In recent years, there has been much interest in close-proximity (10-150m) formation flying of small satellites. Autonomous guidance, navigation and control of satellite formation in Low Earth Orbits (LEO) is a challenging problem and requires sophisticated on-board control systems. This paper describes further progress in the state-of-the-art of modeling and control of satellite formations for circular orbits around the Earth. The dynamics of the satellites are governed by the Hill-Clohessy-Wiltshire (HCW) equations and a nonlinear, robust controller based on Sliding Mode Control (SMC) is implemented for demonstrating how a group of satellites can aggregate from their initial positions to form a desired formation. Collision free navigation is achieved using the Artificial Potential Filed (APF) method - a popular path planning technique used in terrestrial robotics. The simulation results demonstrate that the APF method can provide simple and effective path planning for satellite formation flying missions. The drift of the formation centre of mass can be prevented by integrating APF with SMC and by eliminating the reaching phase of the controller. The efficacy of the proposed algorithm is presented through demonstrating a tetrahedron formation flying scenario.