The research on space-based electromagnetic environment sensing constellations holds significant scientific importance and broad application value. As the key medium for electromagnetic wave propagation, the electromagnetic environment directly affects the operational efficiency of global information infrastructures such as communication, navigation, and security systems. By constructing constellation-based systems, it becomes possible to achieve wide-area, real-time, and high-resolution monitoring of the global electromagnetic environment. This not only provides essential data support for scientific fields such as space weather forecasting, natural disaster monitoring, and climate change research but also plays a vital role in applications like maritime supervision, aviation safety, spectrum management, and national defense reconnaissance. Meanwhile, space-based observation effectively compensates for the limitations of ground-based systems—overcoming sparse stations, observation gaps in oceans and polar regions, terrain occlusions, and other constraints, thus greatly enhancing the spatial continuity and global consistency of observations, promoting space-ground complementarity and multi-scale collaboration. Consequently, it will comprehensively strengthen global electromagnetic situational awareness capabilities and provide a solid technological foundation for national security and high-quality socio-economic development.

The development of space-based electromagnetic environment sensing constellations can be divided into three major stages: the military reconnaissance-dominated stage, the global cooperation and competition stage, and the commercial-national co-led stage. Representative constellations—such as HawkEye 360, Unseenlabs, Kleos Space, Spire Lemur, and China′s Tianmu and Yunyao series—demonstrate the overall trend of evolution from single-purpose missions to multimodal collaborative sensing architectures. Significant breakthroughs have been achieved in key technologies, including GNSS radio occultation for tropospheric and ionospheric sensing, multi-satellite time-frequency difference localization, blind coherent integration, onboard signal de-collision processing, and spaceborne multimodal integrated sensing. These technological advances have enabled global-scale and fine-grained observation of the ionosphere, troposphere, and electromagnetic spectrum, substantially enhancing the spatiotemporal resolution and dynamic sensing capability of electromagnetic environment monitoring. Meanwhile, representative applications—such as RF-optical/SAR data fusion by HawkEye 360 and AI-enabled onboard processing by OPS-SAT—further underscore the accelerating trend toward space-ground collaborative networking and intelligent development in space-based electromagnetic environment sensing.

The development of space-based electromagnetic environment sensing constellations is driving the global electromagnetic environment sensing system toward four major transformation directions: integration of space-and ground-based systems, inter-satellite networking and collaborative operations, multimodal and comprehensive payload development, and onboard real-time intelligent processing. Future research will focus on space-ground data fusion, high-speed inter-satellite networking, multimodal information integration, and autonomous intelligent sensing. With the continuous improvement of constellation intelligence and interconnectivity, these systems will provide more efficient and reliable technical support for situational awareness and anomaly detection in complex and dynamic electromagnetic environments.