ESA GNC Conference Papers Repository

In previous decades, the vision-based navigation problem based on 2D imaging has been largely studied and applied in space, for rendezvous and docking, as well as rover navigation, or Entry Descent and Landing. By providing measurement of the third dimension (range), 3D camera technology looks a promising alternative for many applications. Stereoscopic camera is one option to measure the third coordinate, but relies on significant CPU capabilities, which are generally not available for space applications. Scanning LIDAR (LIght Detection And Ranging) is also an existing solution, but it is relatively large and heavy and the refresh rate, lifetime and reliability is mainly determined by moving parts. 3D Time-Of-Flight (TOF) technology offers a reliable alternative. By illuminating a whole scene at a time and thus providing a whole array image, there is no need for complex processing nor moving mechanisms, which clearly appears as an advantage for space applications. This paper presents the ongoing study conducted under ESA contract in the field of 3D TOF technology. Its goal is to evaluate the suitability of a 3D TOF camera for space applications, to derive requirements and a preliminary design, and finally to create and test a breadboard model. Performance budget, cost, and a development plan of a versatile spatialized 3D TOF camera are also outputs of the study, in addition to a high fidelity simulator, allowing further studies by generating representative images and depth maps. In order to fulfill this project, a European team has been created, gathering Thales Alenia Space, TERMA, and SINTEF. This paper describes the key requirements for a 3D TOF camera applied to different kinds of space missions. Rendezvous & docking, rover, EDL (Entry, Descent & Landing, NEO (Near Earth Object) approach missions are analyzed for that purpose. The 3D technology survey and trade-off is also addressed. Several 3D Time-Of-Flight measurement technologies currently exist, which strongly drive the camera sensor and light sources specifications. These may be broadly categorized as either phase-based or pulse-based methods, the latter being split into gate and clock measurement principles. Based on the selected technology, our preliminary design for a spatialized 3D TOF camera is presented, with focus on size, mass, power and space issues. The expected performances are also discussed, and our 3D camera simulator is described. Finally, the camera breadboard is presented, as well as the validation tests foreseen on our rendezvous and rover test benches.