2020 Dec 22, China launched a cluster of five satellites from its Wenchang Space Centre using a CZ 8 rocket. They went to near sun-synchronous orbits at around 500 km altitude with LTDN near noon. The main payload, XJY 7 soon adjusted its orbit downwards to 495 km while the remaining satellites continued in their original orbits.

None of the satellites is tasked with a mission that requires a truly sun-synchronous orbit and none of the orbits are truly sun-synchronous. Choice of the orbital inclination was probably based on convenience because there is ground infrastrucure set up to be best suited to sun-synchronous inclinations.


XJY 7

Since the initial orbit adjustment, XJY 7 has trimmed its orbit slightly at roughly five week intervals in order to counteract air drag and maintain a ground track that repeats itself every nine days. This provides regular re-visits to any particular spot on the Earth at a similar viewing angle.

It is probably carrying an imaging radar so sun angle is not important but a polar orbit is required to cover the whole of the Earth's surface.


HiSea 1

Hisea is known for sure to be equipped with an imaging radar.

From launch, HiSea remained inert until 2021 May 13 when the orbit height started to reduce more quickly than through the effects of air drag. From May 17 it started to maintain its height, using a thruster to counteract the air drag. The ground track now makes a near repeat of itself every five days.


Other Satellites

The other three satellites carried by the CZ 8 were Yuanguang, Tianqi 8 and Zhixing 1. Up-to-date notes covering all satellites can be found in the zarya.info launch list for 2020.