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 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.
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.