Artist’s illustration of the swarm. NASA/Blue Canyon Technologies
A first-ever test of autonomous navigation for a swarm of satellites was carried out in orbit.
The concept of swarms — in which a group of smaller satellites work together — is an emerging trend in space technology.
Although single satellites have provided essential data for communication, weather prediction, and research, their capabilities are inherently limited. Importantly, swarms provide a more cost-effective option than massive, pricey single satellites.
Moreover, this approach has the potential to increase accuracy, flexibility, and autonomy.
Researchers from Stanford University’s Space Rendezvous Lab conducted this first in-space test known as the Starling Formation-Flying Optical Experiment (StarFOX).
“Starling is the first demonstration ever made of an autonomous swarm of satellites,” said Simone D’Amico, associate professor of aeronautics and astronautics.
D’Amico stated: “Advantages include improved accuracy, coverage, flexibility, robustness, and potentially new objectives not yet imagined.”
The four swarm spacecraft during integration and testing at NASA Ames. | NASA/Dominic Hart
Satellite navigation test
D’Amico’s team’s eleven years of research and development paid off with this successful test.
In the experiment, the four small satellites (CubeSats) were successfully maneuvered as a group, using only visual measurements from onboard cameras to calculate their orbits. Each satellite is equipped with a 2D camera, which aids in precision navigation and preventing any collisions.
Similar to how sailors used to rely on celestial bodies for navigation, these satellites use fixed locations of stars to determine their direction. After this, the advanced on-board algorithms transform these observations into exact orbital data.
“These angles are then processed onboard through accurate physics-based force models to estimate the position and velocity of the satellites with respect to the orbited planet; in this case, Earth–but the moon, Mars, or other planetary objects would work as well,” the press release explained.
Advanced algorithms
The satellites incorporate the Absolute and Relative Trajectory Measurement System (ARTMS) for precise trajectory measurement.
ARTMS entails three innovative space algorithms, namely image processing, batch orbit determination, and sequential orbit determination.
An image processing algorithm identifies and follows various celestial targets, calculating their angular positions. The Batch Orbit Determination method uses these angles to calculate a tentative orbital route for each satellite.
Lastly, the Sequential Orbit Determination algorithm continually updates satellite paths using new image data to instruct autonomous systems.
“At its core, angles-only navigation requires no additional hardware even when used on small and inexpensive spacecraft. And exchanging visual information between swarm members provides a new distributed optical navigation capability,” D’Amico added in the press release.
To date, achieving precise and dependable navigation for a satellite swarm has posed significant technological challenges. Current approaches rely on ground-based technology and have limited capabilities beyond Earth’s orbit. Moreover, neither can avoid space debris.
In the near future, this first autonomous swarm navigation system may pave the way for the deployment of a fleet of satellites for precise science data collection and Earth observations.
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The researchers presented their preliminary StarFOX findings at the Small Satellite Conference in Logan, Utah.
The study findings have been uploaded on the arXiv preprint server.
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Mrigakshi Dixit Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.
