探空气球

例句：

1. 1. The balloon was released into the sky to mark the start of the race.
   气球被释放到天空中，标志着比赛的开始。
2. 2. The balloon pilot had to make a quick decision about where to land the balloon.
   气球飞行员必须迅速决定在哪里降落气球。
3. 3. The balloon was filled with helium and floated above the clouds.
   气球充满了氦气，飘浮在云层之上。