Square Kilometre Array: Difference between revisions

Coordinates: 30°43′16″S 21°24′40″E / 30.72113°S 21.4111278°E / -30.72113; 21.4111278
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The SKA is projected to cost €1.5 billion for phases 1 and 2 completing in 2024, this includes €300 million for Phase 1 completing 2019. The funding will come from many international funding agencies. Preliminary expectations are that Europe, the United States and the rest of the world will each contribute a third of the project's funding. The SKA and the [[European Extremely Large Telescope]] (E-ELT) are the two flagship facilities for ground-based astronomy in the future. They are equal high priority projects in the [[ASTRONET]] roadmap for European astronomy.
The SKA is projected to cost €1.5 billion for phases 1 and 2 completing in 2024, this includes €300 million for Phase 1 completing 2019. The funding will come from many international funding agencies. Preliminary expectations are that Europe, the United States and the rest of the world will each contribute a third of the project's funding. The SKA and the [[European Extremely Large Telescope]] (E-ELT) are the two flagship facilities for ground-based astronomy in the future. They are equal high priority projects in the [[ASTRONET]] roadmap for European astronomy.

==Project risks==
Potential risks for priority astronomical sites in South Africa are protected by the [[Astronomy Geographic Advantage Act]] of 2007. Put in place to specifically support the South African SKA bid, it outlaws all activities that could endanger scientific operation of core astronomical instruments. In 2010, concerns were raised over the will to enforce this law when [[Royal Dutch Shell]] applied to explore the [[Karoo]] for [[shale gas]] using [[hydraulic fracturing]], an activity that would have the potential to increase [[radio interference]] at the site.<ref>{{cite news|last=Nordling|first=Linda|title=Mining plans pose threat to South African astronomy site|url=http://www.nature.com/news/2011/110322/full/news.2011.174.html?s=news_rss|accessdate=27 June 2011|newspaper=[[Nature (journal){{!}}Nature]]|date=22 March 2011}}</ref>

In February 2012, a former Australian SKA Committee chairman raised concerns about risks at the Australian candidate site, particularly in terms of cost, mining interference and land agreements. SKA Australia was "deeply stunned and disappointed" by the negative publicity and assured that all points have been addressed in the site bid.<ref>{{cite news
|url=http://www.iol.co.za/the-star/oz-telescope-body-under-microscope-after-ex-chairman-raises-difficult-questions-1.1239657
|title=Oz telescope body under microscope after ex-chairman raises difficult questions
|last=Carpenter
|first=Avery
|date=22 February 2012
|newspaper=[[The Star (South Africa)|The Star]]}}</ref>


==See also==
==See also==

Revision as of 15:04, 9 May 2012

Square Kilometre Array (SKA)
An artist's impression of the central core of dish antennas of the SKA.
Alternative namesSKA Edit this at Wikidata
Named aftersquare kilometre, antenna array Edit this on Wikidata
Location(s)Australia/NZ / South Africa
Coordinates30°43′16″S 21°24′40″E / 30.72113°S 21.4111278°E / -30.72113; 21.4111278 Edit this at Wikidata
BuiltPhase 1 2019
Phase 2 2024
Phase 3 2022 onwards
First light2020 (planned)
Telescope stylePhased array
Collecting area1,000,000 m²
Websiteskatelescope.org
Square Kilometre Array is located in South Africa
Square Kilometre Array
Location of Square Kilometre Array (SKA)
  Related media on Commons
[edit on Wikidata]

The Square Kilometre Array (SKA) is a radio telescope in development which will have a total collecting area of approximately one square kilometre.[1] It will operate over a wide range of frequencies and its size will make it 50 times more sensitive than any other radio instrument. It will require very high performance central computing engines and long-haul links with a capacity greater than the current global Internet traffic.[2] It will be able to survey the sky more than ten thousand times faster than ever before. With receiving stations extending out to distance of at least 3,000 km from a concentrated central core, it will continue radio astronomy's tradition of providing the highest resolution images in all astronomy. The SKA will be built in the southern hemisphere, in either South Africa or Australia and New Zealand, where the view of our own galaxy, the Milky Way, is best and radio interference least. With a budget of €1.5 billion, construction of the SKA is scheduled to begin in 2016 for initial observations by 2019 and full operation by 2024.[3][4]

Organisation

The SKA is a global collaboration of 20 countries which is aimed to provide answers to fundamental questions about the origin and evolution of the Universe.[5]

In April 2011, Jodrell Bank Observatory (of the University of Manchester) in Cheshire, England was announced as the location of the headquarters office for the project.[6]

In November 2011 the SKA Organisation was formed and the project moved from a collaboration to an independent, not for profit, company.[citation needed] As of May 2012 the members of the SKA Organisation are:[citation needed]

Description

SKA participating countries marked on a map of the world as dark blue.

The SKA will combine the signals received from thousands of small antennas spread over a distance of more than 3000 km to simulate a single giant radio telescope capable of extremely high sensitivity and angular resolution. The SKA will also have a very large field-of-view (FOV) with a goal at frequencies below 1 GHz of 200 square degrees and of more than 1 square degree (about 5 full Moons) at higher frequencies. One innovative development is the use of Focal Plane Arrays using phased-array technology to provide multiple FOVs. This will greatly increase the survey speed of the SKA and enable multiple users to observe different pieces of the sky simultaneously. The combination of a very large FOV with high sensitivity means that the SKA will transform the exploration of the Universe.

The SKA will provide continuous frequency coverage from 70 MHz to 10 GHz in the first two phases of its construction. A third phase will then extend the frequency range up to 30 GHz.

  • Phase 1: Providing ~20% of the total collecting area at low and mid frequencies by 2019.
  • Phase 2: Completion of the full array at low and mid frequencies by 2024.
  • Phase 3: Building of the high frequency array from 2022.

The frequency range from 70 MHz to 10 GHz, spanning more than two decades, cannot be realized using one design of antenna and so the SKA will comprise arrays of three types of antenna elements that will make up the SKA-low, SKA-mid and dish arrays:

Artist's Impression of a Low-Band SKA Sparse Aperture Array Station
Artist's Impression of a Mid Band SKA Dense Aperture Array Station
  1. SKA-low array - A phased array of simple dipole antennas to cover the frequency range from 70 - 200 MHz. These will be grouped in 100m diameter stations each containing about 90 elements.
  2. SKA-mid array - This is likely to be a phased array of "tiles" to cover the medium frequency range from 200 to 500 MHz. The 3 metre x 3 metre tiles will be grouped into circular stations, 60 m in diameter.
  3. Dish Array - several thousand dish antennas to cover the frequency range 500 MHz to 10 GHz. It is expected that the antenna design will follow that of the Allen Telescope Array using an offset Gregorian design having a height of 15 metres and a width of 12 metres. It is hoped that the parabolic dishes will be equipped with focal plane arrays at their focus. This would allow the dishes to observe over a far wider field of view than that achieved with a single element feed. Prototypes of such multiple element feeds are now under development for the pathfinder arrays described below.

The area covered by the SKA - extending out to ~3000 km - will comprise three regions:

  1. A central region containing 5 km diameter cores of dish antennas, SKA-mid stations and SKA-low antennas. This central region will contain approximately half of the total collecting area of the three SKA arrays.
  2. A mid region extending out to 180 km. This will contain dishes and pairs of SKA-mid and SKA-low stations. In each case they will be randomly placed within the area with the density of dishes and stations falling off towards the outer part of the region.
  3. An outer region from 180 km to 3000 km. This will comprise five spiral arms along which dishes, grouped into stations of 20 dishes, will be located. The separation of the stations increases towards the outer ends of the spiral arms.

Key projects

Artist's Impression of the Offset Gregorian Antennas
Schematic of the SKA Central Region

The capabilities of the SKA will be designed to address a wide range of questions in astrophysics, fundamental physics, cosmology and particle astrophysics as well as extending the range of the observable universe.

A number of key science projects have been selected to be undertaken by the SKA and are listed below.

Extreme tests of general relativity

Main article: Tests of general relativity

For almost ninety years, Einstein's theory of general relativity has precisely predicted the outcome of every experiment made to test it. Most of these tests, including the most stringent ones, have been carried out using radio astronomical measurements. By using pulsars as cosmic gravitational wave detectors, or timing pulsars found orbiting black holes, astronomers will be able to examine the limits of general relativity such as the behaviour of space and time in regions of extremely curved space. The goal is to reveal whether Einstein was correct in his description of space, time and gravity, or whether alternatives to general relativity are needed to account for these phenomena.

Galaxies, cosmology, dark matter and dark energy

Main articles: Galaxy formation and evolution and Dark matter

The sensitivity of the SKA in the 21-cm hydrogen line will map a billion galaxies out to the edge of the observable Universe. The large-scale structure of the cosmos revealed will give constraints to determine the processes resulting in galaxy formation and evolution. Imaging hydrogen through the Universe will provide a three-dimensional picture of the first ripples of structure which formed individual galaxies and clusters. This may also allow the measurement of effects hypothetically caused by dark energy and causing the increasing rate of expansion of the universe.[7]

Epoch of re-ionization

The SKA is intended to provide observational data to fill the gap—the dark ages; between 300,000 years after the Big Bang when the Universe became transparent, and a billion years later when young galaxies are seen. By observing the primordial distribution of gas, the SKA should be able to see how the Universe gradually lit up as its stars and galaxies formed and then evolved.

Cosmic magnetism

It is still not possible to answer basic questions about the origin and evolution of cosmic magnetic fields, but it is clear that they are an important component of interstellar and intergalactic space. By mapping the effects of magnetism on the radiation from very distant galaxies, the SKA will investigate the form of cosmic magnetism and the role it has played in the evolving Universe.

Transient radio phenomena caused by extraterrestrial life

The SKA will be capable of detecting extremely weak extraterrestrial signals if existing, and may even detect planets capable of supporting life. Astrobiologists will use the SKA to search for amino acids by identifying spectral lines at specific frequencies.

Possible locations

An automatic wideband radio scanner system was used to survey the radio frequency noise levels at the various candidate sites in South Africa

Suitable sites for the SKA need to be in unpopulated areas with guaranteed very low levels of man-made radio interference. Four sites were initially proposed in South Africa, Australia, Argentina and China.[8] After considerable site evaluation surveys, Argentina and China were dropped and two sites are now shortlisted:

Australia and New Zealand: The core site is located near Boolardy 26°59′S 116°32′E / 26.983°S 116.533°E / -26.983; 116.533 in Western Australia 315 km north-east of Geraldton[9] on a flat desert-like plain at an elevation of about 460 metres. The most distant stations will be located in New Zealand.[10] [11]

South Africa: The core site is located at 30°43′16.068″S 21°24′40.068″E / 30.72113000°S 21.41113000°E / -30.72113000; 21.41113000 at an elevation of about 1000 metres in the Karoo area of the arid Northern Cape Province, about 75 km north-west of Carnarvon, with distant stations in Ghana, Kenya, Madagascar, and Mauritius.

On 10 March 2012 it was reported that the SKA Site Advisory Committee had made a confidential report in February that the South African bid was stronger.[12]

The final decision on the site to be made by the projects board of directors was expected on 4 April 2012.[12] However a scientific working group has been set up to explore possible implementation options of the two candidate host regions, and its report is expected in mid May 2012.[13]

Precursors, Pathfinders and Design Studies

Many groups are working globally to develop the technology and techniques required for the SKA. Their contributions to the international SKA project are classified as either: Precursors, Pathfinders or Design Studies.

  • Precursor facility: A telescope on one of the two SKA candidate sites, carrying out SKA-related activity.
  • Pathfinder: A telescope or programme carrying out SKA-related technology, science and operations activity.
  • Design Study: A study of one or more major sub-systems of the SKA design, including the construction of prototypes

Precursor facilities

CSIRO's ASKAP antennas at the MRO in Western Australia.

Australian SKA Pathfinder (ASKAP)

Main article: Australian Square Kilometre Array Pathfinder

The Australian SKA Pathfinder, or ASKAP, is an A$100 million project to build a telescope array of thirty-six twelve-metre dishes. It will employ advanced, innovative technologies such as phased array feeds to give a wide field of view (30 square degrees).

ASKAP is being built by CSIRO at the Murchison Radio-astronomy Observatory site, located near Boolardy in the Mid West region of Western Australia. All 36 antennas and their technical systems are expected to be completed by 2013.[14]

MeerKAT

Main article: MeerKAT

MeerKAT is a South African project to build an array of sixty-four 13.5-metre diameter dishes as a world class science instrument and also to enable technology required for the SKA to be developed. KAT-7, a seven-dish engineering and science testbed instrument for MeerKAT, located near Carnarvon in the Northern Cape Province of South Africa is already up and running and the full MeerKAT array is expected to be ready by 2015-2016. The dishes will be equipped with a number of high performance single pixel feeds to cover frequencies from 580 MHz up to 14 GHz.[15]

Murchison Widefield Array (MWA)

Main article: Murchison Widefield Array

The Murchison Widefield Array[16] is a low-frequency radio array operating in the frequency range 80-300 MHz also under construction at the Murchison Radio-astronomy Observatory site in Western Australia.

Pathfinders

Allen Telescope Array

Main article: Allen Telescope Array

The Allen Telescope Array uses innovative 6.1m offset Gregorian dishes equipped with wide band single feeds covering frequencies from 500 MHz to 11 GHz. The 42-element array now in operation is to be extended to 350 elements. The dish design has explored methods of low-cost manufacture.[22]

LOFAR

Main article: LOFAR

LOFAR is a €150 million Dutch-led project building a novel low frequency phased aperture arrays spread over northern Europe. An all-electronic telescope covering low frequencies from 10 to 240 MHz which has been coming online through 2009 to 2011. LOFAR will demonstrate crucial processing techniques vital to the SKA.[23]

Design Studies

Technology Development Project (TDP)

The Technology Development Project, or TDP, is a US$12 million project to specifically develop dish and feed technology for the SKA. It is operated by a consortium of universities led by Cornell University and will be completed in 2012.[27]

Timeline and funding

The SKA was originally conceived in the early 1990s with an international working group set up in 1994. This led to the signing of the first Memorandum of Agreement in 2000. Considerable early development work then followed. This culminated in the commencement of PrepSKA in 2008 leading to a full SKA design in 2012. Construction of Phase 1 will take place from 2016 to 2019 providing an operational array capable of carrying out the first science. Phase 2 will then follow for completion in 2024 providing full sensitivity for frequencies up to 10 GHz.

The SKA is projected to cost €1.5 billion for phases 1 and 2 completing in 2024, this includes €300 million for Phase 1 completing 2019. The funding will come from many international funding agencies. Preliminary expectations are that Europe, the United States and the rest of the world will each contribute a third of the project's funding. The SKA and the European Extremely Large Telescope (E-ELT) are the two flagship facilities for ground-based astronomy in the future. They are equal high priority projects in the ASTRONET roadmap for European astronomy.

See also

References

  1. ^ Square Kilometre Array website.
  2. ^ [1], The Square Kilometre Array, p.24
  3. ^ "SKA announces Founding Board and selects Jodrell Bank Observatory to host Project Office". SKA 2011. 2 April 2011. Retrieved 14 April 2011.
  4. ^ "The project timeline | SKA Telescope". SKA 2011. Retrieved 14 April 2011.
  5. ^ Redfern, Martin (31 March 2011). "World's biggest radio telescope, Square Kilometre Array". BBC News Online. Retrieved 2 April 2011.
  6. ^ "Jodrell Bank chosen as base for largest radio telescope". BBC News Online. 2 April 2011. Retrieved 2 April 2011.
  7. ^ http://www.skatelescope.org/the-science/ska-key-science-projects/ska-key-science-projects/galaxy-evolution/
  8. ^ Koenig, Robert (18 August 2006). "RADIO ASTRONOMY: Candidate Sites for World's Largest Telescope Face First Big Hurdle". Science. 313 (5789). AAAS: 910–912. doi:10.1126/science.313.5789.910. PMID 16917038.
  9. ^ "Aiming for the skies". The Age. 7 April 2008.
  10. ^ Amos, J. Nations vie for giant telescope, BBC News, 28 September 2006.
  11. ^ Science Network WA, 16 February 2007
  12. ^ a b Flitton, Daniel (10 March 2012). "Australia on the outer for largest space telescope". The Age. Retrieved 9 March 2012 (UTC). {{cite news}}: Check date values in: |accessdate= (help)
  13. ^ "Further delays signalled in super-telescope plan". AFP. the australian. April 05, 2012. Retrieved 10 April 2012. {{cite news}}: Check date values in: |date= (help)
  14. ^ ASKAP website
  15. ^ South African SKA website
  16. ^ Murchison Widefield Array website
  17. ^ EMBRACE website
  18. ^ e-MERLIN website
  19. ^ EVLA website
  20. ^ LWA website
  21. ^ SKAMP website
  22. ^ ATA website
  23. ^ LOFAR website
  24. ^ AAVP website
  25. ^ Canadian SKA Program website
  26. ^ PREPSKA website
  27. ^ SKATDP website

External links

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