Fade statistics of a ground-to-satellite optical link in the presence of lead-ahead and aperture mismatch

Abstract

In a recent publication [J. Opt. Soc. Am. A25, 1594-1608 (2008).JOAOD60740-323210.1364/JOSAA.25.001594] we developed expressions for the tilt errors that arise from the effects of lead-ahead and aperture mismatch when transmitting a laser beam from the ground to a satellite. We extend these results to examine the fade statistics of the irradiance at the satellite due to these tilt errors and turbulence induced scintillation. The system concept is that the light from a beacon on the satellite is received by the ground station and a derived signal is used to drive a tracking/pointing system for the uplink beam. However, the beam must be pointed ahead along the satellite track to intercept the satellite (lead-ahead), and physical constraints may require that the beam transmit aperture is different in size or location than the aperture receiving the beacon signal (aperture mismatch). These two issues cause the light entering the receiving aperture (tracker) and the beam exiting the transmit aperture (pointer) to traverse somewhat different turbulence volumes, which limits the ability of the tracking/pointing system to place the maximum flux on the satellite.

Statistical and temporal irradiance fluctuations modeling for a ground-to-geostationary satellite optical link

“…Contrary to many works in the literature ( [4,5,22]), which focus on the mean fade duration and mean number of fades per second, our model can create time series of the irradiance fluctuations. This approach will be useful to work on the contributions of interleaving and on the error correction codes.…”

“…We justify here our choice of Baker's model [10] as base for our model by comparing it with other usual models in the literature where the defocus and the astigmatism are not taken into account and rely for the higher orders on the Rytov approximation( [5,8,21]). In Figure 17, we compare the scintillation results from the LOT model to results obtained from Dios' methodology [8].…”

“…Most models found in the literature do not take into account the impact of the beam truncation ( [5,8,21]). However, we show that its influence is not always negligible and it is therefore an important parameter to take into account if the objective is to optimize the architecture of an optical ground station.…”

“…There have been many studies aiming to give a thorough de-scription of the irradiance fluctuations on a ground-to-satellite propagation. These studies' objectives are usually to present analytical expressions for the scintillation index (the normalized irradiance variance), the irradiance probability density functions and even for the probability of fades ( [4,5]). These studies usually rely on the Rytov perturbation method (RPM) [6].…”

Point-ahead demonstration of a transmitting antenna for satellite quantum communication

“…Consequently, the point-ahead technique is indispensable for such quantum communication terminals. In previous works [22,23], the discussions of point-ahead focus on complex coordinate transformations. However, discussions and detailed data analyses on actual implementation are sparse.…”