China Launches First Geosynchronous Orbit Radar Satellite

China launched what is thought to be the world's first geosynchronous orbit synthetic aperture radar satellite on Saturday. SpaceNews reports: A Long March 3B rocket lifted off from Xichang Satellite Launch Center in southwest China at 1:36 p.m. Eastern (1736 UTC) Aug. 12. The Land Exploration-4 01 (Ludi Tance-4 (01)) satellite successfully entered geosynchronous transfer orbit, the China Aerospace Science and Technology Corp., (CASC) announced within an hour of liftoff. Few details of the satellite were provided by CASC. However the group's "blue book" outlining plans for 2023 released in January noted the launch of a "high-orbit 20-meter [resolution] SAR satellite." The L-band synthetic aperture radar (SAR) satellite will provide all-day, all-weather observation of China and surrounding areas, boosting the country's disaster prevention, reduction, and relief capabilities. The land observation satellite series and "high-orbit SAR technology" are listed in the country's Medium and Long Term Development Plan for Civilian Space Infrastructure (2015-2025). The plan includes establishing high and medium resolution optical and synthetic aperture radar constellations for a range of land, marine and atmospheric monitoring. The series is separate from the China High-resolution Earth Observation System (CHEOS), which consists of Gaofen ("high resolution") satellites. China's Gaofen-4 satellite is a GEO optical satellite. SAR at GEO, while providing much lower resolution than satellites in low Earth orbit, can provide constant coverage and imagery despite cloud cover. It is not yet known what orbital scheme the Land Exploration-4 (01) satellite will enter. An inclined GEO orbit would produce a "figure eight" ground track over the area of intended coverage. Chinese academics from the Beijing Institute of Technology have produced a study of various schemes, while others have published research into modified signal models for GEO SAR. The (01) designation suggests China could launch other SAR satellites into geosynchronous orbits. The satellite was developed by the China Academy of Spacecraft Technology (CAST.)

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