We have developed an improvement of the well-known SLODAR (Slope Detection and Ranging) technique which
allows us to monitor the ground layer throughout the night with resolution of a few tens of meters. We will present data
we have obtained during two one-week observing sessions at the Las Campanas Observatory, Chile. The first observing
session we have often observed a persistent, low ground layer which dominates the seeing. The second observing session
the free-atmosphere dominated the seeing. We will present the instrument design; real-time software; describe the
observing sessions, the data and results.
The Gemini South Adaptive Optics Imager (GSAOI) to be used with the Multi-Conjugate Adaptive Optics (MCAO) system at Gemini South is currently in the final stages of assembly and testing. GSAOI uses a suite of 26 different filters, made from both BK7 and Fused Silica substrates. These filters, located in a non-collimated beam, work as active optical elements.
The optical design was undertaken to ensure that both the filter substrates both focused longitudinally at the same point. During the testing of the instrument it was found that longitudinal focus was filter dependant. The methods used to investigate this are outlined in the paper. These investigations identified several possible causes for the focal shift including substrate material properties in cryogenic conditions and small amounts of residual filter power.
The Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) at Mt Stromlo Observatory is developing a wide-field Cassegrain Imager for the new 1.3m SkyMapper Survey Telescope under construction for Siding Spring Observatory, NSW, Australia. The Imager features a fast-readout, low-noise 268 Million pixel CCD mosaic that provides a 5.7 square degree field of view. Given the close relative sizes of the telescope and Imager, the work is proceeding in close collaboration with the telescope's manufacturer, Electro Optics Systems Pty Ltd (Canberra, Australia).
The design of the SkyMapper Imager focal plane is based on E2V (Chelmsford, UK) deep depletion CCDs. These devices have 2048 x 4096 15 micron pixels, and provide a 91% filling factor in our mosaic configuration of 4 x 8 chips. In addition, the devices have excellent quantum efficiency from 300nm-950nm, near perfect cosmetics, and low-read noise, making them well suited to the all-sky ultraviolet through near-IR Southern Sky Survey to be conducted by the telescope.
The array will be controlled using modified versions of the new IOTA controllers being developed for Pan-STARRS by Onaka and Tonry et al. These controllers provide a cost effective, low-volume, high speed solution for our detector read-out requirements. The system will have an integrated 6-filter exchanger, and Shack-Hartmann optics, and will be cooled by closed-cycle helium coolers.
This paper will present the specifications, and opto-mechanical and detector control design of the SkyMapper Imager, including the test results of the detector characterisation and manufacturing progress.
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.
The Wide Field Spectrograph (WiFeS) is a high-throughput double-beam
image-slicing spectrograph that will operate over the visible
wavelength range 320nm to 1000nm. Designed by the Australian National
University's Research School of Astronomy and Astrophysics (RSAA) at
Mount Stromlo, WiFeS is based on an Integral Field Unit (IFU) and
Volume Phased Holographic (VPH) grating technology.
Central to the IFU design is a visible wavelength image
slicer. Traditionally, such a slicer has been difficult to realise,
due to the requisite high surface quality demanded to reduce scatter
from each slice.
In this paper, we discuss both the novel design and manufacture of the
WiFeS slicer assembly. Preliminary results are presented that clearly
demonstrate the effectiveness of the design.
NIFS is a near-infrared integral field spectrograph designed for near diffraction-limited imaging spectroscopy with the ALTAIR facility adaptive optics system on Gemini North. NIFS is currently under construction at the Research School of Astronomy and Astrophysics of the Australian National University. Commissioning is planned for 2003. NIFS uses a reflective concentric integral field unit to reformat its 3.0"x3.0" field-of-view into 29 slitlets each 0.1" wide with 0.04" sampling along each slitlet. The NIFS spectrograph has a resolving power of ~ 5300, which is large enough to significantly separate terrestrial airglow emission lines and resolve velocity structure in galaxies. The output format is matched to a 2048x2048 pixel Rockwell HAWAII-2 detector. The detector is read out through a SDSU-2 detector controller connected via a VME interface to the Gemini Data Handling System. NIFS is a fast-tracked instrument that reuses many of the designs of the Gemini Near-InfraRed Imager (NIRI); the cryostat, On-Instrument Wave Front Sensor, control system, and control software are largely duplicates.
An Australian consortium of astronomers and engineers (based at AAO, MSSSO and UNSW) were contracted by the European Southern Observatory to carry out a one-year concept design study for a near-infrared multi-object spectrograph for the VLT. The primary scientific motivation for this instrument was the detection and study of high-redshift galaxies. The scope of the study included the elucidation of the main science drivers and the development of a VLT instrumentation strategy best suited to those goals. The underlying instrumental philosophy was to supply a significant object multiplex at a high enough spectral resolution to resolve the internal kinematics of galaxies. This science-driven goal also permitted digital OH sky-suppression, yielding better S/N and spectral coverage than at lower resolutions. A full contiguous wavelength coverage from 0.9 micrometer to 1.8 micrometer is achieved through the use of multiple HgCdTe-based spectrograph cameras. A preliminary optical design for the spectrographs has been achieved as has a detailed concept design for the 400-fiber positioner and multiple integral field units. With these capabilities, the proposed instrument is highly effective both for statistical studies of large numbers of object and detailed studies of individual objects. In addition, the development of a novel fiber optic switching facility permits simultaneous wavelength coverage over the entire optical and near-infrared windows (from 0.45 micrometer to 1.8 micrometer) by the use of dichroics and additional CCD- based spectrographs. The very broad range of science that can be carried out with AUSTRALIS spans fields as diverse as galaxy evolution and large-scale structure, the detection of primeval galaxies, the spatially-resolved kinematics of nearby AGN and star-forming regions, globular cluster dynamics and follow-ups to all-sky surveys.