In-orbit operation of Resolve onboard the XRISM satellite

The initial on-orbit checkout of the soft X-ray spectroscopic system (Resolve) on board the XRISM satellite is summarized. XRISM was launched on September 6, 2023 (UT) and has been undergoing initial checkout since then. Immediately after launch, cooling of the vessel covering the sensor (Dewar) was advanced, and the first cycle of adiabatic demagnetization refrigerator (ADR) was performed on Day 32 to transition the sensor to steady-state operational temperature conditions. Subsequently, the filter wheel which supports energy calibration, was started up. The energy scale is highly sensitive on the temperature environment around the sensor. The gain correction by referring to the calibration X-ray lines together with the temperature of the sensor. For an optimization of the cooler frequency, we took the noise spectra by scanning the coolers frequencies, which were made with three steps and were taken over six consequent days at the last step. In addition, the gate valve (GV), which protects the inside of the Dewar from outside air pressure at launch, will be opened to bring the system to a state where it is ready for regular operations.