The future of the Anglo Australian Telescope

Dirk Goës
Sep 3
4 min read

A historic photo of the Anglo Australian Telescope. The dome is 50 metres high and 36 metres in diameter (Credit: David Malin, Australian Astronomical Observatory)

By Dirk Goës

On the 8th of July 2025 at the Annual Scientific Meeting (ASM) of the Astronomical Society of Australia (ASA) Associate Professor Christian Wolf, the new director of Siding Spring Observatory (SSO) outlined the future for the venerable Anglo Australian Telescope (AAT).

The AAT along with its exquisite 4-metre mirror turned 50 years old in October 2024. Australia’s largest optical telescope has a proud history of cutting-edge research and innovative instrumentation. Before the Hubble Space Telescope, David Malin’s astrophotography from the AAT was world renowned and many of his images still appear in astronomical textbooks and publications. The AAT and its innovative staff led the development of multi-fibre spectroscopy, the ability to capture the spectra of hundreds of stars or galaxies in a single observing run.

In 2002 the 2dF (two-degree field) survey of 221,000 galaxies was the first to identify the link between the temperature fluctuations in the cosmic microwave background and the large-scale structure of galaxies in our universe. Between 2001 and 2003 the AAT was the most productive 4-metre class telescope in the world in terms of the number of science papers produced.

The long running GALAH (GALactic Archaeology with HERMES) survey has captured the detailed spectra and chemical abundances of one million Milky Way stars, enabling the study of the formation history of the Milky Way. In 2021 the GALAH 3^rd data release paper was the most cited paper in the prestigious MNRAS (Monthly Notices of the Royal Astronomical Society) journal.

The AAT 4-metre telescope showing the giant equatorial horseshoe mount, the telescope, and the exchangeable top-end. The exchangeable top-ends allow different focal ratios and/or different instrumentation to be installed (Credit: Dirk Goës).

However, the AAT can no longer compete with the large 8-metre plus optical telescopes in the high deserts of Chile. As part of the Australian Decadal Plan for Astronomy 2026-2035 the Australian astrophysical research community aims to achieve permanent membership of ESO (European Southern Observatory) and continued access to ESO’s existing and future large optical facilities. Australia is also heavily invested in the SKA (Square Kilometre Array) and other partnerships such as the new Vera C. Rubin Observatory. Given these large investments it is most likely that there will be less funding available for the AAT in the future.

At the recent ASM Dr Wolf announced that the AAT has secured continued Commonwealth funding from July 2025 to June 2027. It has also secured continued funding up until December 2028 from the AAT Consortium, the group of nine universities led by the ANU (Australian National University) that have research interests in the AAT. The AAT is also available for use by outside organisations via paid time. It is hoped that this income will make up about 10% of the budget.

There are currently four key projects running at the AAT, some of which hope to be able to use the AAT through to 2030:

Exoplanets with Veloce: calculating the mass of Exoplanets detected by the TESS (Transiting Exoplanet Survey Satellite) mission.
Hector Galaxy Survey: survey of 15,000 galaxies to understand galaxy diversity and the role of different physical processes in galaxy formation and evolution.
OzARCH Survey: Studying the formation history of the Milky Way via the Milky Way halo.
GALAHAD: Studying the formation history of the Milky Way via the Milky Way disc. The next generation of the successful GALAH survey.

Beyond these key projects the future of the AAT for astronomy is unclear. There is interest from the space industry in using the telescope as a commercial facility. Some of these potential uses, such as space domain awareness (satellite tracking), are being tried out now. Another possibility is laser-based communication with satellites and space craft as in NASA’s Deep Space Optical Communications (DSOC) technology demonstration. Laser communication will allow larger volumes of data (bandwidth) to be transmitted than is possible with radio waves. Another possibility is a new telescope in the AAT dome. Therefore, at some point in the future the AAT may transition from being a public facility to a commercial one with a combination of space related and astronomy related applications.

However, another 4-metre telescope of similar age and design was recently upgraded with one of the most advanced spectroscopic instruments ever built. The Dark Energy Spectroscopic Instrument (DESI) sits on top of the Mayall 4-metre telescope at Kitt Peak National Observatory in Arizona USA. The DESI survey is building a 3D map of the universe to study the behaviour of dark energy and can be viewed as a more advanced version of the successful 2dF galaxy survey conducted at the AAT. The AAT has a couple of notable advantages over the Mayall 4-metre. Firstly, it suffers less from light pollution as it is in the Warrumbungle Dark Sky Park whereas the Mayall telescope suffers from light pollution from nearby Tucson Arizona. Secondly the instrumentation on the top of the AAT can be exchanged in as little as a day via an internal crane whereas the DESI instrument had to be installed via an external crane in a semi-permanent alteration.

There was interest expressed at the ASM in future astronomical research projects at the AAT. The AAT Council chaired by Professor Julia Bryant (Sydney University) will be studying all the possibilities early on, with the goal of having a solid plan in place before the current funding ends.

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