© 2009 EUCA.Propulsion, path planning and control of satellite formations in Geostationary Earth Orbits (GEO) and other high Earth Orbits is a challenging problem. This paper presents the results of the analysis of two types of controllers for satellite formation flying; the first one linear, using classical Proportional-Derivative (PD) control, and the second one nonlinear, using Sliding Mode Control (SMC). The Artificial Potential Field (APF) method is used for collision-free path planning of the satellites in the formation. The satellites are propelled using Coulomb forces and conventional electric/ion thrusters. This hybrid propulsion is more efficient as it minimizes the use of on-board power. Simulation results show that for the formation flying scenario considered in this study, the sliding mode controller gives better performance over the PD controller. Simulation results prove that for the tetrahedron formation considered in this study, both the control effort and drift in the geometric center of the formation are less when a sliding mode controller is used.