Towards final characterisation and performance of the GCT prototype telescope structure for the Cherenkov Telescope Array

Abstract: The Gamma-ray Cherenkov Telescope (GCT) is an innovative dual-mirror solution proposed for the Small Size Telescopes of the future Cherenkov Telescope Array (CTA), capable of imaging the showers induced by cosmic gamma-rays with energies from a few TeV up to 300 TeV. The Schwarzschild Couder design on which the telescope optical design is based makes possible the construction of a fast telescope (primary mirror diameter 4 m, focal length 2.3 m) with a plate scale well matched to compact photosensors, such as multi anode or silicon photomultipliers (MAPMs and SiPMs, respectively) for the camera. The prototype GCT on Meudon's site of the Observatoire de Paris saw first Cherenkov light from air showers in November 2015, using an MAPM based camera. In this contribution, we firstly report on the prototype GCT telescope's performance during its assessment phase. Secondly, we present the telescope configuration during a campaign of observations held in spring 2017. Finally, we describe studies of the telescope structure, such as the pointing and tracking performance.