MARVEL is a new facility at the Mercator Observatory (La Palma) which comprises an array of four 0.8 metre 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.
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 MCAO Assisted Visible Imager and Spectrograph (MAVIS) is a new high-resolution instrument operating in the visible band (370-935 nm) that will be installed at the Nasmyth A focus of the ESO VLT UT4. The system is characterized by an Adaptive Optics Module (AOM), a Calibration Unit, an Imager and an IFU Spectrograph. The project recently passed the Preliminary Design Review and is currently in the Final Design phase which is expected to end in December 2024, according to the current schedule. In this paper we present the improvements in the AOM control electronics architecture, the new control cabinets layout and the strategy adopted to cable the AO sub-modules.
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 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.
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.
Hector is a multi-integral-field-unit instrument for the Anglo-Australian Telescope (AAT). It simultaneously feeds two spectrographs, the existing AAOmega spectrograph and the new higher-resolution Spector spectrograph. Both are fed with new generation hexabundles. Spector has an all refractive 2- arm design which delivers 1.3A fixed resolution across the full wavelength range has higher resolution in the blue end and R=5000 in the red which makes Spector uniquely powerful spectrograph. The mechanical assembly of the spectrograph is designed to provide specific solutions to the tight spacing between component assemblies with strict tolerance constraints which makes Spector an interesting challenging instrument. The components start with a custom slit assembly providing precise positioning of 855 fibres which forms the interface point for light injection to the spectrograph. This paper presents a detail overview of opto-mechanical component design of Spector spectrograph along with technical specifications. Component fabrication, assembly, testing alignment was completed by early 2021 and received first light in December 2021.
The Gemini High-Resolution Optical SpecTrograph (GHOST) instrument is the next generation high resolution spectrograph for the Gemini telescope. The GHOST instrument was developed for the Gemini telescope as a collaboration between Australian Astronomical Optics (AAO) at Macquarie University, the Herzberg Astronomy and Astrophysics (HAA) in Canada and the Australian National University (ANU). The instrument is a fiber fed spectrograph with R<50,000 in two-object mode and R<75,000 in single object mode. The bench spectrograph was integrated at Gemini South from April to June 2022. This paper presents the final integration and alignment of the spectrograph at Gemini South and the measured spectrograph performance at the telescope.
The Many Instrument Fiber System (MANIFEST) is a facility fiber system for the Giant Magellan Telescope (GMT). MANIFEST will be capable of feeding current and upcoming GMT instruments light from the telescopes full 20-arcmin field of view. The MANIFEST concept uses “Starbugs” – self-motile fiber heads deployed on a glass plate. MANIFEST will enhance the capabilities of different optical and near-infrared spectrographs at the GMT by feeding fibres and providing simultaneous observations. We have so far developed 15 science cases for MANIFEST which are listed under five broad science themes. Many science cases from galactic surveys, nearby galaxy surveys, intergalactic medium tomography, and spatially resolved studies of distant universe are of interest. These science cases drive the instrument requirements, modes of observations, and operation conditions for MANIFEST. Defined from the science cases, MANIFEST offers nine different modes of observations including high multiplexing, multiple and high sensitivity integral-field spectroscopy, polarimetry, and near-infrared spectroscopy. We discuss in this paper the latest developments of GMT/MANIFEST.
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 TAIPAN instrument is installed on the UK Schmidt Telescope and has undergone 5 years of commissioning and verification. It utilizes the Starbug fibre positioning technology and is a proof-of-concept design for future Starbug-based instrumentation. The installation and commissioning of this new technology has provided opportunities to understand the Starbugs in detail. Science verification began in 2021 and has demonstrated the sub-10 minute configuration time, efficiency of small field ‘tweaks’ to correct for atmospheric refraction, and positioning accuracy of the Starbugs. Lessons learned from the commissioning of TAIPAN will directly impact future projects in which the Starbug technology is proposed, such as MANIFEST and FOBOS.
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 Hector instrument was installed at the Anglo-Australian Telescope in December 2021 and received the first light. It consists of three major subsystems, namely, the positioner, spectrograph and optical cable. Spector is the new spectrograph with an average spectral resolution of R=4500 designed for hexabundles, the fiber integral field units. Details of the integration and testing of the spectrograph optics are presented here. Each assembled subsystem was interferometrically checked for wavefront quality. The system spectral performance was fine tuned using a test fiber slit to achieve required resolution across the field of view. The absolute transmittance of the spectrograph bulk optics was measured in both blue and red channels.
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.
KEYWORDS: Prototyping, Interfaces, Telescopes, Structured optical fibers, Green fluorescent protein, Systems engineering, Glasses, Electronics, Manufacturing, Control systems design
Appropriate project costing for astronomy instrumentation in early phases is pivotal to support the process of acquiring suitable funding. It also sustains the effective project cost management and increases the chances of project success. The absence of a clear method to project costing in the industry might lead projects to be undertaken at below cost at the risk of compromising quality and performance, eventually resulting in onerous cost overruns, and in worst cases, in failure and loss of reputation. This paper explores the use of techniques from the Project Management Body of Knowledge PMBOK applied to the cost estimate from conceptual design through to completion of one of instruments proposed for the Giant Magellan Telescope: MANIFEST, a robotic multi-fibre positioner that enhances the capabilities of other instruments in the telescope and enables the use of the telescope’s full field of view. Whilst the accuracy of the cost estimate results cannot be asserted until the project reaches more maturity, the MANIFEST cost estimate has proven to be a useful tool for cost control, more efficient resource allocation and forecast, and decision enabling during the MANIFEST Conceptual Design Phase 1. The cost basis of estimate used establishes the starting point to measure the project costing efficacy and the baseline required for the future program costing updates.
The instrument group of the Herzberg Astronomy and Astrophysics has been subcontracted by Australian Astronomical Optics (AAO) at Macquarie University to design and build the bench spectrograph for the Gemini High-Resolution Optical SpecTrograph (GHOST) instrument. The GHOST instrument is being developed for the Gemini telescope and is a collaboration between AAO, the Herzberg Astronomy and Astrophysics (HAA) in Canada and the Australian National University (ANU). The instrument is a fiber fed spectrograph with R<50,000 in two-object mode and R<75,000 in single object mode. This paper presents the i ph and the performance results for the laboratory testing of the spectrograph.
Starbugs are robotic devices that have the capability to simultaneously position many optical fibers, over the telescope’s focal plane to carry-out efficient spectroscopic surveys. The conceptual design of FOBOS, the Fiber-Optic Broadband Optical Spectrograph, deploys Starbugs at the Keck II focal plane to enable high-multiplex, deep spectroscopic follow-up of upcoming deep-imaging surveys. FOBOS requires configured fields of many-hundreds of targets (significantly more than TAIPAN and MANIFEST instruments) in a few minutes, consistent with typical detector readout times. FOBOS also requires the inclusion of different optical payloads, like integral field-units, calibration bundles, coherent imaging bundles and perhaps wavefront sensors. Therefore, with these new challenges, it is important to optimize the target allocation and routing algorithms for Starbugs that yield the best configuration times and science outcomes for FOBOS. We provide a description of the Starbug parameters required by the FOBOS conceptual design, perform relevant allocation simulations, and discuss their performance.
MANIFEST is a multi-object fibre positioner 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 seeing-limited instruments, GMACS and GCLEF, offers access to: larger fields of view; higher multiplex gains; versatile focal plane reformatting of the focal plane via multiple integral-field-units; increased spectral resolution using image-slicers; the capability for simultaneous observations with multiple instruments; the possibility of a gravity-invariant spectrograph mounting; the potential for OH suppression via fiber systems in the near-infrared; and the versatility of adding new instruments in the future. We have now completed the pre-concept phase for MANIFEST. This phase has focused on developing the science case and requirements, further developing high risk aspects of the instrument design, designing the opto-mechanical interfaces to the GMACS and GCLEF instruments, and detailing the interfaces to the GMT.
KEYWORDS: Visible radiation, James Webb Space Telescope, Observatories, Adaptive optics, Large telescopes, Spectrographs, Spatial resolution, Hubble Space Telescope, Telescopes
A consortium of several Australian and European institutes – together with the European Southern Observatory (ESO) – has initiated the design of MAVIS, a Multi-Conjugate Adaptive Optics (MCAO) system for the ground- based 8-m Very Large Telescope (VLT). MAVIS (MCAO-assisted Visible Imager and Spectrograph) will deliver visible images and integral field spectrograph data with 2-3x better angular resolution than the Hubble Space Telescope, making it a powerful complement at visible wavelengths to future facilities like the space-based James Webb Space Telescope and the 30 to 40m-class ground-based telescopes currently under construction, which are all targeting science at near-infrared wavelengths. MAVIS successfully passed its Phase A in May 2020. We present the motivations, requirements, principal design choices, conceptual design, expected performance and an overview of the exciting science enabled by MAVIS.
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.
The Gemini High-resolution Optical SpecTrograph (GHOST) is fed by an optical cable linking the telescope and environmentally stabilized spectrograph room. Telescope input is injected into integral field units that are translated along the focal surface by positioners. Each integral field unit serves as an image slicer partitioning the seeing limited image with the help of a hexagonal microlens array. An additional microlens array is used to inject light telecentrically into each fiber which maximizes the efficiency of the cable. Spectral measurements of the optical cable throughput are presented for the design wavelength range.
The problem of atmospheric emission from OH molecules is a long standing problem for near-infrared astronomy. We are now close to solving this problem for the first time with the PRAXIS instrument. PRAXIS is a unique spectrograph which is fed by fibres that remove the OH background, and is optimised specifically to benefit from OH-Suppression. The OH suppression is achieved with fibre Bragg gratings, which were tested successfully on the GNOSIS instrument. The OH lines are suppressed by a factor of ~1000, leading to a reduction of the integrated background of a factor ≈9. A future upgrade to multicore fibre Bragg gratings will further increase this reduction. PRAXIS has had two commissioning runs, with a third commissioning run planned for July 2019, which will be presented at the conference. PRAXIS has a measured throughput of ≈20 %, demonstrating high efficiency in an OH suppression instrument for the first time. Science verification observations of Seyfert galaxies demonstrate the potential of OH suppression.
The Starbug technology1 developed by AAO-MQ allows fibre positioners to be built with large multiplexing capabilities. The Starbug robots are positionable individually and in parallel, which results in significant configuration time improvements over what can be achieved by single-arm pick and place robots. Their design allows the Starbugs to carry a complex payload, and their movement mechanism and vacuum adhesion to the instrument's glass field plate at the telescope's focal plane means that they can be used to position fibres on a non-planar surface.
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.
In this paper we present recent progress on the Australian Astronomical Observatory’s AESOP2 fiber positioner for 4MOST (on VISTA). As an evolution of the Echidna “spine” technology used for FMOS (on Subaru), AESOP has challenging requirements to position 2,448 fibers in parallel, within 1 minute, to an accuracy of < 10 um RMS. AESOP successfully passed ESO’s official final design review and manufacturing has commenced. We present performance results from the first batch of newly-manufactured positioners and also report on how the AESOP project is tracking in terms of schedule, budget and risk.
Large-amplitude anomalous events have been observed in CCDs due to radioactive emission from high-index optical glasses, some producing charge-trapping like artefacts. We have identified the source of these events from one glass (Ohara S-YGH51) as α-particles from trace amounts of nuclides in the actinium decay series, parent 235U. We present measurements of the anomalous event rate for samples of 15 separate optical glasses with nd ≥ 1.6. There is a variation in anomalous count rates of orders of magnitude range over these materials. Care should be taken in the selection of optical glasses to be located in close proximity to detectors.
The AAO’s TAIPAN instrument is a multi-object fibre positioner and spectrograph installed on the 1.2m UK-Schmidt telescope at Siding Spring Observatory. The positioner, a prototype for the MANIFEST positioner on the Giant Magellan Telescope, uses independently controlled Starbug robots to position a maximum of 300 optical fibres on a 32cm glass field plate (for a 6 degree field of view), to an accuracy of 5 microns (0.3 arcsec). The Starbug technology allows multi-object spectroscopy to be carried out with a minimum of overhead between observations, significantly decreasing field configuration time. Over the next 5 years the TAIPAN instrument will be used for two southern-hemisphere surveys: Taipan, a spectroscopic survey of 1x10^6 galaxies at z<0.3, and FunnelWeb, a stellar survey complete to Gaia G=12.5. In this paper we present an overview of the operational TAIPAN instrument: its design, construction and integration, and discuss the 2017 commissioning campaign and science verification results obtained in early 2018.
The Australian Astronomical Observatory’s (AAO’s) AESOP project is part of the 4 metre Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fiber 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. Prototype tests, which were completed early in 2017 demonstrated that the instrument requirements are satisfied by the design. The project final design stage has recently been completed. In this paper, key features of the AESOP positioning system design, along with the techniques developed to overcome key mechanical, electronic, and software engineering challenges are described. 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 µm 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 µm and allows iterative positioning until all fiber tips are within tolerance. Maintaining co-planarity of the fiber tips requires accurate control in the assembly of several components that contribute to such errors. Assembly jigs have been developed and proven adequate for this purpose. Attaining high reliability in an assembly with many small components of disparate materials bonded together, including piezo ceramics, carbon fiber reinforced plastic, hardened steel, and electrical circuit boards, has entailed careful selection and application of cements and tightly controlled soldering for electrical connections.
VELOCE is an IFU fibre feed and spectrograph for the AAT that is replacing CYCLOPS2. It is being constructed by the AAO and ANU. In this paper we discuss the design and engineering of the IFU/fibre feed components of the cable. We discuss the mode scrambling gain obtained with octagonal core fibres and how these octagonal core fibres should be spliced to regular circular core fibres to ensure maximum throughput for the cable using specialised splicing techniques. In addition we also describe a new approach to manufacturing a precision 1D/2D array of optical fibres for some applications in IFU manufacture and slit manufacture using 3D printed fused silica substrates, allowing for a cheap substitute to expensive lithographic etching in silicon at the expense of positional accuracy. We also discuss the Menlo Systems laser comb which employs endlessly-singlemode fibre to eliminate modal noise associated with multimode fibre transmission to provide the VELOCE spectrograph with a stable and repeatable source of wavelength calibration lines.
The problem of atmospheric emission from OH molecules is a long standing problem for near-infrared astronomy. PRAXIS is a unique spectrograph which is fed by fibres that remove the OH background and is optimised specifically to benefit from OH-Suppression. The OH suppression is achieved with fibre Bragg gratings, which were tested successfully on the GNOSIS instrument. PRAXIS uses the same fibre Bragg gratings as GNOSIS in its first implementation, and will exploit new, cheaper and more efficient, multicore fibre Bragg gratings in the second implementation. The OH lines are suppressed by a factor of ∼ 1000, and the expected increase in the
signal-to-noise in the interline regions compared to GNOSIS is a factor of ∼ 9 with the GNOSIS gratings and a
factor of ∼ 17 with the new gratings.
PRAXIS will enable the full exploitation of OH suppression for the first time, which was not achieved by GNOSIS (a retrofit to an existing instrument that was not OH-Suppression optimised) due to high thermal emission, low spectrograph transmission and detector noise. PRAXIS has extremely low thermal emission, through the cooling of all significantly emitting parts, including the fore-optics, the fibre Bragg gratings, a long length of fibre, and the fibre slit, and an optical design that minimises leaks of thermal emission from outside the spectrograph. PRAXIS has low detector noise through the use of a Hawaii-2RG detector, and a high throughput through a efficient VPH based spectrograph. PRAXIS will determine the absolute level of the interline continuum and enable observations of individual objects via an IFU. In this paper we give a status update and report on acceptance tests.
GHOST is a high resolution spectrograph system currently being built for the Gemini South Observatory in Chile. In the Cassegrain unit, the observational targets are acquired on integral field units and guided during science exposures, feeding the fiber cable to the temperature-stabilized echelle spectrograph. The Cassegrain unit is mounted on the Gemini telescope, and consists of a main structural plate, the two object positioners and ballast frame. The image from each of the two science beams passes through a field lens and a mini-atmospheric dispersion corrector and is then captured by the integral field unit. The positioner moves each corrector-integral field unit assembly across the focal surface of the telescope. The main structural plate provides the interface for the positioner and ballast frame to the telescope structure. In this paper we describe the final design and assembly of the GHOST Cassegrain unit and report on the outcome of on-sky testing at the telescope in Chile.
The Gemini High-Resolution Optical SpecTrograph (GHOST) is the newest instrument being developed for the Gemini telescopes, in a collaboration between the Australian Astronomical Observatory (AAO), the Herzberg Institute for Astrophysics, National Research Council (HIA-NRC) in Canada, and the Australian National University. This paper describes the design of the fiber optic system, developed by AAO. This system links the GHOST multi-object positioner, mounted on Gemini's Cassegrain focus, with the HIA-NRC developed spectrograph, located in the pier lab, 20 meters below the main observatory floor. The GHOST optical cable consists of 62 fibers, Polymicro FBP53/74/94P (53 μm core, 94 μm polyimide buffer), packed into 8 furcation tubes. The optical fibers are held inside the furcation tubes by friction, with between one and twelve fibers in each of the individual tubes. The furcation tubes are mechanically secured to manifold and anchor assemblies by bonding to integral Kevlar yarn within the tubing. The cable includes an interlock switch, linked to the telescope control system, to halt all telescope motions if the cable becomes overstressed. Fibers are terminated by two integral field units (IFU1 and IFU2), guiding and science slits and a calibration light entry port. Mode scrambling is achieved by mechanical agitation in two orthogonal directions, with adjustable frequency and amplitude of up to 10 Hz and 50 mm, respectively.
In this paper we present the Australian Astronomical Observatory’s concept design for Sphinx - a fiber positioner with 4,332 “spines” on a 7.77mm pitch for CFHT’s Mauna Kea Spectroscopic Explorer (MSE) Telescope. Based on the Echidna technology used with FMOS (on Subaru) and 4MOST (on VISTA), the next evolution of the tilting spine design delivers improved performance and superior allocation efficiency. Several prototypes have been constructed that demonstrate the suitability of the new design for MSE. Results of prototype testing are presented, along with an analysis of the impact of tilting spines on the overall survey efficiency. The Sphinx fiber positioner utilizes a novel metrology system for spine position feedback. The metrology design and the careful considerations required to achieve reliable, high accuracy measurements of all fibers in a realistic telescope environment are also presented.
MANIFEST is a facility multi-object fibre system for the Giant Magellan Telescope, which uses ‘Starbug’ fibre positioning robots. MANIFEST, when coupled to the telescope’s planned seeing-limited instruments, GMACS, and G-CLEF, offers access to: larger fields of view; higher multiplex gains; versatile reformatting of the focal plane via IFUs; image-slicers; and in some cases higher spatial and spectral resolution. The Prototyping Design Study phase for MANIFEST, nearing completion, has focused on developing a working prototype of a Starbugs system, called TAIPAN, for the UK Schmidt Telescope, which will conduct a stellar and galaxy survey of the Southern sky. The Prototyping Design Study has also included work on the GMT instrument interfaces. In this paper, we outline the instrument design features of TAIPAN, highlight the modifications that will be necessary for the MANIFEST implementation, and provide an update on the MANIFEST/instrument interfaces.
TAIPAN will conduct a stellar and galaxy survey of the Southern sky. The TAIPAN positioner is being developed as a prototype for the MANIFEST instrument on the GMT. The TAIPAN Spectrograph is an AAO designed all-refractive 2-arm design that delivers a spectral resolution of R>2000 over the wavelength range 370-870 nm. It is fed by a custom fibre cable from the TAIPAN Starbugs positioner. The design for TAIPAN incorporates 150 optical fibres (with an upgrade path to 300). Presented is an engineering overview of the UKST Fibre Cable design used to support Starbugs, the custom slit design, and the overall design and build plan for the TAIPAN Spectrograph.
TAIPAN will conduct a stellar and galaxy survey of the Southern sky. The TAIPAN positioner is being developed as a prototype for the MANIFEST instrument on the GMT. The design for TAIPAN incorporates 150 optical fibres (with an upgrade path to 300) situated within independently controlled robotic positioners known as Starbugs. Starbugs allow precise parallel positioning of individual fibres, thus significantly reducing instrument configuration time and increasing the amount of observing time. Presented is an engineering overview of the UKST upgrade of the completely new Instrument Spider Assembly utilized to support the Starbug Fibre Positioning Robot and current status of the Starbug itself.
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.
We present advances in the patented Echidna 'tilting spine' fiber positioner technology that has been in operation since 2007 on the SUBARU telescope in the FMOS system. The new Echidna technology is proposed to be implemented on two large fiber surveys: the Dark Energy Spectroscopic Instrument (DESI) (5000 fibers) as well the Australian ESO Positioner (AESOP) for 4MOST, a spectroscopic survey instrument for the VISTA telescope (~2500 fibers). The new 'superspine' actuators are stiffer, longer and more accurate than their predecessors. They have been prototyped at AAO, demonstrating reconfiguration times of ~15s for errors of <5 microns RMS. Laboratory testing of the prortotype shows accurate operation at temperatures of -10 to +30C, with an average heat output of 200 microwatts per actuator during reconfiguration. Throughput comparisons to other positioner types are presented, and we find that losses due to tilt will in general be outweighed by increased allocation yield and reduced fiber stress FRD. The losses from spine tilt are compensated by the gain in allocation yield coming from the greater patrol area, and quantified elsewhere in these proceedings. For typical tilts, f-ratios and collimator overspeeds, Echidna offers a clear efficiency gain versus current r-that or theta-phi positioners.
MANIFEST is a fibre feed system for the Giant Magellan Telescope that, coupled to the seeing-limited instruments
GMACS and G-CLEF, offers qualitative and quantitative gains over each instrument’s native capabilities in terms of
multiplex, field of view, and resolution. The MANIFEST instrument concept is based on a system of semi-autonomous
probes called “Starbugs” that hold and position hundreds of optical fibre IFUs under a glass field plate placed at the
GMT Cassegrain focal plane. The Starbug probes feature co-axial piezoceramic tubes that, via the application of
appropriate AC waveforms, contract or bend, providing a discrete stepping motion. Simultaneous positioning of all
Starbugs is achieved via a closed-loop metrology system.
The 4MOST[1] instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the
ESO VISTA telescope designed to perform a massive (initially >25x106 spectra in 5 years) combined all-sky public
survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial
velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of
galaxies, X-ray AGN/galaxy evolution to z~5, Galactic X-ray sources and resolving the Galactic edge;
Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be
undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data
reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of
~1600 targets at R~5,000 from 390-900nm and ~800 targets at R<18,000 in three channels between ~395-675nm
(channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of ~ 4.1 degrees. The initial
5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: optomechanical,
control, data management and operations concepts; and initial performance estimates.
The new HERMES spectrograph represents the first foray by AAO into the use of commercial off-the-shelf industrial field bus technology for instrument control, and we regard the final system, with its relatively simple wiring requirements, as a great success. However, both software and hardware teams had to work together to solve a number of problems integrating the chosen CANopen/CAN bus system into our normal observing systems. A Linux system running in an industrial PC chassis ran the HERMES control software, using a PCI CAN bus interface connected to a number of distributed CANopen/CAN bus I/O devices and servo amplifiers. In the main, the servo amplifiers performed impressively, although some experimentation with homing algorithms was required, and we hit a significant hurdle when we discovered that we needed to disable some of the encoders used during observations; we learned a lot about how servo amplifiers respond when their encoders are turned off, and about how encoders react to losing power. The software was based around a commercial CANopen library from Copley Controls. Early worries about how this heavily multithreaded library would work with our standard data acquisition system led to the development of a very low-level CANopen software simulator to verify the design. This also enabled the software group to develop and test almost all the control software well in advance of the construction of the hardware. In the end, the instrument went from initial installation at the telescope to successful commissioning remarkably smoothly.
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.
TAIPAN is a spectroscopic instrument designed for the UK Schmidt Telescope at the Australian Astronomical Observatory. In addition to undertaking the TAIPAN survey, it will serve as a prototype for the MANIFEST fibre positioner system for the future Giant Magellan Telescope. The design for TAIPAN incorporates up to 300 optical fibres situated within independently-controlled robotic positioners known as Starbugs, allowing precise parallel positioning of every fibre, thus significantly reducing instrument configuration time and increasing observing time. We describe the design of the TAIPAN instrument system, as well as the science that will be accomplished by the TAIPAN survey. We also highlight results from the on-sky tests performed in May 2014 with Starbugs on the UK Schmidt Telescope and briefly introduce the role that Starbugs will play in MANIFEST.
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 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.
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 Australian Astronomical Observatory (AAO) has recently completed a feasibility study for a fiber-positioner facility proposed for the Giant Magellan Telescope (GMT), called MANIFEST (the Many Instrument Fiber System). The MANIFEST instrument takes full advantage of the wide-field focal plane to efficiently feed other instruments. About 2000 individually deployable fiber units are envisaged, with a wide variety of aperture types (single-aperture, image- or pupil-slicing, IFU). MANIFEST allows (a) full use of the GMT's 20' field-of-view, (b) a multiplexed IFU capability, (c) greatly increased spectral resolution via image-slicing, (d) the possibility of OH-suppression in the near-infrared.
Starbugs are miniature piezoelectric 'walking' robots with the ability to simultaneously position many optical fibres
across a telescope's focal plane. Their simple design incorporates two piezoceramic tubes to form a pair of concentric
'legs' capable of taking individual steps of a few microns, yet with the capacity to move a payload several millimetres
per second. The Australian Astronomical Observatory has developed this technology to enable fast and accurate field
reconfigurations without the inherent limitations of more traditional positioning techniques, such as the 'pick and place'
robotic arm. We report on our recent successes in demonstrating Starbug technology, driven principally by R&D efforts
for the planned MANIFEST (many instrument fibre-system) facility for the Giant Magellan Telescope. Significant
performance gains have resulted from improvements to the Starbug system, including i) the use of a vacuum to attach
Starbugs to the underside of a transparent field plate, ii) optimisation of the control electronics, iii) a simplified
mechanical design with high sensitivity piezo actuators, and iv) the construction of a dedicated laboratory 'test rig'. A
method of reliably rotating Starbugs in steps of several arcminutes has also been devised, which integrates with the pre-existing
x-y movement directions and offers greater flexibility while positioning. We present measured performance data
from a prototype system of 10 Starbugs under full (closed-loop) control, at field plate angles of 0-90 degrees.
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.
We describe the design of a new CCD system delivered to the Automated Patrol Telescope at Siding Springs NSW
Australia operated by UNSW. A very fast beam (f/1) with a mosaic of two MITLL CCID-34 detectors placed only 1
mm behind the field flattener which also serves as the dewar window, have called for innovative engineering solutions.
This paper describes the design and procedure of the field-flattener mounting, differential screw adjustable detector
mount and dewar suspension on the external ring providing tip/tilt and focus adjustment.
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.
AAOmega is the new spectrograph for the 2dF fibre-positioning system on the Anglo-Australian Telescope. It is a bench-mounted, double-beamed design, using volume phase holographic (VPH) gratings and articulating cameras. It is fed by 392 fibres from either of the two 2dF field plates, or by the 512 fibre SPIRAL integral field unit (IFU) at Cassegrain focus. Wavelength coverage is 370 to 950nm and spectral resolution 1,000-8,000 in multi-Object mode, or 1,500-10,000 in IFU mode. Multi-object mode was commissioned in January 2006 and the IFU system will be commissioned in June 2006.
The spectrograph is located off the telescope in a thermally isolated room and the 2dF fibres have been replaced by new 38m broadband fibres. Despite the increased fibre length, we have achieved a large increase in throughput by use of VPH gratings, more efficient coatings and new detectors - amounting to a factor of at least 2 in the red. The number of spectral resolution elements and the maximum resolution are both more than doubled, and the stability is an order of magnitude better.
The spectrograph comprises: an f/3.15 Schmidt collimator, incorporating a dichroic beam-splitter; interchangeable VPH gratings; and articulating red and blue f/1.3 Schmidt cameras. Pupil size is 190mm, determined by the competing demands of cost, obstruction losses, and maximum resolution. A full suite of VPH gratings has been provided to cover resolutions 1,000 to 7,500, and up to 10,000 at particular wavelengths.
IRIS2 is a near-infrared imager and spectrograph based on a HAWAII1 HgCdTe detector. It provides wide-field (7.7’×7.7’) imaging capabilities at 0.4486”/pixel sampling, long-slit spectroscopy at λ/Δλ≈2400 in each of the J, H and K passbands, and the ability to do multi-object spectroscopy in up to three masks. These multi-slit masks are laser cut, and have been manufactured for both traditional multiple slit work (≈20-40 objects in a 3’×7.4’ field-of-view), multiple slit work in narrow-band filters (≈100 objects in a 5’×7.4’ field-of-view), and micro-hole spectroscopy in narrow-band filters allowing the observation of ≈200 objects in a 5’×7.4’ field.
The AAOmega project replaces the two 2dF spectrographs, which are mounted on the top end of the Anglo Australian Telescope, with a bench mounted double beam spectrograph covering 370 to 950nm. The 2dF positioner, field plate tumbler mechanism, and fiber retractors will be retained. The new spectrograph will be fed by 392 fibers from either of the two 2dF field plates, or by the 512 fiber Spiral integral field unit, located at the Cassegrain focus. New instrument control electronics has also been designed to drive the spectrograph.
Stability will be improved by locating the spectrograph off the telescope, but the 2df fibers must be extended to thirty-eight metres length. Despite this, using fibers with improved characteristics, increased pupil diameter, volume phase holographic (VPH) gratings with articulated cameras, and more efficient coatings on optics we achieve a minimum twofold increase in throughput. We will also fit larger (4k x 2k pixel) detectors.
The spectrograph comprises: a F/3.15 Schmidt collimator, incorporating a dichroic beamsplitter; interchangeable VPH gratings; and articulating red and blue F/1.3 Schmidt cameras. The beamsplitter may be exchanged with others which cut off at different wavelengths. A full suite of VPH gratings are provided to cover resolution to 8000.
IRIS2, the infrared imager and spectrograph for the Cassegrain focus of the Anglo Australian Telescope, has been in service since October 2001.
IRIS2 incorporated many novel features, including multiple cryogenic multislit masks, a dual chambered vacuum vessel (the smaller chamber used to reduce thermal cycle time required to change sets of multislit masks), encoded cryogenic wheel drives with controlled backlash, a deflection compensating structure, and use of teflon impregnated hard anodizing for gear lubrication at low temperatures. Other noteworthy features were: swaged foil thermal link terminations, the pupil imager, the detector focus mechanism, phased getter cycling to prevent detector contamination, and a flow-through LN2 precooling system. The instrument control electronics was designed to allow accurate positioning of the internal mechanisms with minimal generation of heat. The detector controller was based on the AAO2 CCD controller, adapted for use on the HAWAII1 detector (1024 x 1024 pixels) and is achieving low noise and high performance.
We describe features of the instrument design, the problems encountered and the development work required to bring them into operation, and their performance in service.
KEYWORDS: Clocks, Digital signal processing, Sensors, Charge-coupled devices, Video, Analog electronics, Video processing, Control systems, Power supplies, Connectors
The Anglo-Australian Observatory has developed a 2nd generation optical CCD controller to replace an earlier controller used now for almost twenty years. The new AAO2 controller builds on the considerable experience gained with the first controller, the new technologies now available and the techniques developed and successfully implemented in AAO's IRIS2 detector controller. The AAO2 controller has been designed to operate a wide variety of detectors and to achieve as near to detector limited performance as possible. It is capable of reading out CCDs with one, two or four output amplifiers, each output having its own video processor and high speed 16-bit ADC. The video processor is a correlated double sampler that may be switched between low noise dual slope integration or high speed clamp and sample modes. Programmable features include low noise DAC biases, horizontal clocks with DAC controllable levels and slopes and vertical clocks with DAC controllable arbitrary waveshapes. The controller uses two DSPs; one for overall control and the other for clock signal generation, which is highly programmable, with downloadable sequences of waveform patterns. The controller incorporates a precision detector temperature controller and provides accurate exposure time control. Telemetry is provided of all DAC generated voltages, many derived voltages, power supply voltages, detector temperature and detector identification. A high speed, full duplex fibre optic interface connects the controller to a host computer. The modular design uses six to ten circuit boards, plugged in to common backplanes. Two backplanes separate noisy digital signals from low noise analog signals.
KEYWORDS: Sensors, Control systems, Fiber optics, Data processing, Image processing, Data acquisition, Interfaces, Charge-coupled devices, Human-machine interfaces, Computing systems
The AAO's new AAO2 detector controllers can handle both infra-red detectors and optical CCDs. IR detectors in particular place considerable demands on a data handling system, which has to get the data from the controllers into the data processing chain as efficiently as possible, usually with significant constraints imposed by the need to read out the detector in as smooth a manner as possible. The AAO2 controller makes use of a VME chassis that contains both a real-time VxWorks system and a UNIX system. These share access to common VME memory, the VxWorks system reading from the controller into the shared memory and the UNIX system reading it from the shared memory and processing it. Modifications to the DRAMA data acquisition environment's bulk-data sub-system hide this use of VME shared memory in the normal DRAMA bulk-data API. This means that the code involved can be tested under UNIX, using standard UNIX shared memory mechanisms, and then deployed on the VxWorks/UNIX VME system without any code changes being needed. When deployed, the data transfer from the controller via VxWorks into the UNIX-based data processing chain is handled by consecutive DMA transfers into and out of VME memory, easily achieving the required throughput. We discuss aspects of this system, including a number of the less obvious problems that were encountered.
OzPoz is a multi-fiber positioner to feed spectrographs from a Nasmyth focus of VLT Unit Telescope 2. The concept follows that of the 2dF system on the AAT: a robot re-positions magnetically attached buttons on one of a pair of steel plates while the other plate is observing. But the large scale and the curvature of the VLT Nasmyth focal surface led to the design being very different. Its combination of large moving elements with high precision and the need to survive severe earthquakes presented special challenges. Electrical interlocking of the many functions had to be very comprehensive to minimize risks of damage to the instrument and harm to personnel. Despite the valuable inheritance from 2dF, considerable effort had to be devoted to software to fit the ESO VLT environment and to deal with the complexity of the interacting elements. Integration on the VLT commenced in March 2002, followed by commissioning runs with Giraffe in June, August, and October. Some instrument defects were uncovered during installation and commissioning but none was fundamental and they were readily fixed in between night runs. The time taken to reconfigure a plate, an average of ten seconds/fiber, meets specification and the accuracy of alignment of fiber apertures with stars is limited mostly by the astrometry of target fields.
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.
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