1 Robotics and Machine Learning Section, Dynamics and Control Systems Branch, Spacecraft Engineering Division, United States Naval Research Laboratory, Naval Center for Space Technology, Washington, DC, United States.
2 Institute of Perception, Action and Behaviour, School of Informatics, University of Edinburgh, Edinburgh, United Kingdom.
3 Bernstein Center for Computational Neuroscience, Third Institute of Physics, Georg-August-Universität Göttingen, Göttingen, Germany.