Infrared Astronomy: in the Heat of the Night
The 1999 Ellery Lecture
J.W.V. Storey, PASA, 17 (3), 270.
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Subsections
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.
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
The IRPS was finally decommissioned in 1994, after nearly two decades of
exceptionally productive work on the Anglo-Australian Telescope (AAT). Even
then it refused to give up. In 1994 it was loaned to the University of New
South Wales, who ``winterised'' it and installed it at the South Pole for site
testing studies (Ashley et al. 1995). When its work was completed there it was
returned to the AAO where, at the time of writing, it is still being
used--this time as a test bed for cryogenic infrared fibres!
In 1978, Terry Jones and Harry Hyland designed a cooled-grating spectrometer
(CIGS) which employed novel cylindrical optics to allow for large beam
observations at intermediate resolving power (
)
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).
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).
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
Contents Page: Volume 17, Number 3
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© Copyright Astronomical Society of Australia 1997