Algorithms for safe spacecraft proximity operations

Future spacecraft missions requiring in-space servicing, repair, inspection, or rendezvous and docking need algorithms for safe, autonomous proximity operations. Emergent Space Technologies, Inc. has developed algorithms for safe, autonomous proximity operations, including accurate relative navigation, spacecraft separation trajectory design, and circumnavigation trajectory design. The algorithms rely on safe natural motion trajectories and covariance information from the relative navigation system to minimize the probability of collision while meeting mission objectives. In this paper, we describe the algorithms in the context of a hypothetical space inspection mission where two initially attached spacecraft safely separate and then one spacecraft circumnavigates the other. The algorithms can also be applied to a variety of rendezvous missions or other missions requiring spacecraft to safely operate near each other, whether autonomous or manually operated. An example is presented in which safe natural motion trajectories are utilized to design a passively safe rendezvous trajectory for a spacecraft visiting the International Space Station (ISS).