Sun sensor

The second vector that will be used to establish the attitude of the satellite will be a solar vector. This vector will be calculated using a software link between the solar panels and the computer. Our power control board has a set of commands that will allow us to access the voltage and current on each solar panel, and we can use this information to find the fraction of power being produced by each solar panel. When the power control board is functioning correctly, the fraction of the total power being produced by each individual solar panel will be proportional to the angle at which the light is striking the solar panel. This will give us our solar vector.

A model is currently being made which will show the change in solar vector in relation to the cubesat over time. This will be merged with the model made from the magnetic attitude determination system to create, a hopefully more accurate model of the cubesat. The combined model will show the coordinates of the cubesat along with the direction the cubesat is facing. This will be crucial for the camera. The attitude determination will tell the camera when it is facing the Earth so it can take a picture. If the camera was to take a picture when facing the Sun, then the camera would overpower and break.

Because PLUME is a random tumbling satellite, we can assume that any incident radiation that might degrade the solar cells will affect the entire surface equally. Poor temperature regulation may also affect the life of the solar panels, and it will degrade different panels at different rates. There is little we can do to compensate for this beyond doing a good job with the temperature control system.

The Power Control Board's 10-bit ADC gives two bytes of data per reading, and each reading takes between 1 and 2 milliseconds. The signal commands and pinouts can be found on the control board's datasheet; if you want to learn more you should contact Tim Trent as it is commercially sensitive.

The model is being created and tested as part of a third year pair project by Christopher Powel and Thomas Searle.

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