AstraTag: new fiducial marker for spacecraft docking outperforms ArUco on curved surfaces

Performing autonomous rendezvous and docking in space is unforgiving—loss of visual tracking during the final meters can mean mission failure. Existing fiducial markers like ArUco and AprilTag are designed for terrestrial robotics and typically work at a single scale, causing them to drop out of the camera’s field of view precisely when reliable tracking is most critical. To solve this, Ravi Kumar Thakur and colleagues from the Czech Technical University present AstraTag, a fiducial marker built specifically for space robotics operations.

AstraTag’s design centers on a square Spidron pattern: a recursive, self-similar shape that remains detectable across multiple spatial scales—from hundreds of meters down to centimeters. Marker identification relies on a 48‑bit signature extracted from triangular sub‑regions and encoded with a Generalised Reed‑Solomon (GRS) code for error resilience. The detection pipeline uses contour‑based quadrilateral localization followed by perspective normalization. Crucially, for markers mounted on curved spacecraft surfaces, AstraTag incorporates a Thin‑Plate Spline (TPS) re‑warp fallback that exploits the marker’s internal rectangular borders as additional geometric correspondences. Benchmarking against three‑layer Fractal ArUco and AprilTag on both flat and curved spacecraft mockups shows that AstraTag achieves a higher detection rate on curved surfaces, offering a robust, recursive‑marker option for space missions.