Development of a Free Space Optical Isl Network Between Leo Constellations & a Geo Satellite

Inter-satellite links (ISLs) have become a pivotal solution for space communication in recent years. ISLs very effectively remove the requirement of the satellite connecting to a ground station every now and then by directly communicating from one satellite to another. While traditional radio-frequencybased ISLs are capable of transmitting data directly between satellites, free-space optical (FSO) communication presents an alternative approach. This technology has emerged as a powerful system for inter-satellite communication, delivering high-speed, secure, and low-latency data transmission as compared to RF based ISLs. This paper presents the development and analysis of a FSO ISL network between Low Earth Orbit (LEO) constellations and a Geostationary Earth Orbit (GEO) relay satellite. The proposed network consists of a LEO Walker constellation with 8 satellites per plane across 3 planes, with each plane having one designated hub satellite. These hub satellites establish FSO links with a GEO relay satellite, which in turn transmits the collected data back to Earth. A comprehensive link budget and data rate analysis for the FSO ISL network has been conducted, with simulations performed using NASA's General Mission Analysis Tool (GMAT) and MATLAB. The results demonstrate the feasibility of achieving high-speed, low-latency communication within the constellation and efficient data transmission to the GEO satellite, highlighting the potential of FSO technology for future satellite networks.