Abstract
Optical satellite communication has received considerable attention as a promising alternative to radio frequency communication because of its potential advantages including higher data rates and license free spectrum. Many studies have conducted performance analyses of optical communication channels, but few have investigated beacon tracking channels under atmospheric turbulence. The centroid accuracy of beacon tracking channels is limited by not only noise sources, but also a finite delay time, which also fluctuates due to atmospheric turbulence. Consequently, the centroid error is an important figure of merit when evaluating the performance of a beacon tracking system. In this study, the closed-form expressions were derived for average centroid error and fade probability, based on received photoelectron counts depending on exposure time, taking into account the log-normal tracking channels. We analyzed the angular positioning performance of beacon tracking detectors onboard small satellites in the presence of atmospheric turbulence, in terms of centroid error and fade probability. We found that an optimal exposure time exists, which minimizes the centroid error, and that fade probability is inversely proportional to the exposure time. These are significant properties to consider in the design of beacon tracking systems.
Highlights
Optical satellite communication has received significant attention as a promising advance in satellite communication, with the potential advantages of higher data rate, license free spectrum, better security, smaller size, lower mass, and lower power consumption [1,2,3,4,5]
The PAT system is normally composed of three components that deal with different requirements: a coarse pointing assembly (CPA), a fine pointing assembly (FPA), and a point-ahead assembly (PAA)
We found from numerical simulations that an optimal exposure time exists, which minimizes the centroid error resulting from noise sources and the exposure time latency
Summary
Optical satellite communication has received significant attention as a promising advance in satellite communication, with the potential advantages of higher data rate, license free spectrum, better security, smaller size, lower mass, and lower power consumption [1,2,3,4,5]. An accurate centroid estimation is critical to the beacon tracking system to point the optical beam toward the partner terminal, so that sufficient optical power is received to meet the data rate and bit error rate performance requirements. This makes it essential, when evaluating the pointing capability of a PAT system, to analyze the centroid error intrinsic to noise sources and the finite delay time under atmospheric turbulence. Fade probabilities decreased rapidly as the exposure time was extended and atmospheric turbulence became strong These characteristics should be taken into account in a trade-off of the design of the beacon tracking system requiring high bandwidth and high positioning accuracy
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