First Flight Results of the MOVE-II CubeSat

MOVE-II (Munich Orbital Verification Experiment) is the second satellite of the Technical University of Munich’s educational CubeSat program. On December 3, 2018, the satellite was launched on the SSO-A SmallSat Express from the Vandenberg Air Force Base. The following paper shows on-orbit results of the first eight months of operations. It includes analyses based on our own data as well as the open-source ground station network SatNOGS. Lessons learned from mission operations and recommendations for future educational missions are provided. The technical goals of the mission are verifying the satellite’s bus and the qualification of a novel type of quadro-junction solar cells. Over 200 students have been developing and testing all components of the satellite since the beginning of the project in April 2015. During the course of the project, the students designed all necessary technology for a CubeSat bus, with the exception of the electrical power system and the on-board computer’s hardware. Furthermore, the students developed ground station software as well as an operations interface from scratch. The technological achievements of the mission range from a linux-based onboard computer software over a magnetorquer-based attitude determination and control system to two novel transceivers for UHF/VHF and S-Band. A reusable mechanism, based on shape-memory-alloys, deployed the four solar panels, providing the necessary power. Only hours after the deployment, we received the first signals of the satellite. The commissioning of the ground station and the effects of an insufficient power budget of the tumbling satellite preoccupied us during the first month, as well as frequent watchdog resets. During the commissioning of the Attitude Determination and Control System (ADCS), a spin rate of 200 °/s was observed, although the actuators were not activated yet. Detailed analysis with the help of recordings provided by our own ground station as well as the SatNOGS ground station network revealed a slow increase of the spin rate since the launch. In the following weeks the spin rate further increased to over 500 °/s. Afterwards we were able to modify our ADCS actuation in a way to reduce the spin rate again. Currently MOVE-II is detumbled and we are moving towards regular scientific operation. After a presentation of the results, lessons learned from our mission operations are discussed. The paper discusses the measured values and analyzes the reasons for the observed behaviour. Also the changes made on MOVE-IIb, a slightly improved copy of MOVE-II, will be explained. The paper concludes with recommendations for designers of upcoming educational satellite missions, especially regarding resilience against negative power budgets