Square kilometer array

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Artist's impression of the center of the parabolic antennas

The Square Kilometer Array ( SKA ) is a planned radio telescope which will have a total collecting area of ​​approximately one square kilometer . It is said to operate over a wide frequency range; Due to its size, the sensitivity should be increased by 50 times compared to other radio telescopes. To evaluate the data, high-performance computers and long-distance networks with a capacity that exceeds today's global Internet traffic are required. With the SKA it should be possible to search the sky ten thousand times faster than before. With receiving stations that are set up up to a distance of 3000 km from a center, it should generate extremely high-resolution images of the sky. The SKA is to be built in South Africa and Australia , where the best view of the galactic center and minimal radio interference are guaranteed. Construction will continue for many years.

The SKA is to be operated by a collaboration of 15 countries (as of 2020). The researchers hope to find answers to fundamental questions about the origin and development of the universe .

description

The plan is for the SKA to combine signals received by thousands of small radio antennas. Due to the large spatial distance of up to 3000 km, it would be possible to simulate a huge radio telescope with extremely high sensitivity and angular resolution. The SKA will also be a very large field of view (FOV, English field of view ), having the goal of 200 square degrees at frequencies below 1 GHz and more than 1 square degree (about five moon slices) at higher frequencies. A planned innovation is the simultaneous use of several fields of view through phased array antennas . The aim is to significantly improve the speed of patterning and to enable different users to observe different parts of the sky at the same time.

In the first two construction phases, continuous coverage from 70 MHz to 10 GHz should be guaranteed. An expansion to 30 GHz is planned in a third phase.

  1. Phase 1: ≈20% of the total collecting area at low and medium frequencies.
  2. Phase 2: Full array size for low and medium frequencies.
  3. Phase 3: Building the array for high frequencies.

The entire frequency range from 70 MHz to 10 GHz (more than two decades ) cannot be sensibly received with a single antenna design . Therefore, the SKA should have three types of antenna elements, SKA-low, SKA-mid and parabolic antennas.

Illustration of the center of the SKA-low array
Illustration of a station of the SKA-mid array
Illustration of the offset Gregory dish antennas
  1. SKA-low Array (phases 1 and 2): An array of phase-controlled, simple dipole antennas for the frequency range from 70 MHz to 200 MHz. These antennas should be set up in groups of 90 on an area with a diameter of 100 m.
  2. SKA-mid array (phase 2): This array should consist of phase-controlled antennas, which enable frequencies from 200 MHz to 500 MHz to be covered. The antennas with dimensions of 3 m × 3 m should be set up in circular groups with a diameter of 60 m.
  3. Dish array (phases 1 and 2): Several thousand parabolic antennas for frequencies from 500 MHz to 10 GHz. Is scheduled an antenna design as in the Allen Telescope array with an offset - Gregory m design with a height of 15 m and a width of 12th The parabolic antennas should, if possible, be equipped with focal plane arrays in their focus. This structure would give the parabolic antennas a far larger field of view than would be possible with a single receiver. Prototypes of these focal plane arrays are currently under development.
Scheme of the central region of the SKA

The SKA will be divided into three regions:

  1. A central region with collections of parabolic antennas and SKA-mid stations in the inner 2.5 km and SKA-low antennas up to 5 km. This central region should contain about half of the total reception area of ​​1 km².
  2. A medium region up to 180 km. Parabolic antennas and pairs of SKA-mid and SKA-low stations will be located in this region. All antennas should be distributed randomly, with an outwardly sloping density of antennas.
  3. An outer region from 180 km to 3000 km. It contains five spiral arms with groups of 20 parabolic antennas. The distance between the stations increases with increasing distance.

Scientific goals of the SKA

The SKA is to be used as a highly flexible instrument to answer a wide range of questions in basic physics, particle physics, astrophysics and cosmology. It should be able to explore previously unknown parts of the distant universe. The following scientific projects were selected as the main fields of activity of the SKA:

Extreme tests of general relativity

For more than ninety years, Einstein's general theory of relativity has correctly predicted the results of any experiments designed to test it. Most of these tests, including the most stringent, were carried out using radio-astronomical methods. With the SKA, astronomers should be able to use pulsars as cosmic detectors for gravitational waves or in binary systems with black holes to investigate the limits of general relativity, such as the behavior of space and time in regions with extreme space curvatures. This could provide information on new physical effects.

Galaxies, cosmology, dark matter and dark energy

The sensitivity of the SKA in the 21 cm hydrogen line should make it possible to map billions of galaxies up to the limit of the visible universe. The large-scale structure of these galaxies enables conclusions to be drawn about how galaxies were formed and developed. The distribution of hydrogen gas throughout the universe will show where the first structures on the continuum formed, from which galaxies and clusters emerged. This would allow quantitative conclusions to be drawn about the effects of dark energy .

Measurement of the "Dark Ages"; the first black holes and stars

The SKA is said to be able to study the void in the history of the universe, which begins 300,000 years after the Big Bang , when the universe became transparent to radiation, and extends up to a billion years after the Big Bang when the first young galaxies light up. By measuring the primordial gas distribution, the SKA should be able to understand how the universe was gradually lit up as the first stars and galaxies formed and then evolved.

Origin and evolution of cosmic magnetism

It is still not possible to answer simple questions about the origin and development of cosmic magnetic fields. As is well known, these represent an important part of interstellar and intergalactic space . The SKA is intended to clarify the form of the cosmic magnetic field and its role in the evolution of the universe.

Others

In the Cradle of Life program, topics such as cosmochemistry , astrobiology and SETI are to be researched.

Locations

Automatic broadband scanner for noise level determination in South Africa.

Possible locations for the SKA had to be in uninhabited areas with very little artificial radio interference. After extensive tests, two locations remained to choose from:

Compromise solution: After a long competition between the two locations, the decision was made on May 25, 2012 on a compromise solution: The majority of the parabolic antennas, antennas for phases 1 and 2 and the SKA-mid array for phase 2 will be built in South Africa Part of the parabolic mirror for phase 1 as well as the SKA-low array for phases 1 and 2 in Australia and New Zealand.

Pathfinder arrays and technology development

Many groups of scientists around the world are working to develop the technology and procedures that will be used by the SKA. For this purpose, antenna arrays are being created that are not intended to become part of the SKA. Some are listed below. The Giant Metrewave Radio Telescope (GMRT) of the Indian National Center for Radio Astrophysics (NCRA) of the TIFR , which was built in 1995/96, was granted Pathfinder status at the beginning of 2015.

MeerKAT

MeerKAT is a project for 860 million Rand , which tests the foundations for the SKA's technology with an array of 50 or more parabolic antennas with a diameter of 12 m. KAT-7, a seven-bowl test bed near Carnarvon in the Northern Cape Province of South Africa, should be fully operational in 2012. The parabolic antennas were equipped with individual broadband receivers for frequencies from 800 MHz to 8 GHz. In July 2016, around 1200 new galaxies were discovered during an initial test recording with 16 of the planned 64 parabolic antennas.

Australian SKA Pathfinder

The Australian SKA Pathfinder, or ASKAP for short , was an AU $ 100 million project with the aim of building an array of 36 antennas for the SKA at the Australian site by 2012 in order to develop technology for the SKA. The parabolic antennas have a diameter of 12 m and 188 receivers in the image plane for a field of view of 30 square degrees . The frequency coverage extends from 700 MHz to 1.8 GHz. Scientific operations began in October 2016, initially with twelve antennas. In spring 2019, all 36 antennas were operated together for the first time.

On September 24, 2018, ASKAP registered a fast radio burst , which was localized to 0.04 arc seconds using the automatically triggered raw data recording using VLBI methods and assigned to a galaxy.

LOFAR

LOFAR is a 120 million euro European project, planned and built by the ASTRON institute in the Netherlands, which is building a novel array of antenna stations for low frequencies with phased opening, distributed across northern Europe, and has been using it since 2011. Received data at low frequencies of 10 MHz to 240 MHz are sent directly to a central computer, where they are superimposed and evaluated. LOFAR is currently developing basic processing techniques that are of crucial importance for the SKA. The extension NenuFAR of the French LOFAR station FR606 at the Nançay radio telescope was granted Pathfinder status in August 2014.

Allen Telescope Array

The Allen Telescope Array (ATA) consists of innovative offset Gregory parabolic antennas with a diameter of 6.1 m, equipped with broadband receivers for 500 MHz to 11 GHz. 42 elements are currently interconnected to form a functional array (as of 2010), with a planned expansion to 350 antenna elements. Special inexpensive manufacturing methods were tried out for the design of the parabolic antennas.

Square Kilometers Array Design Study

The Square Kilometer Array Design Study, or SKADS for short , is a European project worth 38 million euros, which is developing a whole range of technologies and scientific studies in the context of the SKA. The focus of technical developments is on high-frequency phase arrays for 300 MHz to 1 GHz. Such a fully electronic telescope delivers a large number of simultaneous beams for highest speeds when surveying the sky .

Technology Development Project

The Technology Development Project, or TDP for short, was a US $ 12 million program aimed at developing technologies for parabolic dishes and their integration specifically for the SKA. It was operated by a consortium of universities led by Cornell University and should be completed in 2012.

MWA

The Murchison Widefield Array is similar to the LOFAR, a radio telescope for the frequency range up to 300 MHz with a synthetic aperture. Relevant technologies are being developed for the development of the SKA:

  • Time-of-flight controlled beam shaping with antenna matrices from inexpensive dipole antennas
  • Data collection and synchronization from a large number of antenna groups
  • FX technology of the receiver and digitizer components.

The MWA is at one of the possible locations for the SKA in Australia.

Schedule and funding

The SKA was originally conceived in the early 1990s by an international group that was formed in 1994. In 2000 the first "Memorandum of Agreement" was signed. Considerable energy was then put into preparatory work. In 2008, the full design was planned for 2012, with a budget of 1.5 billion euros. However, the ASTRONET timetable for European astronomy recommended the E-ELT with higher urgency. The construction plans should then be drawn up by 2018. The first observations are planned for 2020. However, this will only involve the use of part of the entire array, since it is unlikely to be completed by then.

Member states

Map of the member states

The SKA is funded by fifteen states. The members and partners are currently (as of 2020) Australia, Germany, France, India , Italy , Canada , New Zealand, the Netherlands , Portugal , Sweden , Switzerland , Spain , South Africa, the United Kingdom and the People's Republic of China . In June 2014, Germany declared its withdrawal at the end of June 2015; the Max Planck Society joined in 2019. The founding members of the "SKA Organization" founded in December 2011 were Australia, Germany, France , Italy, New Zealand, the Netherlands, South Africa, the United Kingdom and the People's Republic of China.

See also

Web link

Commons : Square Kilometer Array  - collection of images, videos and audio files
Australia
Europe
South Africa

Individual evidence

  1. ^ Signal Transport and Networks. Square Kilometer Array, 2018, accessed December 5, 2018 .
  2. ^ A b Claus Stäcker : South Africa and Australia build the world's largest telescope. In: Tagesschau.de. Norddeutscher Rundfunk, May 25, 2012, archived from the original on September 25, 2012 ; accessed on December 5, 2018 (English, original website no longer available).
  3. ↑ Cradle of Life skatelescope.org
  4. ^ Aiming for the skies . The Age . April 7, 2008. Retrieved February 15, 2011.
  5. ↑ Amos, J. Nations vie for giant telescope , BBC News , September 28, 2006.
  6. ^ Science Network WA , February 16, 2007
  7. ↑ skatelescope.org: India's GMRT telescope granted SKA pathfinder status . News, February 2015.
  8. ^ South Africa SKA website.
  9. ↑ South African radio telescope MeerKAT switched on: 1200 galaxies discovered. In: heise online. Heise Medien, July 18, 2016, accessed on July 18, 2016 .
  10. ↑ ASKAP website
  11. ↑ Depths of the universe: Researchers determine the origin of the mysterious radio flash . In: Spiegel Online . June 27, 2019 ( spiegel.de [accessed June 27, 2019]).
  12. ^ CD Wilson, MA Voronkov, TW Shimwell, DN Roxby, J. Reynolds: A single fast radio burst localized to a massive galaxy at cosmological distance . In: Science . June 27, 2019, doi : 10.1126 / science.aaw5903 .
  13. ↑ LOFAR website
  14. ↑ skatelescope.org: French NenuFAR telescope granted SKA Pathfinder status . Latest News, August 2014.
  15. ↑ SKADS website
  16. ^ William Garnier : Start of the 2016 SKA Engineering Meeting in South Africa. Square Kilometer Array, 2016, archived from the original on October 3, 2016 ; accessed on December 5, 2018 (English, original website no longer available).
  17. ^ The SKA Project. Square Kilometer Array, 2018, accessed December 5, 2018 .
  18. ↑ Participating Countries. Square Kilometer Array, 2018, accessed December 5, 2018 .
  19. ↑ skatelescope.org: India's National Center for Radio Astrophysics becomes the 11th full SKA Organization member . Latest News, August 11, 2014.
  20. ↑ Germany announces its intent to leave the SKA Organization , www.skatelescope.org - Latest News, June 5, 2014 (English)
  21. ↑ Christoph Seidler: Square Kilometer Array: Germany gets out of mega telescope. In: Spiegel Online , June 11, 2014, accessed on July 29, 2017.
  22. ↑ Joining the Square Kilometer Array. Retrieved July 20, 2020 .
  23. ↑ Founding Board of the SKA , www.skatelescope.org - SKA Project - The History of the SKA Project, 2014 (English)