Seven identical X-ray and gamma-ray spectrometers have been fully tested and calibrated at FBK, IAAT/EKUT and INAF facilities.
Although very compact and lightweight (1U=10×10-10cm, 1.6kg) these miniaturized instruments are quite advanced: they cover the very broad 3-1000 keV energy range with a resolution of about 300eV in the X-dray band and 6% in the gamma-ray band. The total collecting area and field of view of each instrument is about 50cm2 and more than 3 steradiants respectively. The temporal resolution is better than half microsecond. The GAGG scintillator crystals are hosted in a stainless steel case, with tungsten shields on the bottom and on the sides to reduce the Cosmic X-ray background.
The instruments will monitor the High Energy sky to catch and localize transients such as Gamma Ray Bursts and the electromagnetic counterparts of gravitational wave events like neutron star binary mergers.
FM1-SpiRIT has been already integrated in the Payload Management System at University of Melbourne labs on March/April 2023. The PMS will be integrated in the S/C on May/June 2023.
HERMES Pathfinder PFM is at Politecnico di Milano premises and will be integrated in the S/C PFM on May/June 2023.
FM2-FM6 will be integrated in their S/C during the second half of 2023.
The launch of SpIRIT is foreseen by the end of 2023, while the launch of the HERMES Pathfinder constellation of six CubeSat is at the moment foreseen for mid 2024.