Defence of doctoral thesis in the field of Space Science and Technology, M.Sc.(Tech.) Bagus Riwanto

The title of the thesis is Calibration and testing techniques for nanosatellite attitude system development in magnetic environment
Magnetic testbed, with visual markers attached on the device-under-test and sensing magnetometer, set up inside a cage of Helmholtz coils

M.Sc.(Tech.) Bagus Riwanto will defend the thesis "Calibration and testing techniques for nanosatellite attitude system development in magnetic environment" on 3 September 2021 at 12 (EET) in Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering.

Opponent: Prof. Stefano Speretta, TU Delft, Netherlands
Supervisor: Prof. Jaan Praks, Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering

The public defense will be organized via remote technology. Follow defence:
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Press release:

Magnetic environment is an important factor in spacecraft design. Rigorous magnetic testing of the satellite and its components is required to validate the magnetic sensor accuracy and magnetic properties of the spacecraft. New generation of nanosatellites and decreasing mission cost also bring new challenges to the field of magnetic testing and calibration of space systems. This research investigates different techniques and provides new tools to improve magnetic testing of nanosatellites under 10 kg category.

In this research, we developed a calibration algorithm that is capable of correcting rotational error factor, which is often insufficiently accounted for in many existing algorithms. The proposed novel method is better suited for space application: by using the knowledge of the spacecraft rotation axis, which can be obtained from the spacecraft telemetry. The algorithm is tested with simulations and real flight data of two different satellites, namely with the data from the first Finnish satellite Aalto-1 and the first Estonian satellite ESTCube-1. Rotation correction accuracy of ~0.1 degree was achieved.

Moreover, an automated testbed for magnetic testing facility at Aalto University was developed. Instead of motor-controlled armature, the novel system uses camera and visual markers to automate data acquisition and integration. This allows mechanically simpler setup and makes rigorous testing much faster and more affordable. Our tests show magnetic dipole moment estimation accuracy in the ~10 mm (for position) and ~10 mAm2 (magnetic field strenght), depending on the size of the device-under-test relative to its magnetic moment strength. The work also investigated the effect of spacecraft remanent magnetic moment on attitude control performance in order to design our in-house built magnetorquer for attitude actuation.

The results of this research provide modern spacecraft engineers with better options for spacecraft magnetic design and testing campaign depending on the system capabilities and requirements. Analysis on real flight data of Aalto-1 satellite also gives an insight on the possible challenges that shows up during operation of nanosatellites and the lessons learned for future developments. The results of the work are already utilized in designing the new generation of Finnish Science satellites, Foresail-1 and Foresail-2, built at Aalto in the framework of Finnish Centre of Excellence in  Research of Sustainable Space.

Contact information of doctoral candidate

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