The satellite must determine its position, velocity and orientation. The determination is the most important point, because we must know where the payload is pointing to characterise the nightglow phenomenon. The major concern of the control is to reduce the spinning rate of the satellite after the launch and, if it is technically possible, to orient the payload in a precise direction in order to take pictures.
The attitude determination algorithm of the satellite has to determine the position of the captured image with a precision of ±° in latitude, ±[7.5]° in longitude (which can be correlated to the solar local time at zenith) and ± km in altitude to guarantee that the atmosphere limb is within the telescope's field view.
To determine its orientation, the satellite has the following sensors:
- A 3-axis magnetometer to measure the Earth’s magnetic field intensity and direction and then compare it with the model. This model can locally have important errors due to special temporarily conditions (Ex: Sun storm).
- 6 Sun sensors to find the direction of the Sun; they provide a 2nd set of measurements which increase the final determination accuracy and robustness.It is important to note that these sensors are not available during the eclipse period (about half of the orbit).
- A 3-axis gyroscope to measure the spinning rate for each axis.
- Temperature sensors to compensate the temperature drift of the other sensors.