Use of spacecraft solar panels and Sun sensors for estimation of the Sun-pointing direction in the UPMSat-2 mission

Solar panels are a key component for most spacecraft as they provide energy to the vehicle. However, their possible use is not limited only to power generation, as they can also be used as solar sensors for attitude determination. To calculate the direction of the Sun, photovoltaic models (two of them explicit, and the well-known 1-D/2-R equivalent circuit) that simulate the performance of the solar panel (including environmental conditions such as temperature, irradiance and Earth’s albedo, to obtain accurate results) are described in this paper. These models are used to estimate the Sun incidence angle in relation to a spacecraft based on solar panel generation data. This methodology is checked with data from the UPMSat-2 mission and compared with independent measurements derived from this satellite magnetometer data. The Sun direction results are finally compared to the results obtained from the low-cost solar sensors on board the UPMSat-2. The results included in this paper hint at the possibility of using spacecraft solar panels as an additional attitude determination instrument to improve the accuracy of the estimation of the sun direction