BEIJING - China has completed an upgrade of the ground system for its first-generation relay satellite, Tianlian I, according to the Beijing Space Information Transmission Center on Friday.

The system upgrade marks a major advance for China in the space-based tracking, telemetry and control (TT&C) sector, said the center.

The four-year upgrade was successfully completed following maintenance downtime for the Tianlian I-02 relay satellite's ground system.

The upgrade enables the country to operate its two generations of relay satellite systems, Tianlian I and Tianlian II-1, in an integrated manner, said the center.

It also greatly enhances the reliability of the relay satellite systems, as well as their maintainable and automatic natures.

The relay satellite systems will further support the country in improving its TT&C capacity, and they will have roles in the country's upcoming space station mission, according to the center.

From 2008 to 2016, China launched four relay satellites to form the Tianlian I system, making China the second country in the world to establish a relay satellite system that is able to cover the entire world. The system can provide global real-time information transmission.