periscopic depth

例句：

1. 1. The scientist used a periscope to observe the distant planets.
   科学家使用了一个望远镜来观察遥远的行星。
2. 2.The astronaut's periscope was the only way to communicate with the space station.
   宇航员的望远镜是唯一与太空站进行通信的方式。
3. 3. The periscope allowed us to see the ocean floor clearly for the first time.
   这个望远镜让我们第一次清晰地看到了海底。