Cherenkov Telescope Array

The Cherenkov Telescope Array or CTA is a multinational, worldwide project to build a new generation of ground-based gamma-ray instrument in the energy range extending from some tens of GeV to about 300 TeV. It is proposed as an open observatory and will consist of two arrays of Imaging Atmospheric Cherenkov telescopes (IACTs), a first array at the Northern Hemisphere with emphasis on the study of extragalactic objects at the lowest possible energies, and a second array at the Southern Hemisphere, which is to cover the full energy range and concentrate on galactic sources. The physics program of CTA goes beyond high energy astrophysics into cosmology and fundamental physics.[1]

Cherenkov Telescope Array
Artistic drawing of the CTA site (G. Perez, IAC)
Alternative namesCTA
Telescope styleoptical telescope
gamma-ray telescope 
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Building on the technology of current generation ground-based gamma-ray detectors (MAGIC, HESS, and VERITAS), CTA will be ten times more sensitive and have unprecedented accuracy in its detection of high-energy gamma rays. Current gamma-ray telescope arrays host up to five individual telescopes, but CTA is designed to detect gamma rays over a larger area and a wider range of views with more than 100 telescopes located in the northern and southern hemispheres. At least three classes of telescopes are required to cover the full CTA energy range (20 GeV to 300 TeV): Large-Sized Telescope (LST), Medium-Sized Telescope (MST) and Small-Sized Telescope (SST).[2]

The project to build CTA is well-advanced: prototypes exist for all the proposed telescope designs and significant site characterization and preparations are underway. An inter-governmental agreement for construction and subsequent operation of the observatory, a European Research Infrastructure Consortium (ERIC), is in preparation and the financial threshold is expected to be reached in 2019.[3]

The project was promoted to a Landmark on the road-map of the European Strategy Forum on Research Infrastructures (ESFRI), and is on the roadmaps for the European Astroparticle Physics network ASPERA and the European Astrophysics network ASTRONET.

Cost for base-line design of the project is estimated at €300 million (US$350 million).[4]

Network should start taking data in 2022.[5]

CTA Consortium Members and CTAO Shareholders

As of December 2018, the CTA Consortium includes more than 1,420 members from 210 institutes in 31 countries: Armenia, Australia, Austria, Brazil, Bulgaria, Canada, Chile, Croatia, Czech Republic, Finland, France, Germany, Greece, India, Ireland, Italy, Japan, Mexico, Namibia, Netherlands, Norway, Poland, Slovenia, South Africa, Spain, Sweden, Switzerland, Thailand, the United Kingdom, Ukraine and the United States. The group of scientists and engineers are engaged in the scientific and technical development of CTA. Its internal authority, the Consortium Board, includes representatives from each of the Consortium institutes and is responsible for endorsing all major Consortium decisions.[6]

The CTA Observatory gGmbH (CTAO gGmbH) is the legal entity for CTA in the preparation of the implementation of the CTA Observatory. The CTAO gGmbH works in close cooperation with the CTA Consortium. The CTAO is governed by the CTA Council, composed of shareholders from 11 countries (Australia, Austria, Czech Republic, France, Germany, Italy, Japan, Slovenia, Spain, Switzerland, United Kingdom) and associate members from two countries (Netherlands and South Africa).[7]

Array Sites
Southern array site near Paranal Observatory in Chile.[8]
Prototype of 12 meter CTA telescope under construction (Berlin, 2013)

On 15 and 16 July 2015, the CTA decided to enter into detailed contract negotiations for hosting CTA on the European Southern Observatory (ESO) Paranal Observatory in Chile and at the Instituto de Astrofisica de Canarias (IAC),Roque de los Muchachos Observatory in La Palma, Spain. On 19 September 2016, the Council of the Cherenkov Telescope Array Observatory (CTAO) concluded negotiations with the IAC to host CTA's northern hemisphere array at the Roque de los Muchachos Observatory in La Palma, Spain. On 19 December 2018, the final agreements were signed for the southern array to be hosted near the ESO's Paranal Observatory in northern Chile.[9]

CTA's southern hemisphere site is only 11 km southeast of the ESO's existing Paranal Observatory in the Atacama Desert in Chile, which is considered one of the driest and most isolated regions on earth – a paradise for stargazers.[10][11]

CTA's northern hemisphere site is located on the existing site of the IAC's Roque de los Muchachos Observatory on the island of La Palma, the fifth largest island in the Canary Islands. At 2,200 metres altitude and nestled on a plateau below the rim of an extinct volcanic crater, the site currently hosts an operating gamma-ray observatory, the Major Atmospheric Gamma Ray Imaging Cherenkov (MAGIC) telescopes, as well as a wide variety of optical telescopes of various sizes.[12]

Science
Image illustrates all three classes of the telescopes planned.[13]

CTA will look at the sky in higher energy photons than ever measured before. In fact, the cosmic particle accelerators can reach energies inaccessible to human-made accelerators like the Large Hadron Collider. CTA's unique capabilities will help us to address some of the most perplexing questions in astrophysics. CTA will seek to understand the impact of high-energy particles in the evolution of cosmic systems and to gain insight into the most extreme and unusual phenomena in the Universe. CTA will search for annihilating dark matter particles and deviations from Einstein's theory of special relativity and even conduct a census of particle acceleration in the Universe.[14]

CTA will seek to address questions in and beyond astrophysics. These questions fall under three major themes of study: Understanding the Origin and Role of Relativistic Cosmic Particles, Probing Extreme Environments, Exploring Frontiers in Physics. To address these themes, CTA will observe the following key targets: Galactic Centre, Large Magellanic Cloud, Galactic Plane, Galaxy Clusters, Cosmic Ray PeVatrons, Star Forming Systems, Active Galactic Nuclei, Transient Phenomena.[15]

Access

Unlike current instruments, CTA will be operated as a proposal-driven open observatory. Observations will be carried out by observatory operators, then the data will be calibrated, reduced and, together with analysis tools, made available to the principal investigator in FITS data format. After a proprietary period, data will be made openly available through the CTA data archive.[16]

References
  1. The CTA Consortium (2019). Science with the Cherenkov Telescope Array. World Scientific. doi:10.1142/10986. ISBN 978-981-3270-08-4.
  2. "CTA Technology" (dated listing on website, as of 2018). cta-observatory.org. 12 March 2018. Retrieved 12 March 2018.
  3. "CTA Technology" (dated listing on website, as of 2018). cta-observatory.org. 12 March 2018. Retrieved 12 March 2018.
  4. "Cherenkov Telescope Array Status And Outlook" (PDF). 30 October 2015. Retrieved 24 July 2017.
  5. "A brand new technique to research high-energy gamma rays | Internet Shots". Retrieved 2019-11-03.
  6. "Countries and Institutes in CTA Consortium" (dated listing on website, as of 2018). cta-observatory.org. 12 March 2018. Retrieved 12 March 2018.
  7. "Shareholders and Associate Members of CTAO gGmbH" (dated listing on website, as of 2018). cta-observatory.org. 12 March 2018. Retrieved 12 March 2018.
  8. name="eso-ann15058"
  9. "CTA Site Locations". CTAO gGmbH. 12 March 2018. Retrieved 12 March 2018.
  10. "CTA's Southern Hemisphere Array Site". CTAO gGmbH. 28 July 2017. Retrieved 28 July 2017.
  11. "Final Agreements Signed for CTA Southern Hemisphere Site in Chile". Retrieved 20 December 2018.
  12. "CTA's Northern Hemisphere Array Site". CTAO gGmbH. 28 July 2017. Retrieved 28 July 2017.
  13. "ESO to Host Cherenkov Telescope Array-South at Paranal - ESO enters partnership with the world's largest gamma-ray observatory". www.eso.org. Retrieved 20 December 2018.
  14. "CTA's Northern Hemisphere Array Site". CTAO gGmbH. 28 July 2017. Retrieved 28 July 2017.
  15. "CTA's Northern Hemisphere Array Site". CTAO gGmbH. 28 July 2017. Retrieved 28 July 2017.
  16. "CTA's Northern Hemisphere Array Site". CTAO gGmbH. 28 July 2017. Retrieved 28 July 2017.
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