BEIJING — China plans to launch two more meteorological satellites in 2021, sources with the China Aerospace Science and Technology Corporation said on Aug 5.

One of the planned satellites is called Fengyun-3E (FY-3E). It will be the fifth member of the country's Fengyun-3 series of satellites in polar orbit and the world's first meteorological satellite in dawn-dusk orbit.

A dawn-dusk orbit is a sun-synchronous orbit in which the satellite tracks but never moves into the Earth's shadow. Since the satellite is close to the shadow, the part of Earth the satellite is directly above is always at sunset or sunrise, giving the orbit its name.

As the sun's light is always shining upon the satellite, it can make constant use of its solar panels. Once in orbit, the FY-3E satellite will improve the accuracy and efficiency of global numerical weather prediction, according to the company.

The other satellite is Fengyun-4B (FY-4B), which will be the second geostationary meteorological satellite of the Fengyun-4 series. China launched the FY-4A, a scientific experiment satellite, into space in December 2016. The FY-4B will mark an upgrade of China's meteorological satellites in geostationary orbit.

As early as 1969, China started receiving, processing and using foreign meteorological satellite data. Meanwhile, the country has been developing its own meteorological satellite system.

Over the past 50 years, China's meteorological services have made huge progress. So far, the country has launched a total of 17 Fengyun meteorological satellites.