Evaluation of Thermal System Based on Flight Result of Nano Moon Lander OMOTENASHI

OMOTENASHI is a CubeSat that was launched by a NASA SLS rocket in November 2022. Its mission was to demonstrate that a CubeSat can make a semi-hard landing on the Moon. The 6U-size spacecraft weighs 12.6 kg, and consists of an orbiting module, a rocket motor for deceleration on the Moon, and a surface probe as the landing module. Tight resource constraints of CubeSat impose the difficulty of mounting a heater and a radiator. The passive thermal control which is the prominent design feature of OMOTENASHI breaks through technical difficulties. In the mission sequence, the heat input changes greatly on orbit and when approaching the moon. In addition, the moon temperature cannot be predicted as a sunshine or shade. Therefore, the spacecraft is coated with APTEK2711 which white paint has high emissivity and reflectivity. This paint can be maintained small changes in temperature even when affected by radiation and albedo from the moon surface. OMOTENASHI established communication with the ground station approximately 30 minutes after SLS separation. In this moment, the solar cells were unexpectedly facing away from the Sun and rotating fast. From the temperature monitoring, the temperature of the spacecraft is gradually decreasing. Then, attitude control was performed by gas jets, but the battery voltage was sharply dropped. As the result, the transmitter turned off due to lack of battery voltage and the communication has not been restored yet. Based on the estimated trajectory, there is the possible that the solar cells will be able to generate power and communications will resume after March 2023. In this paper, the flight result of the thermal status during the first ground station pass is reported. Furthermore, based on the estimated trajectory, the future thermal status of the spacecraft is also evaluated.