On August 21, the China National Space Administration announced the successful launch of the world’s first high-orbit synthetic aperture radar satellite, known as “Land Exploration Satellite No. 4-01” (Ludi Tance-4 (01)). The satellite has now successfully entered its operational orbit.
Land Exploration Satellite No. 4-01 is capable of round-the-clock, all-weather terrestrial observation. While it is designed to assist with disaster prevention, earthquake monitoring, and land resource exploration, it also considerably enhances military capabilities.
On the previous Sunday, August 13, the satellite was launched from the Xichang Satellite Launch Center aboard the Long March 3B rocket. After its launch, it smoothly transitioned to its planned transfer orbit.
Unlike conventional optical remote-sensing satellites, the observation equipment on Land Exploration Satellite No. 4-01 is a synthetic aperture radar. It works by transmitting electromagnetic waves to the Earth and then receiving the reflected waves to produce radar images packed with a wealth of information.
Being the world’s first of its kind in high orbit, the satellite can continuously monitor not only mainland China but also its surrounding regions. It meets the requirements of various sectors, including disaster prevention, earthquake monitoring, land and maritime resource exploration, water conservation, meteorology, agriculture, environmental protection, and forestry.
Beyond terrestrial observation, Land Exploration Satellite No. 4-01 has military applications, especially with drones. For instance, its simulated radar aperture can achieve maximum specification requirements, thus enhancing the reconnaissance capabilities of drones. The clearer the imaging, the stronger the detection capacity for enemy targets. This directly relates to the precision of strikes, making the technology’s future applications critically essential.
According to Zhang Qingjun, a researcher from the Aerospace Science and Technology Corporation’s Fifth Research Institute, the satellite uses synthetic aperture radar for imaging and doesn’t rely on light, allowing it to penetrate cloud layers and observe the world below. This makes it incredibly adaptable to applications like disaster prevention.
Moreover, the satellite’s orbit is notably high, almost 40,000 kilometers in a geosynchronous orbit. Satellites in this orbit appear to trace a figure-eight pattern, enabling relatively constant observation of vast areas. This provides short revisit cycles and wide imaging swaths.
It was mentioned that satellites typically operating in lower orbits of around 500 or 700 kilometers stay over a specific area for just several minutes and revisit the same area days later. In contrast, Land Exploration Satellite No. 4-01, due to its high orbit, can observe larger areas more frequently, complementing the capabilities of lower orbit satellites.