The 1999 Ellery Lecture
J.W.V. Storey, PASA, 17 (3), 270.
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Title/Abstract Page: Infrared Astronomy: in the
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TWENTY-FIVE YEARS OF AUSTRALIAN IR
This section is not intended to be an exhaustive history of Australian infrared astronomy, but rather to be illustrative of some of the major advances that have shaped our present knowledge and expertise. These advances have of course been driven by the development of ever more capable instrumentation.Near Infrared
In 1971, Harry Hyland noted in an article in PASA (Hyland, 1971) that virtually all infrared observations conducted to that time had been undertaken in the northern hemisphere, and correctly predicted that ``...the Southern Hemisphere is still a virtually untapped reservoir, and offers wide scope for major advances in the field.'' For the next few years, Harry and his colleagues at Mount Stromlo Observatory and elsewhere used a single-pixel bolometer instrument to make the first forays into this ``untapped reservoir''. This infrared photometer was further upgraded, moving from the initial bolometer system for observations from 2 - 20
m, through a PbS system for short wavelength photometry, to a modern high sensitivity 1 - 5m InSb system. This was one of the first fully automated and computer controlled infrared photometers constructed and led, among other things, to the discovery of young stars in the LMC. In 1978 the Infrared Photometer/Spectrometer (IRPS) was developed at the Anglo-Australian Observatory (AAO) by David Allen and the AAO engineers (Barton & Allen 1987). The IRPS represented a huge leap forward in ``user friendliness''. No longer was it necessary for the observer to understand all the intricacies of the infrared detection process. With its digital integration technology and simple menu-driven software, the IRPS was the first truly civilised infrared instrument available to astronomers anywhere in the world. The IRPS thus brought IR astronomy into the mainstream. Its discoveries included: - Images of the surface of Venus
- Molecular hydrogen in many planetary nebulae
- Polarimetric studies
- Complex structure of the Galactic Centre region
) while nevertheless fitting within a conventionally sized dewar (Jones et al. 1982). This instrument proved extremely powerful in observations of extended sources, and in obtaining very high signal/noise data of sources such as SN1987A. A modified version of this spectrometer was designed for the AAT, where it was known as FIGS, The Fabry-Perot Infrared Grating Spectrometer (Bailey et al. 1988). (The ``Fabry-Perot'' part referred to an ingenious but ultimately ill-fated plan to use a thin silicon wedge in front of the entrance window as a tunable Fabry-Perot.) FIGS used cylindrical optics and an array of 16 discrete detectors. FIGS was available on the AAT from 1985 to 1991. Perhaps its best known scientific result was its observation of the evolution of Supernova 1987A, in which it was able to detect a vast array of atomic and ionic species, plus CO, CO+ and possibly CS (Meikle et al. 1989). In the early eighties, although 2-dimensional monolithic detector arrays were starting to find their way into the hands of US astronomers, strict military controls prevented their export to even friendly nations such as Australia. This prompted the University of New South Wales to embark on an ambitious program in 1982 to fabricate monolithic infrared detector arrays based on platinum silicide technology (see, for example; Kurianski, Green & Storey 1986). A 32 x 4 pixel device was ultimately tested on the AAT; it was able to detect Sirius through thick clouds but was never used for any serious astronomical research. In the meantime, export controls were beginning to relax and the Anglo-Australian Telescope was able to obtain one of the early ``NICMOS'' detectors (so-called because their development was funded not through defence channels but for use on the NICMOS instrument of the Hubble Space Telescope). This detector is of a hybrid type, where the detector material (in this case mercury cadmium telluride) is bump-bonded via indium balls onto a silicon multiplexer. With 128 x 128 pixels, the NICMOS detector represented a major advance. It was built into IRIS, a versatile infrared camera/spectrometer designed once again by David Allen and the AAO engineers (Gillingham & Lankshear 1990; Allen et al. 1993; Gillingham 1993a). IRIS was a technological tour-de-force, winning the prestigious Bradfield Award of the Sydney Division of the Institution of Engineers, Australia in 1993. For the past decade IRIS has made a major contribution to southern hemisphere astronomy. One of its images even appeared on the front cover of Nature--the molecular hydrogen and [FeII] ``bullets'' in Orion (Allen & Burton 1993). IRIS was subsequently enhanced by the addition of a polarimetry module (Hough, Chrysostomou & Bailey 1994; Gledhill, Chrysostomou & Hough 1996) and a Fabry Perot (UNSWIRF1; Ryder et al. 1998). Perhaps David Allen's final legacy to infrared instrumentation in Australia was to set in motion the construction of a successor to IRIS. IRIS-II (a wide field IR camera/spectrometer with a 1024 x 1024 pixel detector) is currently under construction at the AAT and due for commissioning on the telescope in 2000/2001 (Gillingham & Jones 2000). In the late 1990s the ``3D'' instrument of the Max-Planck-Institut für extraterrestrische Physik (MPE) was made available on the AAT. With the ability to produce 256 simultaneous spectra over a 16 x 16 pixel region of the sky, 3D was the first of a new generation of ``integral field'' spectrometers (Weitzel et al. 1996). Its success was largely responsible for the current resurgence of interest in integral field techniques. Shortly after IRIS was built, Peter McGregor and the MSSSO engineers developed CASPIR for the 2.3 metre telescope on Siding Spring (McGregor et al. 1994). Sporting a 256 x 256 indium antimonide array, CASPIR was able to operate out to 5.6 microns (compared to IRIS's limit of 2.5 microns). Amongst CASPIR's best-known results were a spectacular set of images of the impact of Comet Shoemaker-Levy 9 on Jupiter in July 1994 (McGregor, Nicholson, & Allen 1996). CASPIR is currently the only instrument in Australia covering this wavelength range, and continues to produce excellent science. In parallel with the instrumentation development of the past quarter century was another crucial area that required painstaking attention before near-infrared astronomy could become routine: precision photometry of standard stars. Early work on JHKL standards (Jones & Hyland 1982; Allen & Cragg 1983) allowed the field to get underway and tied the southern hemisphere standards to those of the north (Elias et al. 1983); work which was further refined by McGregor (1994) and Carter & Meadows (1995). Mid-infrared
The early days of mid-infrared were pioneered by Harry Hyland (at MSSSO) and John Thomas (at the RAAF Academy--then part of the University of Melbourne) using single-element bolometer systems (See, for example, Robinson, Hyland & Thomas 1973; Thomas, Hyland & Robinson 1973). The field received an enormous boost in 1978 with the arrival at the Anglo-Australian Observatory of David Aitken and Patrick Roche, who brought with them the ``UCL'' mid-infrared grating spectrometer (Aitken et al. 1979). This simple but remarkably effective instrument used an array of 5 discrete detectors (later upgraded to 16 and then to 30), and dominated the field of mid-infrared spectroscopy for the next decade. It remained the only mid-infrared instrument available in Australia until the early nineties, when MIRAS/NIMPOL was commissioned on the AAT by Craig Smith (Smith et al. 1997), followed by MANIAC by the UNSW group in collaboration with the MPE (Boeker et al. 1997).Far-infrared
Blocked by water vapour in the earth's atmosphere, far-infrared radiation can only be observed from space, balloon or aircraft platforms. In the mid-seventies John Thomas carried out Australia's first pioneering work in this region with a balloon-borne telescope (Thomas 1977). In 1977, the Kuiper Airborne Observatory, a NASA-operated C-141 Starlifter fitted with a 90cm telescope (Cameron et al. 1971), visited Australia to observe the occultation by Uranus of a background star (an observation which, incidentally, first detected the rings of Uranus; Elliot, Dunham & Mink 1977). The success of this visit led to considerable enthusiasm in Australia for a formal program of expeditions to be established (Storey 1982). In 1983, the Kuiper Airborne Observatory returned to fly a series of missions from Richmond Airforce Base in NSW. Once again a block of time was set aside for Australian astronomers; this time to fly six flights as principal investigators. Just when it appeared that these collaborations would grow to the point where the Kuiper Airborne Observatory would become a regular visitor to Richmond, political machinations within the Royal Australian Air Force forced the cancellation of the 1987 visit (which was planned to coincide with the return of Comet Halley). At the last moment NASA was forced to shift its operations to Christchurch, New Zealand. The Kuiper Airborne Observatory has made regular visits there ever since, until its recent decommissioning to make way for SOFIA.Next Section: NEW DEVELOPMENTS
Title/Abstract Page: Infrared Astronomy: in the
Previous Section: THE INFRARED ADVANTAGE
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