Satellites flying in formation has been the focus of current research. Sometimes,there are issues with the amount of information available about the satellites. Due to hardware limitations, full measurements of relative positions and velocities of the spacecraft may not be available. In the long-term, the only information available might be the inter-satellite ranges between the satellites. The first part of the present work aims at the reconstruction of the trajectory of a satellite from this limited information, i.e., the time history of inter-satellite range. The present work deals with the case of three satellites in formation. One satellite is at the reference in a near circular orbit and the other two satellites trace Hill’s orbits relative to the reference. The geometry and phasing of one satellite is assumed to be known and the trajectory parameters of the other satellite relative to the reference are computed. Due to atmospheric drag there is a possibility that one of the satellites may drift and slip out of the formation. This may lead to a collision between the two satellites which might damage any appendages on the spacecraft like the antennas. The objective of the second part of the thesis is to devise a strategy to avoid the collision. The solution from the first part will be used to predict a possible collision in the future and a suitable thrusting technique will be applied to avoid the collision. The only collision scenario considered, in the present work, is 'tangential orbits'.