Abstract
An improved approach for the measurement of the relative pose between a target and a chaser spacecraft is presented. The selected method is based on a single camera, which can be mounted on the chaser, and a plurality of fiducial markers, which can be mounted on the external surface of the target. The measurement procedure comprises of a closed-form solution of the Perspective from n Points (PnP) problem, a RANdom SAmple Consensus (RANSAC) procedure, a non-linear local optimization and a global Bundle Adjustment refinement of the marker map and relative poses. A metrological characterization of the measurement system is performed using an experimental set-up that can impose rotations combined with a linear translation and can measure them. The rotation and position measurement errors are calculated with reference instrumentations and their uncertainties are evaluated by the Monte Carlo method. The experimental laboratory tests highlight the significant improvements provided by the Bundle Adjustment refinement. Moreover, a set of possible influencing physical parameters are defined and their correlations with the rotation and position errors and uncertainties are analyzed. Using both numerical quantitative correlation coefficients and qualitative graphical representations, the most significant parameters for the final measurement errors and uncertainties are determined. The obtained results give clear indications and advice for the design of future measurement systems and for the selection of the marker positioning on a satellite surface.
Highlights
There are two main applications that require an accurate measurement of the relative pose between two Spacecraft: the autonomous rendezvous and docking for on-orbit servicing and the formation flight of two or more Spacecraft
The uncertainties evaluated for the output relative roto-translations allow us to verify the compatibility of the experimentally obtained errors
For the two additional methods (Gao and EPnP) the implemented code can be found from the internet: the Gao solution is comprised in the Computer Vision Toolbox of Matlab, while the EPnP implementation can be downloaded from a web link reported in Reference [9]
Summary
There are two main applications that require an accurate measurement of the relative pose (position and orientation) between two Spacecraft: the autonomous rendezvous and docking for on-orbit servicing and the formation flight of two or more Spacecraft. All the reported examples cope with the same geometrical problem: the evaluation of the relative chaser-target pose from a set of 3D points (fiducial markers) known in the target frame of reference and from the 2D measurements of their projections on a chaser camera. Since the considered parameters can be adjusted by a proper selection and positioning of the fiducial markers on the satellite surface, the aim of the proposed analysis is to yield useful advice in the design of future systems for relative pose measurement. Thethe proposed work wants to provide useful indications to improve the instant pose measurement, and definition and analysis of these requirements (on frame rate, computational time) are beyond main purpose.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
