KEYWORDS: Telescopes, Spectrographs, Calibration, Fabry Perot interferometers, Observatories, Control systems, Sensors, Control software, Equipment, Domes
MARVEL is a new facility at the Roque de los Muchachos Observatory (La Palma) which comprises an array of four 0.8m telescopes, each feeding via fibre link into a single high-resolution spectrograph. The facility will provide dedicated target vetting and follow-up capability to support large exoplanet surveys through radial velocity measurements with precision at the metre-per-second level. The observatory site, with four new domes and a standalone stabilised spectrograph building, will soon be complete and ready for hardware installation and commissioning. Here we present an overview of the facility and a status update on several component subsystems: the telescope hardware, control software, and scheduling software; the fibre injection units at each telescope; the optical and mechanical design and tolerances of the spectrograph and vacuum vessel; the calibration system hardware and calibration strategies; and the progress in development of the instrument’s data reduction pipeline.
We present a design for a wide-field spectroscopic telescope. The only large powered mirror is spherical, the resulting spherical aberration is corrected for each target separately, giving exceptional image quality. The telescope is a transit design, but still allows all-sky coverage. Three simultaneous modes are proposed: (a) natural seeing multi-object spectroscopy with 12m aperture over 3° FoV with ~25,000 targets; (b) multi-object AO with 12m aperture over 3° FoV with ~100 AO-corrected Integral Field Units each with 4” FoV; (c) ground layer AO-corrected integral field spectroscopy with 15m aperture and 13' FoV. Such a telescope would be uniquely powerful for large-area follow-up of imaging surveys; in each mode, the AOmega and survey speed exceed all existing facilities combined. The expected cost of this design is relatively modest, much closer to $500M than $1000M.
The Gemini North Adaptive Optics (GNAO) facility is the upcoming Adaptive Optics (AO) facility for Gemini North providing a state-of-the-art AO system for surveys and time domain science in the era of James Webb Space Telescope (JWST) and Rubin operations. GNAO will be optimized to feed the Gemini Infrared Multi Object Spectrograph (GIRMOS).
The GNAO project includes the development of a new laser guide star facility which will consist of four side launched laser beams supporting the two primary AO modes of GNAO: a wide-field mode providing an improved image quality over natural seeing for a 2-arcminute circular field-of-view using Ground Layer AO (GLAO) and a narrow-field mode providing near diffraction-limited performance over a 20 × 20 arcsecond square field-of-view using Laser Tomography AO (LTAO).
After a competitive phase A study among three teams for the conceptual design of the AO bench, one team has been selected to complete the design, build and commissioning it at the telescope. We will be presenting the overall GNAO facility design, including specifics related to the AO bench and its architectural design. We will provide updates on all subsystems of the facility.
MAVIS passed the Preliminary Design Review in March 2023 and kick started its phase C early June. We are aiming at a Final Design Review in December 2024. I will report on the state of MAVIS design, as well as general project updates, schedule, procurement, risks. We are working on early procurement (Long Lead Item review held on October 2023) as well as on a number of prototype activities I will report on.
AOB is an Adaptive Optics (AO) facility currently designed to feed the Gemini infrared Multi Object Spectrograph (GIRMOS) on the GEMINI North 8m class telescope located in Hawaii. This AO system will be made of two AO modes. A laser tomography AO (LTAO) mode using 4 LGS (laser guide stars) and [1-3] NGS (natural guide stars) for high performance over a narrow field of view (a few arcsec). The LTAO reconstruction will benefit from the most recent developments in the field, such as the super-resolution concept for the multi-LGS tomographic system, the calibration and optimization of the system on the sky, etc. The system will also operate in Ground Layer Adaptive Optics (GLAO) mode providing a robust solution for homogeneous partial AO correction over a wide 2’ FOV. This last mode will also be used as a first step of a MOAO (Multi-object adaptive optics) mode integrated in the GIRMOS instrument. Both GLAO and LTAO modes are optimized to provide the best possible sky coverage, up to 60% at the North Galactic Pole. Finally, the project has been designed from day one as a fast-track, cost effective project, aiming to provide a first scientific light on the telescope by 2028 at the latest, with a good balance of innovative and creative concepts combined with standard and well controlled components and solutions. In this paper, we will present the innovative concepts, design and performance analysis of the two AO modes (LTAO and GLAO) of the AOB project.
MAVIS, the Multi-Conjugate Adaptive Optics Assisted Visible Imager and Spectrograph, is the world’s first facility-grade visible MCAO instrument, currently in the final design phase for ESO’s VLT. The AO system will feed an imager and an integral field spectrograph, with 50% sky coverage at the Galactic pole. MAVIS has unique angular resolution and sensitivity at visible wavelengths, and is highly complementary to both JWST and ELTs. We describe both instruments in detail and the broad range of science cases enabled by them. The imager will be diffraction-limited in V, with 7.36 mas per pixel covering a 30” FOV. A set of at least 5 broad-band, 3 medium-band and 16 narrow-band filters will provide imaging from u to z. The spectrograph uses an advanced image slicer with a selectable spatial sampling of 25 or 50 mas to provide integral field spectroscopy over a FOV of 2.5′′ × 3.6′′, or 5′′ × 7.2′′. The spectrograph has two identical arms each covering half the FOV. Four interchangeable grisms allow spectroscopy with R=4,000 to R=15,000, from 370 – 935 nm.
The Sloan Digital Sky Survey V (SDSS–V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the universe. The Local Volume Mapper (LVM) is a facility designed to provide a contiguous 2500 deg2 integral-field survey over a 3.5 year period from Las Campa˜nas Observatory (LCO) in Chile. The facility comprises four 0.16 m bench-mounted telescopes that feed three multiobject spectrographs with 1801 science fibres, 119 calibration fibres, and 24 sky-background fibres. The fibre cable spans approximately 20 meters from the telescope platform to the spectrograph slits. A sorting hat, located in the spectrograph room, redistributes the 1944 fibres into three 648–element bundles that terminate at the spectrograph slits. In this paper, we briefly summarize the current production progress of the integral-field units, the spectrograph slits, and the sorting hat.
The Australian Astronomical Observatory’s (AAO’s) AESOP project is part of the Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fibre positioner, space frame and electronics enclosures. The AESOP concept and the role of the AAO in the 4MOST project have been described in previous SPIE proceedings. The project final assembly stage has recently been completed. In this paper, key results in accurate manufacturing and assembly of critical AESOP components are discussed. The major performance requirement for AESOP is that all 2436 science fibre cores and 12 guide fibre bundles are to be re-positioned to an accuracy of 10 micron within 1 minute. With a fast prime-focus focal-ratio, a close tolerance of +/-70 microns on the axial position of the fibre tips must be held so efficiency does not suffer from de-focus losses. Positioning accuracy is controlled with the metrology cameras installed on the telescope, which measures the positions of the fibre tips to an accuracy of a few micrometers and allows iterative positioning until all fibre tips are within tolerance on the ultimate position. Maintaining co-planarity of the fibre tips requires accurate control in the assembly of several components that contribute to such errors. Overall, the AESOP design fully complies with all its requirements and in most cases achieves its goals. A thorough consideration of all the relevant interfaces during the design and assembly phases, has resulted in comprehensive set of ICDs for the mechanical, electrical and software aspects of AESOP.
The 4m DAG telescope is under construction at East Anatolia Observatory in Turkey. DIRAC, the “DAG InfraRed Adaptive optics Camera”, is one of the facility instruments. This paper describes the design of the camera to meet the performance specifications. Adaptive and auxiliary optics relay the telescope F/14 input 1:1 into DIRAC. The camera has an all refractive design for the wavelength range 0.9 - 2.4 micron. Lenses reimage the telescope focal plane 33 x 33 as (9 x 9 mm) on a 1k x 1k focal plane array. With magnification of 2x, the plate scale on the detector is 33 mas/pixel. There are 4 standard filters (Y, J, H, K) and 4 narrowband continuum filters. A 12 position filter wheel allows installation of 2 extra customer filters for specific needs; the filter wheel also deploys a pupil viewer lens. Optical tolerancing is carried out to deliver the required image quality at polychromatic Strehl ratio of 90% with focus compensator. This reveals some challenges in the precision assembly of optics for cryogenic environments. We require cells capable of maintaining precision alignment and keeping lenses stress free. The goal is achieved by a combination of flexures with special bonding epoxy matching closely the CTE of the lens cells and crystalline materials. The camera design is very compact with object to image distance <220 mm and lens diameters <25 mm. A standalone cryostat is LN2 cooled for vibration free operation with the bench mounted adaptive optics module (TROIA) and coronagraph (PLACID) at the Nasmyth focus of the DAG telescope.
MAVIS is the world’s first facility-grade visible MCAO instrument, currently under development for the VLT. The AO system will feed an imager and an integral field spectrograph, with 50% sky coverage at the Galactic pole. MAVIS has unique angular resolution and sensitivity at visible wavelengths, and is highly complementary to both JWST and ELTs. We describe both instruments in detail and the broad range of science cases enabled by them. The imager will be diffraction-limited in V, with 7.36 mas per pixel covering a 30” FOV. A set of at least 7 broad-band and 15 narrow-band filters will provide imaging from u to z. The spectrograph uses an advanced image slicer with a selectable spatial sampling of 25 or 50 mas to provide integral field spectroscopy over a FOV of 2.5”x3.6”, or 5”x7.2”. The spectrograph has two identical arms each covering half the FOV. Four interchangeable grisms allow spectroscopy with R=5,000 to R=15,000, from 380-950 nm.
The Australian Astronomical Observatory’s (AAO’s) AESOP project is part of the Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fibre positioner, space frame and electronics enclosures. The AESOP concept and the role of the AAO in the 4MOST project have been described in previous SPIE proceedings. The project final assembly stage has been completed. In this paper, engineering principles applied during assembly of critical components and testing of the instrument are discussed. The major performance requirement for AESOP is that all 2436 science fiber cores and 12 guide fiber bundles are to be re-positioned to an accuracy of 10 micron within 1 minute. With a fast prime-focus focal-ratio, a close tolerance on the axial position of the fiber tips must be held so efficiency does not suffer from de-focus losses. Positioning accuracy is controlled with the metrology cameras installed on the telescope, which measures the positions of the fiber tips to an accuracy of a few micrometers and allows iterative positioning until all fiber tips are within tolerance on the focal surface plane. Maintaining co-planarity of the fiber tips requires accurate control in the assembly of several components that contribute to such errors. AESOP requires a consistent production of high accuracy components and assemblies in a quantity of above 2500 items. To achieve this, we had to apply the highest engineering standards, including assembly procedures, metrology, and control systems. We designed many jigs and fixtures, which enabled us to produce high quality components and assemblies at reasonable cost. The results – working instrument was vastly achieved with the help of university students after providing a training in engineering practices.
The proposed MAVIS instrument for the VLT UT4 delivers a 30" x 30" MCAO-corrected field for 370-950nm. It includes an integral-field spectroscopic mode, whereby a subsection of the field is delivered to an image slicer and spectrograph, with either 25mas or 50mas spatial sampling, and R<4000 and R<10000 modes in either the red or the blue. Three designs are being considered for the image slicer, two with all-reflective optics, and the other, presented here, derived from the existing WiFeS spectrograph and including arrays of small lenses. A spectrograph design is also presented, challenging because of the need to be close to diffraction-limited across the entire wavelength range, while maintaining high throughput, in all 4 modes and over the entire 9cm x 9cm detector.
The MCAO Assisted Visible Imager and Spectrograph (MAVIS) is a facility-grade visible MCAO instrument, currently under development for the Adaptive Optics Facility at the VLT. The adaptive optics system will feed both an imager and an integral field spectrograph, with unprecedented sky coverage of 50% at the Galactic Pole. The imager will deliver diffraction-limited image quality in the V band, cover a 30" x 30" field of view, with imaging from U to z bands. The conceptual design for the spectrograph has a selectable field-of-view of 2.5" x 3.6", or 5" x 7.2", with a spatial sampling of 25 or 50 mas respectively. It will deliver a spectral resolving power of R=5,000 to R=15,000, covering a wavelength range from 380 - 950 nm. The combined angular resolution and sensitivity of MAVIS fill a unique parameter space at optical wavelengths, that is highly complementary to that of future next-generation facilities like JWST and ELTs, optimised for infrared wavelengths. MAVIS will facilitate a broad range of science, including monitoring solar system bodies in support of space missions; resolving protoplanetary- and accretion-disk mechanisms around stars; combining radial velocities and proper motions to detect intermediate-mass black holes; characterising resolved stellar populations in galaxies beyond the local group; resolving galaxies spectrally and spatially on parsec scales out to 50 Mpc; tracing the role of star clusters across cosmic time; and characterising the first globular clusters in formation via gravitational lensing. We describe the science cases and the concept designs for the imager and spectrograph.
MANIFEST is a multi-object fibre facility for the Giant Magellan Telescope that uses ‘Starbug’ robots to accurately position fibre units across the telescope’s focal plane. MANIFEST, when coupled to the telescope’s planned seeinglimited instruments, offers access to larger fields of view; higher multiplex gains; versatile focal plane reformatting of the focal plane via integral-field-units; image-slicers; and in some cases higher spatial and spectral resolution. The TAIPAN instrument on the UK Schmidt Telescope is now close to science verification which will demonstrate the feasibility of the Starbug concept. We are now moving into the conceptual development phase for MANIFEST, with a focus on developing interfaces for the telescope and for the instruments.
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