A multi-sensor optical relative navigation system for small satellite servicing. (June 2023)

• Record Type: Journal Article
• Authors: Napolano, Giuseppe; Vela, Claudio; Nocerino, Alessia; Opromolla, Roberto; Grassi, Michele
• Is Part Of: Acta astronautica. Volume 207(2023)
• Page Start: 167
• Page End: 192
• Publication Date: 2023-06
• Subjects: On-orbit servicing -- Close-proximity operations -- CubeSat -- Spacecraft relative navigation -- Sensor fusion -- Visual-based pose estimation -- Laser range finder; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2023.03.008
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: This paper presents an innovative multi-sensor relative navigation module conceived to enable close-proximity operations for on-orbit servicing of small satellites. The module is composed of a Near-Infrared Laser Range Finder, acting both as range measurer and illuminator, and a monocular camera able to detect a set of reflecting fiducial markers installed on the target for pose estimation. Sensor fusion is performed in several points of the proposed processing pipeline, first following a cross-cueing logic in which the range aids the pose determination process, and later through the integration of both measurements into a Multiplicative Extended Kalman Filter for relative state estimation. The entire relative navigation architecture is first tested by numerically reproducing a close-range rendezvous trajectory of a chaser spacecraft moving toward the target, and using the open-source software Blender for synthetic image generation. Simulations are aimed at determining nominal relative state estimation accuracy (also considering variable sensors' acquisition rates) as well as performance under non-nominal conditions (e.g., due to a temporary loss of measurements). Focusing on the image processing and pose estimation pipeline, an in-depth analysis of the computational efficiency is then carried out by running the proposed algorithms on an embedded processing unit (i.e., the Raspberry Pi 4 Model B) using both synthetic data and real images collected within a dedicated experimental testbed. Numerical and experimental results demonstrate capability to attain pose and relative state estimates in line with accuracy requirements to ensure autonomous and safe close-proximity operations, e.g., up to sub-cm and sub-degree error levels in relative position and attitude respectively. In addition, the algorithm's computational runtime has shown to be compatible with real-time implementation at an acquisition frequency of 2 Hz. Highlights: An original architecture for spacecraft relative navigation in close proximity is proposed. It relies on optical measurements from a monocular camera and a laser range finder. Circular retroreflective markers are mounted on the target satellite. Numerical and experimental tests show sub-cm and sub-degree error levels in pose estimation. Computational efficiency suitable for real time implementation on embedded hardware is proven.