Optical design and calibration of a medium size telescope prototype for the CTA

Bagmeet Behera; Jürgen Bähr; Sandra Grünewald; Gareth Hughes; Igor Oya; David Melkumyan; Stefan Schlenstedt; Ullrich Schwanke

doi:10.1117/12.923728

17 September 2012 Optical design and calibration of a medium size telescope prototype for the CTA

Bagmeet Behera, Jürgen Bähr, Sandra Grünewald, Gareth Hughes, Igor Oya, David Melkumyan, Stefan Schlenstedt, Ullrich Schwanke

Author Affiliations +

Proceedings Volume 8444, Ground-based and Airborne Telescopes IV; 844417 (2012) https://doi.org/10.1117/12.923728
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

The Cherenkov Telescope Array (CTA) is designed to make a major improvement in the sensitivity of ground based VHE (Very High Energy, defined as > 20GeV to 100s of TeV) gamma-ray telescopes. Not only will the differential-flux sensitivity be an order of magnitude better than those of the currently operating Cherenkov telescopes, but there will also be significant improvements in the energy, spectral and angular resolution. Delivering these features cost-effectively requires several telescope sizes and designs - a few large size telescopes (23m diameter) are designed for the lowest energies, a large number of small size telescopes (4-7m diameter) to increase the overall collection area which helps at the highest energies and a number of Medium Size Telescopes (MST, 9.5m or 12m diameter, depending on the mirror design) to provide the greatest sensitivity at ∼ 1 TeV. To provide complete sky coverage, CTA will have both a Northern Hemisphere and a Southern Hemisphere site. A prototype for an MST design (currently under development) will be build in Berlin by 2012. This MST prototype has a modified Davies-Cotton design with a tessellated mirror, with individual facets of ∼ 1.2m in diameter. The facets are three-point mounted on the optical support structure, having two powered actuators for alignment adjustments. In addition a number of CCD cameras will be mounted at various positions on the dis and will be used for calibration. Here we present the various optical calibration tasks - optimization of the optical point-spread-function (PSF) and the pointing of this MST prototype, along with initial results.

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Bagmeet Behera, Jürgen Bähr, Sandra Grünewald, Gareth Hughes, Igor Oya, David Melkumyan, Stefan Schlenstedt, and Ullrich Schwanke "Optical design and calibration of a medium size telescope prototype for the CTA", Proc. SPIE 8444, Ground-based and Airborne Telescopes IV, 844417 (17 September 2012); https://doi.org/10.1117/12.923728

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