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en:sun_subsys

Solar Sensor
Virtual consumption - 45mA

Solar sensors on satellites serve as orientation sensors, determining the satellite's spatial position relative to the sun. Very often they are used for the rough orientation of satellite solar panels on the sun. It should be noted that it is impossible to completely determine the orientation of the satellite only from solar sensor readings - there will always remain an uncertainty with the spacecraft rotation angle around the “satellite-sun” direction.

To obtain raw measurement data, you can use the function

int sunsensor_request_raw(uint16_t num, uint16_t *pRAW_data1, uint16_t *pRAW_data2);

The sensor returns readings from two sensors that examine the left and right hemispheres respectively. When one of the sensors is exposed to a level of illumination, the sun angle can be determined. When both sensors have been illuminated, the more correct approach is to use the ratio of the illumination levels on both sensors.

Calculating the specific dependencies of the angle on the illumination levels is called calibrating the sensor under different conditions. Nevertheless, even without calibration, sensors of similar design can be used to track the position of the sun by analyzing the mutual illumination of the right and the left hemispheres of the sensor.

Accuracy of installation
It should be noted that the accuracy of mounting the sensors inside the solar sensor bodies is not ideal - this is how it happens in real life, making each sensor unique in its own way. This is due to the inaccuracy of the manufacture of the cases relative the required size, the errors of installing electronics boards inside the cases, and the imperfection of the sensors themselves (they all differ slightly from each other). It is understood that most of such errors remain unchanged throughout the service life, although there are also errors that depend heavily on external factors (for example, temperature). In our case, we assume that the measurement errors of each sensor are constant in time and slightly dependent on temperature, which makes it possible to perform a one-time calibration before use. It is recommended to calibrate each of the 4 sensors in the set before use. Think for yourself about how this could be done, or contact us for advice.

Description of the old version of the sensor.

en/sun_subsys.txt · Last modified: 2018/01/22 17:51 by ashley