The burgeoning field of low Earth orbit (LEO) satellites presents unique challenges for ensuring long-term mission success.  Small satellites, often densely packed with high-power components, experience rapid transitions between sunlight and eclipse, making thermal management a critical concern. Furthermore, the longevity of batteries and photovoltaic (PV) panels, crucial for sustained operation, is impacted by cycling, calendar fade, and radiation degradation. This blog post explores a novel methodology for optimizing satellite durability by coupling advanced orbit propagation with high-fidelity 3D thermal-electrical simulation, addressing these critical factors. 

The Challenge of LEO Satellite Durability 

LEO satellites face a harsh environment with extreme temperature swings and constant radiation exposure.  Limited thermal control systems in small satellites exacerbate the challenge of maintaining optimal operating temperatures for sensitive components.  Batteries, essential for powering the satellite during eclipses, degrade over time due to usage (cycling fade) and age (calendar fade), reducing capacity and increasing internal resistance.  Similarly, PV panels, responsible for generating power from sunlight, suffer from radiation-induced degradation, reducing their efficiency over the mission lifetime.  These factors collectively contribute to a decline in satellite performance and can ultimately lead to mission failure. 

A Coupled Simulation Approach for Enhanced Durability 

A comprehensive simulation methodology is crucial to addressing these challenges. Our approach combines advanced orbit propagation with high-fidelity 3D thermal-electrical simulation to provide a holistic view of satellite performance throughout its mission. This coupled approach allows us to predict transient temperatures in orbit, considering solar power capture, electronic loads, and battery charging/discharging cycles. 

The simulation process incorporates a satellite's 3D surface/volume mesh populated with appropriate thermal material properties and active heat sources. A battery management system regulates charging and discharging based on charge status and available solar energy. PV module temperatures, solar incidence angle, and degradation determine solar power conversion efficiency, influencing the power available for electronics and battery charging. The simulation also accounts for declines in battery performance, such as reduced capacity and increased internal resistance, based on lifetime predictions. 

Crucially, the orbital propagation tool provides essential boundary conditions to the transient thermal-electrical solver.  This tool can also model adaptations to the dynamic LEO environment, including adjustments to satellite positioning to minimize exposure to radiation and other environmental stressors. 

 Key Components of the Methodology 

Our methodology leverages several key tools and techniques: 

• MuSES®: A transient thermal-electrical and EO/IR simulation software that predicts heat transfer through radiation, conduction, and convection. It also integrates battery and PV panel models for coupled thermal-electrical analysis. 

• CoTherm®: A process automation software package that manages the coupled thermal-electrical simulations and exchanges data with other applications. 

• FreeFlyer®: An orbit propagation tool that provides dynamic orbital boundary conditions to CoTherm, including satellite position, attitude, and solar loading. 

• Battery Lifetime Prediction: A workflow that estimates changes in battery internal resistance and capacity based on temperature history and usage patterns. 

• PV Radiation Degradation Analysis: A method for calculating proton and electron fluence and estimating the resulting degradation in PV panel efficiency. 

 
 Case Study: Communications Satellite Degradation Model 

We applied this methodology to a communications satellite model, simulating its performance at the beginning of its mission and after several years in orbit. The simulations considered the satellite's coupled thermal-electrical behavior, including the impact of battery and PV degradation. 

The results demonstrated the significant impact of these degradation mechanisms on satellite performance.  Over time, PV efficiency decreased, leading to reduced power generation.  Battery capacity also declined, limiting the satellite's operating ability during eclipses.  These changes affected the overall system performance, including battery charging rates and state of charge. 

Extending Mission Lifetime through Optimization 

The coupled simulation approach provides valuable insights for optimizing satellite durability.  By understanding the impact of thermal and electrical stress on critical components, engineers can make informed decisions regarding material selection, thermal control strategies, and orbital adjustments.  For example, optimizing the satellite's orientation can minimize radiation exposure and improve thermal stability.  Furthermore, advanced thermal control techniques can help maintain battery temperatures within optimal operating ranges, slowing down degradation. 

Conclusion 

The methodology presented in this blog post represents a significant advancement in predicting and improving satellite durability in LEO.  By combining sophisticated orbit propagation with advanced energy generation and storage simulation capabilities, our approach contributes to the sustainability of satellite missions, reducing operational costs and minimizing environmental impact.  This research underscores the importance of developing resilient satellite systems for the future of orbital infrastructure.  Further work will refine the models and explore advanced control strategies to maximize satellite lifespan and performance. 

If you want to learn more about CoTherm and MuSES,  please request a live demo of our software.