The prototype of Gamma-ray Cherenkov Telescope (pGCT) is an Imaging Atmospheric Cherenkov Telescope (IACT) developed to detect Very High Energy (VHE) from various cosmic sources emitting gamma rays. It is based on a Schwarzschild-Couder (SC) dual-mirror configuration resulting in a compact telescope and an optimised PSF over a wide field of view. Moreover, some innovative features were implemented with the aim to ease and to fasten the assembly, integration, test (AIT) and maintenance activities. Both mirrors, the 4-meter tessellated primary mirror and the secondary mirror, are aspherical lightweight mirrors made by a subtractive manufacturing method. This process was improved several times leading to enhanced optical performance of the telescope in terms of Point Spread Function and improved signal to noise ratio. This paper deals with the optomechanical design of the pGCT and its latest measured performance. After a brief overview of the mechanical design of the telescope, the updated manufacturing process of the new generation mirrors and the optical performance of pGCT are given. Finally, recent operational performance of the telescope is given.

MOSAIC is the Multi-Object Spectrograph (MOS) for the 39m Extremely Large Telescope (ELT) of the European Southern Observatory (ESO), with unique capabilities in terms of multiplex, wavelength coverage and spectral resolution. It is a versatile multi-object spectrograph working in both the Visible and NIR domains, designed to cover the largest possible area (similar to 40 arcmin(2)) on the focal plane, and optimized to achieve the best possible signal-to-noise ratio on the faintest sources, from stars in our Galaxy to galaxies at the epoch of the reionization. In this paper we describe the main characteristics of the instrument, including its expected performance in the different observing modes. The status of the project will be briefly presented, together with the positioning of the instrument in the landscape of the ELT instrumentation. We also review the main expected scientific contributions of MOSAIC, focusing on the synergies between this instrument and other major ground-based and space facilities.

The Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument is the next generation multi-object spectrograph for the Very Large Telescope (VLT). The instrument combines the high multiplexing capability offered by 1000 optical fibres deployed by individual robotic positioners with a novel spectrograph able to provide both low- and high-resolution spectroscopy simultaneously across the wavelength range 0.64μm - 1.8μm. Powered by the collecting area of the 8-m VLT, MOONS will provide the astronomical community with a world-leading facility able to serve a wide range of Galactic, Extragalactic and Cosmological studies. This paper provides an updated overview of the instrument and its construction progress, reporting on the ongoing integration phase.

MOONS (Multi-Object Optical and near-Infrared Spectrograph) will be a fibre-fed, optical to near-infrared multi-object spectrograph designed to utilise the full 25 arcminute diameter field-of-view of the Very Large Telescope and provide a multiplex capability of over 1000 fibres. The baseline design includes a single focal plate and fibre positioning subsystem, consisting of 1000 small dual radial arm modules, which are used to place each fibre, in the exact x, y and z position in the telescope focal plane. Each fibre has a microlens to focus the beam into the fibre at a relatively fast focal ratio of F/3.65 to reduce the Focal Ratio Degradation (FRD). The light is then fed through the fibres to two identical, cryogenic triple arm spectrographs, mounted on the instrument platform. In each spectrograph, the light from 512 fibres, arranged in a pseudo-slit, is split by dichroic filters into three channels (RI, YJ and H) and dispersed on to 4k x 4k detectors in each channel. At the slit there are 32 slitlets, each containing 16 fibres, which feed the collimator. They have been co-aligned to minimise the tilt.

MOSAIC is the Multi-Object Spectrograph for the ESO Extremely Large Telescope, approved to enter Phase B beginning 2022. It is conceived as a multi- purpose instrument covering the Visible and Near Infrared bandwidth (0.45 –1.8 μm) with two observing modes: spatially resolved spectroscopy with 8 integral field units; and the simultaneous observation of 200 objects in the VIS and NIR in unresolved spectroscopy. We present an overview of the main MOSAIC science drivers and the actual baseline design for the instrument. The prototyping and developments undertaken by the consortium to evaluate the feasibility of the project are also discussed.

The Heterodyne Receiver for Origins (HERO) is the first detailed study of a heterodyne focal plane array receiver for space applications. HERO gives the Origins Space Telescope the capability to observe at very high spectral resolution (R = 10(7)) over an unprecedentedly large far-infrared (FIR) wavelengths range (111 to 617 mu m) with high sensitivity, with simultaneous dual polarization and dual-frequency band operation. The design is based on prior successful heterodyne receivers, such as Heterodyne Instrument for the Far-Infrared/Herschel, but surpasses it by one to two orders of magnitude by exploiting the latest technological developments. Innovative components are used to keep the required satellite resources low and thus allowing for the first time a convincing design of a large format heterodyne array receiver for space. HERO on Origins is a unique tool to explore the FIR universe and extends the enormous potential of submillimeter astronomical spectroscopy into new areas of astronomical research. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.

MOONS is the new Multi-Object Optical and Near-infrared Spectrograph currently under construction for the Very Large Telescope (VLT) at ESO. This remarkable instrument combines, for the first time, the collecting power of an 8-m telescope, 1000 fibres with individual robotic positioners, and both low- and high-resolution simultaneous spectral coverage across the 0.64–1.8 μm wavelength range. This facility will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic, extragalactic and cosmological studies. Construction is now proceeding full steam ahead and this overview article presents some of the science goals and the technical description of the MOONS instrument. More detailed information on the MOONS surveys is provided in the other dedicated articles in this Messenger issue.

The WEAVE instrument nearing completion for the William Herschel Telescope is a fiber-fed spectrograph operating in three different modes. Two comprise deployable fibers at the prime focus for point-like objects and small integral field units (IFU), the third is a large IFU placed at the center of the field. Three distinct fiber systems support these modes and route the photons to the spectrograph located on the Nasmyth platform 33m away: the first features 960+940 fibers and is duplicated to allow configuring the fibers on one plate while observation is carried out on the other, the second has 20 hexagonal IFUs featuring 37 fibers each, the third is a large array of 609 fibers with twice the former’s diameter. The large number of fibers and the diversity of their instantiation have made procurement of the parts and assembly of the custom cables a challenge. They involve project partners in France, the UK and the Netherlands and industrial partners in France, Canada, the USA and China to combine know-how and compress the schedule by parallelizing assembly of the cables. Besides the complex management that this induces, it has called for revising the fibers’ handling to relax tolerances and for a rigorous assessment of the conformity of the products. This paper tells the story of the making of the fiber links, presents the overall organization of the procurement and assembly chains together with the inspection and testing allowing for assessing the conformance of the hardware delivered.

The Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument is the next generation multi-object spectrograph for the VLT. This powerful instrument will combine for the first time: the large collecting power of the VLT with a high multipexing capability offered by 1000 optical fibres moved with individual robotic positioners and a novel, very fast spectrograph able to provide both low- and high-resolution spectroscopy simultaneously across the wavelength range 0.64 mu m - 1.8 mu m. Such a facility will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic, Extragalactic and Cosmological studies. The final assembly, integration and verification phase of the instrument is now about to start performance testing.

After completion of its final-design review last year, it is full steam ahead for the construction of the MOONS instrument - the next generation multi-object spectrograph for the VLT. This remarkable instrument will combine for the first time: the 8 m collecting power of the VLT, 1000 optical fibres with individual robotic positioners and both medium- and high-resolution spectral coverage acreoss the wavelength range 0.65μm - 1.8 μm. Such a facility will allow a veritable host of Galactic, Extragalactic and Cosmological questions to be addressed. In this paper we will report on the current status of the instrument, details of the early testing of key components and the major milestones towards its delivery to the telescope.

The Origins Space Telescope (OST) is a NASA study for a large satellite mission to be submitted to the 2020 Decadal Review. The proposed satellite has a fleet of instruments including the HEterodyne Receivers for OST (HERO). HERO is designed around the quest to follow the trail of water from the ISM to disks around protostars and planets. HERO will perform high-spectral resolution measurements with 2x9 pixel focal plane arrays at any frequency between 468GHz to 2,700GHz (617 to 111 mu m). HERO builds on the successful Herschel/HIFI heritage, as well as recent technological innovations, allowing it to surpass any prior heterodyne instrument in terms of sensitivity and spectral coverage.

List of contributions from the Cherenkov Telescope Array Consortium presented at the 35th International Cosmic Ray Conference, July 12-20 2017, Busan, Korea.

The Gamma-ray Cherenkov Telescope (GCT) is an innovative dual-mirror solution proposed for the Small-Size Telescopes of the future Cherenkov Telescope Array (CTA), capable of imaging the showers induced by cosmic gamma-rays with energies from a few TeV up to 300 TeV. The Schwarzschild-Couder design on which the telescope optical design is based makes possible the construction of a fast telescope (primary mirror diameter 4 m, focal length 2.3 m) with a plate scale well matched to compact photosensors, such as multi-anode or silicon photomultipliers (MAPMs and SiPMs, respectively) for the camera. The prototype GCT on Meudon’s site of the Observatoire de Paris saw first Cherenkov light from air showers in November 2015, using an MAPM-based camera. In this contribution, we firstly report on the prototype GCT telescope’s performance during its assessment phase. Secondly, we present the telescope configuration during a campaign of observations held in spring 2017. Finally, we describe studies of the telescope structure, such as the pointing and tracking performance.

Current day astronomy projects continue to increase in size and are increasingly becoming more complex, regardless of the wavelength domain, while risks in terms of safety, cost and operability have to be reduced to ensure an affordable total cost of ownership. All of these drivers have to be considered carefully during the development process of an astronomy project at the same time as there is a big drive to shorten the development life-cycle. From the systems engineering point of view, this evolution is a significant challenge. Big instruments imply management of interfaces within large consortia and dealing with tight design phase schedules which necessitate efficient and rapid interactions between all the stakeholders to firstly ensure that the system is defined correctly and secondly that the designs will meet all the requirements. It is essential that team members respond quickly such that the time available for the design team is maximised.In this context, performance prediction tools can be very helpful during the concept phase of a project to help selecting the best design solution. In the first section of this paper we present the development of such a prediction tool that can be used by the system engineer to determine the overall performance of the system and to evaluate the impact on the science based on the proposed design. This tool can also be used in "what-if" design analysis to assess the impact on the overall performance of the system based on the simulated numbers calculated by the automated system performance prediction tool. Having such a tool available from the beginning of a project can allow firstly for a faster turn-around between the design engineers and the systems engineer and secondly, between the systems engineer and the instrument scientist. Following the first section we described the process for constructing a performance estimator tool, followed by describing three projects in which such a tool has been utilised to illustrate how such a tool have been used in astronomy projects. The three use-cases are; EAGLE, one of the European Extremely Large Telescope (E-ELT) Multi-Object Spectrograph (MOS) instruments that was studied from 2007 to 2009, the Multi-Object Optical and Near-Infrared Spectrograph (MOONS) for the European Southern Observatory's Very Large Telescope (VLT), currently under development and SST-GATE.

WEAVE is a new wide-field spectroscopy facility proposed for the prime focus of the 4.2m William Herschel Telescope. The facility comprises a new 2-degree field of view prime focus corrector with a 1000-multiplex fibre positioner, a small number of individually deployable integral field units, and a large single integral field unit. The IFUs (Integral Field Units) and the MOS (Multi Object Spectrograph) fibres can be used to feed a dual-beam spectrograph that will provide full coverage of the majority of the visible spectrum in a single exposure at a spectral resolution of similar to 5000 or modest wavelength coverage in both arms at a resolution similar to 20000. The instrument is expected to be on-sky by the first quarter of 2018 to provide spectroscopic sampling of the fainter end of the Gaia astrometric catalogue, chemical labeling of stars to V similar to 17, and dedicated follow up of substantial numbers of sources from the medium deep LOFAR surveys.After a brief description of the Fibre System, we describe the fibre test bench, its calibration, and some test results. We have to verify 1920 fibres from the MOS bundles and 740 fibres from the mini-IFU bundles with the test bench. In particular, we present the Focal Ratio Degradation of a cable.

The Gamma-ray Cherenkov Telescope (GCT) is a small-sized telescope (SST) that represents one of three novel designs that are based on Schwarzschild-Couder optics and are proposed for use within the Cherenkov Telescope Array (CTA). The GAmma-ray Telescope Elements (GATE) program has led an effort to build a prototype of the GCT at the Paris Observatory in Meudon, France. The mechanical structure of the prototype, known as the SST-GATE prototype telescope, is now complete along with the successful installation of the camera. We present the results of extensive simulation work to determine the optical performance of the SST-GATE prototype telescope. Using the ROBAST software and assuming an ideal optical system, we find the radius of the encircled point spread function (theta(80)) of the SST-GATE to be similar to 1.3 degrees arcmin (similar to 0.02 degrees) for an on-axis (theta(field) = 0 degrees) observation and similar to 3.6 arcmin (similar to 0.06 degrees) for an observation at the edge of the field of view (theta(field) = 4.4 degrees). In addition, this research highlights the shadowing that results from the stopping of light rays by various telescope components such as the support masts and trusses. It is shown that for on-axis observations the effective collection area decreases by approximately 1 m(2) as a result of shadowing components other than the secondary mirror. This is a similar loss (similar to 11%) to that seen with the current generation of conventional Davies-Cotton (DC) Cherenkov telescopes. An extensive random tolerance analysis was also performed and it was found that certain parameters, especially the secondary mirror z-position and the tip and tilt rotations of the mirrors, are critical in order to contain theta(80) within the pixel limit radius for all field angles. In addition, we have studied the impact upon the optical performance of introducing a hole in the center of the secondary mirror for use with pointing and alignment instruments. We find that a small circular area (radius < 150 mm) at the center of the secondary mirror can be used for instrumentation without any significant impact upon optical performance. Finally, we studied the impact of reducing the size of the primary mirror for the prototype telescope and found that this comes at the cost of poorer image quality and light collection efficiency for all field angles, but at a significant cost saving for a one-off prototype. (C) 2016 Elsevier B.V. All rights reserved.

The Cherenkov Telescope Array (CTA) consortium aims to create the next generation Very High Energy gamma-ray observatory. It will be devoted to the observation of gamma rays over a wide band of energy, from 20 GeV to 300 TeV. Three different classes, Large, Medium and Small Size Telescopes, are foreseen to cover the low, intermediate and high energy regions, respectively. The energy range of the Small Size Telescopes (SSTs) extends from 1 TeV to 300 TeV. Among them, the Gamma-ray Cherenkov Telescope (GCT), a telescope based on a Schwarzschild-Couder dual-mirror optical design, is one of the prototypes under construction proposed for the SST sub-array of CTA. This contribution focuses on the mechanical structure of GCT. It reports on last progress on the mechanical design and discusses this in the context of CTA specifications. Recent advances in the assembly and installation of the opto-mechanical prototype of GCT on the French site of the Paris Observatory are also described.

The Observatoire de Paris is involved in the Cherenkov Telescope Array (CTA) project by designing and constructing on the site of Meudon a Small Size Telescope prototype, named SST-GATE, in collaboration with the CHEC team (Compact High Energy Camera) which is providing the camera. The telescope structure is based on the Schwarzschild- Couder optical design which has never been adopted before in the design of a ground-based telescope. This concept allows a larger field of view and cheaper and smaller telescope and camera design with improved performance compared to the Davies-Cotton design traditionally used in very high energy gamma-ray telescopes. The SST-GATE telescope has been designed with the prime objectives of being light, versatile and simple to assemble with a minimal maintenance cost. This papers aims at reviewing the SST-GATE telescope structure from mechanics to optics along with the control command architecture; several innovative developments implemented within the design are discussed. Updates of the project status and perspectives are made.