This paper presents a guidance strategy for a rendezvous with an uncooperative target. In the applied design reference mission, a spiral approach is commanded ensuring a collision-free relative orbit due to e/i-vector separation. The dimensions of the relative orbit are successively reduced by -v commands which at the same time improve the observability of the relative state. The navigation is based on line-of-sight measurements. The relative state is estimated by an extended Kalman ¦lter

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... The performance of this guidance and navigation strategy is demonstrated by extensive Monte Carlo simulations taking into account all major uncertainties like measurement errors, -v execution errors, and di¨erential drag. 3 lack of range measurements leads to the problem that the relative state is not fully observable as long as no manoeuvres are performed by the chaser. Fortunately, the chaser has to perform manoeuvres anyway to approach to the target. However, some strategies require much propellant, others are not passively safe. The presented guidance and navigation strategy is close to the optimum in terms of propellant consumption and the resulting trajectory is always passively safe. The guidance strategy is based on relative orbital elements (ROE) with e/ivector separation. The ROE are a solution of the Clohessy-Wilthire equations [1]. The concept of e/i-vector separation had originally been designed for the safe collocation of geostationary satellites, but has recently been applied also for proximity operations of Low Earth Orbit (LEO) satellites (e. g., Tandem-X [2] and PRISMA [3] ). The EKF is su©cient for the estimation of ROE. Filters like the unscented Kalman ¦lter require more computational e¨ort without providing signi¦cantly better results for this application [4, 5] .