Navigation of spacecraft around asteroids remains a critical challenge due to communication delays, uncertain surface topography, and the absence of reliable gravitational models. Testing such technologies on the ground using robotic systems enables faster and more reliable devel
...
Navigation of spacecraft around asteroids remains a critical challenge due to communication delays, uncertain surface topography, and the absence of reliable gravitational models. Testing such technologies on the ground using robotic systems enables faster and more reliable development. However, publicly available information on how to create operational frameworks for such testbeds is limited, often due to inter-agency competition or safety concerns at military test sites. This thesis investigates how relative asteroid navigation can be supported and replicated in a ground-based robotic laboratory environment. The work is conducted within the newly inaugurated Guidance, Navigation and Control (GNC) laboratory at TU Delft and focuses on supporting the initial global characterisation phase of an asteroid mission specifically, landmark identification and the generation of circular motion profiles using the laboratory hardware.
A robotic testbed is configured using a 6 degrees-of-freedom (dof) UR16e robotic arm, a 3 dof omnidirectional RB-Kairos rover base, and a 1:10,000,000 scale model of asteroid 433-Eros. A Python software framework is developed to define reference frame transformations between hardware components and generate trajectory points. Control commands for the rover base, robotic arm, and camera are synchronised and executed via ROS nodes. To enhance the laboratory's demonstration capabilities, a Gazebo simulation environment is implemented to test the trajectories. Experimental evaluations assess the open-loop motion tracking accuracy of the system. For a circular trajectory of 1200 mm radius, deviations reached 370 mm (width) and 276 mm (length). Additional uncertainties in the robotic arm’s mounting position introduced mean errors between -39 mm and 66 mm (width), -46 mm and 57 mm (length), and 0.76 mm to 12.96 mm (height). These results indicate that closed-loop control is required to mitigate trajectory errors and improve positioning accuracy.
To support relative navigation, a photogrammetry pipeline is introduced to reconstruct the asteroid model from image data. Surface reconstructions using open-source software yield high-resolution meshes with up to 365,930 faces. Lighting configuration, image coverage, and environmental artefacts are identified as key limitations to reconstruction quality. The results demonstrate that the robotic laboratory can simulate circular arcs orbital motion. To further support relative navigation tasks alignment accuracy and feedback control have to be improved. Recommendations for future work include implementing closed-loop controllers, developing object-detection relative navigation, integrating adaptive lighting, and using the surface reconstruction models to estimate the gravity field of the asteroid model used in the laboratory.
