Very fast (f/1.2 and f/1.35) transmissive spectrograph designs are presented for Hector and MSE. The designs have 61mm x 61mm detectors, 4 or 5 camera lenses of aperture less than 228mm, with just 6 air/glass surfaces, and rely on extreme aspheres for their imaging performance. The throughput is excellent, because of the i-line glasses used, the small number of air/glass surfaces.
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.
Optical designs are presented for the Maunakea Spectroscopic Explorer (MSE) telescope. The adopted baseline design is a prime focus telescope with a segmented primary of 11.25m aperture, with speed f/1.93 and 1.52° field-of-view, optimized for wavelengths 360-1800nm. The Wide-Field Corrector (WFC) has five aspheric lenses, mostly of fused silica, with largest element 1.33m diameter and total glass mass 788kg. The Atmospheric Dispersion Corrector (ADC) is of the compensating lateral type, combining a motion of the entire WFC via the hexapod, with a restoring motion for a single lens. There is a modest amount of vignetting (average 5% over the hexagonal field); this greatly improves image quality, and allows the design to be effectively pupil-centric. The polychromatic image quality is d80<0.225"/0.445" at ZD 0/60° over more than 95% of the hexagonal field-of-view. The ADC action allows adjustment of the plate-scale with zenith distance, which is used to halve the image motions caused by differential refraction. A simple design is presented for achieving the required ADC lens shifts and tilts. A two-mirror design was also undertaken for MSE, but was not selected. This is a 12.3m F/2.69 forward Cassegrain design, with a 2.75m diameter M2, and three silica lenses, of largest diameter 1.33m. The field-of-view is again 1.52°. The f/0.95 primary makes the design remarkably compact, being under 10m long. The ADC action involves a small motion of M2 (again via a hexapod), and shifts and tilts of a single lens. The design is effectively pupil-centric, with modest vignetting (5.9% average). The image quality is virtually identical to the prime focus design.
We present an alternative Corrector-ADC design for GMT. The design consists of just 3 silica lenses, of maximum size 1.51m, and includes only a single low-precision asphere for 20' field-of-view, and none for 10'. The polychromatic (360nm-1300nm) image quality is d80<0.043" at zenith and d80<0.20" for ZD<60 degrees. The monochromatic image quality is d80<0.1" everywhere, and typically ~0.05". The ADC action is achieved by tilt and translation of all three lenses; L1 and L2 via simple slide mechanisms each using a single encoded actuator, and L3 via a novel ‘tracker-ball’ support and three actuators. There is also a small motion of M2 via the hexapod, automatically generated by the AGWS system. The ADC action causes a small non-telecentricity, but this is much less than the unavoidable chromatic effects shared with the baseline design. The ADC action also changes the distortion pattern of the telescope, but this can be used positively, to reduce the maximum image motion due to differential refraction by a factor of three. The transmission is superb at all wavelengths, because of the reduced number of air/glass surfaces, and the use only of fused silica.
Hector[1,2,3] will be the new massively-multiplexed integral field spectroscopy (IFS) instrument for the Anglo-Australian Telescope (AAT) in Australia and the next main dark-time instrument for the observatory. Based on the success of the SAMI instrument, which is undertaking a 3400-galaxy survey, the integral field unit (IFU) imaging fibre bundle (hexabundle) technology under-pinning SAMI is being improved to a new innovative design for Hector. The distribution of hexabundle angular sizes is matched to the galaxy survey properties in order to image 90% of galaxies out to 2 effective radii. 50-100 of these IFU imaging bundles will be positioned by ‘starbug’ robots across a new 3-degree field corrector top end to be purpose-built for the AAT. Many thousand fibres will then be fed into new replicable spectrographs. Fundamentally new science will be achieved compared to existing instruments due to Hector's wider field of view (3 degrees), high positioning efficiency using starbugs, higher spectroscopic resolution (R=3000-5500 from 3727-7761Å, with a possible redder extension later) and large IFUs (up to 30 arcsec diameter with 61-217 fibre cores). A 100,000 galaxy IFS survey with Hector will decrypt how the accretion and merger history and large-scale environment made every galaxy different in its morphology and star formation history. The high resolution, particularly in the blue, will make Hector the only instrument to be able to measure higher-order kinematics for galaxies down to much lower velocity dispersion than in current large IFS galaxy surveys, opening up a wealth of new nearby galaxy science.
The Maunakea Spectroscopic Explorer is designed to be the largest non-ELT optical/NIR astronomical telescope, and will be a fully dedicated facility for multi-object spectroscopy over a broad range of spectral resolutions. The MSE design has progressed from feasibility concept into its current baseline design where the system configuration of main systems such as telescope, enclosure, summit facilities and instrument are fully defined. This paper will describe the engineering development of the main systems, and discuss the trade studies to determine the optimal telescope and multiplexing designs and how their findings are incorporated in the current baseline design.
Modern telescopes typically have prime focus speeds too fast for direct use with standard numerical aperture (NA=0.22±0.02) silica-cored fibers. Specifically, the current design for the proposed Maunakea Spectroscopic Explorer (MSE) telescope is ~f/2, requiring fibers with NA>0.25. Micro foreoptics can be used to slow the beam, as used on the prime focus spectrograph (PFS) on Subaru, but this adds cost and complexity, and increases losses. An attractive alternative is offered by high NA pure silica-cored fibers, which can be used directly at f/2, and which are now available from multiple vendors. We present throughput and focal ratio degradation measurements on two samples of these high NA fibers. It is found that the measured attenuation losses are comparable with the best available standard NA fibers. The fibers were also tested for focal ratio degradation, and the fiber from CeramOptec was found to have acceptable FRD, representng additional collimator losses ~1%. The near field performance of the high NA fiber is also investigated and these high NA fibers exhibit very good scrambling performance; we saw no evidence for significant output near-field variations for varying input beam angles or position in a 50m fiber.
Starbugs are miniature piezoelectric ‘walking’ robots that can be operated in parallel to position many payloads (e.g.
optical fibres) across a telescope’s focal plane. They consist of two concentric piezo-ceramic tubes that walk with micron
step size. In addition to individual optical fibres, Starbugs have moved a payload of 0.75kg at several millimetres per
second. The Australian Astronomical Observatory previously developed prototype devices and tested them in the
laboratory. Now we are optimising the Starbug design for production and deployment in the TAIPAN instrument, which
will be capable of configuring 300 optical fibres over a six degree field-of-view on the UK Schmidt Telescope within a
few minutes. The TAIPAN instrument will demonstrate the technology and capability for MANIFEST (Many Instrument
Fibre-System) proposed for the Giant Magellan Telescope. Design is addressing: connector density and voltage
limitations, mechanical reliability and construction repeatability, field plate residues and scratching, metrology stability,
and facilitation of improved motion in all aspects of the design for later evaluation. Here we present the new design
features of the AAO TAIPAN Starbug.
The image quality of a fluid atmospheric dispersion corrector (FADC) is analysed and presented.
The FADC is located at Cassegrain focus to correct the atmospheric dispersion passively at
Australian astronomical telescope. It is shown that an FADC with diameter 10mm can correct
the atmospheric dispersion over a field diameter of 20” in the spectral range between 0.4μm to
1μm, and to zenith distance of 52º. The FADC image quality is well controlled within 0.27” for
the telescope operation range. The residual atmospheric dispersion is 0.1” for on axis field and
0.20” at the extreme field (10”) at zenith distance of 52º. The FADC-induced shift in the
centroids of the images is less than 10μm (0.067”). The FADC can work up to the field of 5’ at
Cassegrain focus and its image quality is similar to its on axis performance. Our on-sky
demonstration results agree well with our simulations.
We present Simulated Annealing fiber-to-target allocation simulations for the proposed DESI and 4MOST massively multiplexed spectroscopic surveys. We simulate various survey strategies, for both Poisson and realistically clustered mock target samples. We simulate both Echidna and theta-phi actuator designs, including the restrictions caused by the physical actuator characteristics during repositioning. For DESI, with theta-phi actuators, used in 5 passes over the sky for a mock ELG/LRG/QSO sample, with matched fiber and target densities, a total target allocation yield of 89.3% was achieved, but only 83.7% for the high-priority Ly-alpha QSOs. If Echidna actuators are used with the same pitch and number of passes, the yield increases to 94.4% and 97.2% respectively, representing fractional gains of 5.7% and 16% respectively. Echidna also allows a factor-of-two increase in the number of close Ly-alpha QSO pairs that can be observed. Echidna spine tilt causes a variable loss of throughput, with average loss being the same as the loss at the rms tilt. The simulated annealing allows spine tilt minimization to be included in the optimization, at some small cost to the yield. With a natural minimization scheme, we find an rms tilt always close to 0.58 x maximum. There is an additional but much smaller defocus loss, equivalent to an average defocus of 30 μm. These tilt losses offset the gains in yield for Echidna, but because the survey strategy is driven by the higher priority targets, a clear survey speed advantage remains. For 4MOST, high and low latitude sample mock catalogs were supplied by the 4MOST team, and allocations were carried out with the proposed Echidna-based positioner geometry. At high latitudes, the resulting target completeness was 85.3% for LR targets and 78.9% for HR targets. At low latitude, the target completeness was 93.9% for LR targets and 71.2% for HR targets.
4MOST, the 4m Multi-Object Spectroscopic Telescope, features a 2.5 degree diameter field-of-view with ~2400 fibers in
the focal plane that are configured by a fiber positioner based on the tilting spine principle (Echidna/FMOS) arranged in
a hexagonal pattern. The fibers feed two types of spectrographs; ~1600 fibers go to two spectrographs with resolution
R>5000 and ~800 fibers to a spectrograph with R>18,000. Part of the ongoing optimization of the fiber feed subsystem
design includes early prototyping and testing of key components such as fiber connectors and fiber cable management.
Performance data from this testing will be used in the 4MOST instrument simulator (TOAD) and 4MOST system design
optimization. In this paper we give an overview of the current fiber feed subsystem design, simulations and prototyping
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.
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.
Spectrograph costs have become the limiting factor in multiplexed fiber-based spectroscopic instruments, because tens of
millions of resolution elements (spectral x spatial) are now required. Catadioptric (Schmidt-like) designs allow faster
cameras and hence reduced detector costs, and recent advances in aspheric lens production make the overall optics costs
competitive with transmissive designs. Classic Schmidt designs suffer from obstruction losses caused by the detector
being within the beam. A new catadioptric design puts the detector close to the spectrograph pupil, and hence largely in
the shadow of the telescope top-end obstruction. The throughput is competitive with the best transmissive designs, and
much better in the Blue, where it is usually most valuable. The design also has milder aspheres and is more compact than
classic Schmidts, and avoids most of their operational difficulties.
The fast cameras mean that with 15micron pixels, the PSF sampling is close to the Nyquist limit; this minimises the
effects of read-noise, which for sky-limited observations, far outweighs any difference in throughput. It does introduce
pixellation penalties; these are investigated and found to be modest.
For 4MOST, low and high resolution designs are presented, with 300mm beams, 3 arms with f/1.3 cameras, and standard
61mm x 61mm detectors. Coverage is 380-930nm at R=5000-7000, or R~20000 in three smaller ranges. A switchable
design is also presented. For Hector, a design is presented with 2 arms, 380-930nm coverage, and R=3000-4500; a 4-
armed design with smaller beam-size and detectors is also presented. The designs are costed, and appear to represent
All spectrographs unavoidably scatter light. Scattering in the spectral direction is problematic for sky subtraction, since atmospheric spectral lines are blurred. Scattering in the spatial direction is problematic for fibre fed spectrographs, since it limits how closely fibres can be packed together. We investigate the nature of this scattering and show that the scattering wings have both a Lorentzian component, and a shallower (1/r) component. We investigate the causes of this from a theoretical perspective, and argue that for the spectral PSF the Lorentzian wings are in part due to the profile of the illumination of the pupil of the spectrograph onto the diffraction grating, whereas the shallower component is from bulk scattering. We then investigate ways to mitigate the diffractive scattering by apodising the pupil. In the ideal case of a Gaussian apodised pupil, the scattering can be significantly improved. Finally we look at realistic models of the spectrograph pupils of fibre fed spectrographs with a centrally obstructed telescope, and show that it is possible to apodise the pupil through non-telecentric injection into the fibre.
4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large
area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with ~2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; ~1600 fibres go to two spectrographs with resolution R<5000 (λ~390-930 nm) and
~800 fibres to a spectrograph with R>18,000 (λ~392-437 nm and 515-572 nm and 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the
southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing
concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020.
This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more
detailed descriptions of the instrument concept, the instrument requirements development, the systems engineering implementation, the instrument model, the fibre positioner concepts, the fibre feed, and the spectrographs.
Hector is an instrument concept for a multi integral-field-unit spectrograph aimed at obtaining a tenfold increase in
capability over the current generation of such instruments. The key science questions for this instrument include how do
galaxies get their gas, how is star formation and nuclear activity affected by environment, what is the role of feedback,
and what processes can be linked to galaxy groups and clusters. The baseline design for Hector incorporates multiple
hexabundle fibre integral-field-units that are each positioned using Starbug robots across a three-degree field at the
Anglo-Australian Telescope. The Hector fibres feed dedicated fixed-format spectrographs, for which the parameter space
is currently being explored.
The 4MOST 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.
A 2.5 degree field diameter corrector lens design for the Cassegrain focus of the VISTA 4 meter telescope is presented.
It comprises four single elements of glasses with high UV transmission, all axi-symmetric for operation at the zenith.
One element is displaced laterally to provide atmospheric dispersion correction. A key feature, especially beneficial for
the VISTA application, is that the ADC element can be mounted so it is driven simply by gravity; thus its operation
needs no motors, encoders, cabling, or software control. A simple mechanical design to achieve this and the optical
performance details are described.
Wide-Field Corrector designs are presented for the Blanco and Mayall telescopes, the CFHT and the AAT. The designs
are Terezibh-style, with 5 or 6 lenses, and modest negative optical power. They have 2.2°-3° ields of view, with curved
and telecentric focal surfaces suitable for fiber spectroscopy. Some variants also allow wide-field imaging, by changing
the last WFC element. Apart from the adaptation of the Terebizh design for spectroscopy, the key feature is a new
concept for a ‘Compensating Lateral Atmospheric Dispersion Corrector’, with two of the lenses being movable laterally
by small amounts. This provides excellent atmospheric dispersion correction, without any additional surfaces or
absorption. A novel and simple mechanism for providing the required lens motions is proposed, which requires just 3
linear actuators for each of the two moving lenses.
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.
We present a concept for a 4000-fibre positioner for DESpec, based on the Echidna ‘tilting spine’ technology. The DESpec focal plane is 450mm across and curved, and the required pitch is ~6.75mm. The size, number of fibers and curvature are all comparable with various concept studies for similar instruments already undertaken at the AAO, but present new challenges in combination. A simple, low-cost, and highly modular design is presented, consisting of identical modules populated by identical spines. No show-stopping issues in accommodating either the curvature or the smaller pitch have been identified, and the actuators consist largely of off-the-shelf components. The actuators have been prototyped at AAO, and allow reconfiguration times of ~15s to reach position errors 7 microns or less. Straightforward designs for metrology, acquisition, and guiding are also proposed. The throughput losses of the entire positioner system are estimated to be ~15%, of which 6.3% is attributable to the tilting-spine technology.
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.
KOALA, the Kilofibre Optimised Astronomical Lenslet Array, is a wide-field, high efficiency integral field unit
being designed for use with the bench mounted AAOmega spectrograph on the AAT. KOALA will have 1000
fibres in a rectangular array with a selectable field of view of either 1390 or 430 sq. arcseconds with a spatial
sampling of 1.25" or 0.7" respectively. To achieve this KOALA will use a telecentric double lenslet array with
interchangeable fore-optics. The IFU will feed AAOmega via a 31m fibre run. The efficiency of KOALA is
expected to be ≈ 52% at 3700A and ≈ 66% at 6563°Å with a throughput of > 52% over the entire wavelength
The next generation of massively multiplexed multi-object spectrographs (DESpec, SUMIRE, BigBOSS, 4MOST,
HECTOR) demand fast, efficient and affordable spectrographs, with higher resolutions (R = 3000-5000) than current
designs. Beam-size is a (relatively) free parameter in the design, but the properties of VPH gratings are such that, for
fixed resolution and wavelength coverage, the effect on beam-size on overall VPH efficiency is very small. For alltransmissive
cameras, this suggests modest beam-sizes (say 80-150mm) to minimize costs; while for cadioptric
(Schmidt-type) cameras, much larger beam-sizes (say 250mm+) are preferred to improve image quality and to minimize
obstruction losses. Schmidt designs have benefits in terms of image quality, camera speed and scattered light
performance, and recent advances such as MRF technology mean that the required aspherics are no longer a prohibitive
cost or risk.
The main objections to traditional Schmidt designs are the inaccessibility of the detector package, and the loss in
throughput caused by it being in the beam. With expected count rates and current read-noise technology, the gain in
camera speed allowed by Schmidt optics largely compensates for the additional obstruction losses. However, future
advances in readout technology may erase most of this compensation.
A new Schmidt/Maksutov-derived design is presented, which differs from previous designs in having the detector
package outside the camera, and adjacent to the spectrograph pupil. The telescope pupil already contains a hole at its
center, because of the obstruction from the telescope top-end. With a 250mm beam, it is possible to largely hide a 6cm ×
6cm detector package and its dewar within this hole. This means that the design achieves a very high efficiency,
competitive with transmissive designs. The optics are excellent, as least as good as classic Schmidt designs, allowing
F/1.25 or even faster cameras. The principal hardware has been costed at $300K per arm, making the design affordable.
We describe the preliminary design of the Dark Energy Spectrometer (DESpec), a fiber-fed spectroscopic instrument
concept for the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory (CTIO). DESpec would take
advantage of the infrastructure recently deployed for the Dark Energy Camera (DECam). DESpec would be mounted in
the new DECam prime focus cage, would be interchangeable with DECam, would share the DECam optical corrector,
and would feature a focal plane with ~4000 robotically positioned optical fibers feeding multiple high-throughput
spectrometers. The instrument would have a field of view of 3.8 square degrees, a wavelength range of approximately
500<<1000 nm, and a spectral resolution of R~3000. DESpec would provide a powerful spectroscopic follow-up
system for sources in the Southern hemisphere discovered by the Dark Energy Survey and LSST.λ
First light from the SAMI (Sydney-AAO Multi-object IFS) instrument at the Anglo-Australian Telescope (AAT) has
recently proven the viability of fibre hexabundles for multi-IFU spectroscopy. SAMI, which comprises 13 hexabundle
IFUs deployable over a 1 degree field-of-view, has recently begun science observations, and will target a survey of
several thousand galaxies. The scientific outputs from such galaxy surveys are strongly linked to survey size, leading the
push towards instruments with higher multiplex capability. We have begun work on a new instrument concept, called
Hector, which will target a spatially-resolved spectroscopic survey of up to one hundred thousand galaxies. The key
science questions for this instrument concept include how do galaxies get their gas, how is star formation and nuclear
activity affected by environment, what is the role of feedback, and what processes can be linked to galaxy groups and
clusters. One design option for Hector uses the existing 2 degree field-of view top end at the AAT, with 50 individual
robotically deployable 61-core hexabundle IFUs, and 3 fixed format spectrographs covering the visible wavelength range
with a spectral resolution of approximately 4000. A more ambitious option incorporates a modified top end at the AAT
with a new 3 degree field-of-view wide-field-corrector and 100 hexabundle IFUs feeding 6 spectrographs.
First identied in 2009 as the site with the lowest precipitable water and best terahertz transmission on Earth,
Ridge A is located approximately 150 km south of Dome A, Antarctica. To further rene this optimum location
prior to deployment in 2012 of a robotic THz observatory, we have modelled the atmospheric transmission as
a function of location over a 1,000,000 km square grid using three years of data from the Microwave Humidity
Sounder on the NOAA-18 satellite. The modelling identies a broad area of exceptionally low water vapour close
to the 4,000 metre elevation contour, reaching below 100 microns for extended periods of time.
Following the successful commissioning of SAMI (Sydney-AAO Multi-object IFU) the AAO has undertaken concept
studies leading to a design of a new instrument for the AAT (Hector). It will use an automated robotic system for the
deployment of fibre hexabundles to the focal plane. We have analysed several concepts, which could be applied in the
design of new instruments or as a retrofit to existing positioning systems. We look at derivatives of Starbugs that could
handle a large fibre bundle as well as modifications to pick and place robots like 2dF or OzPoz. One concept uses large
magnetic buttons that adhere to a steel field plate with substantial force. To move them we replace the gripper with a
pneumatic device, which engages with the button and injects it with compressed air, thus forming a magnet preloaded air
bearing allowing virtually friction-less repositioning of the button by a gantry or an R-Theta robot. New fibre protection,
guiding and retraction systems are also described. These developments could open a practical avenue for the upgrade to a
number of instruments.
A liquid atmospheric dispersion corrector (LADC) is investigated to compensate atmospheric dispersion for modern
extremely large telescopes (ELTs). The LADC uses a pair of immiscible liquids in a small glass container which can be
placed very close to the telescope focal plane. A pair of liquid prisms is formed and the apex of the two prisms varies
with telescope zenith because of gravity. The idea is that a large number of independent deployable units (e.g., AAO's
'Starbugs') would each carry its own LADC. Three pairs of liquids were identified that were found suitable for use in an
LADC after thousands of chemicals were investigated. We have theoretically and experimentally verified that LADC
can correct atmospheric dispersion adaptively. It is demonstrated that a LADC can correct a simulated atmospheric
dispersion of 0.34° at a Zenith of 48°, over a wavelength range of 370nm to 655nm. The experimental results show very
good agreement with the optical (Zemax) model.
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.
Off-axis telescopes with unobstructed pupils offer great advantages in terms of emissivity, throughput, and diffractionlimited
energy concentration. For most telescope designs, implementation of an off-axis configuration imposes
enormous penalties in terms of cost, optical difficulty and performance, and for this reason off-axis telescopes are rarely
constructed. However, for the reflective Schmidt design, implementation of an off-axis configuration is very
straightforward, and involves only a modest optical penalty. Moreover, the reflective Schmidt gets particular benefits,
avoiding the obstruction of its large focal plane and support column, and gaining a highly accessible, gravity-invariant
prime focus, capable of accommodating very large instrumentation. We present an off-axis f/8 reflective Schmidt
design for the proposed 'KDUST' Chinese infrared telescope at Dome A on the Antarctic plateau, which offers
simultaneous diffraction-limited NIR imaging over 1°, and close to diffraction-limited imaging out to 2° for fibre-fed
We report on the technological achievements of our latest Starbug prototypes and their implications for smart focal plane
fiber positioning applications for wide-field astronomy. The Starbugs are innovative self-motile miniature robotic
devices that can simultaneously and independently position fibers or payloads over a field plate located at the telescope's
focal plane. The Starbugs concept overcomes many of the limitations associated with the traditional 'pick and place'
positioners where a robot places fixed buttons onto the field plate. The new Starbug prototypes use piezoelectric
actuators and have the following features: (i) new 'lift-and-step' method (discrete step) for accurate positioning over
different surfaces; and (ii) operate in an inverted hanging position underneath a transparent field plate, removing the need
for fibercable retractors. In this paper, we present aspects of the Starbug prototypes, including the theoretical model,
mechanical design, experimental setup, algorithms, performance and applications for astronomical instrumentation.
MANIFEST (the Many Instrument Fiber System) is a proposed fiber-positioner for the GMT, capable of feeding other
instruments as needed. It is a simple, flexible and modular design, based on the AAO's Starbugs, the University of
Sydney's Hexabundles, and extensive use of standard telecommunications fiber technology. Up to 2000 individually
deployable fiber units are envisaged, with a wide variety of aperture types (single-aperture, image-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) efficient detector packing both spectrally and spatially, (e) the possibility of
OH-suppression in the near-infrared. Together, these gains make GMT the most powerful of the ELT's for wide-field
spectroscopy. It is intended that MANIFEST will form part of the GMT facility itself, available to any instrument able
to make use of it.
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.
We highlight the operational challenges and planned solutions faced by an optical observatory taking advantage of the
superior astronomical observing potential of the Antarctic plateau. Unique operational aspects of an Antarctic optical
observatory arise from its remoteness, the polar environment and the unusual observing cycle afforded by long
continuous periods of darkness and daylight. PILOT is planned to be run with remote observing via satellite
communications, and must overcome both limited physical access and data transfer. Commissioning and lifetime
operations must deal with extended logistics chains, continual wintertime darkness, extremely low temperatures and
frost accumulation amidst other challenging issues considered in the PILOT operational plan, and discussed in this presentation.
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed Australian/European optical/infrared
telescope for Dome C on the Antarctic Plateau, with target first light in 2012. The proposed telescope is 2.4m diameter,
with overall focal ratio f/10, and a 1 degree field-of-view. In median seeing conditions, it delivers 0.3" FWHM wide-field
image quality, from 0.7-2.5 microns. In the best quartile of conditions, it delivers diffraction-limited imaging down
to 1 micron, or even less with lucky imaging. The areas where PILOT offers the greatest advantages are (a) very high
resolution optical imaging, (b) high resolution wide-field optical imaging, and (c) all wide-field thermal infrared
imaging. The proposed first generation instrumentation consists of (a) a fast, low-noise camera for diffraction-limited
optical lucky imaging; (b) a gigapixel optical camera for
seeing-limited imaging over a 1 degree field; (c) a 4K x 4K
near-infrared (1-5 micron) camera with both wide-field and diffraction-limited modes; and (d) a double-beamed midinfrared
(7-40 micron) camera.
We present the Gattini project: a multisite campaign to measure the optical sky properties above the two high altitude
Antarctic astronomical sites of Dome C and Dome A. The Gattini-DomeC project, part of the IRAIT site testing
campaign and ongoing since January 2006, consists of two cameras for the measurement of optical sky brightness, large
area cloud cover and auroral detection above the DomeC site, home of the French-Italian Concordia station. The cameras
are transit in nature and are virtually identical except for the nature of the lenses. The cameras have operated
successfully throughout the past two Antarctic winter seasons and here we present the first results obtained from the
returned 2006 dataset. The Gattini-DomeA project will place a similar site testing facility at the highest point on the
Antarctic plateau, Dome A, with observations commencing in 2008. The project forms a small part of a much larger
venture coordinated by the Polar Research Institute of China as part of the International Polar Year whereby an
automated site testing facility called PLATO will be traversed into the DomeA site. The status of this exciting and
ambitious project with regards to the Gattini-DomeA cameras will be presented.
PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed Australian/European optical/infrared
telescope for Dome C on the Antarctic Plateau, with target first light in 2012. The telescope is 2.4m diameter, with
overall focal ratio f/10, and a 1 degree field-of-view. It is mounted on a 30m tower to get above most of the turbulent
surface layer, and has a tip-tilt secondary for fast guiding. In median seeing conditions, it delivers 0.3" FWHM wide-field
image quality, from 0.7-2.5 microns. In the best quartile of conditions, it delivers diffraction-limited imaging down
to 1 micron, or even less with lucky imaging. The major challenges have been (a) preventing frost-laden external air
reaching the optics, (b) overcoming residual surface layer turbulence, (c) keeping mirror, telescope and dome seeing to
acceptable levels in the presence of large temperature variations with height and time, (d) designing optics that do
justice to the site conditions. The most novel feature of the design is active thermal and humidity control of the
enclosure, to closely match the temperature of external air while preventing its ingress.
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.
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.
The Anglo-Australian Observatory is currently designing a new fibre positioner for the UK Schmidt Telescope. The instrument will have 2250 fibres, positioned with sub-arcsecond accuracy across a six degree field of view, and will have a reconfiguration time of one minute. The instrument is to enable the RAVE survey of high precision abundances and velocities for up to 50 million stars. The design is largely adapted from the AAO's FMOS-Echidna fibre positioner for Subaru. New design challenges for Ukidna include the enormous number of fibres, the large focal surface, and the field curvature of the Schmidt telescope. These features are mostly shared with the expected needs of future prime-focus multi-fibre systems on 8-30m class telescopes. We present details and performance of the multi-actuator design.
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.
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.
An unsolved problem in astronomical instrumentation is an imaging integral field spectrograph where the user has the freedom to specify arbitrarily complex, contiguous or disjoint regions over the focal plane, rather than a contiguous rectangular field. We present a new concept to solve this problem. Our device allows the user to format the field of view with fibre bundles packed into arbitrary patterns. The field of view is segmented by a large N(N microlens array (e.g. N=1000). This element divides the wavefront into small beams which pass through a metal plate drilled with a grid of holes in the same format as the microlens array. On the reverse side of the grid, hexagonal blocks comprising 67 input fibres are plugged into position on the grid with a pair of sliding "croupier" sticks. The fibred blocks transport the light to the spectrograph. The blocks are held magnetically and the plugging ensures accurate and repeatable registration with respect to the microlens array. The grid plate is micromachined with baffled holes in order to ensure photometric uniformity over the field of view.
We present a design concept for a 16 metre, wide-field, fixed-axis, all-reflective, segmented f/4 Schmidt telescope to take advantage of the unique possibilities of Antarctica for both optical and near infrared astronomy. The design allows observation of all RA/dec's accessible from Antarctica, with tracking times of several hours.
Prime and Cassegrain foci are provided, giving plate scales 300-3000microns/", over fields of view 1.5'-0.5°. Diffraction limited, natural guide-star AO-corrected Kdark images are possible over
arc-minute sized fields, over 70% of the sky. The sensitivity, resolution, field of view and cost all compare favourably with current or proposed space or ground-based telescopes.