| Establishing an optical link between a ground station and a geosynchronous orbiting satellite can be aided greatly with the use of a beacon on the satellite. A tracker, or even an adaptive optics system, can use the beacon during communications or tracking activities to correct beam pointing for atmospheric turbulence and mount jitter effects. However, the pointing lead-ahead required to illuminate the moving object and an aperture mismatch between the tracking and pointing apertures can limit the effectiveness of the correction as the sensed tilt will not be the same as the tilt required for optimal transmission to the satellite. This dissertation concentrates on developing an analytical model that addresses the combined impact of these tracking issues in a ground-to-satellite optical link. Expressions for tilt error due to these tracking issues are derived for a variety of tracking scenarios with different tracker-pointer configurations. This tilt error coupled with the atmospheric turbulence induced scintillation causes a randomly fading signal at the satellite. The fade statistics of the link is also analyzed and expressions are derived for the probability of fade, the expected number of fades per second and the mean fade time. The analysis considers geosynchronous Earth orbit satellites as well as low Earth orbit satellites. |
