Space to ground sequential lobe tracking of aircraft

Growing demand for satellite communications capability coupled with shrinking government budgets, has spurred acquisition and repurposing of commercial satellite systems for government missions. One subset of these satellites provides high bandwidth communication with aerial vehicles from geosynchronous orbit. Automated tracking by these satellites of aerial vehicles improves link margin, but is not a typical function of commercial product lines. Additional tracking hardware and flight software development are required to give these commercial products tracking capability. This leads to an inefficient design from a cost and mass standpoint for a large number of slow flying aerial vehicles. Therefore, a need was identified to design a low cost tracking system that minimizes tracking specific spacecraft hardware and flight software development. This paper outlines a sequential lobe tracking system to auto track aerial vehicles and analyzes the algorithm's accuracy and sensitivity in tracking aerial vehicles using their pre-existing uplink signal. The tracking scheme consists of a satellite based RF power meter, automated ground based control of antenna pointing, and ground based processing of the tracking telemetry. The aerial vehicle was modeled as a high altitude, relatively slow moving Ka-band aircraft. To identify and evaluate a feasible design, a MATLAB model was developed to simulate an aerial vehicle, the vehicle's primary uplink signal and its variance, communication and processing latency in the design, and tracking telemetry processing. In addition, the effect on the spacecraft antenna actuators was modeled. The primary output of the model is tracking accuracy and Monte Carlo simulations were used to determine 1, 2, and 3 sigma results. Overall, this paper demonstrates the viability of a sequential lobe scheme with ground based processing as a low cost alternative for Space-to-Ground tracking of slow flying aerial vehicles.