Ground simulation of spacecraft motion simulating all six degrees of freedom is a challenging problem due to several features of the natural dynamics in space that are difficult to reproduce on ground. Unlike terrestrial (aerial, land or underwater) vehicles, space vehicles have an overwhelmingly large percentage of their total energy in their translational motion. Dynamical coupling between the translational and rotational degrees of freedom can significantly affect the attitude motion of spacecraft. The attitude motion is particularly important for a spacecraft tasked to autonomously rendezvous and capture or dock with a target object in space. Here we present a ground simulator design for 6 DOF simulation of spacecraft engaged in autonomous rendezvous and proximity operation(ARPO) with an unaided target space object. These operations are very risky and difficult to carry out in space, since the target's motion is not well known in advance. Ground simulation using 6 DOF motion simulation capabilities can help reduce the risk of actual on-orbit ARPO missions. The novel design "Autonomous Rendezvous and Proximity Operation ground Simulator (ARPOS)" presented here mimics all the six DOFs of rigid spacecraft with high fidelity. ARPOS has the advantage of linear and spherical air bearings to reproduce the near frictionless environment of an actual spacecraft in space.