GPS Tracking for GEO Satellites

Considering the importance of Geosynchronous Orbit (GEO), different countries demand to send more satellites to this orbit therefore nowadays GEO is becoming more and more occupied and crowded. Thismatter highlights the usage of an accurate navigation system for preventing any collision. Among different kinds of navigation systems, due to their accuracy and simplicity, GNSS and specially GPS are among the mostpopular navigation methods. In this paper GPS navigation difficulties in GEO is explained including signal strength, visibility, Doppler and Doppler rate. These parameters are estimated for anarbitrary GEO mission. If the receiver is able to track weak signals, most of problems like visibility and DOP parameters can be solved. The estimated parameters indicate that if the receiver signal strength threshold isabout -29dBHz, it is just able to track main-lobe signals and can never track 4 satellites but if its threshold improves to about 14dBHz in 97% of a day it can track at least 4 satellites.In the next part of this paper, vector trackingmethod along with its principles and performance analysis is explained. The performance analysis proves that it is a suitable tracking method in GEO missions and can track signals stronger than 13dBHz.