Design Satellite Power for Dynamic Orbit Realities

Communication satellites have evolved from simply retransmitting Radio Frequency (RF) signals between ground-based stations to actively participating in the network. With advanced RF systems and increased computing power onboard, modern satellites can direct and shape signal beams, and process networking protocols and applications. The addition of powerful AI processing capabilities could enable satellites to serve as space-based data centers. These trends put intense stress on requirements for satellite power generation and distribution, which remain constrained by size, weight, and power (SWaP), as well as by the physical and economic limits of launch vehicles. By emulating real-world conditions in the lab, engineers can determine performance and reduce the chance of failures in increasingly complex satellite power systems. Solar arrays, for example, now typically consist of multiple panels connected in series and/or in parallel, depending on current and voltage requirements. Battery subsystems must be able to power the entire satellite during periods when illumination is unavailable or impaired, without being oversized beyond reasonable capacity margins. At the same time, power distribution systems must continuously balance solar generation with the battery state of charge to deliver reliable power to each voltage rail for payloads and control systems.

Given the dynamic, complex nature of solar array and battery behavior, testing satellite power under nominal conditions is insufficient. Solar panel performance depends on a variety of conditions experienced in orbits that are often highly kinetic, and panel characteristics typically vary from panel to panel. Battery pack performance ranges in complexity between fully charged and fully discharged states. Both subsystems require robust models and more capable equipment to reproduce and test system behavior under dynamic conditions.

Breaking down satellite power system requirements reveals three common dynamic subsystems: a photovoltaic array for generation, power conversion and management, and energy storage. Requirements vary with satellite size, features, payload, and mission. At the low end are modular Electrical Power System (EPS) cards plugged into a CubeSat backplane, providing a few common voltage rails coupled with a simpler, integral-mount photovoltaic panel and a rechargeable battery or supercapacitor pack.

Higher-end LEO, MEO, and HEO platforms with more power demand may rely on multiple photovoltaic panels, possibly with orientation capability, and a Power-Conditioning and Distribution Unit (PCDU). Often, PCDUs come fully integrated with a solar panel controller, power conversion, and a battery subsystem, with packaging ready for avionics rack mounting. Whatever the configuration, PCDUs must deliver reliable system power under all conditions, maintaining full readiness to ensure proper satellite payload and actuator operation.

Thermal management is also a consideration. Current running through a system leads to power dissipation at points of conversion and switching. Pushing for smaller designs increases power density. If too much power dissipation concentrates in too small a space, however, overheating can occur and cause failures. Elevated temperatures over longer periods reduce reliability and Mean Time Between Failure (MTBF), thereby compromising the intended mission life. Designers must anticipate operating conditions and balance power density with thermal density.

Satellite power systems should receive at least as much design and test attention as payloads and satellite control systems, as a power failure can quickly cripple an entire satellite. A setup for comprehensive satellite power emulation is reusable across multiple satellite programs, perhaps with some scaling as megawatt-ready designs appear. The time spent in lab emulation can help identify potential failures that would otherwise only appear in space, too late to fix and, in most cases, too expensive to fix by another replacement satellite launch.