A new sun tracking attitude mode for Nadir pointing microsatellites

Nanosatellites in ISS orbits experience a fluctuation in the power available to the solar panels during the mission lifetime. If the satellite is continuously operating in Nadir pointing (NP) mode, the power generation presents minima resulting in a non-optimal use of the available power. This study proposes a new attitude mode, called pitch sun tracking (PST), to maximise the power received by the solar panels which can be employed when the minimum values of power production are foreseen. It is shown that a 2U-CubeSat equipped with a momentum wheel can acquire and maintain such an attitude mode with acceptable accuracy. The PST mode can maximise power production by tracking the projection of the Sun vector on the orbital plane. Simulations show that the extended Kalman filter estimator satisfies the required determination accuracy and a linear quadratic regulator controller designed for the NP mode can be adapted for the PST mode.