Thermal analysis of the optical and near-infrared telescope (MONSTER) on board the HiZ-GUNDAM satellite

HiZ-GUNDAM aims to explore the early Universe and advance multi-messenger astrophysics through rapid detection of gamma-ray bursts (GRBs). The MONSTER near-infrared telescope performs five-band imaging from 0.5 to 2.5 µm of GRBs detected by the wide-field X-ray monitor EAGLE and provides photometric redshifts. To ensure high sensitivity, the telescope body and HgCdTe detector must be cooled below 200 K and 120 K by radiative cooling. After GRB detection, the satellite slews toward the GRB, increasing thermal input. We evaluated the thermal worst-case condition, defined as the attitude with maximum heat load at the hottest point, and established a method to compute satellite attitude using rotation matrices based on the Sun’s right ascension and declination. Thermal analysis shows that even in the worst case, the telescope body and detector remain at 171 K and 106 K. In this presentation, we report the development and thermal assessment of the MONSTER telescope onboard HiZ-GUNDAM.