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China launches first low-inclination orbit SAR satellite 'Haishao-1'

A new study in The Innovation highlights the launch of Haishao-1 (HS-1), China's first low-inclination orbit synthetic aperture radar (SAR) satellite. This marks a breakthrough in global Earth observation.

HS-1 was developed by the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences in collaboration with the Innovation Academy for Microsatellites and AIRSAT Technology Group. The satellite features a lightweight design paired with high-performance imaging capabilities.

While SAR technology has revolutionized Earth observation with its ability to provide all-weather, day-and-night imaging, most SAR satellites operate in sun-synchronous polar orbits. This leaves low-latitude regions consistently under-monitored. HS-1 breaks this pattern. Launched on December 4, 2024, it operates in a 43° low-inclination orbit at a very low Earth orbit (VLEO) of just 350 km. This configuration significantly enhances spatial resolution and imaging performance, allowing for clearer and more detailed observations of equatorial and tropical areas.

HS-1's low-inclination orbit enables it to revisit the South China Sea up to 5.7 times daily, which is far more frequently than traditional SAR satellites. Its VLEO position improves radar performance, providing 1-meter resolution imaging in stripmap mode while also reducing power requirements and payload size. These features facilitate more accurate quantitative retrieval of wave spectra and underwater bathymetry, offering critical insights into ocean dynamics.

In addition to its SAR capabilities, HS-1 is equipped with an integrated nightlight sensor to capture low-light emissions from urban and maritime sources. This dual-sensor system provides a multi-dimensional view of urbanization, transportation, and maritime activity. Its non-sun-synchronous orbit allows for flexible revisit schedules, making it ideal for monitoring rapidly changing human activities and environmental processes in tropical regions.

As the first satellite in its series, HS-1 represents an advancement in China's spaceborne SAR technology, laying the groundwork for more comprehensive and responsive Earth observation systems.