我认为这可能是因为奥尔特云受到一个正在把彗星抛出不变轨道的大天体的扰动，其一一小部门彗星可能会达到地球。
I believe it is likely that this is because the Oort Cloud is being disturbed by a massive body that is throwing comets out of stable orbits, a small fraction of which could reach the Earth.
目前，它正在与地球相对位置不变的轨道接受严格的测试，希望2008年第1季度提供服务。
It is now in geosynchronous orbit undergoing rigorous testing and is expected to begin service in the first quarter of 2008.
研究了基于三体问题的不变流形设计低成本登月轨道的问题。
The low-energy lunar landing trajectory design using the invariant manifolds of restricted three body problem is studied.
本文提供一种保持轨道形状和近地点位置不变的控制方法。
This paper offers a method which maintain orbital shape and perigee location.
采用规范不变原子轨道GIAO法，计算它们的1H-NMR和13C-NMR化学位移值。
With the GIAO (gauge-independent atomic orbital) method, the 1H-NMR and 13C-NMR were also calculated theoretically.
同样，由于月亮轨道并不是一成不变，有轻微的变动，所以每次月球运行至近地点的位置与地球的间距是不一样的。
Likewise, because the size of the moon's orbit varies slightly, each perigee is not always the same distance away from Earth.
然后基于不变流形理论和庞加莱截面方法，设计了不同拉格朗日点间转移轨道。
Then on the basis of invariant manifold theory and Poincaré section, a transfer trajetory between L1 and L2 of the Earth-Moon system was given.
然后基于不变流形理论和庞加莱截面方法，设计了不同拉格朗日点间转移轨道。
Then on the basis of invariant manifold theory and Poincaré section, a transfer trajetory between L1 and L2 of the Earth-Moon system was given.
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