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S. Gläsner, B. Grzesik, E. Stoll
Computing platforms, such as FPGAs and SoCs, are delivering high performance systems in a form factor suitable for small satellites. By offering system-on-modules, technology entry has been drastically lowered. A first step to achieve these higher processing capabilities in orbit is envisioned in the EPISODE payload of the 3U InnoCube satellite, set to be launched in 2024, in an effort to contribute to a safer low earth orbit environment. EPISODE is a payload mainly developed by students at TU Berlin, using commercial off the shelf hardware to develop a GNSS receiver, which is based on a software-defined radio receiver. EPISODE aims to use open-source software to calculate its position in orbit in realtime. For this mission, an embedded system of a Xilinx Zynq UltraScale multiprocessor system-on-a-chip (MPSoC) is used, mounted on a Xilinx Kria K26I system-on-module. The module is paired with a commercial front-end receiving chip, MAXIM2769, which is a universal GNSS receiver. Two commercial antennas are used to determine the position in orbit, mounted on the zenith facing cover of the satellite, with one being active and one being passive. For orbit determination, open-source software is being used with the highly flexible software of GNSS-SDR. GNSS-SDR is providing a full navigational solution and is based on GNURadio. As an embedded operating system, the Yocto based PetaLinux project is being implemented on the payload. A system control with latchup-detection and redundancy concept with multiple memory devices is used as a precaution against radiation effects. To optimize the determination algorithm, GNSS-SDR is assisted by an algorithm, comparable to A GNSS on ground. As the motion of a satellite in orbit is highly deterministic and regularly captured by ground-based tracking, TLEs are sent via Telecommand along to provide a position estimate for the acquisition phase, along with a reference time. GNSS satellites in sight are being calculated to filter the list of PRN codes in the search space. Additionally, EPISODE-Assisted-GNSS calculates their respective doppler shift, which should improve the acquisition time even further. Time to first fix with EPISODE assisted GNSS is assumed to be less than 30 s, dramatically reducing the energy and time required to first fix. Additionally, a miniaturized laser ranging retroreflector is mounted on the satellite. In combination with laser ranging experiments, onboard calculated GNSS positions are verified with ground based measurements. Different experiment campaigns are carried out, with the goal of optimizing energy consumption and accuracy of the orbit determination. Finally, EPISODE aims to pave the way for more sophisticated embedded platforms in orbit with high processing capabilities. Further missions may include GNSS reflectometry and radio occultation in a Cubesat.
Deutscher Luft- und Raumfahrtkongress 2023, Stuttgart
Verlag, Ort:
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2023
Conference Paper
21,0 x 29,7 cm, 8 Seiten
Stichworte zum Inhalt:
Technology demonstration, Cubesat, embedded systems, software-defined radio, orbit determination, space safety
Download - Bitte beachten Sie die Nutzungsbedingungen dieses Dokuments: CC BY-NC-ND 4.0OPEN ACCESS
Gläsner, S.; Grzesik, B.; Stoll, E. (2023): Experiment for Precise Orbit Determination on InnoCube. Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V.. (Text). https://doi.org/10.25967/610077. urn:nbn:de:101:1-2023121511532666278241.
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