Terahertz vs. Optical for Inter-Satellite Links: A Comparative Analysis of Pointing Errors and System Performance

With the space industry boom, the demand for more bandwidth has extended from the terrestrial to the non-terrestrial domain, with the promise of ubiquitous coverage that stretches beyond Earth. However, the exponentially increasing number of satellites and the dynamic and unique features of the space environment pose several challenges to the network design. In this paper, we explore the advantages and drawbacks of THz frequencies for Inter-Satellite Link (ISL), comparing them with the commonly adopted optical frequencies. Particularly, we make the case that the THz band can offer substantial performance improvements over optical in terms of received power and outage probability under non-ideal conditions where the beam or laser alignment is not perfect. After analyzing its effect on system performance, we identify the pointing accuracy requirements for both systems and the optimal frequency/gain choice for different pointing error magnitudes and link lengths. We hope that this preliminary analysis broadens the spectrum considered for ISLs, to take advantage of not only optical, but also THz bands.