We introduce MOSES, the new High-Resolution Echelle Spectrograph designated for the 1.2m MONET telescope at McDonald Observatory, Texas, USA. The science drivers are radial velocity experiments and activity monitoring in Sun-like stars. Set for installation in the final quarter of 2025, MOSES features a white pupil design and aims for a spectral resolution greater than 80,000 over the 380-680 nm wavelength range. It incorporates a pixel sampling rate of 3.5 and uses two fibers to facilitate a simultaneous calibration mode. Encased within a vacuum vessel and operating in a temperature-stabilized environment, MOSES is expected to achieve a radial velocity precision below 2 m/s, aided by a Fabry-Pérot etalon calibration system. This paper outlines the implementation of the fiber injection unit, the optical layout of the spectrograph, and the present status of the various subsystems under development.
We report on the design of 2ES (Second Earth Initiative Spectrograph): a new fiber-fed, high-resolution, high-precision radial velocity echelle spectrograph for the 2.2m ESO/MPG telescope in Chile, which will cover the visible wavelength range ∼370nm to 850nm with a resolution of 120, 000. 2ES will be dedicated to a >5-year observing program with access to the majority (2/3) of the telescope time with the goal of discovering temperate terrestrial Earth-mass planets in the habitable zone around the bright solar-type stars. To achieve this goal, 2ES aims for ultra-high instrumental radial-velocity precision and an observing strategy that involves high-cadence observation of the brightest Sun-like stars in the Southern Hemisphere. Here, we present an overview of the project, its observation strategy, the optical design as well as the opto-mechanical concepts and calibration strategies to achieve the required instrument stability.
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.
The Maunakea Spectroscopic Explorer (MSE) will target sources down to mAB = 24 with a signal to noise ratio > 1 from the near UV to H-band. Among MSE’s many science goals, this will allow the efficient spectroscopic follow-up of large imaging surveys anticipated from new facilities such as the Rubin Observatory. Given broadband AR coatings currently feasible for large optics, this poses a unique challenge in terms of controlling contamination from optical ghost reflections. We present exploratory work to identify telescope designs with optical ghost levels that satisfy the observational thresholds required for MSE. We also report on an initial estimate of scattering from the optics that indicates that it will have a minor impact on the accessible sky, does not drive the telescope design selection, but must be accounted for in science/sky fiber placement. The outcome of these studies is that a range of telescope configurations exist that allow MSE’s target sensitivity to be reached without limitation from optical ghosts or scattering from the optics.
The 4-meter Multi-Object Spectroscopic Telescope (4MOST) is a wide-field, high-multiplex spectroscopic survey facility under development for the Visible and Infrared Survey Telescope for Astronomy (VISTA) of the European Southern Observatory (ESO). The 4MOST Wide Field Corrector and Atmospheric Dispersion Corrector (ADC) lenses have been manufactured and tested at KiwiStar Optics, New Zealand. The two ADC wedged doublets form a Risley Prism Pair; are both 650 mm in diameter and relatively thin; and have been cemented using Sylgard 184 silicone elastomer. The cementing procedure and its challenges are reported here. Interferometric measurements of the single surfaces, glass blanks and the finished doublets have been compared in order to assess the effect of the cementing process on the final surface figures of the doublets before and after positioning in their cells.
We describe the camera articulation prototype (CAP) for the Giant Magellan Telescope Multi-object Astronomical and Cosmological Spectrograph (GMACS), which is a wide field, multi-object, moderate-resolution, optical spectrograph of the Giant Magellan Telescope (GMT). The GMACS will have the Camera and Grating Articulation System (CGAS) which has two independent cameras and grating modules. The grating angles and the camera angles can be changed to adjust the dispersed light bands on the detector. The electronics components of this system include motors with encoder, pneumatic brakes, and limit switches. We demonstrate how to control the camera angles using a prototype that is designed for the camera articulation controller as a miniature model of the GMACS. The prototype was built with commercially-available extruded aluminum struts and 3D-printed parts and includes two motors with encoders. The prototype was produced quickly and inexpensively, but replicates all functions of the camera articulation mechanism in GMACS. We have developed the control package for the prototype that will be one of the GMACS Device Control System (DCS). The software is designed by the Agile development process and SysML, and developed using Visual C++ on Windows OS. This software has five major control functions: power, homing, resolution mode changing, limit detection, and emergency process. The limit detection is implemented by setting up the limit angle range in the software, because the limit switches are not included in the prototype. We present the demonstration result and discuss the details of the communication route about data flow between high-end user software and hardware components.
The Giant Magellan Telescope Multi-object Astronomical and Cosmological Spectrograph (GMACS) is a first light instrument for the Giant Magellan Telescope (GMT). It will provide multi-object spectroscopy in wide wavelength coverage and wide field of view. The scientific objectives include exoplanet atmospheres, star formation and chemical evolution studies, galaxy assembly histories, and intergalactic medium tomography. The optical layouts are optimized to have high throughput in the natural seeing limit. In this presentation, we report the current status of the instrument development.
We describe the current electronics prototypes for the Flexure Compensation System (FCS) and the Slit Mask Exchange Mechanism (SMEM) for GMACS, a wide-field, multi-object, moderate-resolution optical spectrograph for the Giant Magellan Telescope (GMT). We discuss the details of the FCS and SMEM prototypes, how the prototypes relate to the preliminary conceptual designs of these systems, and what information the prototypes give that can be applied to the final design, as well as the possible next steps for each prototype.
We describe the optical design of GMACS, a multi-object wide field optical spectrograph currently being developed for the Giant Magellan Telescope (GMT). Optical spectrographs for the emerging generation of Extreme Large Telescopes (ELTs) have unique design issues. For example, the combination of both the largest field of view practical and beam widths achieving the desired spectral resolutions force the design of seeing limited ELT optical spectrographs to include large refractive elements, which in turn requires a compromise between the optical performance, manufacturability, and operability. We outline the details of the GMACS optical design subsystems, their individual and combined optical performance, and the preliminary flexure tolerances. Updates to the detector specifications, field acquisition/alignment optics, and optical considerations for active flexure control are also discussed. The resulting design meets the technical instrument requirements generated from the GMACS science requirements, is expected to satisfy the available project budget, and has an acceptable level of risk for the subsystem manufacture and assembly.
An important tool for the development of the next generation of extremely large telescopes (ELTs) is a robust Systems Engineering (SE) methodology. GMACS is a first-generation multi-object spectrograph that will work at visible wavelengths on the Giant Magellan Telescope (GMT). In this paper, we discuss the application of SE to the design of next-generation instruments for ground-based astronomy and present the ongoing development of SE products for the GMACS spectrograph, currently in its Conceptual Design phase. SE provides the means to assist in the management of complex projects, and in the case of GMACS, to ensure its operational success, maximizing the scientific potential of GMT.
We describe the latest optomechanical design of GMACS, a wide-field, multi-object, moderate-resolution optical spectrograph for the Giant Magellan Telescope (GMT). Specifically, we discuss the details of the structure, mechanisms, optical mounts and deflection tracking/compensation as well as the requirements and considerations used to guide the design. We also discuss GMACS’s interfaces with GMT and other instruments.
We discuss the latest developments of a spectrograph for the Giant Magellan Telescope. The instrument is designed to provide high throughput, moderate resolution, optical spectra for the telescope and be capable of flexible and rapid reconfiguration. The focal plane can be populated with custom slit masks or multiple fibers, allowing for observations of multiple objects simultaneously.
Hanle echelle spectrograph (HESP) is a high resolution, bench mounted, fiber-fed spectrograph at visible wavelengths. The instrument was recently installed at the 2m Himalayan Chandra Telescope (HCT), located at Indian Astronomical Observatory (IAO), Hanle at an altitude of 4500m. The telescope and the spectrograph are operated remotely from Bangalore,(∼ 3200km from Hanle), through a dedicated satellite link. HESP was designed and built by Kiwi Star Optics, Callaghan Innovation, New Zealand. The spectrograph has two spectral resolution modes (R=30000 and 60000). The low resolution mode uses a 100 micron fiber as a input slit and the high resolution mode is achieved using an image slicer. An R2 echelle grating, along with two cross dispersing prisms provide a continuous wavelength coverage between 350-1000nm. The spectrograph is enclosed in a thermally controlled environment and provides a stability of 200m/s during a night. A simultaneous thorium-argon calibration provides a radial velocity precision of 20m/s. Here, we present a design overview, performance and commissioning of the spectrograph.
Veloce is an ultra-stable fibre-fed R4 echelle spectrograph for the 3.9 m Anglo-Australian Telescope. The first channel to be commissioned, Veloce ‘Rosso’, utilises multiple low-cost design innovations to obtain Doppler velocities for sun-like and M-dwarf stars at <1 ms -1 precision. The spectrograph has an asymmetric white-pupil format with a 100-mm beam diameter, delivering R>75,000 spectra over a 580-930 nm range for the Rosso channel. Simultaneous calibration is provided by a single-mode pulsed laser frequency comb in tandem with a traditional arc lamp. A bundle of 19 object fibres ensures full sampling of stellar targets from the AAT site. Veloce is housed in dual environmental enclosures that maintain positive air pressure at a stability of ±0.3 mbar, with a thermal stability of ±0.01 K on the optical bench. We present a technical overview and early performance data from Australia's next major spectroscopic machine.
We present the current optical design of GMACS, a multi-object wide field optical spectrograph currently being developed for the Giant Magellan Telescope, a member of the emerging generation of Extremely Large Telescopes (ELTs). Optical spectrographs for ELTs have unique design challenges and issues. For example, the combination of the largest practical field of view and beam widths necessary to achieve the desired spectral resolutions force the design of seeing limited ELT optical spectrographs to include aspheric lenses, broadband dichroics, and volume phase holographic gratings - all necessarily very large. We here outline details of the collimator and camera subsystems, the design methodology and trade-off analyses used to develop the collimator subsystem, the individual and combined subsystem performances and the predicted tolerances.
We present a preliminary conceptual optical design for GMACS, a wide field, multi-object, optical spectrograph currently being developed for the Giant Magellan Telescope (GMT). We include details of the optical design requirements derived from the instrument scientific and technical objectives and demonstrate how these requirements are met by the current design. Detector specifications, field acquisition/alignment optics, and optical considerations for the active flexure control system are also discussed.
We describe a preliminary conceptual optomechanical design for GMACS, a wide-field, multi-object, moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT). This paper describes the details of the GMACS optomechanical conceptual design, including the requirements and considerations leading to the design, mechanisms, optical mounts, and predicted flexure performance.
The 4-meter Multi-Object Spectroscopic Telescope (4MOST) is a wide-field, high-multiplex spectroscopic survey facility under development for the Visible and Infrared Survey Telescope for Astronomy (VISTA) of the European Southern Observatory (ESO). The primary and secondary mirrors (M1 and M2) together with the Wide Field Corrector (WFC) system provide a pupil-centric and aberration corrected focal surface. The WFC is also an integral part of the metrology system. At the focal surface, we meet two wave front sensing (WFS) systems, a deployable camera at commissioning, an acquisition and guiding (A and G) unit and a secondary guiding unit. This paper provides an overview of design details and Manufacture, Assembly, Integration and Verification (MAIV) processes for the 4MOST WFC system.
BOMBOLO is our instrument proposal for covering a series of scientific cases, in the not-so-explored time window of tens of seconds to minutes exposures, to be installed at the SOAR observatory. BOMBOLO is a wide field imager, capable of simultaneous, synchronous and independent observations in three different bands of the near-UV and visible wavelengths. BOMBOLO will be located at one of the Bent Cassegrain focal stations. Given its length, weight and mounting limitations, we discuss the current mechanical and opto-mechanical design of the instrument, given flexures caused by a changing gravity vector. In order to validate our designs, a Monte-Carlo simulation is used to explore different observing conditions, as the starting point for static and dynamic studies of the structure using Finite Element Analysis tools. A quick update on the current state of the instrument related to the optical design and manufacturing as well as the CCD cameras is included.
We report on the development and construction of a new fiber-fed, red-optical, high-precision radial-velocity spectrograph for one of the twin 6.5m Magellan Telescopes in Chile. MAROON-X will be optimized to find and characterize rocky planets around nearby M dwarfs with an intrinsic per measurement noise floor below 1ms-1. The instrument is based on a commercial echelle spectrograph customized for high stability and throughput. A microlens array based pupil slicer and double scrambler, as well as a rubidium-referenced etalon comb calibrator will turn this spectrograph into a high-precision radial-velocity machine. MAROON-X will undergo extensive lab tests in the second half of 2016.
The High Efficiency and Resolution Multi Element Spectrograph, HERMES, is a facility-class optical spectrograph for the Anglo-Australian Telescope (AAT). It is designed primarily for Galactic Archaeology, the first major attempt to create a detailed understanding of galaxy formation and evolution by studying the history of our own galaxy, the Milky Way. The goal of the GALAH survey is to reconstruct the mass assembly history of the Milky Way through a detailed chemical abundance study of one million stars. The spectrograph is based at the AAT and is fed by the existing 2dF robotic fiber positioning system. The spectrograph uses volume phase holographic gratings to achieve a spectral resolving power of 28,000 in standard mode and also provides a high-resolution mode ranging between 40,000 and 50,000 using a slit mask. The GALAH survey requires an SNR greater than 100 for a star brightness of V=14 in an exposure time of one hour. The total spectral coverage of the four channels is about 100 nm between 370 and 1000 nm for up to 392 simultaneous targets within the 2-degree field of view. HERMES has been commissioned over three runs, during bright time in October, November, and December 2013, in parallel with the beginning of the GALAH pilot survey, which started in November 2013. We present the first-light results from the commissioning run and the beginning of the GALAH survey, including performance results such as throughput and resolution, as well as instrument reliability.
BOMBOLO is a new multi-passband visitor instrument for the SOAR observatory. It is a three-arm imager covering the
near-UV and optical wavelengths. The three arms work simultaneously and independently, providing synchronized
imaging capability for rapid astronomical events. BOMBOLO leading science cases are: 1) Simultaneous Multiband
Flickering Studies of Accretion Phenomena; 2) Near UV/Optical Diagnostics of Stellar Evolutionary Phases; 3)
Exoplanetary Transits; 4) Microlensing Follow-Up and 5) Solar Systems Studies. The instrument is at the Conceptual
Design stage, having been approved by the SOAR Board of Directors as a visitor instrument in 2012 and having been
granted full funding from CONICYT, the Chilean State Agency of Research, in 2013. The Design Phase has begun and
will be completed in late 2014, followed by a construction phase in 2015 and 2016A, with expected Commissioning in
2016B and 2017A.
The High Efficiency and Resolution Multi Element Spectrograph, HERMES is an facility-class optical spectrograph for
the AAT. It is designed primarily for Galactic Archeology [21], the first major attempt to create a detailed
understanding of galaxy formation and evolution by studying the history of our own galaxy, the Milky Way. The goal of
the GALAH survey is to reconstruct the mass assembly history of the of the Milky Way, through a detailed spatially
tagged abundance study of one million stars. The spectrograph is based at the Anglo Australian Telescope (AAT) and is
fed by the existing 2dF robotic fiber positioning system. The spectrograph uses VPH-gratings to achieve a spectral
resolving power of 28,000 in standard mode and also provides a high-resolution mode ranging between 40,000 to 50,000
using a slit mask. The GALAH survey requires a SNR greater than 100 for a star brightness of V=14. The total spectral
coverage of the four channels is about 100nm between 370 and 1000nm for up to 392 simultaneous targets within the 2
degree field of view. Hermes has been commissioned over 3 runs, during bright time in October, November and
December 2013, in parallel with the beginning of the GALAH Pilot survey starting in November 2013. In this paper we
present the first-light results from the commissioning run and the beginning of the GALAH Survey, including
performance results such as throughput and resolution, as well as instrument reliability. We compare the abundance
calculations from the pilot survey to those in the literature.
The KOALA optical fibre feed for the AAOmega spectrograph has been commissioned at the Anglo-Australian
Telescope. The instrument samples the reimaged telescope focal plane at two scales: 1.23 arcsec and 0.70 arcsec per
image slicing hexagonal lenslet over a 49x27 and 28x15 arcsec field of view respectively. The integral field unit consists
of 2D hexagonal and circular lenslet arrays coupling light into 1000 fibres with 100 micron core diameter. The fibre run
is over 35m long connecting the telescope Cassegrain focus with the bench mounted spectrograph room where all fibres
are reformatted into a one-dimensional slit. Design and assembly of the KOALA components, engineering challenges
encountered, and commissioning results are discussed.
The High Efficiency and Resolution Multi Element Spectrograph, HERMES is an optical spectrograph designed
primarily for the GALAH, Galactic Archeology Survey, the first major attempt to create a detailed understanding of
galaxy formation and evolution by studying the history of our own galaxy, the Milky Way1. The goal of the GALAH
survey is to reconstruct the mass assembly history of the of the Milky way, through a detailed spatially tagged
abundance study of one million stars in the Milky Way. The spectrograph will be based at the Anglo Australian
Telescope (AAT) and be fed with the existing 2dF robotic fibre positioning system. The spectrograph uses VPH-gratings
to achieve a spectral resolving power of 28,000 in standard mode and also provides a high resolution mode ranging
between 40,000 to 50,000 using a slit mask. The GALAH survey requires a SNR greater than 100 aiming for a star
brightness of V=14. The total spectral coverage of the four channels is about 100nm between 370 and 1000nm for up to
392 simultaneous targets within the 2 degree field of view.
Current efforts are focused on manufacturing and integration. The delivery date of spectrograph at the telescope is
scheduled for 2013. A performance prediction is presented and a complete overview of the status of the HERMES
spectrograph is given. This paper details the following specific topics:
The approach to AIT, the manufacturing and integration of the large mechanical frame, the opto-mechanical slit
assembly, collimator optics and cameras, VPH gratings, cryostats, fibre cable assembly, instrument control hardware and
software, data reduction.
Claudia Rodrigues, Keith Taylor, Francisco Jablonski, Marcelo Assafin, Alex Carciofi, Deonisio Cieslinski, Joaquim E. Costa, Ruben Dominguez, Tania Dominici, Gabriel A. Franco, Damien Jones, Antonio Kanaan, René Laporte, Antonio Magalhaes, André Milone, José Neri, Antonio Pereyra, Luiz A. Reitano, Karleyne M. Silva, Cesar Strauss
We present a summary of the concept design report of a new astronomical instrument: SPARC4, Simultaneous
Polarimeter and Rapid Camera in 4 bands. SPARC4 will provide photometry and polarimetry in four optical
broad bands (griz SDSS) simultaneously. This is achieved by the use of dichroic beam splitters. The square eld
of view is around 5.6 arcmin on a side. SPARC4 time resolution is sub-second for photometry and somewhat
longer for polarimetry. This is provided by the use of fast EMCCDs. The main motivation for building SPARC4
is to explore astrophysical objects which exhibit fast temporal variability in
ux and polarization. The instrument
will be installed at the 1.6-m telescope of the Observatorio do Pico dos Dias (Brazil).
The Giant Magellan Telescope (GMT) Integral-Field Spectrograph (GMTIFS)c is one of six potential first-light
instruments for the 25m-diameter Giant Magellan Telescope. The Australian National University has completed a
Conceptual Design Study for GMTIFS. The science cases for GMTIFS are summarized, and the instrument capabilities
and design challenges are described. GMTIFS will be the work-horse adaptive-optics instrument for GMT. It contains an
integral-field spectrograph (IFS) and Imager accessing the science field, and an On-Instrument Wave-Front Sensor
(OIWFS) that patrols the 90 arcsec radius guide field. GMTIFS will address a wide range of science from epoch of
reionization studies to forming galaxies at high redshifts and star and planet formation in our Galaxy. It will fully exploit
the Laser Tomography Adaptive Optics (LTAO) system on the telescope. The tight image quality and positioning
stability requirements that this imposes drive the design complexity. Some cryogenic mechanisms in the IFS must set to
~ 1 μm precision. The Beam-Steering mechanism in the OIWFS must set to milli-arcsecond precision over the guide
field, corresponding to ~ 1 μm precision in the f/8 focal plane. Differential atmospheric dispersion must also be corrected
to milli-arcsecond precision. Conceptual design solutions addressing these and other issues are presented and discussed.
CYCLOPS2 is an upgrade for the UCLES high resolution spectrograph on the Anglo-Australian Telescope, scheduled for commissioning in semester 2012A. By replacing the 5 mirror Coud´e train with a Cassegrain mounted fibre-based image slicer CYCLOPS2 simultaneously provides improved throughput, reduced aperture losses and increased spectral resolution. Sixteen optical fibres collect light from a 5.0 arcsecond2 area of sky and reformat it into the equivalent of a 0.6 arcsecond wide slit, delivering a spectral resolution of R= 70000 and up to twice as much flux as the standard 1 arcsecond slit of the Coud´e train. CYCLOPS2 also adds support for simultaneous ThAr wavelength calibration via a dedicated fibre. CYCLOPS2 consists of three main components, the fore-optics unit, fibre bundle and slit unit. The fore optics unit incorporates magnification optics and a lenslet array and is designed to mount to the CURE Cassegrain instrument interface, which provides acquisition, guiding and calibration facilities. The fibre bundle transports the light from the Cassegrain focus to the UCLES spectrograph at Coud´e and also includes a fibre mode scrambler. The slit unit consists of the fibre slit and relay optics to project an image of the slit onto the entrance aperture of the UCLES spectrograph. CYCLOPS2 builds on experience with the first generation CYCLOPS fibre system, which we also describe in this paper. We present the science case for an image slicing fibre feed for echelle spectroscopy and describe the design of CYCLOPS and CYCLOPS2.
The Laser Tomographic Adaptive Optics system for Giant Magellan Telescope (GMT) uses a single conjugated
deformable mirror, the segmented Adaptive Secondary Mirror (ASM), to correct atmospheric wavefront aberrations with
the help of a constellation of six laser beacons equally spaced on the sky. We will present different approaches for the
design of the Laser Guide Star (LGS) Wave Front Sensor (WFS) system for GMT to cover all sodium emission altitudes
and telescope elevations, from 80 km to 200 km range and how the preliminary design was derived from these
approaches. The designed LGS WFS system includes a defocus-compensation mechanism working with a simple
zooming optics to achieve the pupil image with constant pupil size, nearly constant wavefront correction, as well as pupil
distortion correction. Either a trombone-mirror structure or a direct LGS-WFS translation is used for the defocus
compensation, when conjugating the LGS altitudes in the sky. In the designs, a zooming collimator images the ASM in
the GMT at the exit pupil of the LGS WFS system, where the designed lenslet-array is tailored for the selected CCD
format for the required plate scale on the sky. Additionally, we have proposed a novel and simple solution for pupilimage
segmentation when working with smaller CCD arrays. This novel solution consists of a single multi-aperture
blaze grating for pupil segmentation in the system.
SIFS is a lenslet/fiber Integral Field Unit Spectrograph which has just been delivered to the SOAR 4.1m telescope in
Chile. The instrument was designed and constructed by the National Laboratory of Astrophysics (MCT/LNA) in
collaboration with the Department of Astronomy of the Institute of Astronomy, Geophysics and Atmospheric Sciences of
the University of Sao Paulo (IAG/USP). It is designed to operate at both the raw Nasmyth and the SAM (the SOAR
Adaptive Optics Module) which delivers GLAO-corrected images in optical wave-bands longward of 500nm. The
lenslets have a 1mm pitch feeding a set of 1,300 fibres in a 26-by-50 format. Sets of deployable fore-optics convert the
f/16.5 input beam to give samplings between ~0.1 and 0.3 arcsec. The fiber output is in the form of a curved, pupil-centric,
long-slit which is fed into a bench-mounted spectrograph. An off-axis Maksutov collimates the beam onto a set
of VPH gratings and thence imaged by an f/3 refractive camera onto a 2-by-1 mosaic of 2k-by-4k E2V CCDs. The
camera is articulated over a >90 deg. angle to allow the grating/camera combination to operate in a transmission Littrow
configuration. The wavelength range is limited by the CCDs to the 350 to 1000nm range with spectral resolution
maxima of ~20,000. The paper will review the optical design of the spectrograph and the methods used to fabricate the
lenslet/fiber IFU.
The AAO is building an optical high resolution multi-object spectrograph for the AAT for Galactic Archaeology. The
instrument has undergone significant design revision over that presented at the 2008 Marseilles SPIE meeting. The
current design is a 4-channel VPH-grating based spectrograph providing a nominal spectral resolving power of 28,000
and a high-resolution mode of 45,000 with the use of a slit mask. The total spectral coverage is about 1000 Angstroms
for up to 392 simultaneous targets within the 2 degree field of view. Major challenges in the design include the
mechanical stability, grating and dichroic efficiencies, and fibre slit relay implementation. An overview of the current
design and discussion of these challenges is presented.
SALT HRS is a fiber-fed cross-dispersed echelle spectrograph designed for high resolution and high efficiency seeing-limited
spectroscopy on the Southern African Large Telescope. The spectrograph, which has a dual channel white
pupil design, uses a single R4 echelle grating, a dichroic beam-splitter, and volume phase holographic gratings
as cross-dispersers. The echelle grating has 41.6 grooves/mm and is illuminated with a 200mm diameter beam.
This allows R = 16,000 with a 2.2" fiber and complete wavelength coverage from 370 nm to 890 nm. Resolving
powers of R ≈ 37,000 and 67,000 are obtained using image slicers. The dichroic beam-splitter is used to split the
wavelength coverage between two fully dioptric cameras. The white pupil transfer optics are used to demagnify
the pupil to 111mm which ensures that the camera dimensions are kept reasonable whilst also allowing the
efficient use of VPH gratings. The spectrograph optics are enclosed inside a vacuum tank to ensure immunity to
atmospheric pressure and temperature changes. The entire spectrograph is mechanically and thermally insulated.
Construction of SALT HRS began at Durham University's Centre for Advanced Instrumentation in August 2007
and is expected to be complete in 2009. The spectrograph optical design is largely based on work completed at
the University of Canterbury's Department of Physics and Astronomy.
Mapping out stellar families to trace the evolutionary star formation history of the Milky Way requires a spectroscopic facility able to deliver high spectral resolution (R≥30k) with both good wavelength coverage (~400 Ang) and target multiplex advantage (~400 per 2 degree field). Such a facility can survey 1,200,000 bright stars over 10,000 square degrees in about 400 nights with a 4-meter aperture telescope. Presented are the results of a conceptual design study for such a spectrograph, which is under development as the next major instrument for the Anglo-Australian Observatory. The current design (that builds upon the AAOmega system) makes use of a White Pupil collimator and an R3 echelle that is matched to the existing AAOmega cameras. The fibre slit can be reconfigured to illuminate the Pupil relay side of the collimator mirror bypassing the echelle, thus preserving the lower dispersion modes of the AAOmega spectrograph. Other spectrograph options initially considered include use of an anamorphic collimator that reduces the required dispersion to that achievable with VPH grating technology or possible use of a double-pass VPH grating.
The Gemini South Adaptive Optics Imager (GSAOI) to be used with the Multi-Conjugate Adaptive Optics (MCAO) system at Gemini South is currently in the final stages of assembly and testing. GSAOI uses a suite of 26 different filters, made from both BK7 and Fused Silica substrates. These filters, located in a non-collimated beam, work as active optical elements.
The optical design was undertaken to ensure that both the filter substrates both focused longitudinally at the same point. During the testing of the instrument it was found that longitudinal focus was filter dependant. The methods used to investigate this are outlined in the paper. These investigations identified several possible causes for the focal shift including substrate material properties in cryogenic conditions and small amounts of residual filter power.
The Gemini/Subaru WFMOS project has given the stimulus for considering new concepts for massively multiplexed
fiber positioning schemes. The problem of acquiring many thousands of objects within a ~1.5° field at Subaru's ~f/2
prime-focus station represents a challenge to normal concepts of fiber positioning. Solutions usually involve imposing
limits to the patrol field of each fiber. Using this simplification, a new concept is proposed which moves objects onto a
fixed array of fibers rather than moving the fiber themselves. Such a scheme may simplify the manufacturing and
assembly processes and may result in a more robust solution compatible with the challenging prime-focus environment.
We describe the POSM concept and present an initial opto-mechanical layout.
WiFeS is a powerful integral field, double-beam, concentric, image-slicing spectrograph designed to deliver excellent thoughput, precision spectrophotometric performance and superb image quality along with wide spectral coverage throughout the 320-1000 nm wavelength region. It is currently under construction at the Research School of Astronomy and Astrophysics of the Australian National University (ANU), and will be mounted on the ANU 2.3m telescope at Siding Spring Observatory. It will provide a 25x31 arc sec field with 0.5 arc sec sampling along each of twenty five 31x1.0 arc sec slitlets. The output format is arranged to match the 4096x4096 pixel CCD detectors in each of two cameras individually optimized for the blue and the red ends of the spectrum, respectively. A process of "interleaved nod-and-shuffle" will be applied to permit quantum noise-limited sky subtraction. Using VPH gratings, spectral resolutions modes of 3000 and 7000 will be provided. The full spectral range is covered in a single exposure in the R=3000 mode, and in two exposures in the R=7000 mode. The use of transmissive coated optics, VPH gratings and optimized mirror coatings ensures a throughput (including telescope and atmosphere) that peaks above 30%. The concentric image-slicer design ensures an excellent and uniform image quality across the full field. To maximize the scientific return, the whole instrument is configured for remote observing, pipeline data reduction, and the accumulation of calibration image libraries.
The Gemini South Adaptive Optics Imager (GSAOI) is the science camera and commissioning instrument for the Multi-Conjugate Adaptive Optics (MCAO) system on the Gemini South telescope. GSAOI is required to deliver diffraction-limited performance at near-infrared wavelengths over a 85"×85" field of view. It must be delivered on a short timescale commensurate with MCAO delivery. GSAOI will use a high throughput, all-refractive optical design and a mosaic of four HAWAII-2RG detectors to form an imager focal plane of 4080x4080 pixels with a fixed scale of 0.02"/pixel. The On-Detector Guide Window (ODGW) capability of the HAWAII-2RG detectors will be used for flexure monitoring and as near-infrared substitutes for MCAO natural guide star wave front sensors. The imager will include a pupil viewer for accurate alignment to MCAO and defocus lenses to measure wave front phase errors at the science detector using the curvature technique. Non-common path wave front errors will be nulled by setting the base shapes of the three MCAO deformable mirrors. The science drivers, performance predictions, optical design issues, and detector system for the instrument are described.
AAOmega is a new spectrograph for the existing 2dF and SPIRAL multifibre systems on the Ango-Australian Telescope. It is a bench-mounted, dual-beamed, articulating, all-Schmidt design, using
volume phase holographic gratings. The wavelength range is 370-950nm, with spectral resolutions from 1400-10000. Throughput, spectral coverage, and maximum resolution are all more than doubled compared with the existing 2dF spectrographs, and stability is increased by orders of magnitude. These features allow entirely new classes of observation to be undertaken, as well as dramatically improving
existing ones. AAOmega is scheduled for delivery and commissioning in Semester 2005B.
NIFS is a near-infrared integral field spectrograph designed for near diffraction-limited imaging spectroscopy with the ALTAIR facility adaptive optics system on Gemini North. NIFS is currently under construction at the Research School of Astronomy and Astrophysics of the Australian National University. Commissioning is planned for 2003. NIFS uses a reflective concentric integral field unit to reformat its 3.0"x3.0" field-of-view into 29 slitlets each 0.1" wide with 0.04" sampling along each slitlet. The NIFS spectrograph has a resolving power of ~ 5300, which is large enough to significantly separate terrestrial airglow emission lines and resolve velocity structure in galaxies. The output format is matched to a 2048x2048 pixel Rockwell HAWAII-2 detector. The detector is read out through a SDSU-2 detector controller connected via a VME interface to the Gemini Data Handling System. NIFS is a fast-tracked instrument that reuses many of the designs of the Gemini Near-InfraRed Imager (NIRI); the cryostat, On-Instrument Wave Front Sensor, control system, and control software are largely duplicates.
We present the project of an optical spectrograph equipped with a 1300-element Integral Field Unit (IFU), that will be one of the main instruments of the SOAR (4m) telescope. The instrument consists of two separate parts, the fore-optics and the bench spectrograph, that are connected by an 11 m long fiber bundle. The fore optics system is installed at one of the Nasmyth focii of the telescope, and
produces an image of the observed object on a 26x50 array of square microlenses, each 1 mm x 1 mm lens feeding one fiber. The fibers have 50 micron cores, and are aligned at the entrance of bench spectrograph to form a slit that feeds a 100 mm beam collimator.
A set of Volume Phase-Holographic (VPH) transmission gratings can be interchanged by remote control, providing a choice of resolution and wavelength coverage. The spectrograph is tunable over the wavelength range 350 to 1000 nm, with resolution R from about 5000 to 20000. This spectrograph is ideally suited for high spatial resolution studies, with a sampled area of the sky 8" x 15", with 0.30" per microlens, in the mode to be used with the tip-tilt correction of SOAR. The project has been approved at the Project Design Review and the spectrograph is presently being constructed.
The Fiber Multi-Object Spectrograph (FMOS) project is an Australia-Japan-UK collaboration to design and build a novel 400 fiber positioner feeding two near infrared spectrographs from the prime focus of the Subaru telescope. The project comprises several parts. Those under design and construction at the Anglo-Australian Observatory (AAO) are the piezoelectric actuator driven fiber positioner (Echidna), a wide field (30 arcmin) corrector and a focal plane imager (FPI) used for controlling the positioner and for field acquisition. This paper presents an overview of the AAO share of the FMOS project. It describes the technical infrastructure required to extend the single Echidna "spine" design to a fully functioning multi-fiber instrument, capable of complete field reconfiguration in less than ten minutes. The modular Echidna system is introduced, wherein the field of view is populated by 12 identical rectangular modules, each positioning 40 science fibers and 2 guide fiber bundles. This arrangement allows maintenance by exchanging modules and minimizes the difficulties of construction. The associated electronics hardware, in itself a significant challenge, includes a 23 layer PCB board, able to supply current to each piezoelectric element in the module. The FPI is a dual purpose imaging system translating in two coordinates and is located beneath the assembled modules. The FPI measures the spine positions as well as acquiring sky images for instrument calibration and for field acquisition. An overview of the software is included.
EMIR is a near-IR, multi-slit camera-spectrograph under development for the 10m GTC on La Palma. It will deliver up to 45 independent R equals 3500-4000 spectra of sources over a field of view of 6 feet by 3 feet, and allow NIR imaging over a 6 foot by 6 foot FOV, with spatial sampling of 0.175 inch/pixel. The prime science goal of the instrument is to open K-band, wide field multi-object spectroscopy on 10m class telescopes. Science applications range from the study of star-forming galaxies beyond z equals 2, to observations of substellar objects and dust-enshrouded star formation regions. Main technological challenges include the large optics, the mechanical and thermal stability and the need to implement a mask exchange mechanism that does not require warming up the spectrograph. EMIR is begin developed by the Instituto de Astrofisica de Canarias, the Instituto Nacional de Tecnica Aeroespacial, the Universidad Complutense de Madrid, the Observatoire Midi-Pyrennees, and the University of Durham. Currently in its Preliminary Design phase, EMIR is expected to start science operation in 2004.
IRIS2 will provide direct imaging and low dispersion spectroscopy on the Anglo-Australian Telescope (AAT) using a 1K by 1K HgCdTe array and be capable of a future upgrade - by installing a new camera - to use a 2K by 2K array. It will be used primarily with the f/8 telescope configuration but can also be used with f/15 and f/36 configurations. The optics will be entirely transmissive with all spherical surfaces. The collimator will have four elements and the camera, five. With a 50mm collimated beam diameter and an f/2.2 camera, the 1K array will provide a field 7.6 arcmin square with pixels equivalent to 0.45 arcsec. If a 2K array is fitted later, an f/4 camera will give an 8.0 arcmin square field with pixels 0.24 arcsec square. Zemax was used to optimize the design as a multi-configuration system, so that a balance was maintained between direct imaging and spectroscopic performance and between the three atmospheric windows. For direct imaging with the f/2.2 camera, a diffraction based calculation indicates the energy inside a circle inscribed within one pixel is always better than 80 percent of that for a diffraction limited system. Particular care was taken to provide good imaging of the telescope pupil onto the cold stop in K.
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