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.
