Mitigation of Misalignment Error Over Inter-Satellite FSO Energy Harvesting

In this paper, the impact of the acquisition, tracking, and pointing (ATP) module utilization on inter-satellite energy harvesting in low-earth orbit (LEO) is investigated for various beam divergence angles. Random elevation and azimuth misalignment error angles at both the transmitter and the receiver are modeled with Gaussian distribution hence the radial pointing error angle can be modeled with Rayleigh distribution statistically. Then, the misalignment loss factors at the transmitter and receiver are obtained independently. The harvested power as a function of the transmit power and inter-satellite distance is analyzed along with the maximum achievable range that satisfies the 1U (i.e., 0.1$\times$0.1$\times$0.1 m) small satellite power requirement on space tasks. Our simulation results show that in a free space optics (FSO) link without the ATP module, a laser with a wider beam divergence angle $\theta$ puts an effort to compensate for the loss of misalignment and hence provides higher harvested power than narrow ones. However, when the ATP module is in use, the laser with narrower $\theta$ outperforms the laser with wider $\theta$ in harvested power. Furthermore, the utilization of the ATP module leads to a significant improvement in the maximum achievable range.