VOA标准英语2014--Scientists Deliberate Cleaning Space Junk
时间：2018-12-08 作者：英语课 分类：VOA标准英语2014年(六月)
Scientists Deliberate Cleaning Space Junk
WASHINGTON — Everything that we launch into an orbit around the earth eventually becomes space debris 1. Scientists say the increasing number of unusable objects circling our planet is threatening functioning satellites as well as humans flying into space. The European Space Agency, or ESA, plans to solve the problem.
The U.S. space agency NASA says there are half a million pieces of space debris, with more than 20,000 larger than an apple. Most are speeding along at about seven kilometers per second, or more than 25,000 kilometers per hour.
At that speed, the impact of even a cherry-sized piece of metal is enormous, said the deputy head of ESA Space Debris Office, Holger Krag.
“At this velocity 2 both objects will shatter into pieces, this will be bad for the object concerned but it will also be bad for the rest of the environment, because we will add additional fragments which again then are candidates for future collisions,” said Krag.
Scientists monitor the path of space debris and sometimes reposition satellites or even the International Space Station to avoid collisions. But, Krag said, keeping track of the orbiting junk requires powerful sensors 3.
“The U.S. Space Strategic Command is in possession of those sensors, it's a relic 4 of the Cold War, to detect approaching missiles. And it is a global network of radar 5 and telescope stations on the ground observing space continuously all of the time,” said Krag.
Loss of communications, GPS or a scientific satellite could have potentially devastating 6 effects, so scientists are exploring options for removing dangerous debris.
“That means planning a mission that goes there, approaches, rendezvous 7 and captures the object, berths 8 it, and then does the controlled orbit maneuver 9. This is a very complex technology that will be required for that,” explained Krag.
Several designs are in consideration, such as a satellite that fires beams of charged particles that gradually slow down flying objects, dragging them into the atmosphere where they will burn up.
Smaller objects could be shot down with ground-based lasers, while large ones that could break up into thousands of smaller pieces may be brought down with special robotic satellites.
Even though such missions could cost up to $200 million, Krag says they should start as soon as possible to prevent the chance of larger collisions that could send many thousands of additional pieces on a deadly flight around the earth.
- After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
- Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。
- Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
- The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。
- There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
- Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句
- This stone axe is a relic of ancient times.这石斧是古代的遗物。
- He found himself thinking of the man as a relic from the past.他把这个男人看成是过去时代的人物。
- They are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
- Enemy ships were detected on the radar.敌舰的影像已显现在雷达上。
- It is the most devastating storm in 20 years.这是20年来破坏性最大的风暴。
- Affairs do have a devastating effect on marriages.婚外情确实会对婚姻造成毁灭性的影响。
- She made the rendezvous with only minutes to spare.她还差几分钟时才来赴约。
- I have a rendezvous with Peter at a restaurant on the harbour.我和彼得在海港的一个餐馆有个约会。