Routing Algorithm for Low-Density Satellite Constellation for Urgent Message Relay

6th Generation (6G) communication technology provides ubiquitous communication services to users regardless of their location on Earth, utilizing low Earth orbit (LEO) and medium Earth orbit (MEO) satellite constellations comprising a massive number of satellites. Standard communication satellite constellations are designed to maintain continuous connectivity, allowing routing algorithms to determine the overall communication path based on these stable links. However, satellite constellations intended for purposes such as military or commercial observation often feature sparse satellite distribution. This can lead to difficulties in delivering or modifying missions during emergencies or when transmitting urgent commands. To overcome these limitations, this study proposes an algorithm capable of planning communication paths in environments with intermittent link connectivity by employing two concepts: Stepping satellite and waiting. Using the proposed algorithm, the shortest path was determined under a simulated scenario of transmitting urgent commands within a constellation not originally designed for communication. This approach is expected to contribute to mission expansion and efficiency improvements for various small-scale satellite constellations.