NASA’s Jet Propulsion Laboratory, Pasadena, California
A six-degrees-of-freedom (DOF) testbed was developed for evaluating microgravity and low-gravity proximity and contact operations, e.g. in the vicinity of a near Earth orbit, for simulation of proximity operations for a human mission to an asteroid. This is accomplished using an “inverted Stewart platform” where the vehicle under test — in this case, the ATHLETE (All-Terrain Hex-Limbed Extra-Terrestrial Explorer) — is suspended by six computer-controlled cable winches so that it can be maneuvered in all six degrees of freedom. Position feedback is provided by both the encoders at the winch motor, and a motion capture system installed on the testbed structural frame. The payload is attached to the work platform at the end of the six cables.