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| Last Updated | 10/12/2025, 12:48:54 PM |
| Last Author | Kai Berszin |
GNSS
Scope
This section briefly summarises the findings of the Master project related to the GNSS payload board. For more information consider the report.
Fundamental Technical Specifications
There are three different scenarios: the nominal scenario for the position, velocity and time (PVT) solution, one scenario for precise orbit determination and one for attitude determination. It is declared which GNSS messages are used as well as how much power consumption and data volume can be expected. Based on these scenarios, the receivers can be configured.
Parsing Algorithm
To extract the important data from the various messages, a Python code is written. The script is able to parse the received messages and store the relevant information in CSV-files. It can be used as a reference for the OBC Team to implement the GNSS software on the Zephyr driver.
Attitude Determination Experiment
On the basis of the third observation scenario, the attitude can be determined. Therefore, the gathered data is used to compute a baseline between the two antennas in post-processing. Using this baseline, the orientation, i.e. the attitude, of the satellite can be determined in two directions. For the third direction, another antenna and receiver would be needed but this is not possible due to lack of space.
Using a prototype sharing the same characteristics as the CubeSat and a mount enabling the rotation of the CubeSat, an experiment is performed to valid whether the attitude can be determined while the satellite rotates around itself. Therefore, measurements are performed while the prototype is static and while it rotates.
Due to time restrictions, the experiment is performed but the data are not fully analysed. So far the carrier noise density as well as the number of tracked satellites are evaluated. The analysis of the tracked satellites shows that the number of tracked satellites is more or less constant over time but varies more if the satellite rotates. The standard deviation of the carrier noise density is likewise higher during the rotation. Moreover, the rotation can be seen in the periodicity of the carrier noise density. These results show that during the rotation signals can still be received although with higher variations.
In a next step, to conclude the experiment, the baseline between the antennas as well as its accuracy should be determined. Afterwards, the baseline can be used to develop an algorithm to determine the attitude. This algorithm should be applied while the satellite is fulfilling its mission in space.