题目

Three-two-one, fire!At the moment of 9:43 a.m., on Tuesday, June 23rd, 2020, at the Xichang Satellite Launch Center(卫星发射中心) in Sichuan Province, the last satellite of the third-generation network(第三代导航系统) was sent into space. It is the 55th member in the family of BeiDou. It belongs to China’s Beidou Navigation Satellite System(BDS北斗卫星导航系统). So far, 59 satellites, including the first four test ones, have been launched from Xichang. With the development of China, we have already owned three other famous satellitle launch centers — Jiuquan, Taiyuan a10．青海湖高于海平面3193米，应记作+3193米，太平洋的马里亚纳海沟最大深度为地平面下10911米，应记作-10911米．