Abstract
The low cost, compact design, and flexible mission capabilities of microsatellites have accelerated the growth of the microsatellite industry. However, their limited weight and volume budgets constrain the number of available onboard transceivers, posing a fundamental challenge known as the Contact Plan Design (CPD) problem, which involves scheduling inter-satellite communications. While several approaches, such as MILP and heuristic methods, have been proposed to address the CPD problem, these methods either incur high computational complexity or suffer from suboptimal end-to-end delay, making them unsuitable for online, time-critical missions in microsatellite networks. To overcome these limitations, we propose an efficient graph-based online contact plan design scheme. We first construct a novel graph representation, referred to as the contact plan graph, that unifies the modeling of transceiver availability and constraints, as well as storage and communication resources in the satellite network. This formulation transforms the online CPD into a pathfinding problem, significantly reducing computational overhead. Building on this, a customized shortest-path algorithm is developed, tailored to transceiver constraints such as half-duplex operation and single transceiver limitation. Simulation results under realistic satellite network settings demonstrate that our method achieves substantial improvements of up to 29% in end-to-end delay and over 6400\times in runtime compared to state-of-the-art baselines.