A Novel Approach towards Establishing Free Space Optical Inter Satellite Links beyond the Kármán Line

The rapid surge in the technological advancement of humanity calls for development of faster, reliable & effective communication methods between satellites orbiting in outer space. The infamous inter-satellite link technology, coupled with free space optical communication is a robust solution for the same. While establishing this for low earth orbit satellites, it is critical to ensure that the links established across the two satellites avoid the atmosphere, i.e., the links stay above the Kármán Line. This becomes necessary as optical beams suffer a lot of attenuation due to atmosphere. This research aims to calculate the maximum possible perpendicular range at which two low earth orbit satellites can be offset, while avoiding the atmospheric interference in the links. By using simple Pythagorean mathematics and spacecraft simulations, the results provide a promising solution for the placement of satellites in low earth orbits. Along-with the maximum range determination, a comprehensive power analysis is conducted theoretically using MATLAB and then the same is simulated in OptiSystem software. The power analysis provides insights that are crucial for determining optical receiver sensitivity, link budget and data rates supported by the link. Both range and power analysis is performed for multiple circular low earth orbits ranging from 400 km to 1200 km with a 100 km step size. The results demonstrate a lowest maximum range value of 4511.6 km & the highest received power value of −48.69 dBm for the 400 km orbit and the highest maximum range value of 14,075 km & the lowest received power value of −58.57 dBm for the 1200 km orbit. A high data-rate of 2.5 Gb/s is obtained between the satellites in the 400 km orbit with an acceptable bit-error ratio value of 4.17 × 10−8.