At the Julius-Maximilians-University of Würzburg, four micro-satellites are currently being prepared for take-off. They are to move in a formation and, for the first time in the world, independently control their three-dimensional arrangement in orbit.
If an object like Planet Earth is to be captured completely without blind spots, it must be viewed from different directions and the image information must be combined. The techniques required for the optimal self-organization of a satellite formation in three-dimensional space are now being tested for the first time with four miniature satellites.
"This opens up new perspectives for earth observation and climate research, but also for future communication networks," says Professor Klaus Schilling, head of the Department of Computer Science VII (Robotics and Telematics) at the Julius Maximilian University (JMU) Würzburg. He developed the satellites with his team; he was supported by the European Union with the ERC Grant NetSat.
Final refinement at the Center for Telematics
The four smallest satellites weigh only four kilograms each. At the Center for Telematics in Würzburg, they will receive their final tuning by the end of May 2020; presumably in August 2020 they will then be transported by a Russian Soyuz rocket into their orbit at an altitude of 600 kilometers. Long-term task planning will then be carried out from the operations center in Würzburg. In contrast, reactions to deviations from the plan and the fine adjustment of the formation will be carried out autonomously by the software on board.
What distinguishes the smallest satellites
"Techniques for formation flight have so far only been investigated with two satellites," explains Schilling. NetSat should now achieve scientific breakthroughs in the necessary techniques for controlling a three-dimensional arrangement for optimal observations. For this purpose, the satellites have a very efficient electric propulsion system, manufactured by the Austrian company Enpulsion. In addition, the satellites have high-precision alignment capabilities with extremely small precision reaction wheels, supplied by S4 - Smart Small Satellite Systems and Wittenstein Cyber Motors. The radio link between the satellites enables data exchange on position, alignment and planned manoeuvres. "In combination with advanced control methods, this enables the coordination of this team of four to be realized," says the JMU professor.
Background of the NetSat mission
The NetSat mission was made possible by a prestigious award from the European Research Council (ERC) and the support of the Bavarian Ministry of Economic Affairs. Professor Schilling had received the ERC Advanced Grant 2012, which is endowed with 2.5 million euros, to achieve scientific breakthroughs in the field of control technology and space travel.
The independent research institute "Zentrum für Telematik (ZfT)" in Würzburg was selected to implement NetSat because it has an outstanding test infrastructure for multi-satellite systems throughout Europe. At JMU, the NetSat satellites are also used for experiments on multi-satellite operation.
Results will be used immediately
The NetSat results are directly incorporated into the next Würzburg micro-satellite missions for innovative applications in earth observation: TIM - Telematics International Mission: ZfT and JMU coordinate partners from five continents to realize an innovative 3D earth observation for volcanic eruptions, earthquakes and ship movements with nine satellites.
The mission will be started in 2021 and is part of the Regional Leaders Summit (RLS), a network of the regions Bavaria, Upper Austria, Georgia (USA), Quebec (Canada), São Paulo (Brazil), Shandong (China) and Western Cape (South Africa).
Starting in 2022, the self-organization of ten miniature satellites will be used to characterize the interior of clouds using computer tomography methods. In this way, important parameters for climate models that have not yet been recorded will be obtained. The European Research Council is supporting this project with an ERC Synergy Grant of 14 million euros; research partners from Israel are involved in the project.
"The exciting further use of the NetSat results is thus guaranteed," Schilling is pleased to say. "The micro-satellite measurement networks in orbit can quickly provide better bases for decision-making in emergency situations and for challenges such as climate change.
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Julius-Maximilians-Universität Würzburg, elektroniknet