Annino Vaccarella

The SkyMapper Telescope and The Southern Sky Survey

This paper presents the design and science goals for the SkyMapper telescope. SkyMapper is a 1.3-m telescope featuring a 5.7-square-degree field-of-view Cassegrain imager commissioned for the Australian National Universitys Research School of Astronomy and Astrophysics. It is located at Siding Spring Observatory, Coonabarabran, NSW, Australia and will see first light in late 2007. The imager possesses 16 384 × 16 384 0.5-arcsec pixels. The primary scientific goal of the facility is to perform the Southern Sky Survey, a six-colour and multi-epoch (four-hour, one-day, one-week, one-month and one-year sampling) photometric survey of the southerly 2π sr to g ∼23 mag. The survey will provide photometry to better than 3% global accuracy and astrometry to better than 50 milliarcsec. Data will be supplied to the community as part of the Virtual Observatory effort. The survey will take five years to complete.

The Murchison Widefield Array: Design Overview

The Murchison Widefield Array is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It is capable of a wide range of science investigations but is initially focused on three key science projects: detection and characterization of three-dimensional brightness temperature fluctuations in the 21 cm line of neutral hydrogen during the epoch of reionization (EoR) at redshifts from six to ten; solar imaging and remote sensing of the inner heliosphere via propagation effects on signals from distant background sources; and high-sensitivity exploration of the variable radio sky. The array design features 8192 dual-polarization broadband active dipoles, arranged into 512 ldquotilesrdquo comprising 16 dipoles each. The tiles are quasi-randomly distributed over an aperture 1.5 km in diameter, with a small number of outliers extending to 3 km. All tile-tile baselines are correlated in custom field-programmable gate array based hardware, yielding a Nyquist-sampled instantaneous monochromatic uv coverage and unprecedented point spread function quality. The correlated data are calibrated in real time using novel position-dependent self-calibration algorithms. The array is located in the Murchison region of outback Western Australia. This region is characterized by extremely low population density and a superbly radio-quiet environment, allowing full exploitation of the instrumental capabilities.

Interferometric Imaging with the 32 Element Murchison Wide-Field Array

The Murchison Wide-Field Array (MWA) is a low-frequency radio telescope, currently under construction, intended to search for the spectral signature of the epoch of reionization (EOR) and to probe the structure of the solar corona. Sited in western Australia, the full MWA will comprise 8192 dipoles grouped into 512 tiles and will be capable of imaging the sky south of 40° declination, from 80 MHz to 300 MHz with an instantaneous field of view that is tens of degrees wide and a resolution of a few arcminutes. A 32 station prototype of the MWA has been recently commissioned and a set of observations has been taken that exercise the whole acquisition and processing pipeline. We present Stokes I, Q, and U images from two ~4 hr integrations of a field 20° wide centered on Pictoris A. These images demonstrate the capacity and stability of a real-time calibration and imaging technique employing the weighted addition of warped snapshots to counter extreme wide-field imaging distortions.

Adaptive optics tracking and pushing system for space debris manoeuvre

As space debris in lower Earth orbits are accumulating, techniques to lower the risk of space debris collisions must be developed. Within the context of the Space Environment Research Centre (SERC), the Australian National University (ANU) is developing an adaptive optics system for tracking and pushing space debris. The strategy is to pre-condition a laser launched from a 1.8 m telescope operated by Electro Optics Systems (EOS) on Mount Stromlo, Canberra and direct it at an object to perturb its orbit. Current progress towards implementing this experiment, which will ensure automated operation between the telescope and the adaptive optics system, will be presented.

GMTIFS: The Giant Magellan Telescope integral fields spectrograph and imager

GMTIFS is the first-generation adaptive optics integral-field spectrograph for the GMT, having been selected through a competitive review process in 2011. The GMTIFS concept is for a workhorse single-object integral-field spectrograph, operating at intermediate resolution (R~5,000 and 10,000) with a parallel imaging channel. The IFS offers variable spaxel scales to Nyquist sample the diffraction limited GMT PSF from λ ~ 1-2.5 μm as well as a 50 mas scale to provide high sensitivity for low surface brightness objects. The GMTIFS will operate with all AO modes of the GMT (Natural guide star - NGSAO, Laser Tomography – LTAO, and, Ground Layer - GLAO) with an emphasis on achieving high sky coverage for LTAO observations. We summarize the principle science drivers for GMTIFS and the major design concepts that allow these goals to be achieved.

Veloce Rosso: Australia's new precision radial velocity spectrograph

Veloce is an ultra-stable fibre-fed R4 echelle spectrograph for the 3.9 m Anglo-Australian Telescope. The first channel to be commissioned, Veloce ‘Rosso’, utilises multiple low-cost design innovations to obtain Doppler velocities for sun-like and M-dwarf stars at <1 ms -1 precision. The spectrograph has an asymmetric white-pupil format with a 100-mm beam diameter, delivering R>75,000 spectra over a 580-930 nm range for the Rosso channel. Simultaneous calibration is provided by a single-mode pulsed laser frequency comb in tandem with a traditional arc lamp. A bundle of 19 object fibres ensures full sampling of stellar targets from the AAT site. Veloce is housed in dual environmental enclosures that maintain positive air pressure at a stability of ±0.3 mbar, with a thermal stability of ±0.01 K on the optical bench. We present a technical overview and early performance data from Australias next major spectroscopic machine.

Cryogenic detector preamplifer developments at the ANU

We present a summary of the cryogenic detector preamplifier development programme under way at the ANU. Cryogenic preamplifiers have been demonstrated for both near-infrared detectors (Teledyne H1RG and Leonardo SAPHIRA eAPD as part of development for the GMTIFS instrument) and optical CCDs (e2v CCD231-84 for use with the AAT/Veloce spectrograph). This approach to detector signal conditioning allows low-noise instrument amplifiers to be placed very close to an infra-red detector or optical CCD, isolating the readout path from external interference noise sources. Laboratory results demonstrate effective isolation of the readout path from external interference noise sources. Recent progress has focussed on the first on-sky deployment of four cryogenic preamp channels for the Veloce Rosso precision radial velocity spectrograph. We also outline future evolution of the current design, allowing higher speeds and further enhanced performance for the demanding applications required for the on instrument wavefront sensor on the Giant Magellan Integral Field Spectrograph (GMTIFS).

Commissioning of cryogenic preamplifiers for SAPHIRA detectors

SAPHIRA detectors, which are HgCdTe linear avalanche photodiode arrays manufactured by Leonardo, enable high frame rate, high sensitivity, low noise, and low dark current imaging at near-infrared wavelengths. During all University of Hawaii Institute for Astronomy lab testing and observatory deployments of SAPHIRA detectors, there was approximately one meter of cables between the arrays and the readout controllers. The output drivers of the detectors struggled to stably send signals over this length to the readout controllers. As a result, voltage oscillations caused excess noise that prevented us from clocking much faster than 1 MHz. Additionally, during some deployments, such as at the SCExAO instrument at Subaru Telescope, radio-frequency interference from the telescope environment produced noise many times greater than what we experienced in the lab. In order to address these problems, collaborators at the Australia National University developed a cryogenic preamplifier system that holds the detector and buffers the signals from its outputs. During lab testing at 1 MHz clocking speeds, the preamplifiers reduced the read noise by 45% relative to data collected using the previous JK Henriksen detector mount. Additionally, the preamplifiers enabled us to increase the clocking frequency to 2 MHz, effectively doubling the frame rate to 760 Hz for a full (320x256 pixel) frame or 3.3 kHz for a 128x128 pixel subarray. Finally, the preamplifiers reduced the noise observed in the SCExAO environment by 65% (to essentially the same value observed in the lab) and eliminated the 32-pixel raised bars characteristic of radio-frequency interference that we previous observed there.

Design evolution of the Giant Magellan Telescope Integral Field Spectrograph, GMTIFS

We report the design evolution for the GMT Integral Field Spectrograph, (GMTIFS). To support the range of operating modes – a spectroscopic channel providing integral field spectroscopy with variable spaxel scales, and a parallel imaging channel Nyquist sampling the LTAO corrected field of view - the design process has focused on risk mitigation for the demanding operational tolerances. We summarise results from prototype components, confirming concepts are meeting the necessary specifications. Ongoing review and simulation of the scientific requirements also leads to new demonstrations of the science that will be made possible with this new generation of high performance AO assisted instrumentation.

Stirling cycle cryocooler exported vibration analysis

The Australian National University (ANU), we are undertaking to deploy a Lucky Imaging instrument on the 2.3 m telescope at Siding Springs using a Leonardo SAPHIRA near-infrared electron Avalanche Photo-Diode (eAPD) array, capable of high cadence imaging with frame rates of 10 - 5,000 Hz over the wavelength range of 0.8 μm to 2.5 μm. compact cryocooler capable of cooling the Leonardo SAPHRA APD and associated cryogenic electronics to temperatures below 100K with little to no vibration. An ideal candidate cryocooler is the Sunpower Cryotel GT with active vibration cancellation. The Cryotel GT is an orientation independent, Stirlng cycle cooler with water jacket heat rejection. This cooler will meet the system cooling requirements. The cryocooler has been integrated with the APD Lucky Imager cryostat through 3 rubber isolating mounts and bellows and tested while suspended from a stable frame. The tethers supporting the cryostat and cooler assembly are not attached to the cryostat and cooler. The exported vibration was measured simultaneously in all 3 axis on the external cryostat wall and internally on the cryostat getter attached directly to the cold tip of the cooler. The test results were collected while the cryocooler was cooling and at the stable set point, at various levels of cooling power and with thermal control enabled and disabled.