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This paper covers the operations and lessons learned for the MOVE-II and MOVE-IIb satellites. Both are 1U CubeSats, with their purpose being hands-on education for students of all technical fields related to aerospace. The hardware of the spacecraft consists of a commercial on-board computer and an electrical power system, while all other systems, including the software, were designed by the student team. The MOVE-II CubeSat was successfully launched on December 3rd, 2018 and remains active in orbit to this day with almost daily commanding. The operations were full of surprises that pre-launch simulations did not foresee. With on-orbit data, we were able to correlate thermal, electrical and attitude dynamics simulations, thus uncovering flaws in former assumptions. We present the evolution of key properties of the spacecraft over its lifetime, such as the internal battery resistance, temperature and hardware defects. Compared to the expected 23°C average temperature, the satellite is quite cold at 3°C average. Furthermore, it shows a tendency to spin up uncontrollably due to a current loop in the solar cell wiring. To replicate the real behavior with simulations, a thermal model and a solar cell wiring current loop were added to the model. We also corrected the internal resistance of the battery in the model from 0.42 Ω to 1.26 Ω and added a temperature dependency to the internal resistance. The tendency to spin up, combined with a tight power budget, has remained a problem since the beginning of on-orbit operations. Although the anomaly shows non-deterministic behavior, regular detumbling maneuvers keep the spacecraft at tumbling rates between 2.5°s−1 and 200°s−1. At low turn rates, we downloaded a significant amount of data from the attitude determination and control system, enabling us to calibrate the magnetometer on ground with data recorded and downlinked over a span of several months. Additionally, we were also able to conduct payload measurements. The MOVE-IIb CubeSat, which launched on July 5th 2019 from the Vostochny Cosmodrome, is a copy of MOVE-II with minor improvements to correct the flaws of its predecessor. Unfortunately, a signal strength of 15 dB less than MOVE-II hindered any practical operations but it has been confirmed as alive in space. As possible causes we analyzed our initial guesses of a faulty deployment of the solar panels and antennae but also a malfunction of the transmitter. With the lessons learned from the MOVE-II/IIb missions, critical mistakes can be avoided for future CubeSat missions. As part of these lessons learned, the most useful and most hindering features of the spacecraft and its ground infrastructure are discussed. Furthermore, the training routine for the Mission Control team and its changes over time are described. The impact of the COVID-19 pandemic on spacecraft operations is also discussed, including lessons learned for future missions. This paper takes a look at the evolution of this mission since 2018. It discusses new findings, degradation of the spacecraft, lessons-learned and operations of the CubeSats.

Objectives: Modular ADCS based on CubeSat flight experience, space heritage hardware and rad hard components for small satellites Project goal: Integration of independent modules based on electronic data sheets (EDS) configuration system Capabilities: Attitude determination and control Boot and self-recovery Plug and play interface to sensor and actuators Fault Detection, Isolation & Recovery (FDIR) Data management and storage External control interface

This article reports the ongoing work on an environment for hardware-in-the-loop (HIL) and software-in-the-loop (SIL) tests of CubeSats and the benefits gained from using such an environment for low-cost satellite development. The satellite tested for these reported efforts was the MOVE-II CubeSat, developed at the Technical University of Munich since April 2015. The HIL environment has supported the development and verification of MOVE-II&rsquo, s flight software and continues to aid the MOVE-II mission after its launch on 3 December 2018. The HIL environment allows the satellite to interact with a simulated space environment in real-time during on-ground tests. Simulated models are used to replace the satellite&rsquo, s sensors and actuators, providing the interaction between the satellite and the HIL simulation. This approach allows for high hardware coverage and requires relatively low development effort and equipment cost compared to other simulation approaches. One key distinction from other simulation environments is the inclusion of the electrical domain of the satellite, which enables accurate power budget verification. The presented results include the verification of MOVE-II&rsquo, s attitude determination and control algorithms, the verification of the power budget, and the training of the operator team with realistic simulated failures prior to launch. This report additionally presents how the simulation environment was used to analyze issues detected after launch and to verify the performance of new software developed to address the in-flight anomalies prior to software deployment.

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.

MOVE-II (Munich Orbital Verification Experiment) will be the first CubeSat of the Technical University of Munich (TUM) utilizing a magnetorquer-based active attitude determination and control system (ADCS). The ADCS consists of six circuit boards (five satellite side panels and one central circuit board in satellite stack), each equipped with a microcontroller, sensors and an integrated coil. The design enables redundancy and therefore forms a fault-tolerant system with respect to sensors and actuators. The paper describes the hardware implementation, algorithms, software architecture, and first test results of the integrated ADCS on the engineering unit. A possibility to upgrade and extend our software after launch will enable further research on new and innovative attitude determination and control strategies and distributed computation on satellites. The MOVE-II flight unit is in the integration and test phase with an intended launch date in early 2018.

This paper presents the fundamental work on the attitude control design using solely magnetic actuation for the MOVE-II mission. Two control modes are primarily considered: detumbling and sun pointing control. Regarding the sun pointing control, two approaches are discussed. The first is the Spin Stabilized Sun Pointing Control (SSPC) which provides gyroscopic stiffness against disturbances. The second is a non-spinning approach called Reduced Sun Pointing Control (RSPC). Simulation results have shown satisfactory performance providing proof of concept and motivation for further work.