The variations of velocity difference have obvious periodicity, which coincides with the satellite orbit period.

速度差各分量的变化具有很明显的周期性且与卫星轨道的运行周期相吻合。

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Global coverage and sun synchronization are the essential properties of the earth observation satellites, which are assumed by designing the orbit period and inclination.

对地观测卫星轨道具有全球目标覆盖和太阳同步两种特性，通过设计轨道周期和轨道倾角可以获得这些特性。

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The shape of this orbit isn't consistent; it varies over time, over a period of about a thousand years.

轨道的形状并不是始终如一的；它会随时间变化，变化周期为一百年左右。

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Long-period comets,however, may take several hundred years to orbit the sun.

VOA: special.2011.02.09

To do this the satellite would need to be in a synchronous orbit (one whose orbital period is the same as the period of revolution of the planet underneath), and the descending cable would have to be counterbalanced by an ascending one extending off into space.

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That is because the two smaller stars orbit each other in 0.9 days, whereas the expected period of oscillations from the red giant's rumblings is almost exactly half that.

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The asteroid orbits the Sun in 368 days - a period similar to Earth's year - but it does not orbit in the same plane as the Earth.

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