Ground-based angular rate reconstruction with intermittent magnetometer data from Phoenix Cubesat

PHOENIX is a 2U CubeSat, which was designed, assembled, integrated, tested and operated by National Cheng Kung University (NCKU), Taiwan. After the deployment from International Space Station (ISS) in May 2017, a series of attitude control processes has been implemented by the satellite operators to make PHOENIX align with orbit-reference frame for the scientific research. However, it was found that the results of in-flight attitude estimation were discordant with the observation of magnetometer data and scientific sensor measurements. To confirm and resolve such issues about the attitude determination and control subsystem (ADCS), attitude and angular rate reconstruction had to be implemented by analysing the in-flight sensor data from PHOENIX CubeSat. Moreover, owing to some limitations, all the in-flight data were recorded at a low sampling rate with interval of 60 seconds, which was viewed as the major challenge for the post attitude estimation. This paper presents an estimation method for the reconstruction of attitude behavior with low sampling rate and intermittent magnetometer data from PHOENIX based on extended Kalman filter (EKF). A novel model and architecture is applied to deal with the long period of measurement update. Finally, the result of 3-axis angular rate reconstruction shows similar estimates with the rate sensor measurements. With the proposed angular rate reconstruction approach, it is believed to be beneficial for optimizing the parameters like moment of inertia and state noise covariance. This, in turns, leads to the better performance of attitude control laws, attitude estimators, and the in-flight ADCS operation.