To validate guidance, navigation and control algorithms and to test flight hardware for orbital rendezvous, robotic facilities are an appealing choice. They offer a good reproduction of the orbital dynamics, enabling the testing of rendezvous, docking and in-orbit servicing. To test these procedures, Delft University of Technology has developed its own facility, called the GNC Robotics Lab. This facility consists of two robots with omnidirectional wheels, enabling free-floating movement of flight hardware. These wheels offer an alternative method for the flexibility offered by a robot on a moving rail. On the other side, such wheels represents the main error source due to their peculiar movement. To mitigate this, a closed-loop approach can be exploited. The purpose of this work is to illustrate the effectiveness of such a closed-loop, where the manipulator compensates for the base errors. It is shown that the tracking error can be reduced to less than 1 mm for realistic trajectories.

The AltiCube+ mission involves the on-orbit assembly of multiple CubeSats to build two radar interferometers. To accomplish this, vision-based relative navigation is required both for target localization during rendezvous and for post-docking relative displacement estimation of structural deformation. This paper presents the design, simulation, and experimental validation of a compact monocular vision-based system capable of fulfilling both functions using a single camera architecture. The proposed system consists of a camera mounted on the chaser spacecraft and an active LED fiducial marker configuration on the target spacecraft. A non-planar marker geometry combined with colour-based segmentation enables robust detection over distances ranging from 10 m to close contact. Sub-pixel marker localization is performed using weighted centroiding and Gaussian fitting, followed by pose estimation through an Efficient Perspective-n-Point (EPnP) algorithm with iterative refinement. The results show that the proposed architecture can support both rendezvous localization and micrometre-scale structural deformation monitoring, providing a compact sensing solution for CubeSat assembly missions.

Robotics facilities have a long history in the development of space equipment, since they allow to perform tests on systems like guidance, navigation and control, visual-based navigation and docking mechanisms. Those facilities are based on two manipulators, one representing the a target satellite, the other the chaser satellite which perform a relative motion with respect to the first. This approach has been used in the past to perform tests on docking operations, visual-base navigation system to populate databases. Delft University of Technology recently developed its own robotics facility for GNC and multisatellite systems applications. It hosts two robots on a moving base, which work in synergy to extend the operational space. They operate in a dark environment, where there are lights to simulate the sun disturbance and a beamer that projects the Earth to have a representative background. The purpose of this paper is to describe the laboratory, along with the control architecture of the robots and provide some tests executed to assess the accuracy of them in tracking a given trajectory.