随着航天活动的开展，空间碎片环境严重地威胁着在轨航天器的安全运行。
With the increase of the human aerospace activities, space debris environment is seriously threatening in-orbit spacecraft safe operation.
人类日益频繁而复杂的空间探索活动，使得空间飞行器在轨服务技术成为近年来研究热点。
On-orbit service techniques of spacecraft become the hot spot for the space explorations of human which are more and more frequent and complicated.
现代社会保障轨制树立之前，各类非营利组织就以各种方式从事社会救助等社会保障活动。
Before the modern social security system is set up, such social security activities as all kinds of nonprofit organization is engaged in society's succoring by various ways.
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