SinoSat-3 (ChinaSat-5C, Eutelsat-3A, Eutelsat 8 West D) was a Chinese geostationary communications satellite developed to support domestic broadcasting and telecommunications services across China and neighboring regions.

The satellite was built by the China Academy of Space Technology (CAST), a key subsidiary of the China Aerospace Science and Technology Corporation (CASC). SinoSat-3 is based on a mature Chinese satellite bus platform designed for reliability and long operational life in geostationary orbit (GEO).

SinoSat-3 was launched on 31 May 2007 aboard a Long March 3A (CZ-3A) rocket from the Xichang Satellite Launch Center in China. After launch, it was positioned in geostationary orbit to provide continuous coverage over its service area.

The satellite is equipped with multiple C-band and Ku-band transponders, enabling a wide range of applications including television broadcasting, radio distribution, data transmission, and secure communications. It plays a role in supporting China’s national broadcasting infrastructure as well as government and commercial communication needs.

A key milestone associated with SinoSat-3 is its role as a replacement and backup satellite following earlier issues with SinoSat-2, helping to ensure continuity and reliability of China’s satellite communications network. Its deployment marked an important step in strengthening China’s independent space-based telecom capabilities.

The primary customer base included state broadcasters, telecommunications providers, and government agencies, with services focused mainly on the Chinese domestic market but also extending to parts of Asia.

In 2010, the satellite was taken over by China Satcom and renamed ZX 5C (ChinaSat 5C) and in July 2011, it was leased to satellite operator Eutelsat, renamed Eutelsat 3A and moved to the 3° East position as a placeholder for the new Eutelsat 3B satellite. In 2014 it was renamed Eutelsat 8 West D and moved to the 8° West position to operate in an inclined orbit.

It was retired of service and has been moved to a graveyard orbit above GEO.