New scientific space missions are using active actuator systems for the spacecraft attitude and translation control. Such drag-free satellites require precise actuators to generate forces and torques, thereby their accurate knowledge is necessary for the success of a mission. The thruster-configuration may vary due to the extreme environmental conditions, and mechanical effects during the launch. In addition, there are uncertainties in this configuration because it can be determined only with a limited accuracy before the launch. For that reason an in-orbit calibration is needed. Estimation methods can be applied to solve the problem. However, the data used for the estimation process has many noise sources, and the satellite itself is under the influence of many disturbances resulting in errors on the estimates. To overcome such problems, methods to improve the accuracy of the estimates are proposed and evaluated. In this paper different estimation algorithms are used and compared, and some methods to improve the accuracy of the estimates are suggested. Furthermore, the research gave the necessary information to choose the better option for the calibration in terms of estimation algorithm, control method, and type of excitation. The problems generated by the actuator system in the parameter estimation were recognized and identified. A depth discussion is carried out and a calibration procedure is proposed.
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