The Small-Sized Telescopes (SSTs) will outnumber all the other telescopes with 70 planned to be spread out over several square kilometers in the southern hemisphere array only. This is because very high-energy gamma-ray showers produce a large amount of Cherenkov light over a large area, and the SST’s smaller mirror is sensitive to the highest energy gamma rays (between a few TeV and 300 TeV). The SSTs’ wide coverage and high sensitivity improve CTA’s chances of detecting the highest energy gamma rays.
Three different SST implementations are being prototyped and tested: one single-mirror design (SST-1M) and two dual-mirror designs (SST-2M ASTRI and SST-2M GCT). In May 2018, it was decided that a single design for the SST will be developed for the observatory. The project manager will work with each of the teams to harmonise the designs into one. The SSTs prototypes are being built by international collaborations with contributions from institutes and universities in Czech Republic, Ireland, Poland, Switzerland and Ukraine (SST-1M); in Brazil, Italy and South Africa (ASTRI); and in Australia, France, Germany, Japan, the Netherlands and the United Kingdom (GCT).