探月飞行的调相轨道

早期的探月飞行都采用直接由地球飞到月球的地月转移方式,探测器由运载火箭直接发送到地月转移轨道,这样做的好处是飞行时间比较短,只需3至5天的时间。20世纪90年代开始的新一轮探月活动中采用了一种新的飞行方式,探测器飞离地球前,先在绕地球飞行的调相轨道上运行若干圈,这样做的好处有三：一是可以在运载火箭能力不够的情况下,由探测器来补充;二是可以减小转移轨道中途修正的负担;三是可以扩大发射机会窗口。文章以嫦娥一号探测器及美、日的两个月球探测器为例,详细讨论了这种新的飞行方式,同时还对我国后续探月计划的飞行轨道提出了初步建议。

Phasing Orbit for Lunar Exploration

In the early age of lunar exploration,spacecraft was sent directly to the Moon on launch vehicles.The advantage of this way is to save the transfer time,usually three to five days are enough.In the new period of lunar exploration activities starting from 1990s,a new measure is adopted in which spacecraft would orbit the Earth for several revolutions before transfering toward the Moon.Compared with the old way of flight,the new one has three advantages.The first is that spacecraft could share part of energy required to reach the Moon with launch vehicle;the second is to reduce the burden for midcourse correction;the last is the possibility of increasing the launch opportunity.In this paper,a detailed discussion about this new type of flight is carried out based on Chinese CE-1 mission as well as two other lunar missions of USA and Japan.And a preliminary suggestion of flight orbits for the above-mentioned missions is also offered.