Because the moon's body blocks direct radio communication with a probe, China first had to put a satellite in orbit above the moon in a spot where it could send signals to the spacecraft and to Earth.

由于月球阻碍了与探测器的直接无线电通信，中国首先必须把一颗人造卫星送入月球轨道上的一个点，人造卫星可以从那里向航天器和地球发射信号。

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Adjoint function algorithms and direct collocation and nonlinear programming methods are applied to resolve the non-coplanar optimal orbit transfers problem.

分别利用了共轭函数法与直接配置和非线性规划方法对异面最优变轨问题进行了求解。

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For example, instead of the lunar rendezvous method that NASA chose for the Apollo program, the player can opt for Earth-orbit rendezvous or even direct-ascent where a single giant spacecraft lifts off from Earth and lands on the Moon.

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If Apophis passes the earth at a distance of exactly 18, 893 miles it will open a "gravitational keyhole" causing it to enter a new orbit that would put it on a direct collision course with earth seven years later.

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Dr Murray stressed there was no direct evidence these stars did have Earth-sized planets in orbit about them, but modelling had shown that if sufficient terrestrial material existed in a system it would eventually clump together into bodies as big as the Earth.

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