Satellite Power Analysis: A Fast, Composable, High-Fidelity Approach

Designing reliable satellite power systems requires accurately predicting how much power solar panels will generate as the spacecraft moves through its orbit. This is a complex challenge because solar power availability depends on both the satellite’s orbital dynamics and the behavior of the solar panel itself. To build a realistic power budget, engineers must combine orbital analysis (determining sunlight exposure, eclipse periods, and panel orientation relative to the sun) with a detailed solar panel model (capturing how voltage, current, and efficiency vary under changing conditions). Without integrating these two aspects, power predictions risk being overly simplistic and missing critical mission constraints.

Traditional workflows for this type of analysis are often fragmented, with separate tools for orbital mechanics and electrical system modeling. This separation forces manual data transfers, custom scripts, and difficulty scaling models as new components are added. A unified modeling environment that couples orbital analysis with solar panel and power electronics simulation offers a faster, high-fidelity, and mission-relevant way to design and validate spacecraft power systems. 

Dyad for Space Power Modeling

Dyad is a declarative modeling language purpose-built for physical and hardware system modeling, providing tight integration with the Julia and SciML ecosystem.  With Dyad, we can integrate composable, acausal models of satellite power systems and space mission analysis into one streamlined platform. By leveraging Julia and the SatelliteToolbox.jl ecosystem under the hood, Dyad ensures that orbital mechanics such as eclipse periods, sun-satellite geometry, and solar exposure — directly feed into the power generation models. 

Solar Panel Model

Satellite solar panels must be modeled with precision to capture their real-world performance. The solar panel model consists of multiple components, each built using Dyad, integrating the orbital analysis data obtained with SatelliteToolbox.jl.   

We created these components in Dyad using only the standard libraries:

• A Temperature Sensor that calculates temperature and irradiance, by sampling from the orbital analysis
• A Photovoltaic Cell that exhibits a nonlinear I-V relationship based on temperature and irradiance from the sensor
• A DC-DC Converter that adjusts voltage and current draw from PV Cell
• A Maximum Power Point Tracker that dynamically calculates voltage to maximize power output
• An idealized Battery that absorbs power from PV Cell
• And finally, a Load that will draw power from the battery.

By combining these component models with orbital sunlight predictions, Dyad allows engineers to simulate the power budget throughout the mission and explore what-if scenarios without complex data handoffs.

Orbital Analysis with SatelliteToolbox.jl

The SatelliteToolbox.jl ecosystem in Julia provides a comprehensive set of open-source packages for orbital mechanics and space mission analysis. It supports orbit propagation (including SGP4 and numerical propagators), coordinate transformations, attitude modeling, time systems, and atmospheric density analysis. The ecosystem is designed for flexibility and composability, enabling engineers and researchers to quickly prototype and simulate realistic orbital scenarios.

The advantage of Dyad models having native representations in Julia is that they can call out arbitrary functionality from the Julia ecosystem.  In this case, we are able to run the orbital analysis via SatelliteToolbox.jl, create a quadratic interpolation from DataInterpolations.jl, and refer to that in memory in our Dyad model.  This also offers the option to swap out the orbital parameters at any point during the simulation, or after it, for maximum flexibility.  No need to wrangle CSVs from multiple tools anymore - you can do it all in one language!

Orbit-Coupled Power Simulations

A satellite’s orbit directly determines its solar exposure, which in turn drives power availability. By combining SatelliteToolbox.jl for orbital analysis with Dyad for solar panel and electronics modeling, we can:

• Calculate when the spacecraft enters and exits eclipse
• Calculate the temperature and irradiance experienced at the solar panels
• Understand the I-V behavior in the photovoltaic cells
• Simulate the solar panel power output as the satellite moves throughout its orbit
• Optimize battery sizing and load scheduling to handle periods without sunlight

Closing Thoughts

Dyad eliminates the need for multiple disjointed software tools by providing a streamlined solution for modeling satellite power systems. By combining accurate orbital analysis with detailed solar panel and battery models, Dyad allows engineers to confidently predict power generation and availability across an orbit. This unified approach improves accuracy, reduces workflow complexity, and accelerates design decisions for spacecraft power systems.

Watch the webinar of this workflow in action here.