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土星探测器卡西尼号明天执行“自我焚毁”指令 差一个月满“20岁”

2017-09-14 20:31:49   央广网

央广网北京9月14日消息(记者张加宁)据中国之声《新闻晚高峰》报道,人类历史上最遥远的环绕探测器——卡西尼号即将主动陨落到土星。再过一个月,10月15日本该是卡西尼号的20周年纪念日,不过它等不到这一天了。明天(北京时间9月15日傍晚),卡西尼号将执行来自美国国家航空航天局(NASA)的最后一条指令:自我焚毁。这艘20世纪末的行星际飞船,将点燃推进器,一头扎进土星大气层与这颗探测了13年的气态行星融为一体。卡西尼号为何要执行“自杀”指令?NASA又为什么将“卡西尼”号火红且壮观的死亡时刻称为“盛大落幕”?

作为美国深空探测旗舰项目 卡西尼号工作20年收获满满

今年4月26日,卡西尼号首次从土星与土星环之间俯冲而过,之后卡西尼号在这片神秘的未知之地完成了22次穿越,期间使出浑身解数收集数据。国际宇航联空间运输委员会秘书长、中国航天科工集团公司二院二部研究员杨宇光今天接受中国之声采访时表示,卡西尼号是美国深空探测的旗舰项目,“一般来说深空探测有两种:一种是经过一个大的天体周围进行拍照等,缺点是一掠而过、时间短、得到的数据有限;另一种是一圈一圈环绕目标天体探测,可以进行长期探测,得到更丰富的数据成果。这个过程中耗能巨大,航天器规模也比较大,所以卡西尼是美国深空探测的旗舰项目。”

1997年10月15日,卡西尼号从美国的卡纳维拉角发射升空,从地球到土星卡西尼号飞了7年。它借用引力弹弓效应,先后两次掠经金星、一次掠经地球、一次掠经木星,最终抵达土星。这段迂回路线是土星距离地球最近距离的将近三倍。这样的绕道飞行并未更加耗时,反而大大节省了燃料。杨宇光指出:“整个太阳系中太阳的重量占99%,在这剩下的不到1%中,木星的重量占了一半还多,因为木星这么大有很强的引力,可以改变很多从外太阳系进入内太阳系的彗星和小行星的轨道,不会撞倒地球上。有一种说法是地球上之所以有人类这样的高等生命存在,与木星的保护有很大关系。包括卡西尼号的深空探测器都需要借助木星的引力加速,否则到达这些天体需要的时间太长,很难承受。”

北京时间2004年7月1日12时,借力使力的卡西尼号终于进入土星轨道。在太空的20年间,“卡西尼”号拍摄了近50万张图像、执行了250万条指令,收获满满,尤其是对土卫二和土卫六、这两颗具备生命存在条件的土星卫星的探索。土卫六是土星最大的“月亮”,叫作泰坦;而土卫二则是一颗被冰雪覆盖的“冰月”,冰层下隐藏着流动的海洋。卡西尼磁力仪项目首席研究员多尔蒂表示:“我的团队在土卫二上发现了水蒸气,而且冰层下不仅有液态水,还存在有机材料和热源。”这三样如果在稳定的情况下,将是创造生命的重要元素。发现外星生命,正是人类进行无数太空探索的重要动力之一。

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