VOA慢速英语2021 美国宇航局准备启动小行星防御试验任务（在线收听）

The American space agency NASA is preparing to launch a spacecraft that will attempt to strike an asteroid to see how the crash affects the space object's path.
美国宇航局正准备发射一颗试图撞击小行星的航天器，以了解撞击会如何影响太空物体的运动轨迹。

The test mission is designed to demonstrate a possible method for changing the direction of asteroids that are considered threats to Earth.
这次试验任务旨在展示一种改变被认为对地球构成威胁的小行星运动方向的潜在办法。

NASA is calling the world's fist planetary defense mission the Double Asteroid Redirection Test, or DART. The DART spacecraft is set to launch November 24 aboard a SpaceX Falcon 9 rocket from Vandenberg Air Force Base in California.
美国宇航局将全球首项行星防御任务称之为双小行星重定向测试（简称 DART）。这颗DART航天器将于11月24日在加州范登堡空军基地搭乘SpaceX公司的猎鹰9号火箭发射升空。

The DART spacecraft was built and is operated by the Johns Hopkins Applied Physics Laboratory in Maryland. The project is directed by NASA's Planetary Defense Coordination Office.
这颗DART航天器由马里兰州约翰霍普金斯应用物理实验室建造和运营。该项目由美国宇航局行星防御协调办公室指导。

The mission's target will be an asteroid called Dimorphos, part of a two-body asteroid system. Dimorphos is a small "moonlet" that orbits a larger asteroid named Didymos. Didymos is about 780 meters across, while Dimorphos is 160 meters. It is expected to take DART about a year to reach its target.
该任务的目标是一颗名为“二态磷”的小行星，它是一个双体小行星系统的一部分。二态磷是一颗小型的卫星，围绕着一颗名为“迪迪莫斯”的大一点的小行星运行。迪迪莫斯直径约780米，而二态磷直径为160米。预计DART航天器需要大约1年时间才能抵达目标。

Clayton Kachele is a mission manager for DART. He recently explained that the targeted asteroid system does not currently present any threat to Earth. Rather, the mission is meant to demonstrate a defensive method that could be used in the future if actual asteroid threats are identified. Kachele said the DART demonstration had been carefully designed to make sure the mission itself does not "create a threat."
克莱顿·卡谢尔是DART项目的任务经理。他最近解释说，目标小行星目前对地球没有任何威胁。更确切地讲，这次任务旨在展示一种防御方法，如果未来遇到真实的小行星威胁可以使用这个方法。卡谢尔表示，DART展示经过精心设计，以确保任何本身不会“制造威胁。”

NASA and its international partners continuously search the skies for what scientists call near-Earth objects (NEOs). Such objects include asteroids and comets that come within 50 million kilometers of Earth's orbit. Scientists estimate there are billions of asteroids and comets orbiting our sun.
美国宇航局及其国际合作伙伴不断在天空中寻找科学家们所谓的近地天体。此类天体包括距离地球轨道5000万公里以内的小行星和彗星。科学家们估计有数十亿颗小行星和彗星围绕我们的太阳运转。

NASA records show that about once a year, an asteroid around the size of an automobile enters Earth's atmosphere. Such objects turn into fireballs and burn up before reaching Earth's surface.
美国宇航局的记录显示，大约每年有一颗汽车大小的小行星进入地球大气层。这类物体在到达地球表面之前会变成火球燃烧殆尽。

About every 2,000 years, a much larger object strikes Earth and causes damage. But NASA experts say an object large enough to threaten Earth's civilization only comes along once every few million years.
大约每两千年会有一个更大的物体撞击地球并造成破坏。但是美国宇航局专家表示，大到足以威胁地球文明的物体要几百万年才出现一次。

The DART spacecraft will travel to Dimorphos to demonstrate what NASA calls a "kinetic impactor" method. This method involves the spacecraft purposefully crashing into the asteroid at a high speed to change the object's motion in space.
DART航天器将前往二态磷小行星，展示美国宇航局所谓的“动能撞击器”的方法。这种方法是指航天器故意高速撞击小行星以改变该物体在太空中的运动。

Lindley Johnson is NASA's Planetary Defense Officer. He said in a statement this method is currently considered "the most technologically mature" way to redirect a possibly dangerous asteroid.
林德利·约翰逊是美国宇航局的行星防御官。他在一份声明中表示，这种方法目前被认为是偏转潜在危险小行星的最成熟技术。

After DART strikes Dimorphos, an investigative team will use telescopes on Earth and in space to measure how much the asteroid moved.
在DART航天器撞击二态磷小行星后，一个调查小组将使用地面和太空中的望远镜来测量小行星位移了多少。

Results of the test will then be examined so that scientists can create small impact experiments in a laboratory. The team will also use DART data to build new computer models in order to understand how such defensive impacts could affect a range of near-Earth objects.
然后将检查试验结果，以便科学家可以在实验室中进行小规模冲击试验。该小组还将使用DART数据构建新的计算机模型，以了解此类防御性撞击如何影响一系列近地天体。

NASA says the DART mission is testing several new space technologies. One of them is a navigation system known as SMART Nav, which permits the spacecraft to guide itself without operator assistance.
美国宇航局表示，这次DART任务将测试几种太空新技术。其中之一被称为SMART Nav的导航系统，它允许航天器在没有操作人员协作的情况下自行引导。

Another new technology is a power-producing solar system that is expected to provide three times more electricity than similar systems used in the past.
另一项新技术是太阳能发电系统，预计可提供比过去使用的类似系统多三倍的电力。