The Small-Size 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). The current expectation is that the array will include a mixture of these designs. The SSTs will be built by international collaborations with contributions from institutes and universities in Poland and Switzerland (SST-1M); in Brazil, Italy and South Africa (ASTRI); and in Australia, France, Germany, Japan, the Netherlands, the United Kingdom and the United States (GCT).