Design and on-orbit verification of an integrated multiplexing modulator for laser communication and VDES payloads in satellite communication systems

Satellite missions increasingly require integrated communication architectures capable of supporting heterogeneous payloads and high-efficiency onboard data processing. In this paper, an integrated multiplexing modulator designed for satellite communication systems supporting both laser communication payloads and VDES payloads is presented. The proposed system performs multiple key functions, including multi-payload data reception and transmission, protocol processing, real-time cross-payload data forwarding, onboard mass storage management, and S-band telemetry and data communication. The multiplexing modulator adopts a modular architecture composed of a storage unit and a modulation–demodulation unit. The storage unit integrates a 4-Tbit NAND Flash array to support large-capacity onboard data storage and flexible playback. The modulation–demodulation unit performs baseband processing, channel coding, QPSK modulation, and RF frequency conversion for reliable S-band data transmission. A unified onboard data processing framework is developed to enable efficient interaction among VDES payloads, laser communication payloads, and the satellite telemetry subsystem through protocol encapsulation and virtual channel management. The proposed multiplexing modulator has been successfully integrated into a satellite system launched from the Jiuquan Satellite Launch Center on 5 December 2025 using a Kuaizhou-1 launch vehicle. As of 30 June 2026, the unit had accumulated more than 4,900 h of on-orbit operation in a 900-km circular orbit with an inclination of 80.4 deg. The on-orbit telemetry packet records and mission operation logs indicate normal operation of the unit, including conventional storage operation outside domestic ground-station coverage and ground data-transmission operation over domestic ground-station coverage. Ground RF measurements further verified the modulation, frequency-accuracy, occupied-bandwidth and phase-noise performance before launch.