In the future, space exploration may rely not on individual, expensive satellites, but on teams of smaller satellites working together as a “swarm.” These swarms will enhance accuracy, agility, and autonomy in space missions. Researchers at Stanford University’s Space Rendezvous Lab are at the forefront of this innovation, recently completing the first-ever in-orbit test of a prototype system that navigates a swarm of satellites using only visual information shared through a wireless network.
“It’s a milestone paper and the culmination of 11 years of effort by my lab, which was founded with this goal of surpassing the current state of the art and practice in distributed autonomy in space,” said Simone D’Amico, associate professor of aeronautics and astronautics and senior author of the study published on the arXiv preprint server. “Starling is the first demonstration ever made of an autonomous swarm of satellites.”
The StarFOX Test: A Leap Forward in Satellite Swarm Navigation
The test, named the Starling Formation-Flying Optical Experiment (StarFOX), successfully navigated four small satellites working in tandem using only visual information gathered from onboard cameras to calculate their orbits. The research team presented their findings at the Small Satellite Conference in Logan, Utah, a key event for swarm satellite experts.
“Our team has been advocating for distributed space systems since the lab’s inception. Now it has become mainstream. NASA, the Department of Defense, the U.S. Space Force—all have understood the value of multiple assets in coordination to accomplish objectives which would otherwise be impossible or very difficult to achieve by a single spacecraft,” said D’Amico. “Advantages include improved accuracy, coverage, flexibility, robustness, and potentially new objectives not yet imagined.”
Overcoming the Challenges of Swarm Navigation
Navigating a swarm of satellites autonomously presents significant technological challenges. Current systems depend heavily on the Global Navigation Satellite System (GNSS) and frequent contact with terrestrial systems. Beyond Earth’s orbit, there is the Deep Space Network, but it is relatively slow and not easily scalable for future missions. Furthermore, these systems cannot help satellites avoid “non-cooperative objects” like space debris, which pose collision risks.
D’Amico and his team recognized the need for a self-contained navigation system that offers high autonomy and robustness. Such a system is also appealing due to the minimal technical requirements and lower costs of today’s miniaturized cameras and hardware. The StarFOX test utilized proven, cost-effective 2D cameras known as star-trackers, which are already common on satellites. “At its core, angles-only navigation requires no additional hardware even when used on small and inexpensive spacecraft,” D’Amico explained. “And exchanging visual information between swarm members provides a new distributed optical navigation capability.”
How StarFOX Works
StarFOX combines visual measurements from cameras mounted on each satellite in a swarm. Like mariners navigating the seas with a sextant, the system uses the field of known stars in the background to extract bearing angles to the swarming satellites. These angles are processed onboard using accurate physics-based force models to estimate the position and velocity of the satellites relative to the orbited planet—whether Earth, the Moon, Mars, or other celestial bodies.
The system employs the Space Rendezvous Lab’s Absolute and Relative Trajectory Measurement System (ARTMS), integrating three new space robotics algorithms. An Image Processing algorithm detects and tracks multiple targets in images, computing target-bearing angles—the angles at which objects, including space debris, move relative to one another. The Batch Orbit Determination algorithm estimates each satellite’s coarse orbit from these angles. Finally, the Sequential Orbit Determination algorithm refines swarm trajectories over time as new images are processed, potentially feeding autonomous guidance, control, and collision avoidance algorithms onboard.
The Future of Space Exploration
Stanford’s StarFOX test marks a significant step forward in the development of autonomous satellite swarms. With further advancements, these swarms could revolutionize space exploration, offering greater flexibility, accuracy, and resilience in missions beyond Earth’s orbit. As D’Amico noted, this technology opens up new possibilities that were once thought impossible, paving the way for more ambitious and complex space missions in the future.
By Impact Lab
