First results from the ASTRI mini-array air-Cherenkov cameras

Abstract

The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) that will deploy nine dual-mirror air-Cherenkov telescopes at the Teide Observatory (Tenerife). The telescopes adopt, for the first time in a scientific facility, the Schwarzschild–Couder aplanatic dual-mirror configuration, which reduces the plate scale and enables the use of compact cameras specifically designed for array operations. We have installed nine telescopes, and three of them already acquire Cherenkov data, undergoing the commissioning and science verification phase. The ASTRI camera is one of the most advanced subsystems of the array. It offers a wide 10.5° Field of View and detects Cherenkov light through 2,368 Silicon Photomultiplier (SiPM) pixels (7 mm×7 mm), read out by the CITIROC-1A front-end ASIC developed by Weeroc and INAF. CITIROC-1A integrates high-dynamic-range preamplifiers and an efficient peak detector, enabling fast signal extraction with very low power consumption and minimal data output. These features have directly supported and streamlined the design of the focal-plane thermal-control system, which is implemented as a compact and robust Peltier-based solution that eliminates the need for external liquid cooling. The SiPM bias system can supply the high currents required for sustained high-duty-cycle observations, including operations under elevated Night Sky Background conditions. The camera Back-End Electronics manages all operations through advanced hardware–software solutions and achieves sub-nanosecond synchronization thanks to the array’s White Rabbit timing system. The integrated calibration unit improves the efficiency of relative calibration procedures and continuously monitors subsystem performance before each scientific acquisition. This contribution presents the architecture, implementation, and first performance results of the ASTRI Mini-Array Cherenkov cameras, demonstrating that the adopted design fully satisfies the scientific and operational requirements for the array's complete deployment.