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Dear Reader,
Welcome to our first issue of the CTA Newsletter, which, together with our new website and social media channels, serves to inform interested persons about the status and progress of the implementation of the Cherenkov Telescope Array, the unique facility defining the future of very-high energy gamma-ray astronomy.
Current instruments like H.E.S.S., MAGIC, VERITAS and, most recently, HAWC are demonstrating an unexpectedly rich image of the sky at Tera-Electronvolt energies, which corresponds to 1012 times the energy of visible light. Close to 200 sources of very-high energy radiation were discovered in the Galaxy and beyond, each presumably representing a cosmic particle accelerator, creating the observed gamma rays when high-energy particles collide with ambient gas or lower-energy radiation. Yet, while current instruments reveal an intriguing glimpse of the sky at very-high energies, they are not yet sensitive enough to conclusively answer questions such as:
- Where are cosmic rays accelerated?
- How do they influence the evolution of galaxies?
- How are particles accelerated around black holes?
- Is dark matter made of heavy particles that can annihilate, creating gamma rays?
- Is the speed of light the same at low and high photon energies, or do effects of quantum gravity modify the propagation of shortest-wavelength gamma rays?
CTA – combining 10-fold sensitivity with a larger field of view, wider energy coverage and better angular resolution – is designed to overcome limitations of current instruments and to tackle these questions.
CTA is designed by a worldwide consortium of more than 1,350 scientists and engineers from more than 210 institutes in 32 countries. Work started as early as 2005, but the past two years have seen enormous progress towards realizing CTA. On the technical side, the exact array layout was optimized, on the basis of a massive simulation effort consuming tens of millions of CPU hours. The southern hemisphere array will encompass four 23-m Large-Size Telescopes (LST), twenty-five 12-m Medium-Size Telescopes (MST) and seventy Small-Size Telescopes (SST) spread across an area of five square kilometres. The northern hemisphere array, with a focus on extragalactic objects, will include four LSTs and fifteen MSTs. The telescope designs are complete and prototypes exist for all but the LST, where construction of the first telescope has started on La Palma, to serve as the first telescope of the final array in the northern hemisphere. CTA telescopes have seen first Cherenkov images, and the novel dual-mirror optics design of the SSTs was demonstrated to work according to specifications.
A very important step towards realizing CTA was the foundation of the CTA Observatory (CTAO) limited liability company to serve as (interim) legal framework for the project. Most of the major countries involved in CTA are now represented as shareholders of the company: Austria, the Czech Republic, France, Germany, Italy, Japan, Spain, Switzerland and the UK. Another major step was the choice by the CTAO Council of the array sites. For the northern array on the Canary island of La Palma, the hosting agreement with the Instituto de Astrofísica de Canarias was signed in September 2016. The southern array will be located on the ESO area in Chile and be operated by ESO; the agreement between CTAO and ESO is finalized and will be signed early in 2017. The Council also agreed to locate CTAO Headquarters in Bologna, Italy; the move of the CTA Project Office from Heidelberg to Bologna is in progress. The CTA Science Data Management Centre will be located in Zeuthen, Germany.
While construction of CTA will ultimately proceed under the framework of an international convention, a Memorandum of Understanding (MoU) is being signed as a first step towards this convention. The MoU lists planned investments of countries for CTA construction and allows the initial deployment of pre-production telescopes that serve to verify and streamline the process of mass production, deployment and commissioning. Our goal is to reach enough commitments to match the agreed funding threshold for CTA in early 2017. According to the CTA Business Plan, regular user operation could then start in 2022, while it is likely to take a few more years to fully complete the array.
In parallel, the CTA Consortium is intensely preparing for science with CTA, with a newly defined structure of its science working groups, and is testing the tools that will enable users to efficiently extract science from the CTA data. Whether the data is obtained on the basis of proposals or as archival data – all CTA data will become openly available after a proprietary period of one year.
In summary, this is a very exciting time for CTA, and we encourage everyone to browse the various sections of this newsletter to get more first-hand information and insight.
Sincerely,
Werner Hofmann, CTA Spokesperson, and Rene Ong, CTA Co-Spokesperson
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CTA's new public website is live! Head to www.cta-observatory.org to learn about CTA, how it works, its science goals and expected performance, the construction project and its status, the technology behind CTA and much more.
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News from the CTA Consortium
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Provided by Jürgen Knödlseder, Consortium Board Chair
The CTA Consortium, the group responsible for conceiving CTA and designing and prototyping its instruments, includes more than 1,350 scientists and engineers from more than 210 institutes in 32 countries. Highlighted in the map below, the member countries span the globe – evidence that CTA is truly a worldwide endeavour.
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The CTA Consortium meets bi-annually with the latest taking place near the future premises of the CTA Headquarters in Bologna, Italy. Topics included prototyping progress reports, science goals discussions and preparations for the impending CTA construction and operations. For the latter, the CTA Consortium will adapt its internal organisation to be structured around working groups for Science, Analysis and Simulations, and Instrumentation. The Science working groups were formed recently and delivered their first report at the Bologna meeting. The Analysis and Simulations working group will be established before the end of the year, while the Instrumentation working group will come at a later stage.
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Above: Nearly 250 CTA Consortium members from 25 of its 32 member countries came together in Bologna to discuss the science and construction of CTA.
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The Speaker’s and Publication Office (SAPO), which reviews all of the Consortium’s scientific and technical publications, is seeing a continued increase in the productivity of the CTA Consortium. The next major milestone will be the publication of the CTA Science Overview document that provides a comprehensive collection of the CTA Science Case and develops the Key Science Projects that will be conducted by CTA during the first ten years of operations. This document will be made available on the “Library” page of the new public website.
Additionally, Jean-Pierre Ernenwein was nominated to replace Javier Rico as the chair of SAPO. A big thank you to Javier for his enormous investment and devotion over the past two years and a warm welcome to Jean-Pierre.
As 2016 comes to a close, there is an immense amount of enthusiasm among Consortium members as the project moves from the prototyping phase to the construction phase. The next gathering of the CTA Consortium will be in Rio de Janeiro the week of 15-19 May 2017.
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CTA's Galactic Plane Survey Will Provide Unprecedented View of Our Galaxy
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Provided by Jürgen Knödlseder, Consortium Board Chair
Astronomical surveys of our Milky Way present a fundamental means to discover and understand the objects that populate our local neighbourhood in the Universe. Surveys of the Milky Way have been conducted at nearly all wavelengths of the electromagnetic spectrum, revealing the stars and the matter between them that form our Galaxy. At the highest photon energies that will be explored by CTA, our knowledge about the Milky Way is still incomplete, and to fill this gap, CTA will conduct a complete and deep survey of the Galactic Plane during its first decade of operations. The plan is to dedicate more than 1,600 hours of observing time to scrutinizing our Galaxy, which will provide an unprecedented legacy dataset that will form the basis for countless follow-up studies.
The below image represents what CTA may observe during its Galactic Plane Survey. It is based on a simulation of the events that will be recorded by both CTA arrays, which, when combined, will provide an unprecedented view of our Milky Way. The simulation reflects our current knowledge about the population of very-high-energy sources in our Galaxy and comprises objects such as the remnants of supernova explosions, the nebulae created by young energetic pulsars and diffuse emission components arising from the interaction of energetic particles with the interstellar medium and radiation fields. In total, we expect to be able to detect about 500 individual sources of gamma-ray emission in the course of the survey. An important fraction of these sources will be spatially resolved by CTA, providing insights into the physics that accelerate particles to the highest energies and how these particles leave their accelerating sources.
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It also is expected that the survey will lead to the discovery of new and unexpected phenomena in our Galaxy, such as new source classes and new types of transient phenomena. The detection of hundreds of new very-high-energy gamma-ray sources will substantially increase the galactic inventory and permit high statistics population studies for the first time. The survey also will be fundamental to unveiling sources that are capable of accelerating particles to PeV energies, which is key to understanding the origin of the cosmic rays that permeate our Milky Way.
To learn more about CTA’s Galactic Plane Survey and other key targets, visit the CTA website or read our CTA Science Overview document (accessible in the Library when it is published in early 2017).
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Visit the News & Media page of the CTA website for more news. |
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CTA has made significant progress in 2016. Working prototypes exist or are under construction for all three classes of CTA’s telescope designs, site negotiations have come to a close and site characterization is underway. An agreement for construction and operation of the Observatory is in preparation and funding for the project as a whole is progressing.
On 19 September 2016, the Council of the Cherenkov Telescope Array Observatory (CTAO) concluded negotiations with the Instituto de Astrofisica de Canarias (IAC) to host CTA’s northern hemisphere array at the Roque de los Muchachos Observatory in La Palma, Spain. The agreement allows the construction of the CTA northern array to proceed at the Roque de los Muchachos site and ensures access to the infrastructure and common services needed for the operation of the Observatory. Negotiations with the European Southern Observatory (ESO) for the southern hemisphere site near ESO’s existing Paranal Observatory in Chile have concluded. If all goes as planned, construction in the south will begin in 2017, with first telescopes on site in 2018.
Final telescope array layouts for both the northern and southern hemispheres have been fixed and now provide a basis for the sites’ infrastructure design. In the southern hemisphere, preparations are underway for a topographical and geotechnical survey to take place during the first half of 2017. For the northern hemisphere site, arrangements are being made for conceptual design studies and electrical supply and lightning protection studies.
Construction of a Large-Size Telescope (LST) prototype is currently underway on the La Palma site and the Schwarzschild-Couder Telescope (SCT) prototype is being built at the Whipple Observatory south of Tucson, Arizona. Click on the images below to watch the construction live on their webcams:
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Top: LST construction in La Palma. Bottom: SCT construction in Arizona.
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ASTRI Demonstrates Viability of Novel Schwarzschild-Couder Design
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In October 2016, the ASTRI telescope prototype, a novel dual-mirror Schwarzschild-Couder telescope design proposed for CTA, passed its biggest test yet by demonstrating a constant point-spread function of a few arc minutes over a large field of view of 10 degrees.
The ASTRI telescope is one of three proposed SST designs being prototyped and tested for CTA’s southern hemisphere array. The ASTRI telescope uses an innovative dual-mirror Schwarzschild-Couder configuration initially developed in 1905 by the German physicist and astronomer Karl Schwarzschild and enhanced in 1926 by André Couder. It was in 2007 that a study by Vladimir Vassiliev and colleagues at the University of California Los Angeles (UCLA) demonstrated the design’s usefulness for atmospheric Cherenkov telescopes.
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The ASTRI prototype (pictured to right), the first Schwarzschild-Couder telescope to be built and tested, was inaugurated in September 2014 and has been undergoing testing in Serra La Nave, Italy ever since.
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The technical challenges of the design were overcome by recent advances, particularly in dual-mirror technology, making it a feasible implementation for the observation of Cherenkov light.
Pictured below, Polaris, the North Star, as observed by ASTRI with different offsets from the optical axis of the telescope. The recorded images have approximately the same angular size, each one from a different observational direction in the field of view showing that the optical point-spread function of the telescope is approximately constant across the full field of view.
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“This is also the first time that a Cherenkov telescope with two focusing mirrors has been completely characterized from the opto-mechanical point of view,” said Giovanni Pareschi, astronomer at the INAF-Brera Astronomical Observatory and principal investigator of the ASTRI project. “This is an important result because it allows us to move immediately to the next step: to mount a Cherenkov camera by December 2016 with the aim to observe the first gamma-ray light with ASTRI.”
The Schwarzschild-Couder design is being used in two additional CTA prototypes (the SST-2M GCT and the SCT), but the ASTRI is the first to conclusively demonstrate the viability of the system.
For more information, read the full press release.
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SST-1M Prototype Prepares for First Light
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The Single-Mirror Small-Size Telescope (SST-1M) team has made significant progress recently with the telescope/camera control and the complete integration of the camera with the prototype structure. The advances bring the team much closer to their ultimate goal: the telescope’s first observation of Cherenkov light.
The telescope and camera control software was successfully tested in two end-to-end tests, controlling the SST-1M telescope prototype (located in Krakow) and its camera, the DigiCam, (located in Geneva) from the INTEGRAL Science Data Centre, Department of Astronomy in Geneva. The video below shows the SST-1M in action during one of the tests.
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All sub-systems of the telescope have been interfaced with the official CTA framework (the ACS - ALMA Common Software). The software for the drive system responsible for moving the telescope and the charge-couple device (CCD) cameras responsible for aligning mirror facets and pointing to sources is almost complete. The master control process to coordinate all software components and to provide the high-level interface with the common software to all CTA telescopes is under development, as well.
The SST-1M’s camera, DigiCam, was assembled this fall and has been undergoing testing at the Département de Physique Nucleaire et Corpusculaire (DPNC) at the University of Geneva. This innovative camera uses 1,296 silicon photomultipliers (SiPMs), acquiring data on photons hitting the pixels of the camera at a huge rate (6.6 Terabytes per second) so it can efficiently capture a snapshot of the sky 10,000 times per second.
The fully digital readout and trigger electronics have been integrated into the camera and cooling and vibration tests are complete. After more testing in December, it will be installed on the roof the Geneva observatory to test its ability to detect Cherenkov light from cosmic rays. The camera will be integrated with the prototype telescope structure in Krakow to test the complete assembly and to prepare the SST-1M prototype for gamma-ray light detection.
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Light in Astronomy Event Promotes CTA and ASTRI in Italy
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Light in Astronomy is an annual event devoted to astrophysics outreach in Italy that is organized by the National Institute for Astrophysics (INAF) and the Italian Astronomical Society (SAIT). This year’s event took place 14-20 November in Padova with a focus on CTA science and technology, specifically the ASTRI telescope project. The theme of the event was “CSI: Earth – ASTRI Cosmo Scene Investigation” and included three separate events. The first event, CSI Academy, invited more than 60 university students to learn about ASTRI and the science behind CTA at a two-hour workshop. The second event, CSI Science, hosted more than 50 at a winery for dinner, a piano concert and an explanation of the electromagnetic spectrum and the very-high-energy gamma rays CTA will detect. At the final event, CSI technology, 40 were treated to cocktails during an informal talk about the technology of CTA and ASTRI. Visit the event website to learn more about the event and plans for next year’s activities.
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International Cosmic Day Challenges Students to Think Like an Astrophysicist
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On 2 November, 46 groups including students, teachers and scientists from 16 countries came together to discuss and learn about cosmic rays at the fifth International Cosmic Day. The event, organized by Deutsches Elektronen-Synchrotron (DESY), challenged the groups to answer a question concerning the zenith angle distribution of air shower particles by conducting their own experiments.
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Measurements were taken around the clock for 24 hours using a variety of home-made detectors, including a scintillation counter, Kamiokannen, Medipix, Geiger-Müller counter and photomultipliers.
The groups reached out to each other across the globe via Skype to compare and discuss results. Scientists from ATLAS and IceCube even helped analyze their own data and presented their findings via video calls. A summary of the results will be published in a conference booklet and distributed to all participants.
Learn more about the event at https://icd.desy.de/. (Image credit: DESY)
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How to Build CTA (in LEGO)
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This year, the Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP) celebrated its 40th anniversary. The LAPP studies particle physics, gravitational waves and astroparticles under France’s National Centre for Scientific Research (CNRS).
To help celebrate, LAPP staff working on the CTA project constructed CTA’s southern hemisphere array in LEGO.
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For the Fête de la Science event in October, the LSTs were motorized to rotate on the azimuth axis and light effects were use to reproduce the footprint made by Cherenkov light. The animation was presented to more than 2,000 visitors, including students (8-18 years).
For additional information about the event and how to build your own CTA telescopes in LEGO, go to https://lapp.in2p3.fr/spip.php?rubrique1166&lang=en.
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CTA Participation Workshop
Armagh Observatory and Planetarium, Ireland
27 January 2017, 10 am – 4 pm
Description: This workshop will discuss opportunities for scientists across Ireland to engage in CTA.
More information: https://star.arm.ac.uk/
Contact: Aileen McKee
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Upcoming Conferences & Abstract Deadlines
Conferences
American Physical Society April Meeting 2017
28-31 January – Washington, D.C., USA
Bright & Dark Universe Workshop
29 January - 2 February – Naples, Italy
International Astronomical Union Symposium 3331 – SN 1987A, 30 years later
20-24 February – Saint-Gilles, La Réunion Island, France
Conference Abstract Deadlines
Bright & Dark Universe Workshop
29 January - 2 February – Naples, Italy
Abstract due: 21 December
Spie Optics + Photonics 2017
6-10 August – San Diego, CA
Abstract Due: 23 January
35th International Cosmic Ray Conference
12-20 July – Busan, South Korea
Abstract Due: 15 February
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The CTA Newsletter is your resource for CTA information and news. Your feedback is welcome! Direct all inquiries to the editor, Megan Grunewald.
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