这些轨道飞船上，小组测试新技术，开展研究，开展维修轨道卫星和其它工艺。
Aboard these orbiting craft, crews test new technologies, conduct research and launch and repair orbiting satellites and other craft.
43分钟电影记录了哈勃20年历史，包括从2009年维修任务到绕地轨道天文台的热点和宇航员拍的镜头。
The 43-minute movie chronicles the 20-year life of Hubble and includes highlights from the May 2009 servicing mission to the Earth-orbiting observatory, with footage taken by the astronauts.
地铁正在进行维修，有时两列对开的地铁只能轮流共用一条轨道。
The subway is undergoing repairs, and sometimes trains going in opposite directions take turns using the same track.
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