PROBA-3 Rendezvous Experiment Design and Development

Recent years have seen a growing interest towards the development of the GNC functions associated to RV and Formation Flying (FF) scenarios, motivated by the need of increasing the Technology Readiness Level (TRL) of different technologies required to successfully accomplish several of the future planetary and science missions. Moreover, different sources (for instance, [1]) have demonstrated the benefits of running planetary RV in non-circular orbits, since though circular relative motion is simpler, and better known and tested (from ISS-ATV experience, see [2]), elliptical option is being identified as interesting for a cost-effective mission delivering heavy vehicles for planetary exploration. On the other hand, data fusion is of paramount importance for having a robust enough mission design in RV scenarios. Particularly important is the selection of a reliable set of sensors for measuring the relative motion, since for close distance between the two satellites (up to few tens of km, as a maximum) Navigation function must be based on it, instead of estimating two absolute motions (which is instead the Navigation approach for longer distances). Several sensors combinations are possible, being those based on optical devices, on one hand, and on radiofrequency signals, on the other, the two best suited candidates. This article presents the design and development of a Rendezvous Experiment (RVX) to be flown by PROBA-3 mission. This RVX is based on only-camera measurements (images) taken on a target in free flight. The main advantage of this solution is that it is simpler and hence more robust than if considering additional sensors for relative motion. The work presented in this paper is part of the activities performed by DEIMOS Engenharia and FFCUL (Portugal) in the frame of the PROBA-3 Phase B2. Contents are as follows: Section 2 presents the generals about the PROBA-3 RVX, including mission constraints, main drivers and objectives of RVX itself. Section 3 presents the design of a nominal RVX profile compatible with the constraints imposed by the main requirements on RVX design. Section 4 presents the relative navigation system definition the RVX rely on, while Section 5 finally presents some results obtained during the first analyses performed on the current RVX design.