HELSINKI —A Chinese Shiyan satellite appears in a low-inclination orbit never before used by the country, after a week-long detection delay and uncertainty over its mission.
China launched the classified Shiyan-28B (01) satellite July 3 on a Long March 4C rocket from Xichang spaceport. The China Aerospace Science and Technology Corporation (CASC) announced launch success within an hour of liftoff. No clear payload information was provided.
Airspace closure notices suggested Shiyan-28B (01) would enter a 35-degree inclination low Earth orbit (LEO), with no signs of a significant dogleg maneuver. However, U.S. space tracking did not register the spacecraft in as timely a manner as expected. Objects from launches—such as spacecraft, rocket stages and related debris—are typically cataloged within a day or two.
Unusually, U.S. Space Force’s space domain awareness only cataloged Shiyan-28B (01) six days after launch. Shiyan-28B (01) was finally cataloged July 9 as 2025-145A, reporting the spacecraft to be in a 793 by 796-kilometer orbit inclined by 11 degrees.
This suggests that, assuming the rocket followed its designated flight path, the Long March 4C third stage executed a fuel-intensive dogleg maneuver to substantially alter its orbital inclination to 11 degrees.
Jonathan McDowell, an astrophysicist and spaceflight activity tracker, told SpaceNews that U.S. Space Force tracking is weaker at lower inclinations.
The Long March 4C, with a 4,200 kg payload capacity to LEO, was chosen for the mission, launching from Xichang spaceport, located at 28 degrees North latitude. Wenchang Satellite Launch Center is located at 19 degrees, offering greater fuel efficiency to low inclination LEO, but currently only much larger and more capable Long March rockets launch from the spaceport.
The only earlier Long March 4C launch from Xichang—the 2018 launch of the Queqiao lunar relay satellite—launched initially into a lower inclination orbit than the 35 degrees indicated by the Shiyan-28B (01). It is unclear why the 35 degree flight path was chosen for Shiyan-28B (01), or why the dogleg was performed late in the launch phase, though launches from inland Xichang involve careful calculation to limit the chances of spent stages falling in inhabited areas.
It is unclear what the Shiyan-28B (01) mission is, with only a terse description provided in post-launch statements. “The satellite will be mainly used for space environment exploration and related technology tests,” a Xinhua state media report read.
Analysts believe Shiyan satellites are used to trial new systems such as sensors, communications subsystems and environmental instruments, forming part of China’s efforts to validate new space technologies in orbit. These satellites may act as precursors to operational platforms, verifying designs and payloads before wider deployment.
The Innovation Academy for Microsatellites of the Chinese Academy of Sciences (IAMCAS) developed Shiyan-28B (01). IAMCAS develops small, experimental, and often dual-use satellites, and possesses expertise in telecommunications, remote sensing, navigation, micro/nano satellites and dedicated science satellites, such as the DAMPE dark matter probe and QUESS quantum science spacecraft. An IAMCAS mission patch included three eight-pointed stars and apparent bonfire imagery.
The low inclination orbit would see the spacecraft pass over portions of the South China Sea, as well as the Indian Ocean. It is unknown if its purposes will be for uses such as regional monitoring, communications tests or signal intelligence capabilities. The “B” designation and sequence number suggest further satellites may follow in this new low-inclination test series.