Abstract: From 2021 to 2025 (the "14th Five-Year Plan" period), China established an operational space-based ocean observation system composed of the HY-1, HY-2, and ocean surveillance and monitoring (e.g., GF-3) satellite series. This achievement marks a historic leap from single-satellite detection to integrated constellation networking. This paper systematically reviews the major progress during this phase:
At the system level, the HY-1C/D/E three-satellite network achieved high-frequency collaborative observation of global ocean color and sea surface temperature. The HY-2B/C/D three-satellite constellation improved the revisit capability for global sea surface wind fields to within 6 hours. The HY-4A satellite filled the technological gap in active-passive microwave coordinated inversion of sea surface salinity using domestically developed satellites. The GF-3 satellite series enhanced the revisit capability of synthetic aperture radar (SAR) over key areas to an hourly level. At the technological level, significant improvements in payload performance, coupled with enhanced capabilities in data fusion and calibration, led to systematic breakthroughs in information processing—from algorithms to platforms. Notably, the successful development of "AI large models for remote sensing tailored to deep-sea applications" has driven a fundamental transformation in space-based ocean observation, shifting from two-dimensional sea surface remote sensing to three-dimensional stereoscopic perception of the deep ocean. At the application level, the system now fully supports marine environmental monitoring, disaster emergency response, and global ecological assessments. Finally, the paper outlines future directions, including next-generation satellite stereoscopic detection, full-chain intelligentization, and international cooperation.