Editing Molonglo Observatory Synthesis Telescope

{{Use dmy dates|date=April 2022}}
{{Infobox telescope}}
The '''Molonglo Observatory Synthesis Telescope''' ('''MOST''') is a [[radio telescope]] operating at 843&nbsp;MHz. It is operated by the School of Physics of the [[University of Sydney]]. The telescope is located in [[Hoskinstown, New South Wales|Hoskinstown]], near the [[Molonglo River]] and [[Canberra]], and was constructed by modification of the east–west arm of the former Molonglo Cross Telescope, a larger version of the [[Mills Cross Telescope]]. Construction of the original "Super Cross" telescope with 1.6-kilometre arms began in 1960 by Professor [[Bernard Y. Mills]]. It became operational in 1967.<ref name=SMHObit>{{cite news |url=http://www.smh.com.au/national/obituaries/engineer-a-star-of-astronomy-20110520-1ewo0.html |title=Engineer a star of astronomy |last=Mills |first=Eric |date=21 May 2011 |publisher=[[Sydney Morning Herald]] |access-date=30 July 2012}}</ref>

== Design ==
The MOST consists of two cylindrical [[parabola|paraboloids]], 778m x 12m, separated by 15m and aligned east–west. A line feed system of 7744 circular [[Dipole antenna|dipoles]] collects the signal and feeds 176 preamplifiers and 88 IF amplifiers.

The telescope is steered by mechanical rotation of the cylindrical paraboloids about their long axis, and by phasing the feed elements along the arms. The feed elements were decommissioned in 2018 so that the telescope began to operate in transit mode only. Prior to this, the `alt-alt' system could follow a field for ± 6 hours (necessary for a complete [[aperture synthesis]] with an east–west array) for fields south of declination -30 degrees. For fields near this limit the signal-to-noise ratio is lower for the first and last hour or so due to the lower gain of the system at large '[[meridian arc]] distance' angles.
[[Image:MOST E-W.JPG|thumb|right|350px|MOST looking along E-W arm from the west.]]

[[Image:MOST N-S.JPG|thumb|right|350px|MCT antennas looking along remaining N-S arm from the north.]]

The Molonglo Cross Telescope was a 408&nbsp;MHz [[radio telescope]] built by [[Bernard Y. Mills]] and collaborators and operated by the [[University of Sydney]].<ref>[http://www.atnf.csiro.au/news/newsletter/jun06/BMills.htm 2006 Grote Reber Gold Medal awarded to Bernard Yarnton Mills, Professor emeritus at Sydney University], [[CSIRO]] [[Australia Telescope National Facility]] newsletter, June 2006, accessed 4 January 2009</ref> It telescope consisted of a north–south arm and an east–west arm in a cross shape. Each arm was approximately one mile in length. The east–west arm was split into 88 individual elements to form the current Molonglo Observatory Synthesis Telescope.{{citation needed|date=September 2019}}

===Grote Reber===
[[Image:Grote Reber memorial Molonglo Observatory.JPG|thumb|Reber memorial]]
The design of the original system owes much to pioneering radio astronomy by [[Grote Reber]] in the US and Australia, that informed Mills' work. A memorial to Reber, including some of his ashes, is sited at the telescope.

==MOST work==
Much pioneering radio astronomy was done with this telescope. The Molonglo Cross Telescope was used for a survey of the Southern sky with a resolution of 2.8 arc-min.

The telescope's main research project was the [[Sydney University Molonglo Sky Survey]] (SUMSS), a sensitive radio imaging survey of the southern sky at 843&nbsp;MHz with  similar resolution and sensitivity to the northern [[NRAO VLA Sky Survey]] (NVSS).  SUMSS is now  complete, and digital images and a source catalogue are available online.<ref>{{cite web
  | title =Sydney University Molonglo Sky Survey Home Page
  | work =Astrophysics Research Group
  | publisher =[[University of Sydney]]
  | url =http://www.astrop.physics.usyd.edu.au/SUMSS
  | access-date =2007-01-30  }}</ref>

After a five-year break in which analog equipment was upgraded the observatory is now used to detect [[fast radio burst]]s and do research on [[pulsar]]s.<ref>{{cite web
  | title = This 51-year-old telescope is searching 1,000 times a second for one of the rarest events in the Universe 
  | work =Science Alert
  | publisher =Science Alert ply. ltd.
  | date =2016-02-16
  | url  = http://www.sciencealert.com/this-51-year-old-telescope-is-searching-1-000-times-a-second-for-one-of-the-rarest-events-in-the-universe/page-2
  | access-date =2016-02-21  }}</ref>
The equipment for fast radio burst detection is called UTMOST.<ref name=caleb>{{cite journal| arxiv=1703.10173| last1= Caleb| first1= M.|author1-link=Manisha Caleb| title= The first interferometric detections of Fast Radio Bursts| last2=  Flynn| first2= C.| last3=  Bailes| first3= M.| last4=  Barr| first4= E. D.| last5=  Bateman| first5= T.| last6=  Bhandari| first6= S.| last7=  Campbell-Wilson| first7= D.| last8=  Farah| first8= W.| last9=  Green| first9= A. J.| last10=  Hunstead| first10= R. W.| last11=  Jameson| first11= A.| last12=  Jankowski| first12= F.| last13=  Keane| first13= E. F.| last14=  Parthasarathy| first14= A.| last15=  Ravi| first15= V.| last16=  Rosado| first16= P. A.| last17=  van Straten| first17= W.| last18=  Venkatraman Krishnan| first18= V.| year= 2017| doi=10.1093/mnras/stx638| volume=468| issue= 3| journal=Monthly Notices of the Royal Astronomical Society| pages=3746–3756| doi-access= free| bibcode=2017MNRAS.468.3746C}}</ref>

==Square Kilometre Array development==
MOST is being used to develop technology for the Australian site of the [[Square Kilometre Array]] telescope. Since 2003 work has proceeded on the SKA Molonglo Prototype (SKAMP) which has included fitting new wide-band feeds, low-noise amplifiers, digital filterbanks and correlator, in order to demonstrate 300-[[Hydrogen line|1420&nbsp;MHz]] continuous frequency coverage and multibeam mode operation.

The new correlator is a 96 input continuum correlator using [[Field Programmable Gate Array]] (FPGA) chips.<ref>{{cite web
  | title =The SKA Molonglo Prototype (SKAMP) - Prototyping SKA Technologies at the Molonglo Radio Telescope
  | work =Sydney Institute for Astronomy
  | publisher =[[University of Sydney]]
  | date =2009
  | url =http://www.physics.usyd.edu.au/sifa/Main/SKAMP
  | access-date =2009-06-13
  | archive-url =https://web.archive.org/web/20170218230743/http://www.physics.usyd.edu.au/sifa/Main/SKAMP
  | archive-date =2017-02-18
  | url-status =dead
  }}</ref>

This effort is a collaboration between the [[Australia Telescope National Facility]] (ATNF), the Australian [[Commonwealth Scientific and Industrial Research Organisation]] (CSIRO) [[Information technology|Information and Communications Technology]] Centre, and the University of Sydney.

==UTMOST==

Since 2015, the telescope has been operated in a collaboration between the University of Sydney and Swinburne University of Technology. The goal is to probe the radio transient sky in real time, monitoring pulsars and magnetars, and searching for Fast Radio Bursts. The telescope sensitivity was improved by a refit of receiver technologies on one of its arms (in the east–west direction), and presently (late 2020) the north–south arm is being fitted out with significantly improved receivers as well. This will allow Fast Radio Bursts and similar radio transients to be located on the sky with a few arcseconds of precision, sufficient to identify the host galaxies from which the originate.

==See also==
* [[List of astronomical observatories]]
* [[Lists of telescopes]]

==Notes==
{{reflist}}

==References==
*{{cite web
  | title =The Molonglo Observatory Synthesis Telescope (MOST)
  | work =Sydney Institute for Astronomy
  | publisher =[[University of Sydney]]
  | date =2009
  | url =http://www.physics.usyd.edu.au/sifa/Main/MOST
  | access-date =2009-06-13
  | archive-url =https://web.archive.org/web/20120725143452/http://www.physics.usyd.edu.au/sifa/Main/MOST
  | archive-date =2012-07-25
  | url-status =dead
  }}

==External links==
*{{Commons category-inline}}

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[[Category:Astronomical observatories in New South Wales]]
[[Category:Radio telescopes]]
[[Category:Interferometric telescopes]]
[[Category:University of Sydney]]