Molonglo Reborn: Opening and 50th Anniversary Celebration

26 November 2015

An event will be held on Thursday 3rd December at the Molonglo Observatory to celebrate the 50th anniversary of the opening of the observatory by then Prime Minister Sir Robert Menzies. The event will also look to the future, with the launch of the new telescope in the form of UTMOST, an upgrade of the Molonglo Observatory Synthesis Telescope (MOST).

Sir Robert Menzies at the opening of the Mills Cross Radio Telescope in 1965.
Sir Robert Menzies at the opening of the Mills Cross Radio Telescope in 1965.

The Molonglo Observatory Synthesis Telescope (MOST) is a radio telescope built, operated and owned by the University of Sydney. Opened in 1965, the telescope was originally built as the Molonglo Cross - a telescope with two crossing arms, one north-south and the other east-west, each one mile (1600m) long. Each arm was a parabolic wire trough, which included cosmic radio waves onto a line of 'feeds' running across the trough. In 1978 the north-south arm was shut down, leaving the east-west arm operating in a completely new mode: this created the Molonglo Observatory Synthesis Telescope (MOST). A major upgrade to the telescope was undertaken in 2014-2015 to allow it to do new science - in particular, to hunt for the mysterious 'fast radio bursts' that have tantalised astronomers for almost a decade.

The telescope originated from a 1953 idea by Bernard (Bernie) Mills from CSIR (the forerunner of CSIRO), for a new type of radio telescope that had two crossed arms. This design produced a narrow pencil beam (the region of the sky a telescope 'sees' at any one time), thus giving the telescope high resolution. The telescope's sensitivity (ability to detect weak signals) depended on its collecting area (the surface area capturing radio waves from space), while its resolving power (ability to see detail) depended on its arm length: these two factors could thus be altered independently.

A concept sketch of the Molonglo Cross Telescope.
A concept sketch of the Molonglo Cross Telescope.

Mills later joined the University of Sydney, where he received support from then Head of the School of Physics Harry Messel, who negotiated the purchase of land for the telescope and facilitated a grant of $853 500 (equivalent to millions of dollars today) from the US National Science Foundation (NSF), the first large foreign grant awarded by the NSF. When Prime Minister Sir Robert Menzies opened the telescope on 19th November 1965, the US Ambassador and representatives of the NSF attended as guests.

Some scientific highlights from the 50 years of operation are:

  • A 408 MHz survey of the southern sky. Covering the southern sky from the South Celestial Pole to declination +18 degrees, this survey provided a catalogue of 12 141 radio sources
  • Determination of an absolute flux scale at 408 MHz. This scale was adopted worldwide.
  • Discovery of more than 150 pulsars.
  • Sydney University Molonglo Sky Survey (SUMSS). An 843 MHz survey of the southern sky from the South Celestial Pole to declination -30 degrees, with similar sensitivity and resolution to the NVSS survey carried out for the Northern sky. SUMSS generated a catalogue of 211 063 radio sources.
  • The second-epoch Molonglo Galactic Plane Survey (MGPS-2).The Galactic counterpart to SUMSS, with the same resolution and sensitivity. It generated a catalogue of 48 850 sources. Images from SUMSS and MGPS-2 have been used in over 350 peer-reviewed publications.
  • Detection of Supernova 1987A. Supernova 1987A was the brightest supernova remnant seen since the invention of telescopes. The MOST detected the 'prompt' radio emission at the time of the explosion - the first time this had been done - and in 1990 made the first detection of a radio source emerging from the site of the supernova.
  • Facilitated by the ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), the University of Sydney, Swinburne University, CSIRO and the Australian National University have formed a partnership to carry out a million dollar upgrade of MOST, bringing it into the era of 'big data'. The structure of the telescope remains the same, but it has acquired a new 'backend', a cluster of signal processing computers that incorporate off-the shelf graphics processing cards. These cards can handle up to 22 gigabytes of data per second, and in the course of the year will process almost an exabyte (1018 bytes. As well as entering the era of 'big data', the telescope has had a change of name, going from MOST to (appropriately) UTMOST.

    A group from the University of Sydney's Talented Students Program visiting the telescope.
    A group from the University of Sydney's Talented Students Program visiting the telescope.

    A key science driver for the upgrade of MOST is the search for fast radio bursts (FRBs). FRBs are fleeting cosmic radio signals, lasting just a few milliseconds, that were discovered in 2007. The characteristics of FRBs suggest that the originate in the distant universe. To date most FRBs have been found in archival data; real-time detections (and follow-up at other wavelengths) are essential to determining their true nature.

    Over its lifetime, the telescope has been funded mainly by the Australian Government, through the Australian Research Council and the University of Sydney. In recent years the NSW State Government has also provided funding, through its Science Leveraging Fund. From 2015, fifty years after it first started work, the telescope will begin science operations with its new capabilities as part of Professor Matthew Bailes' Laureate Fellowship project funded by the Australian Research Council.

    Further Reading:

  • Bruce McAdam, "Molonglo Observatory: Building the Cross and the MOST". Journal of Astronomical History and Heritage, 11(1), 63-70 (2008).
  • The MOST page on this website.
  • The UTMOST page on the Swinburne University website
  • The full details of the event celebrating 50 years of the observatory can be found here.