两位作者提出的最大担忧是太空垃圾——环绕地球运行的“垃圾”碎片，如果它们与包括国际空间站在内的运行单位相撞，可能会造成严重损害。
The greatest concern the authors raise is space debris-pieces of "junk" that orbit the earth, with the potential to cause serious damage if they collide with operational units, including the ISS.
环绕地球运行的人造卫星为科学家们提供了大量有关外层空间情况的资料。
Satellites orbiting round the earth have provided scientists with a vast amount of information about conditions in outer space.
极地轨道卫星经两极上空环绕地球运行，期间不断拍摄地球上不同的地区。
Polar-orbiting satellites revolve around the Earth along paths roughly passing over the poles. As they move, they obtain images of different parts of the Earth.
极地轨道气象卫星以大致南北方向环绕地球运行。它的轨迹离地面约数百公里。
Polar-orbiting satellites are low-flying satellites circling the earth in a nearly north-south orbit, at several hundred kilometers above the earth.
因为有卫星的头衔，而且沿椭圆形轨道环绕地球运行，月亮似乎每天平均51分钟返回到天空的同一地点。
Due to the moon's titled and elliptical orbit around Earth, the moon seems to return to the same place in the sky 51 minutes later each day, on average.
泰洛斯1号卫星在两极之间环绕地球运行，每30秒钟拍摄一张照片，如配图中的图像系列所示。
TIROS-1 orbited from pole to pole, snapping photos every 30 seconds, as illustrated in this series of images.
当Nanosail-D环绕地球运行时，会周期性地闪烁出光亮，使人能（通过仪器）轻易地用眼睛看到。
Glinting in the sunlight as it circles planet Earth, the NanoSail-D solar sail will periodically be bright and easily visible to the eye.
环绕地球运行的卫星，为科学家提供了浩如烟海的外层空间的资料，相比之下，对地球内部的结构则知之甚微。
Satellites orbiting round the earth have provided scientists with a vast amount of information about conditions in outer space.
两周以来，哥伦比亚号航天飞机一直在环绕地球运行，但多数世人对此却一无所知，当时人们主要关心的是伊拉克的命运。
For two weeks, the shuttle had been looping the globe to the complete obliviousness of the vast majority of the world's population, which was preoccupied for the most part with the fate of Iraq.
很多天文爱好者最初对该领域的研究都是从业余爱好开始的，他们会用双筒望远镜观察星系的变化，观察人造卫星环绕地球运行的规律。
Astronomy enthusiasts often enter this field as hobbyists, using binoculars or a telescope to observe the motion of planets or artificial satellites orbiting the earth.
在太空飞行时，杨利伟同环绕地球运行的国际空间站的两名宇航员进行了对话，他们是美国宇航员爱德华·卢和俄罗斯宇航员尤里·马林年科。
While he was traveling in space, Yang spoke to two astronauts aboard the International Space Station, which is orbiting the earth, American astronaut Edward Lu and Russian cosmonaut Yuri Malenchenko.
月亮被称为卫星，因为它不仅环绕太阳，而且也围绕地球运行。
The moon is called a satellite because it goes round our earth as well as round the sun.
月亮被称为卫星，因为它不仅环绕太阳，而且也围绕地球运行。
The moon is called a satellite because it goes round our earth as well as round the sun.
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