FALCON: a satellite regains its position in orbit by photographing its neighbours, without GPS

NASA had a satellite of the Starling mission calculate its own orbit by recognizing debris and neighboring craft with a stargazette, without any GPS signal.

The experiment is called FALCON, for Fast Autonomous Lost-in-space Catalog-based Optical Navigation, and it answers a simple question: what does a spacecraft do when it no longer receives a navigation signal? The answer tested by NASA's Ames Research Center consists of making it look around. The stellar tracking cameras already on board, normally dedicated to orientation, are used here to locate other satellites and debris in orbit, which the software then compares with a public catalog of about 20,000 objects on board with it. Each identified object becomes a landmark, and the position of the spacecraft is deduced from the whole.

The test took place on the Starling mission, launched in 2023, and the results go beyond a simple positioning exercise: in three days, and without any instructions sent from the ground, FALCON refined the known orbits of more than 200 objects, with a precision superior to the data in the reference catalogue. In other words, the satellite has not only located itself, it has improved knowledge of its neighbourhood.

NASA plans to extend the experiment by the end of the year with the Era-Core flight software from Stanford's EraDrive. The objective this time is collective: the four Starling spacecraft would share their mutual observations to refine their respective positions together. Beyond emergency navigation, the targeted applications concern orbital traffic monitoring and collision avoidance, two subjects that are becoming more pressing as low orbits become more populated.