SPIRIT: The South Pole Infrared Imaging Telescope
Proposers: L Allen, J Storey, M Dopita, J Mould
The MNRF funding allocation in this area is shared equally between UNSW
and MSSSO. The UNSW has devoted its share of the funds to upgrading the
existing 60 cm SPIREX infrared telescope (operated by CARA - the US Center
for Astrophysical Research in Antarctica) located at the South Pole. MSSSO
efforts have centred on producing a Phase A engineering study for a new
2.5 m class telescope to be located at the remote Dome C site on the high
(5000 m) Antarctic plateau.
The SPIREX upgrade consisted of the addition of a 1024 x 1024 InSb-based
infrared camera, together with a number of smaller projects aimed at improving
the quality of images from the telescope. The infrared camera, known as
Abu, was developed by NOAO. This project has launched a joint Australian-US
partnership, the end result of which will give Australian astronomers access
to a unique infrared telescope boasting the largest thermal detector array
in existence. After appointment of a Project Manager and weekly UNSW and
UNSW-US design meetings throughout 1997, Abu was commissioned successfully
on schedule at the South Pole in December 1997.
As well as the Abu installation, four additional significant upgrades have
been made to SPIREX by the UNSW group. First, an improved electronic temperature
stabilization system (allowing operation at ambient temperatures as low
as -80 C) was installed
in December 1997 and all specifications were verified as met. Second, various
image-quality problems were tackled by the addition of new optical components
and modifications to the optical path. The telescope is now diffraction
limited at 3 mm and
all aberrations and telescope-related imaging problems eliminated (except
for slight astigmatism in the visible guider). Third, an autoguider, based
on an integrating cooled CCD, was added to remove telescope tracking errors.
Finally, a fast guiding system, designed to compensate for shake of the
mounting tower and to make first-order corrections for atmospheric seeing,
was added. This modification involved the addition of a light-weight, honeycomb-structured,
secondary mirror mounted on three piezo-electric transducers. The system
was installed in February 1998 and tests show that it successfully locks
onto stars, providing fast tip-tilt correction. The control loop can be
closed at frequencies up to 70 Hz. First astronomical results are promising,
but additional software development will allow the full potential of the
fast guiding system to be realised.
On the new telescope design front, MSSSO have completed a detailed report
entitled "SPIRIT: The South Pole Infrared Imaging Telescope - The Phase
A Engineering Study" . The report outlines optical, mechanical and
project management considerations for a 2.5 m telescope cabable of yielding
almost diffraction-limited images at 2.4 mm.
The telescope is a wide-field design, operating primarily in the 2-4 mm
and 10-12 mm observing
wavelength ranges. A tip-tilt mirror (oscillating secondary) arrangement
and large-format electronic detector arrays are central to the design. Significantly,
the telescope is designed for largely unattended, open-air, operation in
temperatures as low as -85 C.
Bearing in mind the remote Antarctic location envisaged for the instrument,
the design is optimized for very low power operation.
The scientific projects undertaken by the SPIRIT telescope will most likely
emphasize deep surveys and the instrument design is optimized for the investigation
of the epoch of the initial formation of galaxies (redshift 2 to 5), and
the star formation which occurred within the galaxies at this time. Comparing
the projected performance of the SPIRIT telescope with a number of existing
and future infrared telescopes, it is apparent that SPIRIT is competitive
in many applications, even when large instruments such as the 10 m Keck
telescope are considered.
Allowing for uncertainties in the deployment and operating costs of the
SPIRIT instrument on the high Antarctic plateau, MSSSO estimate that the
project cost would be of order $A15M, of which $A9.4M represents the actual
construction cost of the telescope. If construction were to begin in 2002,
and assuming facilities at the high plateau site are developed on schedule
by collaborating Italian and French agencies, MSSSO estimate that SPIRIT
could be deployed by the end of 2005, with data-taking starting the following
year.
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This page is maintained by Michelle
Storey
Last update by Michelle Storey. 29/10/98