SPIRIT: The South Pole Infrared Imaging Telescope

Funded under the International Collaboration Project of the
MNRF Program


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

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