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国家防总对上海江西启动防汛防台风四级应急响应_我的网站
A | Washington, Oct 12 (UNI) American space agency NASA says its recent attempt to deflect the path of an asteroid was successful, after its Dart probe struck an asteroid head-on.
Scientists have now confirmed the orbit of a 160m-wide space rock known as Dimorphos was altered when the Dart probe struck it head on last month.
Researchers came to the conclusion after making measurements using a range of space and Earth-based telescopes.
The mission was conceived to test a potential strategy to defend the Earth against threatening objects.
Dart's achievement proves such an idea would work, provided it was initiated early enough and the target wasn't overly massive.
"This mission shows that Nasa is trying to be ready for whatever the Universe throws at us," said agency administrator Bill Nelson.
"I believe that Nasa has proven that we are serious as a defender of the planet," he told reporters.
The space agency released a raft of data on Tuesday to support its assessment, including new pictures from the Hubble Space Telescope and from a small Italian spacecraft that stood off from the impact by about 50km (30 miles).
The Double Asteroid Redirection Test (Dart) took place some 11 million km (7 million miles) from Earth.
It saw the refrigerator-sized Nasa satellite drive straight into Dimorphos at 22,000km/h (14,000mph), destroying itself in the process.
The space rock orbits a much larger (780m wide; 2,550ft) object called Didymos. Before impact, the time taken for Dimorphos to make one circuit of its sibling was 11 hours and 55 minutes.
The telescope evidence now indicates this orbital period has been reduced to 11 hours and 23 minutes - a change of 32 minutes. This corresponds to Dimorphos moving closer into to Didymos by "tens of metres".
Nasa had defined a minimum successful period change of Dimorphos of 73 seconds or more. The results released on Tuesday show Dart surpassed this benchmark by more than 25 times.
"This is a 4 percent change in the orbital period of Dimorphos around Didymos. Dart just gave it a small nudge. But if you wanted to do this in the future, you'd want to do it years in advance," commented Nancy Chabot from the Johns Hopkins University Applied Physics Laboratory, which led the mission for Nasa.
"Warning time is really key here in order to enable this sort of asteroid deflection to be used in the future as part of a much larger planetary defence strategy."
Nasa's Dart programme scientist, Tom Statler, also had a word of caution about drawing too many conclusions from the experiment.
Asteroids came in many different guises, he said. Their compositions and constructions were diverse - something that was being emphasised every time a mission visited a new object.
"We should not be too eager to say one test on one asteroid tells us exactly how every other asteroid would behave in a similar situation," he stressed.
"But what we can do is use this test as an anchor point for our physics calculations in our simulations that tell us how different kinds of impacts in different situations should behave."
Four years from now, the European Space Agency (Esa) will have three spacecraft - collectively known as the Hera mission - at Didymos and Dimorphos to make follow-up studies.
UNI ING。 8月9日，国家防总办公室、应急管理部组织中国气象局、水利部、自然资源部、工业和信息化部、住房城乡建设部、交通运输部等部门以及浙江、江苏、安徽等重点省份联合会商，研判台风“白海豚”发展趋势，部署防范应对工作。国家防总办公室主任、应急管理部副部长兼水利部副部长陈敏主持会商。台风“白海豚”于9日傍晚在浙江沿海两次登陆。会商指出，台风登陆期间风雨猛烈，近岸风险管控、海堤水闸安全面临严峻挑战，城镇洪涝、山洪和地质灾害等可能多发重发，其残余环流可能与北方冷涡结合，给华北、山东半岛甚至东北等地带来降雨，防汛防台风工作形势严峻复杂。
B | 会商要求，要认真贯彻习近平总书记关于防汛救灾的重要指示批示精神，按照李强总理指示要求，落实国家防办防台风“12条措施”，全力做好“白海豚”防范应对工作。要梯次做好“三个阶段工作”，加强避风船只和上岸避险人员安全管理，做好风险隐患排查整改和陆上人员转移避险，落实重点领域抢险救援力量，确保第一时间开展抢险抢通，及时开展救灾救助。
C | 要盯紧看牢“三大薄弱环节”，针对中小河流堤防和中小水库、山洪地质灾害风险区和隐患点、城乡内涝等薄弱环节强化巡查防守和应急处置。要继续抓实“三项防汛责任”，层层落实防汛救灾主体责任，全面压实部门责任，紧紧压实基层一线责任，切实把确保人民生命安全放在第一位落到实处。国家防总9日上午针对上海、江西启动防汛防台风四级应急响应，维持针对浙江、福建的防汛防台风三级应急响应和针对江苏、安徽的防汛防台风四级应急响应。国家防总两个工作组继续在浙江、福建一线协助指导防汛防台风工作。
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Published on:03:50:15