A Long March-3A carrier rocket carrying two satellites of the BeiDou Navigation Satellite System (BDS) blasts off from Xichang Satellite Launch Center in Xichang, southwest China's Sichuan Province, on Dec. 16, 2019. The launch marked 24 medium earth orbit satellites in the BDS-3 have all been successfully sent into space, and the deployment of the core BDS-3 constellation system has been completed, according to Yang Changfeng, chief designer of the BDS. (Photo by Guo Wenbin/Xinhua)