Almost 20,000 satellites orbit Earth now, creating a crowded environment where non-functional zombie spacecraft threaten active missions, Universe Today reported.
Zombie Satellites Threaten Orbit
More than 3,500 derelict spacecraft drift without operational signals or the ability to warn nearby assets of their trajectories. Space researchers warn that a single collision could trigger a cascading feedback loop of destruction known as the Kessler syndrome.
Tracked objects in low-Earth orbit surged from about 13,700 in 2019 to more than 24,000 by 2025, according to findings published in Acta Astronautica. That rapid congestion leaves ground operators with little time to manage manual interventions during close approaches.
Autonomous Framework Designs Trajectories
To address the growing density of uncooperative space debris, researchers developed an autonomous system called CORTEX, which stands for Convex Optimization for Rendezvous Trajectory Execution. Minduli Wijayatunga, an aerospace engineering faculty member at The Grainger College of Engineering at the University of Illinois Urbana-Champaign, serves as lead author on the study.
Traditional docking operations relied on bespoke solutions designed for individual missions like the International Space Station. The sheer volume of defunct hardware requires automated guidance systems that can operate independently of ground control delays.
These spacecraft must be able to track the trajectories of uncooperative objects autonomously but also make go/no-go decisions without waiting for the ground to decide,
Wijayatunga said.
Convex Optimization Guides Docking Maneuvers
The CORTEX framework utilizes convex optimization to calculate approach paths and thruster commands mathematically rather than depending entirely on pre-programmed input instructions.
Hardware Testing Validates Recovery Options
When deviations occurred during trials, the software recalculated trajectories or directed the servicer to retreat to a passively safe orbit.
In all cases, the framework either recovered successfully while respecting safety constraints or executed a safe retreat before entering unsafe regions,
the researchers reported.
Practical testing of proximity operations gained momentum when the Japan Aerospace Exploration Agency launched Astroscale’s ADRAS-J in 2024. That mission successfully maneuvered within 50 meters of a spent rocket stage, capturing multi-angle images of an uncooperative target in low-Earth orbit.
Common Questions About Orbit Congestion
How many derelict satellites are currently in orbit?
More than 3,500 satellites are classified as zombies because they are non-functional or fail to transmit operational signals.
What causes the Kessler syndrome in space?
A single collision between two objects creates a debris cloud that generates subsequent impacts in an expanding feedback loop.
How does CORTEX handle thruster failures during an approach?
The framework recalculates the trajectory to re-approach the client or safely retreats to a designated orbit if safety boundaries are violated.
What was the milestone achieved by ADRAS-J?
The spacecraft successfully approached a spent rocket booster within 50 meters to capture detailed images of uncooperative debris.