and a inter-night single-band monitoring for slower transients.

Telescope arrays allow high-performance wide-field imaging systems to be built more quickly and at lower cost than conventional telescopes. Distributed aperture telescopes (the premier example of which is the Dragonfly Telephoto Array) are a special type of array in which all telescopes point at roughly the same position in the sky. In this configuration the array performs like a large and optically very fast single telescope with unusually good control over systematic errors. In a few key areas, such as low surface brightness imaging over wide fields of view, distributed aperture telescopes outperform conventional survey telescopes by a wide margin. In these Proceedings we outline the rationale for distributed aperture telescopes, and highlight the strengths and weaknesses of the concept. Areas of observational parameter space in which the design excels are identified. These correspond to areas of astrophysics that are both relatively unexplored and which have unusually strong breakthrough potential.

The opportunity given with cubesats opens new scenarios in the field of astronomy, due to (among the other advantages) the relatively low budget and the replicability features of such devices. This push the research efforts towards the miniaturization and compactness of the traditional optical devices and layouts. The possibility of having small telescopes in operation without the atmospheric disturbances allows newer possibilities for astronomical targets. In this paper, we will describe the coupling of newer astrometric techniques with specific optical layout in order to reach the maximum precision and reliability. We propose and describe a simple acquisition system with a multiple field of view (i.e. 4), to verify and prove the robustness of the astrometric techniques. In addition we study the use of a disperser element, in order to have fast and multiple spectra of the selected target.

The Gravitational-wave Optical Transient Observer (GOTO) is a wide-field telescope project focused on detecting optical counterparts to gravitational-wave sources. Each GOTO robotic mount holds eight 40 cm telescopes, giving an overall field of view of 40 square degrees. As of 2022 the first two GOTO mounts have been commissioned at the Roque de los Muchachos Observatory on La Palma, Canary Islands, and construction of the second node with two additional 8-telescope mounts has begin at Siding Spring Observatory in New South Wales, Australia. Once fully operational each GOTO mount will be networked to form a robotic, multi-site observatory, which will survey the entire visible sky every two nights and enable rapid follow-up detections of transient sources.

The New Robotic Telescope will be a fully autonomous, rapid reaction, primarily spectroscopic facility for the classification of astronomical transients. The 4.18m diameter primary mirror is to be composed of 18 hexagonal mirror segments, arranged with a secondary mirror that feeds the Cassegrain focal stations with an F/10.635 beam. The final telescope design does not follow an established prescription, although both primary and secondary remain hyperbolic. However, the tube length is retained from an earlier F/7.5 RC design and secondary mirror size reduced to minimise obscuration of the primary. The optimisation process involved considering the M2 / fold size trade-off while solving the surfaces for image quality, contrast and wavefront error after speeding up the primary mirror. The final effective focal ratio is then slower to allow for workable tolerances through manufacture, installation and operations. In this presentation the optimisation process, trade-offs, tolerances and final design will be summarised.

The primary mirror of ESO’s Extremely Large Telescope contains 798 hexagonal segments, which are equipped with edge sensors (ES) to measure the relative segment displacement. These ES are used for M1 figure control, i.e. for maintaining the reference shape of the primary mirror. Measuring with nanometric precision in three axes with a large dynamic range of hundreds of microns, the figure loop needs to be frequently calibrated. In this paper we present a combination of simulated case studies of operational scenarios and test results gained with a test setup (M1 Test Facility) comprising seven M1 segments, 21 position actuators, and 24 ES (12 around the inner segment, 12 between the outer segments), running a scaled down version of the figure control loop. The impact of ES uncertainties originating from calibration and linearization errors on the figure control of ELT‘s primary mirror is investigated with the purpose of improving the understanding of the ES performance in the ELT covering their complete lifecycle. The paper starts with a description of the relevant subsystems before comparing performance data of the ES validation models against specification values. Then the figure loop that controls the M1 shape is described as well as the simulation environment, including a FE model of the M1 and an ES model. A brief description of the M1 Test Facility is followed by simulations of operational scenarios to study the interaction of ES uncertainties with M1 figure control. Finally, some test results measured with the figure control of the M1 Test Facility are presented.

Photogrammetry technique is widely used for the initial alignment of main-reflector panels of millimeter/ submillimeter-wave telescopes by analyzing a great number of photos of the reflector at the rest state taken from different angles and distances. In this study, we investigated a possibility that the photogrammetry can be applied for real-time surface measurements which is important to realize active surface controls that improve reflector surface accuracy during scientific observations. The technique is important especially for realizing larger aperture and higher frequency telescopes. We developed a simulator to investigate the accuracy of the surface measurements with photos taken with fixed cameras mounted on the stays of the sub-reflector. As a result, we found that the accuracy of surface measurement is roughly inversely proportional to square-root of the number of fixed cameras, and the calculation time roughly proportional to the product of the numbers of cameras and measurement points. For the case of Nobeyama 45-m telescope, the accuracy of 1 mm (rms) was achieved for 164 surface points by 10 cameras with a calculation time of ∼2 sec by a developed python code using a single-core Xeon processor. In order to improve the accuracy with a minimum number of cameras, more various camera positions (e.g., surrounding the vertex hole of the main reflector and surrounding the main reflector) should be investigated, and their combination should be optimized. Applying high-performing technologies such as multiprocessors and/or GPUs, faster calculation is to be considered.

The implementation of the 4MOST Facility at the ESO Paranal 4-meter VISTA wide-field telescope requires a substantial modification of the telescope. Since the current acquisition and guiding (A&G) and wavefront sensing optical systems (WFS) are embedded in VIRCAM and will be removed with it, replacements had to be provided. Although the A&G and WFS cameras will serve different purposes, they share common requirements. Among the shared requirements, a few are particularly challenging. For example, the environmental conditions the cameras will be exposed to require them to have an IP54 protection and due to their location, they cannot dissipate heat to the ambient air. To ensure optical alignment, the cameras must have very accurate housing and mechanical interfaces. In addition, both have to be integrated into an existing telescope control environment, with all that this entails in terms of service interfaces and protocols that can be used (e.g. GigE Vision), as well as operational requirements that must be met. After considering the specific performance requirements for the A&G cameras, the WFS detectors and the secondary guider sensor, a decision was made to use the same custom designed CCD camera model for all of them. These cameras are provided by Spectral Instruments. In this work we present the requirements for such cameras, their opto-mechanical design and the first results of their verification campaign, both at Spectral Instrument and AIP premises.

Indian astronomers are aiming to build a large 10m class optical-NIR telescope, equipped with state-of art instruments. After exploring many potential design options, we ended up with two mirror Ritchey-Chretien (RC) type design, which provide diffraction limited performance over a sufficiently large field and delivers decent image quality over fairly extended field. The segmented primary mirror is a natural choice for the proposed 10m class telescope. However, unlike monolithic primary mirror, various factors linked with the segmentation plays very critical role to decide the performance of the telescope. In great detail, we have also studied the effect of the segment piston, tip and tilt, clocking, the radius of curvature, the shear, the segment size, inter-segment gap as well as figuring error on the telescope performances. All these studies are conducted using a custom developed generic python-based tool that can be used along with ZEMAX ray-tracing software. In this paper we present the optical design of proposed 10m class telescope as well as our extensive study on segmentation and alignment related effects.

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) aims to improve constraints on the dark energy equation of state through measurements of large-scale structure at high redshift (0.8 < z < 2.5), while serving as a state-of-the-art fast radio burst detector. Bright galactic foregrounds contaminate the 400–800 MHz HIRAX frequency band, so meeting the science goals will require precise instrument characterization. In this paper we describe characterization of the HIRAX antenna, focusing on measurements of the antenna beam and antenna noise temperature. Beam measurements of the current HIRAX antenna design were performed in an anechoic chamber and compared to simulations. We report measurement techniques and results, which find a broad and symmetric antenna beam for ν<650MHz, and elevated cross-polarization levels and beam asymmetries for ν <700MHz. Noise temperature measurements of the HIRAX feeds were performed in a custom apparatus built at Yale. In this system, identical loads, one cryogenic and the other at room temperature, are used to take a differential (Y-factor) measurement from which the noise of the system is inferred. Several measurement sets have been conducted using the system, involving CHIME feeds as well as four of the HIRAX active feeds. These measurements give the first noise temperature measurements of the HIRAX feed, revealing a ∼60K noise temperature (relative to 30K target) with 40K peak-to-peak frequency-dependent features, and provide the first demonstration of feed repeatability. Both findings inform current and future feed designs.

This conference presentation was prepared for the Ground-based and Airborne Telescopes IX conference at SPIE Astronomical Telescopes + Instrumentation, 2022.

The Lowell Discovery Telescope (LDT, formerly known as the DCT) is a 4.3-m telescope designed and constructed for optical and near infrared astronomical observation. We present the evolution over time of LDT’s image quality and ways to improve it, upgrades to the instrument suite, and lessons learned from operating during the pandemic.

This paper presents a study of the as-built design and present-day condition of the reflector optics for a 54-year old, out-of-service telecommunications antenna currently being reconditioned for teaching and research in radio astronomy. Reflector surface shape and relative position were mapped using photogrammetry and laser tracker measurements over a range of elevation angles. It was determined that the 32-meter primary reflector has maintained it's original RMS surface error specification of less than 1.4 mm, with the lowest RMS error of 1.09 mm recorded for the antenna at zenith. Similarly the subreflector and tertiary reflector are still within the manufacturer's specification, presenting measured RMS surface errors of 0.2 mm and 0.5 mm respectively. Measurements of subreflector position as a function of elevation angle show that the reflector is displaced vertically by 5 mm at 60°, and 10 mm at 5°, compared to the zenith position, while horizontal displacement remains below 4mm at all elevations. Subreflector defocus increases from zero at zenith to 0.7 mm negative at 45° before reversing direction and reaching 0.6 mm positive for an elevation of 5°. Photogrammetry results confirmed the use of shaped or modified parabolic and hyperbolic surfaces for the primary and subreflector. Principal elevation-independent Zernike terms obtained for the primary surface fit are primary and secondary spherical aberration, while for the subreflector the presence of significant spherical terms up to sixth order is noted. The results were made available to instrumentation groups working on receiver design for the conversion project.

In large astronomical telescopes, the goal of the Active Optics System (AOS) is to provide correction of the telescope's low order aberrations at a low temporal bandwidth. In Active Optics Systems, the wavefront sensor (WFS) is used for the measurement of the telescope optical aberrations. In this paper, we discuss the measurement ability of the INO340’s Shack-Hartmann WFS. During the altitude motion, the primary mirror is positioned at different angles. Due to the gravity and the high weight of the mirror, the surface of the mirror deforms from its ideal shape. We simulate the deformation of the primary mirror surface in ANSYS at different angles. Then through optical simulation, the angular displacements of Shack-Hartmann WFS’s spots are calculated. Then based on the optical specifications of the telescope, the WFS, the guide star and the environmental conditions, we calculate the noise equivalent angle of the WFS, analytically. Finally, by comparing the angular displacement of Shock- Hartmann spots with the equivalent angle of noise, we analyze the performance of the wavefront sensor in terms of the altitude angle of the mirror, the magnitude of the guide star, and the Fried parameters.

An active optics algorithm is developed for the Iranian National Observatory 3.4 [m] telescope (INO340). The primary mirror (M1) and the secondary mirror (M2) are considered flexible and rigid, respectively. M1-Support consists of 60 active axial actuators (AAC), 32 passive lateral actuators (LAC), three axial hard-points (AHP), and three lateral hardpoints (LHP); and an accurate hexapod supports M2. M1 surface shape and M2 positions are actively controlled using an active optics system (AOS) to reach the best image quality. Correction can be done using either a look-up table in open-loop control or the wavefront error in closed-loop control. This paper presents the algorithm and the strategy of INO340 active optics. In this regard, relevant extracted matrices for the INO340 active optics algorithm are derived. The Shack-Hartmann sensor probes the accumulated aberrations and provides a square matrix as feedback. By decomposing the aberrations into the Zernike polynomials, tip-tilt, defocus, and coma aberrations are eliminated by adjustment of M2 positions and other aberrations are removed by deforming the flexible M1. The effective mechanical modes of M1 are selected based on the AACs’ force amplitude, and root mean square (RMS) of the residual surface. The percentage of residual surface error and set of axial forces are shown for each mechanical mode. As a result, mechanical modes No. 1 to 9 and No. 12 to 16 can be corrected. Finally, the algorithm is used to remove the remained aberration after the polishing process, which shows the residual surface after compensation and the required set of AACs’ force.

The Natural Guide Star Adapter (NGSA), a circular structure that is part of the Extremely Large Telescope (ELT) Pre-Focal Station (PFS) [6], defines with its rotation axis one of the reference coordinate systems of the entire telescope and has a key role in the performance of all the instruments. The PFS NGSA hosts three sensor arms (SA), which are free to move in a roughly annulus area to support to support closing control loops on natural guide stars when the light beam is controlled by the telescope[2]. The actuation of these SA’s causes a deformation of the mechanical structure and consequently uncertainty on the position and orientation of the reference coordinate system. Starting from the Finite Element Analysis (FEA) of the PFS, we develop a model that reconstructs the behavior of the structure for all the possible combinations of SA positions, and we conceive strategies for a robust definition of the reference coordinate system, as described in this paper.

The Thirty Meter Telescope primary mirror consists of 492 1.4 m diameter hexagonal segments. A CGH-assisted interferometric testbed has been developed to quickly and accurately measure surface figure error of the 82 different segment prescriptions. In this paper, technical aspects of the testbed will be described, including interferometer design, techniques to reduce sensitivity to vibration and turbulence, use of CGH phase fiducials for 6 degree-of-freedom alignment of the interferometer to the Test Plate, proximity sensors for segment-to-Test Plate alignment, synthetic extended source technique to mitigate coherent artifacts, characterization of instrument transfer function, and system calibration. A surface figure error map of a "Type 0" full-scale segment will also be presented.

The facility instrument suite at the Southern African Large Telescope (SALT) is being extended into the near-infrared by the arrival of the SALT-NIR spectrograph in 2022. The SALT-NIR is fiber-fed via a set of integral field units that interfaces with the existing Fiber Instrument Feed. Extending the operational wavelength range of SALT from 320 - 900 nm to 320 - 1700 nm requires a number of changes to the physical and optical telescope subsystems and places new demands on its control and pointing software. We present the requirements, design and implementation of these updated systems.

The prototype of KASI-Deep Rolling Imaging Fast-optics Telescope (K-DRIFT) pathfinder is a 300 mm confocal off-axis freeform three-mirror system that has been developed for the detection of extended low surface brightness (LSB; below μV = 28 mag arcsec^-2) structures. Until now, it is still very difficult to observe the LSB features due to systematic errors introduced by natural and instrumental effects. To overcome these, we apply the confocal off-axis telescope design theory that removed linear astigmatism, and each mirror made of Zerodur is set as a freeform surface to remove the residual aberration. Through the design, we can get high-quality images in a wide field of view and minimize sky background fluctuations. The size of the entrance pupil of the telescope is 300 mm and the focal length is 1200 mm. The field of view of the telescope is ~1° × 1° and the size of the focal plane is 22.5 mm × 22.5 mm. We have measured root mean square wavefront errors of the system after integration of the mirrors, flexures, and housing. At off-axis fields, the maximum root mean square wavefront error before the alignment is 260 nm, and decreased to 115 nm after alignment. Alignment-induced astigmatism and coma were almost eliminated through the process. In this paper, we briefly present the integration and alignment process of the K-DRIFT pathfinder and the current status of the project.

This conference presentation was prepared for the Ground-based and Airborne Telescopes IX conference at SPIE Astronomical Telescopes + Instrumentation, 2022.

Three mirror anastigmatic telescope designs offer excellent imaging performance in a compact optical structure. The introduction of a fourth, fold mirror allows straightforward access to the image surface of the telescope at a Nasmyth position where instrumentation can be located and easily exchanged. The design presented here is of a 14-meter diameter primary providing a 1.5 square degree field of view with an f/4 focus to a pupil-centric image surface. Two fused silica lenses serve as an atmospheric dispersion compensator, a third field lens forms a large radius pupil-centric image. The optical design gives polychromatic (360-1800 nm) encircled energy diameters (EED) of greater than 80% within 0.25 arc-second diameters across the full field at Zenith. Excellent monochromatic image performance extends through and redward of the K-band (2320 nm). The flat fold mirror, located at a pupil, could be upgraded to an adaptive mirror for image correction and/or GLAO. Image performance is given. We believe that this design offers a very powerful, versatile, and scientifically viable facility suitable for the next generation of ground-based facilities for fiber spectroscopy (~18,000 probes), multi-slit spectroscopy, IFU spectroscopy, and imaging.

Small-ELF is a 3.5-meter telescope currently in development that will serve as a technology demonstrator for the much larger telescope named ELF (Exo-Life Finder). The ELF is proposed to be built with a minimum effective diameter of 12- meters and is designed to be scalable to a much larger size. The primary objective of the proposed design approach is to radically improve the system’s capabilities for direct imaging of exoplanets while keeping costs well below the current flagship observatories. The basic optical design of Small-ELF consists of an annulus of 15 primary mirror sub-apertures, mounted on an alt-az configuration. As a technology demonstrator, the mechanical design of Small-ELF intends to deliver a versatile and reliable experimental platform to implement and verify several new techniques: the use of a tensegrity-based configuration for a light-weight supporting structure, the use of tensioned ropes to actively adjust the telescope geometry, methods of accommodating sub-apertures of significant weight variations, and methods of controlling and mitigating vibrations associated with light-weighted structures through active and passive damping systems. The design also adopts techniques for efficient precision manufacturing and cost control. The unique optical layout and application of tensegrity produce significant weight and subsequent cost reductions. This technology demonstrator tackles the cost and scalability problem faced by most existing telescopes and intends to open a new chapter in large telescope structural design methodology.

The Research School of Astronomy and Astrophysics at the Australian National University is currently building the Dynamic REd All-sky Monitoring Survey (DREAMS). DREAMS is a 0.5m wide-field near-infrared survey telescope that will be located at Siding Spring Observatory, Australia. DREAMS will utilise Indium Gallium Arsenide (InGaAs) detectors and a 3.71 sq. degree field-of-view to survey the visible sky to M_AB=17.8 in the J-band every 4-7 days. Due to the noise properties of the InGaAs detectors, DREAMS is required to convert a F/6 telescope beam to an F/2 detector beam. Combining this with the wide-field nature of the telescope, DREAMS requires a large number of additional optical and mechanical elements with relatively tight tolerances to meet the performance requirements. This paper discusses the current status of the assembly and alignment of DREAMS, along with the on-going alignment procedures, techniques, and methods used to meet these survey requirements.

The Stratospheric UV Demonstrator of an Imaging Observatory (STUDIO) is a balloon-borne platform designed and built to carry different astronomical instruments or telescopes. It thereby offers an accessible and affordable platform for observations in atmosphere-constrained wavelength ranges. In its current setup, it houses an imaging micro-channel plate (MCP) detector on a 0.5 m aperture telescope. The first flight of this setup is planned during the summer turnaround conditions over Esrange, Sweden, in the 2023 or 2024 season. This mission will act as a demonstrator and technical test for the versatile and scalable astronomical platform as well as for the aforementioned MCP instrument. If successful, it will furthermore allow first scientific studies of variable hot compact stars and flaring M-dwarf stars within the galactic plane. In this paper, we present the design and current status of testing of the STUDIO platform, particularly including environmental tests of the optical elements, on-sky tests of the gondola attitude control system, and simulation results of the image stabilization system. We furthermore describe the planned system tests as part of the flight preparation. As an outlook, we present details on how the platform can be used to fly different instruments or telescopes, including potential flight routes and science opportunities.

On December 2021, a new camera box for two-colour simultaneous visible photometry was successfully installed on the ASTEP telescope at the Concordia station in Antarctica. The new focal box offers increased capabilities for the ASTEP+ project. The opto-mechanical design of the camera was described in a previous paper.1 Here, we focus on the laboratory tests of each of the two cameras, the low-temperature behaviour of the focal box in a thermal chamber, the on-site installation and alignment of the new focal box on the telescope, the measurement of the turbulence in the tube and the operation of the telescope equipped with the new focal box. We also describe the data acquisition and the telescope guiding procedure and provide a first assessment of the performances reached during the first part of the 2022 observation campaign. Observations of the WASP19 field, already observed previously with ASTEP, demonstrates an improvement of the SNR by a factor 1.7, coherent with an increased number of photon by a factor of 3. The throughput of the two cameras is assessed both by calculation of the characteristics of the optics and quantum efficiency of the cameras, and by direct observations on the sky. We find that the ASTEP+ two-colour transmission curves (with a dichroic separating the fluxes at 690nm) are similar to those of GAIA in the blue and red channels, but with a lower transmission in the ASTEP+ red channel leading to a 1.5 magnitude higher B-R value compared to the GAIA B-R value. With this new setting, the ASTEP+ telescope will ensure the follow-up and the characterization of a large number of exoplanetary transits in the coming years in view of the future space missions JWST and Ariel.

The town of Tulancingo de Bravo in the Mexican state of Hidalgo is the site of Mexico’s original satellite earth station. Although unused for satellite communications for over 15 years, the site hosts two 32-meter dishes and over a dozen smaller dishes, ranging from 2 to 11 meters in size, along with a substantial supporting infrastructure. Beginning in 2018 we have led a project to convert one or more of the earth station’s telecommunications antennas into a radio telescope suitable for research-grade astronomical observations. Here we present a brief history and motivation for the conversion project, provide technical details of the upgraded system with emphasis on the receiver, describe our progress to date, and mention plans for the final stages of the conversion.

Vintage 30-m class telecommunications antennas built in the 1960s and 1970s have been converted into radio telescopes in recent years, with especially notable conversions in the United Kingdom, South Africa, Australia, Ghana, and most recently in Mexico. These antennas were designed and built for operation at C-Band, but in some cases the surface conditions are sufficiently good that observations at Ku-Band and possibly at K-Band may prove feasible. As described in [1] an antenna conversion project is underway for the Tulancingo-I telecommunications antenna, located in Tulancingo de Bravo in the Mexican state of Hidalgo. Although the antenna was in active use for several decades, it has been replaced by other communications technologies and has not been used since early in the new millennium. The antenna uses near-field, shaped Cassegrain optics, consisting of a shaped parabolic primary reflector and a shaped hyperbolic sub-reflector. The primary reflector is 32 meters in diameter with a nominal focal length of 9.6 meters. A tertiary reflector redirects the beam along the elevation axis, following the Nasmyth configuration. This paper describes our work to determine the feasibility of using the antenna reflector optics in the 18 – 24 GHz range of the K-Band. Both photogrammetry and laser tracker measurements were used to determine the geometrical relationship between the primary, sub-reflector, and tertiary surfaces. We use these results, reported in [4], along with computer simulations, to explore the potential of the Tulancingo-I antenna for KBand observing.

Several universities and government organizations in Mexico are working to rehabilitate a 32-meter telecommunications antenna for radio astronomy teaching and research. The antenna is an elevation-over-azimuth design employing a central king post, and was constructed in 1968. While it was envisioned that the motors and electronic drives would require upgrading, a key concern was the condition of the existing power transmission systems. The main components include overly complex gearboxes, equally extravagant lubrication systems, and assorted bearings that had sat idle for years, if not decades. This paper takes a close look at the power transmission system in azimuth and elevation on this heritage antenna, and describes the maintenance work that has been carried out in order to allow safe operation.

We present a coordinated campaign of observations to monitor the brightness of the James Webb Space Telescope (JWST) as it travels toward the second Earth-Sun Lagrange point and unfolds using the network of Unistellar digital telescopes. Those observations collected by citizen astronomers across the world allowed us to detect specific phases such as the separation from the booster, glare due to a change of orientation after a maneuver, the unfurling of the sunshield, and deployment of the primary mirror. After deployment of the sunshield on January 6 2022, the 6-h lightcurve has a significant amplitude and shows small variations due to the artificial rotation of the space telescope during commissioning. These variations could be due to the deployment of the primary mirror or some changes in orientation of the space telescope. This work illustrates the power of a worldwide array of small telescopes, operated by citizen astronomers, to conduct large scientific campaigns over a long timeframe. In the future, our network and others will continue to monitor JWST to detect potential degradations to the space environment by comparing the evolution of the lightcurve.

MegaMapper is a 6.5m Magellan-like telescope fitted with a wide-field-corrector (WFC) and atmospheric-dispersion-corrector (ADC) that delivers a 3° diameter corrected field-of-view. The telescope’s focal surface is populated by ∼25,000 robotic fiber-positioners feeding a cluster of 36 DESI-like medium resolution spectrographs. We present the facility concept for MegaMapper including: conceptual optical and opto-mechanical designs for the telescope and WFC/ADC that deliver ≲ 0.4” image quality over the full FOV for zenith distances ≤ 50°; the development of a new and modular robotic fiber-positioner focal plane design that can populate the focal surface at high densities (6.2 mm pitch or ∼1 per arcmin²); and concepts for hosting the MegaMapper spectrograph cluster under environmentally controlled conditions inside the telescope enclosure. Building on existing and proven designs and technologies, MegaMapper aims to minimize the project’s technical risk and cost while delivering a competitive next-generation massively multiplexed spectroscopic facility. MegaMapper will lead the study of inflation, dark energy, dark matter, and time-domain astronomy over the next decades by carrying out wide-field cosmological galaxy-redshift surveys, massive spectroscopic surveys of stars in the Milky Way halo and satellites, and by providing a spectroscopic follow-up counterpart to wide field imaging facilities like the Vera C. Rubin Observatory and the Nancy Grace Roman space telescope.

We present a description of A dual-Beam polarimetric Robotic Aperture for the Sun (ABORAS), to serve as a Solar input with a dedicated Stokes V polarimeter for the HARPS3 high-resolution spectrograph. ABORAS has three main science drivers: trying to understand the physics behind stellar variability, tracking the long term stability of HARPS3, and serve as a benchmark for Earth-sized exoplanet detection with HARPS3 by injecting an Earth RV signal into the data. By design, ABORAS will (together with the HARPS3 instrument) be able to measure 10cm/s variations in RV of the integrated Solar disk and detect integrated magnetic field levels at sub 1 Gauss level through circularly polarized light.

The concept for the Large Fiber Array Spectroscopic Telescope (LFAST) (Angel et al, these proceedings) is to collect the light from a target object using thousands of individual, small, low-cost telescopes, and bring it via optical fibers to a high resolution (R=150,000) spectrograph. Each mirror has a prime focus corrector feeding a 17 micron fiber at f/3.5, subtending a 1.3 arcsec diameter on the sky. Each LFAST unit has 20 separate 30 inch telescopes carried by a single alt-az mount to provide collecting area equivalent to a 3.5 m traditional aperture. Each mirror has a 4-element corrector provides subarcsecond imaging over an 8 arcmin field. The field is reflected by a mirror puck (which contains the receiving fiber) through relay optics to a CMOS camera for rapid guiding and wavefront measurement. The corrector optical design incorporates elements of common crown and flint glass to obtain achromaticity over a broad wavelength range of 380 nm – 1700 nm. Large, slow lateral translations of the final 4th element correlated with primary mirror tilt correct for atmospheric dispersion, and small, rapid lateral translations correct for image motion without significantly disrupting atmospheric dispersion correction. We have explored both aspherical and spherical primary mirror designs and have chosen spherical, based on impacts to unit telescope cost.

This conference presentation was prepared for the Ground-based and Airborne Telescopes IX conference at SPIE Astronomical Telescopes + Instrumentation, 2022.

Polarization is a fundamental property of the light and is very useful to measure the magnetic field vector of the various features that can be observed in the solar atmosphere. Ideally, a solar telescope should not introduce any polarization to the incoming light that could mask the one coming from the Sun. However, some instrumental polarization is always introduced by the different optical components, because it depends on the coatings used, as well as on the incidence angle and wavelength. The calibration of these instrumental polarization is specially tedious and complicated if it varies with time (as is the usual case for telescopes, when the pointing changes in elevation and azimuth). The European Solar Telescope (EST) has been designed to minimize this spurious temporally-varying instrumental polarization. A numerical model based on geometrical ray tracing has been developed in combination with Zemax Optic Studio (ZOS), in order to estimate the Mueller matrices of the moving optical elements of the telescope. The Mueller matrices have been calculated as a function of wavelength and for different field of view (FoV) positions and telescope (azimuth and elevation) pointing, using generics coatings (aluminium for the primary mirror and silver for the rest of the mirrors). This paper shows the analysis and results of the Mueller matrices that have been obtained, leading to the confirmation that the telescope has an excellent polarimetric performance for all wavelengths, FoVs and pointing directions.

Almost two decades ago, astronomers were looking for the next really big telescope. The so-called Overwhelmingly Large Telescope (OWL) rendered a primary-mirror diameter of 100 m. The OWL was a desktop concept study initiated by the European Southern Observatory (ESO) in 2001 and completed in 2005. SCHOTT participated in the study as manufacturer of the low-thermal-expansion glass ceramic ZERODUR which successfully had been provided to the Very Large Telescope a few years earlier. However, the VLT blanks, with a diameter of 8.2 m, manifested the size limit of monolithic mirror substrate production. Larger-sized primary telescope mirrors were proposed by combining hexagon segments to complete the large mirror optical surface. This approach had been established in the twin KECK telescopes, combining 36 hexagonal segments to form a primary mirror of 10 m in diameter. The OWL study, incorporating the segmented-mirror approach, was targeting at the next level of telescope size: the Extremely Large Telescopes. Three different options on segment size were investigated in the study, yielding segment counts between 1500 and 5000 combined for primary and secondary mirror together. SCHOTT evaluated the technical feasibility of product specification and the process technology required to yield segments at a production frequency large enough to finish the scope of work within a reasonable timescale and budget. Today’s market demands for industrial applications, as well as large telescope projects, triggered SCHOTT to increase capacity and capability via investments enhancing ZERODUR production along the entire production sequence. This contribution comments on the ZERODUR production capacity driven by industrial applications with regard to design options of the OWL study. Today’s installed capacity will enable SCHOTT to deliver the OWL mirror substrates within a timeline comparable to the ELT M1 segment-blank contract. Further capacity expansion required by continuously increase industrial demand will enable even faster timelines.

Starbugs are self-motile fibre optic positioning robots developed by AAO-MQ. The MANIFEST (MANy Instrument FibrE SysTem) is a facility class Instrument which will operate up to 900 Starbugs on the Giant Magellan Telescope (GMT). The FOBOS (Fibre-Optic Broadband Optical Spectrograph) Fibre Positioner is a facility class Instrument which will operate up to 1800 Starbugs on the Keck Telescope. The Starbugs deliver an optical payload to the location of an astronomical object on the telescope focal plane. The Starbugs are made from a pair of concentric Piezoceramic Tubes (PZT), and a high-voltage waveform is applied to the PZT to create an actuation. Staging of the waveform creates successive microsteps, on the order of 3-20 μm each, at a driven frequency of 100Hz. The Starbugs are adhered to the Glass Field Plate (GFP) using an ancillary vacuum system. The Starbugs have an airtight vacuum sealing component between the PZT and the GFP, called Slippers, which serve as a traction surface against the polished GFP. The Slippers set the science fibre focus offset, which has functional requirements that trace to Observatory level requirements. The Slipper components are subject to non-zero centred fully reversed fatigue loading due to the combined load case of the vacuum induced compression and the shear load of the PZT actuation as the Starbug completes the step. The contact interface between the Slipper and the GFP is subject to surface fatigue and functions as a sacrificial wear surface to ensure the longevity of both the PZT and the optical payload. The fatigue life behaviour of the Slipper, with particular interest on this interface, was defined using industry standard methods and informed the trade study to select the appropriate material for the Slippers to survive a nominal period on-sky (fatigue life). The trade study terms were vacuum sealing ability as a function of mechanical hardness versus fatigue life (108 cycles). Several suitable materials were identified and will be physically prototyped, with results reported in this manuscript.

Starbugs are self-motile fibre optic positioning robots developed by AAO-MQ. MANIFEST (MANy Instrument FibrE SysTem) is a facility class Instrument which will operate up to 900 Starbugs on the Giant Magellan Telescope (GMT). The FOBOS (Fibre-Optic Broadband Optical Spectrograph) Fibre Positioner is a facility class Instrument which will operate up to 1800 Starbugs on the Keck Telescope. Starbugs deliver an optical payload to the location of an astronomical object on the telescope focal plane. The Starbugs are made from a pair of concentric Piezoceramic Tubes (PZT), and a high-voltage waveform is applied to the PZT to create an actuation. Staging of the waveform creates successive microsteps, on the order of 3-20 μm each, at a driven frequency of 100Hz. The Starbugs are adhered to the Glass Field Plate (GFP) using an ancillary vacuum system, which must provide sufficient adhesion force to maintain the Starbug GFP position in the high-altitude environmental conditions at Mauna Kea (MKO) and Las Campanas Observatory (LCO) sites. The minimum vacuum adhesion requirements to achieve Starbug GFP position were used to specify the vacuum pump flow rate and operational head pressure. The vacuum adhesion requirements were experimentally obtained using the Starbug Test Stand, located in Sydney, Australia. The Starbugs Test Stand vacuum adhesion requirements were parametised for dry air mass flow rate and head pressure, and then corrected for the 95th percentile environmental conditions at MKO and LCO. The vacuum system numerical model was verified by the TAIPAN instrument. When corrected for ambient atmospheric conditions at the UK Schmidt Telescope (Siding Spring Observatory, Australia), the numerical model could predict the steady state vacuum pump speed with 1.29% variation from the measured vacuum pump speed recorded by the TAIPAN Instrument control software. This capability of the numerical model will be used for real-time condition monitoring of the Starbugs Instruments.

The Prefocal Stations (PFS-A and PFS-B) of the Extremely Large Telescope (ELT) are the last component in the telescope’s light path, right before the light is delivered to the science instruments at the telescope focus. Following the Final Design Review passed in 2020 the efforts were focused on the preparation of the manufacturing documentation and on launching the manufacturing of the Prefocal Stations. The fabrication of the equipment was divided into seven main manufacturing lots based on the nature of the parts with the main aim of minimizing the project risk and optimize the schedule. The ESO's approval of each manufacturing documentation package was obtained by means of individual Manufacturing Readiness Reviews (MRR). The manufacturing of the parts and procurement of the long lead time COTS was launched in 2021 and is coming to an end. The Assembly, Integration and Verification (AIV) activities begin with the end of the manufacturing. The AIV strategy follows the well-established “V-model” methodology. The initial phases are focused on subsystem level and progressively evolves until the work is concluded with the fully assembled, integrated and verified Prefocal Stations in the ELT (Chile). Throughout this process, the fully integrated Prefocal Stations will be completely tested in the factory acceptance test (FAT) campaign in Europe. This paper summarizes the manufacturing status and describes the way Prefocal Stations AIV is planned to be carried out.

The New Robotic Telescope (NRT) conceptual design has been developed to include an autonomous multi-instrument adaptor at the Cassegrain focal station. The focal station assembly is to consist of a field rotator to compensate the earth rotation, cable wrap, instrument adaptor, support structure, and a fold mirror mechanism to bring the telescope optical beam to the instruments. The design supports the use of multiple instruments around the Acquisition and Guidance box (A&G box) a single instrument port is located at the bottom of the box at the straight through port. The A&G box also includes an autoguider which will be mounted at the side of the box and fed a portion of the optical beam via a small pick off mirror. It will use a field outside that of usable the science field, and has been designed to comprise of off-the-shelf lenses, camera system and lens tubes to minimise cost. The field of view is large enough to conduct ‘blind autoguiding’ at an accuracy of 0.2” with the 4m class telescope. The entire assembly will then be mounted to the M1 cell, forming the bottom part of the telescope tube held between the telescope mount forks. The focal station assembly design will be summarised in this paper.

The Filter Exchange System (FES) of the Legacy Survey of Space and Time camera (LSSTCam) for the Vera C. Rubin Observatory has been integrated into the camera assembly before shipping to Chile. It holds five 75-cm filters weighing 25.5 to 38 kg. The main requirement for the FES is to perform each exchange in under 90s, with 100-μm positioning in the focal plane, while operating within the envelope of the camera body. The FES is split into three motorized subsystems: the Carousel stores the filters and rotates the selected filter to the standby position, the Autochanger moves the filter between the standby position and the focal plane, and the Loader can be mounted on the camera body to swap filters in and out during daytime, allowing the use of the full 6-filter set of LSSTCam. The locking mechanisms are also motorized, and their designs and qualifications account for seisms up to magnitude 7. Additional design constraints come from the temperature range at the Observatory and the cleanliness requirements for the filters and lenses. Programmable Logic Controllers enforce the safety equations of the system, and the control of the FES has been integrated into the overall Camera Control System software. After assembly of a full-scale prototype, the FES has been assembled and tested in France on a test-stand simulating telescope attitude, then integrated into the camera body at SLAC National Accelerator Laboratory. It meets its required performances, including an average exchange time of 83s.

This contribution describes the laboratory characterization and calibration of the NectarCAM before deployment. NectarCAM is a camera developed to equip the medium-sized telescopes (MST) of the Cherenkov Telescope Array Observatory (CTAO). It is designed to detect Cherenkov light in the central