We seek to advance the capabilities of photonic technologies in support of ground-based infrared astronomy. Currently, observations in the wavelength range 1.0μm < λ < 2.5μm suffer from an irreducible background generated by emission from OH (hydroxyl) molecules in the upper atmosphere. However, narrow-band notch filters incorporated into the optical path of astronomical instruments can suppress this background with very little accompanying loss of signal from the astronomical sources of interest. Micron-scale ring resonators are one technology that provides a promising method of generating such notch filters. Building on our previous efforts in astrophotonic technology development, our current goals are 1) to optimize the design of ring resonators so that the notch filters they create provide greatest suppression at the wavelengths of the most prominent OH lines, and 2) to optimize the coupling of the resonator-equipped silicon devices with the input fibers (from the sky) and output fibers (to the spectrograph and detector) such that the throughput losses do not completely eliminate the signal-to-noise improvement gained from the OH suppression. To accomplish the former, we introduce heaters that can actively change the wavelength of the notch filters to match the OH emission lines, as well as mechanisms for polarization-dependent and -independent suppression. To accomplish the latter, we incorporate post-fabrication packaging of fibers to ensure optimal alignment.
The Lowell Discovery Telescope (LDT, formerly known as the DCT) is a 4.3-m telescope designed and constructed for optical and near infrared astronomical observation. We present the evolution over time of LDT’s image quality and ways to improve it, upgrades to the instrument suite, and lessons learned from operating during the pandemic.
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.
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.
We seek to advance the capabilities of photonic technologies in support of ground-based infrared astronomy. Currently, observers in this field suffer from an irreducible background generated by emission from OH (hydroxyl) molecules in the upper atmosphere. However, if narrow-band notch filters could be incorporated into the optical path of astronomical instruments prior to any optical elements that would spectrally broaden such emission lines, then this background could be effectively suppressed with very little accompanying loss of signal from the astronomical sources of interest. Micron-scale ring resonators are one technology that provides a promising method of generating such notch filters. Building on our previous efforts in astrophotonic technology development, our current goals are 1) to optimize the design of ring resonators so that the notch filters they create provide greatest suppression at the wavelengths of the most prominent OH lines, and 2) to optimize the coupling of the resonator-equipped silicon devices with the input fibers (from the sky) and output fibers (to the spectrograph and detector) such that the throughput losses do not completely eliminate the signal-to-noise improvement gained from the OH suppression. Theoretical estimates show that suppression (by 20-40dB) of the most prominent OH lines improves the signal to noise of near-IR observations by a factor of 5 or more - this is similar in effect to turning a telescope with a 1m aperture into a telescope with a 5m aperture!
Photonic ring resonator arrays used as notch filters are a promising novel solution to improve the signal-to-noise ratio of ground-based astronomical observations by suppressing OH emission lines in the near-infrared (NIR) wavelength range (0.9-2.5 μm). We aim to fabricate a series of ring resonators connected by a waveguide, each with its resonance wavelength and full-width-half-maximum (FWHM) matched with one of the OH emission lines.
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.
The AAO Starbugs is a multi-functional positioning device used in the TAIPAN instrument currently being commissioned on the UK Schmidt Telescope at Siding Spring Observatory in Australia. TAIPAN is part of a design study for MANIFEST which is a fibre positioning instrument proposed for the Giant Magellan Telescope. The acquisition and guiding system for TAIPAN uses nine standard Starbugs, referred to as Guide Bugs. Each one uses a 7000 core coherent polymer fibre bundle on individual guide stars. This provides an astrometric reference frame for science fibre positioning, telescope guiding, instrument alignment and focus, all of which are invariant to telescope and atmospheric geometric anomalies. Guide Bugs are a technology that will enable improved science results for the TAIPAN instrument. In this paper we outline the design features and provide an update on software development.
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.
KEYWORDS: Resonators, Silicon, Waveguides, Semiconducting wafers, Astronomy, Near infrared, Space telescopes, Electron beams, Linear filtering, Polarization
Photonic ring resonators used as wavelength notch filters are a promising novel solution to enable astronomical instruments to remove the signal from atmospheric OH emission in the near-infrared wavelength range. We derive design requirements from theory and finite difference time domain simulations. We find rings with radii less than 10 microns provide an adequate free spectral range for silicon nitride abd less than 3 microns for silicon. One challenge for this application is the requirement for many rings in series to suppress particular wavelengths within 0.2nm. We report progress in fabricating both silicon and silicon nitride rings for OH suppression.
Integrated optics has the potential to play a transformative role in astronomical instrumentation. It has already made a significant impact in the field of optical interferometry, through the use of planar waveguide arrays for beam combination and phase-shifting. Additionally, the potential benefits of micro-spectrographs based on array waveguide gratings have also been demonstrated.
Here we examine a new application of integrated optics, using ring resonators as notch filters to remove the signal from atmospheric OH emission lines from astronomical spectra. We also briefly discuss their use as frequency combs for wavelength calibration and as drop filters for Doppler planet searches. We discuss the theoretical requirements for ring resonators for OH suppression. We find that small radius (< 10 μm), high index contrast (Si or Si3N4) rings are necessary to provide an adequate free spectral range. The suppression depth, resolving power, and throughput for efficient OH suppression can be realised with critically coupled rings with high self-coupling coefficients.
We report on preliminary laboratory tests of our Si and Si3N4 rings and give details of their fabrication. We demonstrate high self-coupling coefficients (> 0:9) and good control over the free spectral range and wavelength separation of multi-ring devices. Current devices have Q ≈ 4000 and ≈ 10 dB suppression, which should be improved through further optimisation of the coupling coefficients. The overall prospects for the use of ring resonators in astronomical instruments is promising, provided efficient fibre-chip coupling can be achieved.
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.
The Australian Astronomical Observatory's TAIPAN instrument deploys 150 Starbug robots to position optical fibres to accuracies of 0.3 arcsec, on a 32 cm glass field plate on the focal plane of the 1.2 m UK-Schmidt telescope. This paper describes the software system developed to control and monitor the Starbugs, with particular emphasis on the automated path-finding algorithms, and the metrology software which keeps track of the position and motion of individual Starbugs as they independently move in a crowded field. The software employs a tiered approach to find a collision-free path for every Starbug, from its current position to its target location. This consists of three path-finding stages of increasing complexity and computational cost. For each Starbug a path is attempted using a simple method. If unsuccessful, subsequently more complex (and expensive) methods are tried until a valid path is found or the target is flagged as unreachable.
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.
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.
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.
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.
Starbugs are miniaturised robotic devices that position optical fibres over a telescope’s focal plane in parallel operation
for high multiplex spectroscopic surveys. The key advantage of the Starbug positioning system is its potential to
configure fields of hundreds of targets in a few minutes, consistent with typical detector readout times. Starbugs have
been selected as the positioning technology for the TAIPAN (Transforming Astronomical Imaging surveys through
Polychromatic Analysis of Nebulae) instrument, a prototype for MANIFEST (Many Instrument Fiber System) on the
GMT (Giant Magellan Telescope). TAIPAN consists of a 150-fibre Starbug positioner accessing the 6 degree field-ofview
of the AAO’s UK Schmidt Telescope at Siding Spring Observatory. For TAIPAN, it is important to optimise the
target allocation and routing algorithms to provide the fastest configurations times. We present details of the algorithms
and results of the simulated performance.
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.
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