Abstract: This paper gave a solution to emergency task in space. When the emergency task occurred, at first, the existing satellite constellation was used to cover the target locations and the coverage rate was computed. If the coverage performance did not meet the mission requirements, the Non-Dominated Sorting Genetic Algorithm Ⅱ （NSGA-Ⅱ） was used to optimize the layout of satellite constellation, i.e. optimizing the anomaly of each satellite in the constellation. Then the phase modulation maneuver was used to achieve constellation optimization results, i.e. maneuvering the satellites to the specified locations, and calculating maneuver time and energy of each satellite. Finally, an emergency task example and its solution process were provided, and the time and energy of the satellite orbit maneuver were calculated.

Key words: Non-Dominated Sorting Genetic Algorithm Ⅱ （NSGA-Ⅱ）, emergency tasks based on space services, satellite constellation optimization, orbit maneuver, phase modulation maneuver

摘要： 给出了空间应急任务的解决方法，当发生需要空间服务的应急任务时，首先利用现有卫星组成的星座对目标地点进行覆盖计算，如果其覆盖性能不满足任务需求，就用NSGA-Ⅱ算法对卫星星座进行优化设计，这里优化星座中每颗卫星的平近点角;然后利用调相机动实现星座优化结果，将卫星机动到指定位置，并计算每颗卫星的机动时刻以及机动所需要的能量;最后给出了应急任务算例和它的具体解决过程，计算出了卫星机动变轨的时刻和所需能量。

关键词: 非支配排序遗传算法, 空间服务应急任务, 卫星星座优化, 机动变轨, 调相机动