The Small-Sized Telescope (SST) will be built by an international collaboration that includes research institutes and universities from Australia, Brazil, France, Germany, Italy, Japan, Netherlands, Switzerland and UK. The CTAO’s southern array will include 37 SSTs according to the “Alpha Configuration,” largely outnumbering the other CTAO telescopes.
The SSTs will be optimized to observe celestial gamma rays in the range of 5 TeV to 300 TeV, covering the highest end of CTAO’s sensitivity range. These very high-energy gamma-ray showers produce a large amount of Cherenkov light but are less frequent than lower–energy showers. Thus, compared to the other CTAO telescopes, the SSTs have smaller reflectors and a larger field of view to increase their capability to detect these energetic events. Additionally, to increase the probability of detection, there will be a higher number of telescopes spread out over several square kilometers.
The SST relies on a modified Schwarzschild-Couder dual-mirror optical design, providing a good spatial resolution over a large field of view. They are compact telescopes with small focal ratios allowing the use also of compact cameras. Each SST has a primary mirror based on 18 hexagonal segments with a total aperture of 4.3 m and a monolithic secondary mirror of 1.8 m in diameter.