Charon: a system capable of deorbiting satellites with no platform dependencies

The increasing number of satellites launched constitutes a risk in the form of growing space debris, especially in low Earth orbit. With more objects in orbit, the risk of collisions and creation of additional space debris grows significantly. Regulations to address this state that new satellites need to be capable of deorbiting within 5 years of end of mission. This requirement presents a major challenge for nano- and microsatellites, such as CubeSats, which tend to have higher failure rates than larger satellites. In the case of a platform failure, traditional deorbiting systems that are part of the satellite’s AOCS and rely on the platform being functional, cannot fulfill the requirement. As a result, the satellite becomes non-compliant with deorbit regulations and turns into space debris. Additionally, CubeSats are limited in terms of available volume, mass, and power. This makes it difficult to integrate conventional deorbiting technologies such as propulsion systems. To be effective, a deorbiting solution for these satellites must be small, lightweight, affordable, and capable of functioning independently from the satellite platform.Charon is a module designed to fulfill this need: a fully autonomous deorbiting module based on Plasma Brake technology, and in a standard CubeSat form factor of a 0.5U module and an attached TunaCan volume for the plasma brake itself. The system is able to function independently of the host satellite, enabling it to detect a platform failure and deploy its Plasma Brake without any input from the satellite itself. The working principle of the Plasma Brake is based on a long (typically 200 m) microtether charged to a high negative voltage of -1000 V. The charged tether interacts with the plasma in the upper atmosphere, causing a drag force through the Coulomb Drag effect. The Plasma Brake is thus able to provide thrust without any propellant, requiring only constant electric power in the order of 0.1 W from its own solar panels. While the level of thrust is very small, it is sufficient to deorbit a typical CubeSat in a few years.Charon is designed to activate automatically in case of mission failure, also in the case that no communications can be established with a dead-on-arrival host satellite. This is facilitated by a watchdog timer on the module that is periodically reset by the spacecraft; in case of two missed resets of the timer, the module determines that the platform has failed, and commences automatic deorbiting. To be as autonomous and platform independent as possible, the module is equipped with an independent power source and control logic, a small thruster and simple attitude determination system for deployment of the Plasma Brake microtether, and the Plasma Brake itself to deorbit the satellite. The target reliability of above 95% independent of the host satellite is reached by keeping the module architecture simple, and by redundancy of key components. In a standard 0.5U CubeSat form factor and with minimal interfacing to the host satellite, the compact and modular design allows Charon to be integrated into typical CubeSat platforms with minimal impact on payload or mission architecture. By providing a self-contained, platform-independent deorbiting solution, Charon offers a practical path to ensuring regulatory compliance and reducing the long-term risks of space debris for the growing number of small satellites in orbit.