Abstract: Low Earth Orbit (LEO) satellite systems offer advantages such as wide coverage and massive connectivity but also face significant security risks from eavesdropping and interference. This paper investigates a covert communication technology for LEO satellites based on Massive MIMO Integrated Sensing and Communication (ISAC). A comprehensive system model is first established, including both the satellite communication channel and the radar sensing channel, followed by the derivation of the system’s covertness constraint. On this basis, a joint optimization problem is formulated to maximize the total multi-user covert communication rate, subject to constraints on radar sensing performance, covertness requirement, and transmit power limits of the satellite and radar. To tackle the resulting non-convex problem, an alternating optimization framework combined with the Minorize Maximization (MM) algorithm is developed to iteratively obtain a locally optimal solution. Simulation results demonstrate that when the radar transmit power is 80 W, the proposed scheme achieves approximately 80% improvement in the total covert communication rate compared to the benchmark. Compared with conventional LEO covert communication systems without ISAC, the proposed method effectively exploits radar signals to generate friendly interference against the eavesdropper, thereby enhancing both the covert transmission rate and communication covertness simultaneously.

Key words: Satellite communication, ISAC, Covert communication, Massive MIMO, Minorize–Maximization Algorithm