On the Thermo-Electrical Modeling of Small Satellite's Solar Panels

Abstract

The thermal modeling of small satellites (up to 100 kg) is crucial for predicting and managing their operation, and may present significant differences when compared to the thermal modeling carried out in relation to larger spacecraft. In this article, the modeling of their solar panels is underlined as one of these differences. The efficiency of spacecraft solar panels is affected by three main variables: the sun's irradiance, the cells' temperatures, and the operating voltage. Unlike the most common approach, which only takes into account the first two variables and decouples the thermal problem from the electrical one, the coupled thermo-electric problem of the solar panel efficiency as a whole is considered in this article. Using the UPMSat-2 mission as an example, the importance of considering the operating voltage in the thermal analysis of a mission is proven in the present article (for the prediction of temperature and generated power). A simple but accurate I-V (Current-Voltage) curve model to calculate panel efficiency is proposed for modeling the solar panels performance, this method being easily implemented in ESATAN © .

Design, Ground Testing and On-Orbit Performance of a Sun Sensor Based on COTS Photodiodes for the UPMSat-2 Satellite

“…In the case of the photodiodes analyzed, the resistance chosen was 32 Ω, as it met these requirements. Finally, it must be considered that the I-V curve and the parameters that describe it will change depending on the operating temperature [20]. Therefore, it is desirable to include a temperature sensor within the solar sensor.…”

“…However, natural solar light was discarded to avoid uncertainties due to atmospheric absorption of certain wavelengths, and in favor of a more controlled environment in the laboratory. Among the rest of the sources, red LEDs were selected as the best option in terms of cost and due to their well-known spectrum, which is Finally, it must be considered that the I-V curve and the parameters that describe it will change depending on the operating temperature [20]. Therefore, it is desirable to include a temperature sensor within the solar sensor.…”

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

“…However, after several calculations with the incoming results, the imaginary part of these partial results becomes more and more relevant, the convergence to a final solution being compromised. That requires more complex algorithms, as in a previous work [54].…”

On the Performance of Solar Cells/Panels and Li-Ion Batteries: Simplified Models Developed at the IDR/UPM Institute

“…The main motivation for this work was the need for analytical procedures that would generate quick solutions, with the aim to accelerate systems design. At the IDR/UPM Institute, these analytical procedures have been implemented in a Concurrent Design Facility (CDF) for spacecraft mission design [25], [26], and in thermo-electric coupled analysis of satellite power subsystems with ESATAN [27].…”

“…10 Discharging (top) and charging (bottom) curves at constant current rates, plotted in relation to the discharged energy rate, . The simplified linear models (equations(27) and to(28)) have been fitted to these data (dashed lines).…”