Direct Pixel-Level Tightly Coupled Navigation Design with Dual-Pattern LED Markers for Spacecraft Proximity Operation

This study proposes an advanced integrated navigation algorithm based on a monocular camera for cooperative proximity missions of spacecraft in a low Earth orbit (LEO) environment. The proposed framework involves a camera mounted on the chaser spacecraft and LED markers attached to the target spacecraft, where pixel coordinates extracted from camera images are directly utilized as measurements in a tightly coupled extended Kalman filter. Unlike conventional loosely coupled methods based on Perspective-n-Point (PnP) pose estimation, the proposed approach integrates pixel-level feature measurements directly into the filter, reducing computational cost and enabling robust state estimation with a significantly smaller number of valid feature points. To further enhance navigation accuracy, an extended observation matrix incorporating the relative geometric configuration of the LED markers is introduced. Additionally, a dual-pattern LED marker configuration is employed to overcome the limited field of view of the camera. The performance of the proposed algorithm is validated through both Gazebo simulations and lab-scale experiments, demonstrating that the extended observation model significantly contributes to reducing navigation errors.