MeV gamma-ray detector on the 50-kg class satellite

We are planning to launch a 50kg-class satellite named INSPIRE, equipped with a small, high-performance Hybrid Compton Camera (HCC) for MeV gamma-ray astronomy.Since the launch of the COMPTEL satellite in 1991, there have been limited observations in the MeV gamma-ray band. However, this energy range is crucial for studying nucleosynthesis processes. INSPIRE aims to conduct a wide-area survey of nuclear gamma rays from the galactic plane and includes gamma-ray observations of solar flares as one of its objectives. Equipped with a hybrid Compton camera (HCC) system, INSPIRE can perform simultaneous X-ray and gamma-ray imaging. This is achieved by integrating the features of both Compton and pinhole cameras within a single detector system. The system includes two sensor layers of large-area Silicon Photomultiplier (SiPM) arrays, optically coupled with GAGG scintillators. This configuration enables simultaneous imaging of gamma rays from 30 to 200 keV in pinhole mode and from 200 to 3000 keV in Compton mode. Its intrinsic efficiency and angular resolution are comparable to those of COMPTEL.The INSPIRE satellite is being developed as the successor to PETREL, which is currently being prepared for launch, with a planned launch in 2027.