The 50-kg-class Earth observation satellite "RISESAT"is a microsatellite developed mainly by Tohoku University and Hokkaido University, and was successfully launched into orbit by the Epsilon Launch Vehicle No. 4 on January 18, 2019. However, on June 11, 2019, about five months after launch, the three-axis fiber-optic gyroscope (FOG) for attitude control experienced a malfunction, making angular velocity measurement around the satellite's Z-axis unavailable. In this paper, we report our lessons learned on how to solve the single-axis failure of the FOG, which was not expected when RISESAT was developed, by combining the existing functions of the attitude control software. Due to the failure of the FOG, experiments that require high attitude control accuracy, such as high-resolution multispectral observation and laser communication, are now impossible. However, valuable observations such as oceanographic observations and on-orbit monitoring of the radiation environment are still being carried out on a daily basis as of September 2021, more than two years after launch.