Those last decades, gamma astronomy went on the rise with the exploitation of the Cherenkov effect, which is the production of extremely fast blue light flashes (about 10 ns). Thus, several gamma telescopes arrays like HESS, MAGIC or VERITAS, were built and showed the richness of the universe in high energetic emissions (from few GeV to few TeV).
Successes of theses first arrays and the need of improving performances led to the international CTAO project (link) to provide the scientific community with an array of improved gamma telescopes.
Developed by UNIDIA and LUX from the Observatoire de Paris- PSL since 2011, the pGCT prototype (Gamma-ray Cherenkov Telescope) is a technology demonstrator of improved Cherenkov telescope proposed for the SST (Small-Sized Telescope) needed by CTAO.
pGCT prototype in Meudon, May 2024 (4.1m x 4.8m x 8.2m)
This prototype is based on the Schwarzschild-Couder dual-mirror configuration. This new configuration for gamma astronomy needs 2 mirrors with an aspherical profile: the primary mirror M1 of 4m diameter, tessellated into 6 petals, and the secondary mirror M2 of 2m diameter.
Due to the high number of SST needed by CTAO, maintenance topics were fully taken into account. The dish supporting M1 petals can rotate and the arm supporting the camera is movable. These features allow bringing M1 petals and camera to staff height. In this way, maintenance needs less equipment to access these elements, easing the activities and decreasing the costs per telescope. To the scale of the whole SST array, these features allow to save time and money for keeping the observatory in good conditions.
Developed with the support of Observatoire de Paris – PSL and the Île-de-France region, pGCT was assembled on the Meudon site of the Observatoire de Paris in 2015. It was then equipped with the CHEC-S camera, a Cherenkov camera prototype from an international consortium, allowing the detection of Cherenkov light and proving the feasibility and performances of this new kind of gamma telescope. It even became the first Schwarzschild-Couder telescope to detect Cherenkov light!
In order to propose a durable telescope, the process of the lightweight metallic mirrors has been optimised from 2020 to 2022 with the help of the industrial partners, the Observatoire de Paris – PSL and the Île-de-France region.
For now, the pGCT prototype is still used as a technology demonstrator to continue the upgrading of Cherenkov telescopes, like with another R&D campaign to improve further the mirrors’ performances.
Moreover, the recent funding from the Île-de-France region will allow the completion of pGCT with the purchase of a Cherenkov camera. Thus, it will be proposed for educational purposes. Finally, this unique prototype in France is as an educational tool presented to middle and high school students during visits, and is also during the events organised by the Observatoire de Paris - PSL.
pGCT video via drone on the Obs YT channel : https://www.youtube.com/watch?v=wKOPgNrKaT4&t=76s
The pGCT prototype was developed with the support of Observatoire de Paris - PSL, the Île-de-France region and CNRS.
