HERMES (High Energy Rapid Modular Ensemble of Satellites) is a space-borne mission based on a constellation of six 3U CubeSats flying in a low-Earth orbit, hosting new miniaturized instruments based on a hybrid Silicon Drift Detector/GAGG:Ce scintillator photodetector system sensitive to X-rays and 7-rays. Moreover, the HERMES constellation will operate in conjunction with the Australian-Italian Space Industry Responsive Intelligent Thermal (SpIRIT) 6U CubeSat, that will carry in a Sun-synchronous orbit (SSO) an actively cooled HERMES detector system payload. In this paper we provide an overview of the ground calibrations of the first HERMES and SpIRIT flight detectors, outlining the calibration plan, detector performance and characterization.
