* Astronomy

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RE: Cherenkov Telescope Array

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Title: Design of a 7m Davies-Cotton Cherenkov telescope mount for the high energy section of the Cherenkov Telescope Array
Authors: A.C. Rovero, P. Ringegni, G. Vallejo, A.D. Supanitsky, M. Actis, A. Botani, I. Ochoa, G. Hughes, for the CTA Consortium

The Cherenkov Telescope Array is the next generation ground-based observatory for the study of very-high-energy gamma-rays. It will provide an order of magnitude more sensitivity and greater angular resolution than present systems as well as an increased energy range (20 GeV to 300 TeV). For the high energy portion of this range, a relatively large area has to be covered by the array. For this, the construction of ~7 m diameter Cherenkov telescopes is an option under study. We have proposed an innovative design of a Davies-Cotton mount for such a telescope, within Cherenkov Telescope Array specifications, and evaluated its mechanical and optical performance. The mount is a reticulated-type structure with steel tubes and tensioned wires, designed in three main parts to be assembled on site. In this work we show the structural characteristics of the mount and the optical aberrations at the focal plane for three options of mirror facet size caused by mount deformations due to wind and gravity.

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Title: FlashCam: A fully digital camera for CTA telescopes
Authors: G. Pühlhofer (1), C. Bauer (2), A. Biland (3), D. Florin (4), C. Föhr (2), A. Gadola (4), G. Hermann (2), C. Kalkuhl (1), J. Kasperek (5), T. Kihm (2), J. Koziol (6), A. Manalaysay (4), A. Marszalek (6), P. J. Rajda (5), T. Schanz (1), S. Steiner (4), U. Straumann (4), C. Tenzer (1), P. Vogler (3), A. Vollhardt (4), Q. Weitzel (3), K. Winiarski (5), K. Zietara (6), for the CTA consortium (7) ((1) Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Germany, (2) Max-Planck-Institut für Kernphysik, Germany, (3) ETH Zürich, Inst. for Particle Physics, Switzerland, (4) Physik-Institut, Universität Zürich, Zürich, Switzerland, (5) Faculty of Electrical Engineering, Automatics, Computer Science and Electronics, AGH University of Science and Technology, Poland, (6) Jagiellonian University, Poland, (7) See this http URL for full author and affiliation list)

The future Cherenkov Telescope Array (CTA) will consist of several tens of telescopes of different mirror sizes. CTA will provide next generation sensitivity to very high energy photons from few tens of GeV to >100 TeV. Several focal plane instrumentation options are currently being evaluated inside the CTA consortium. In this paper, the current status of the FlashCam prototyping project is described. FlashCam is based on a fully digital camera readout concept and features a clean separation between photon detector plane and signal digitisation/triggering electronics.

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Title: Southern Africa CTA Site Proposal
Authors: P. P. Krüger, D.J. Van der Walt

Southern Africa has some of the world's best sites for air Cherenkov telescopes. South Africa has only one viable site, which is south of Sutherland and also close to the Southern African Large Telescope (SALT). This site has very good infrastructure and is easy to access, but only 47% of the night-time has a cloudless sky usable for observations. Namibia, which already hosts the H.E.S.S telescope, has a number of potential sites with much less cloud coverage. The H.E.S.S. site is one of the highest of these sites at 1840 m a.s.l. with about 64% of the night-time cloudless. It also has very low night sky background levels and is relatively close (about 100 km) to Windhoek. Moving further away from Windhoek to the south, the cloud coverage and artificial night sky brightness becomes even less, with the site at Kuibis (between Keetmanshoop and Luderitz) at 1640 m a.s.l. having clear night skies 73% of the time. Even though this site seems remote (being 660 km from Windhoek by road), it is close to the national B4 highway, a railway line, a power line and an optical fiber line. It is also less than two hours drive away from a harbour and national airports. The Namibian sites also receive very little snow, if any, and the wind speeds are less than 50 km/h for more than 90% of the time with maximum wind speeds of around 100 km/h. Seismically the whole Southern African region is very stable.

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India plans to offer an astronomical site at Hanle in Leh for an international collaboration which is exploring the possibility of setting up two large gamma-ray telescope arrays in the Northern and Southern hemispheres, a senior astronomer said.
The international collaboration is planning Cherenkov Telescope Array (CTA) in both the hemispheres to enhance the understanding of the high energy Unvierse, Prof Ramesh Koul, Head, Astrophysical Sciences Division of Bhabha Atomic Research Centre (BARC) said.

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