The Gemini South Adaptive Optics Imager (GSAOI) is the science camera and commissioning instrument for the Multi-Conjugate Adaptive Optics (MCAO) system on the Gemini South telescope. GSAOI is required to deliver diffraction-limited performance at near-infrared wavelengths over a 85"×85" field of view. It must be delivered on a short timescale commensurate with MCAO delivery. GSAOI will use a high throughput, all-refractive optical design and a mosaic of four HAWAII-2RG detectors to form an imager focal plane of 4080x4080 pixels with a fixed scale of 0.02"/pixel. The On-Detector Guide Window (ODGW) capability of the HAWAII-2RG detectors will be used for flexure monitoring and as near-infrared substitutes for MCAO natural guide star wave front sensors. The imager will include a pupil viewer for accurate alignment to MCAO and defocus lenses to measure wave front phase errors at the science detector using the curvature technique. Non-common path wave front errors will be nulled by setting the base shapes of the three MCAO deformable mirrors. The science drivers, performance predictions, optical design issues, and detector system for the instrument are described.
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.
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.
The Echidna multi-object fiber positioner is part of the Fiber Multi-Object Spectrograph (FMOS) project for the prime focus of the Subaru telescope. Given the physical size of the focal plane and the required number of fibers (400), a positioning system based on the Anglo-Australian Observatory's 2dF instrument, that incorporates the placement of magnetic buttons by a single X/Y/Z robot, was considered impractical. Instead, a solution has been developed in which each fiber is mounted on a tilting spine that allows the fiber to be positioned anywhere in a circle of radius 7 mm. Each of the 400 fibers therefore has a fixed "patrol" area in the field of view, with a significant overlap between neighboring spines. A description of a single Echidna spine is presented. Each spine is driven by a quadrant tube piezoelectric actuator (QTP) that, by a ratcheting mechanism, is able to position the fiber to within 10 μm of any coordinate in the corresponding patrol area. Results of positioning tests for eight of the twenty prototype spines reveal better than specification performance, as well as a durability far in excess of the specified lifetime of the instrument.