The pointing monitoring camera hardware and software systems for the ASTRI Mini-Array project

The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) that foresees the construction and operation of an array of nine Imaging Atmospheric Cherenkov Telescopes at the Observatorio del Teide in Tenerife (Spain). The main purpose of the project is to study gamma-ray astrophysical sources in the very high-energy range, particularly at the multi-TeV energy scale. The camera and electronics used for the detection of the Cherenkov light are designed to trigger on the very fast flashes from atmospheric particle showers. Although the variance method is implemented in ASTRI Mini-Array cameras, it is difficult to obtain an adequate pointing model using only Cherenkov cameras. In order to build the pointing model and to monitor and control the pointing accuracy during observations a Pointing Monitoring Camera will be installed on each telescope. The PMC systems will acquire images of the sky with a machine vision camera in the direction pointed by the telescopes and perform an astrometry check on a dedicated computer hosted in the telescope electronics cabinet. The astrometry results will be fed back to the main Telescope Control System. The PMC system will be controlled and it will exchange data through the OPC-UA protocol. During the Assembly Integration and Verification phase and for maintenance activities, a specifically developed Graphical User Interface will be used. The PMC hardware and software systems are described.