In-orbit calibration of the cold-gas thrusters onboard UoSAT-12

This paper describes the principle and in-orbit test results of an engineering approach of calibrating thruster torque coefficients onboard UoSAT-12. It uses an off-line batch computation. One single thruster is fired for a fixed width pulse, and the disturbance it makes on the attitude is compensated by the reaction wheel attitude control system. By measuring both the effects on the attitude and the control torques, the thruster torque is estimated. A preliminary test with no firing is used to get the estimation of the unmodelled external torque disturbances, which are then compensated during the firing test batch computation. Both simulation and in-orbit test results are presented to evaluate the performance and design objectives. The in-orbit test results converge well to previous in-orbit calibration results with a different approach.