This paper considers the problem of Cooperative Vision Based Tracking of a ground target by a fleet of multiple UAVs. The objective of this work is to present a decentralized control algorithm that enables multiple cooperative vehicles to maintain a horizontal orbital path around the target, while coordinating their space separation. A typical scenario involves multiple aerial surveillance UAVs which are required to monitor a ground object by orbiting around it (target tracking), while maintaining a desired phase shift (coordination). To solve the tracking problem, the angular velocity of each vehicle is used as control input, while the ground speeds are adjusted to ensure coordination. The paper provides a Lyapunov-based solution that guarantees exponential convergence properties of the tracking and distributed time-coordination algorithms. A rigorous proof based on Lyapunov analysis, as well as flight test results demonstrate the effectiveness of the proposed approach.