VOA标准英语2015--James Webb Space Telescope Progresses Toward Launch

James Webb Space Telescope Progresses Toward Launch

WASHINGTON—

While the space community is looking back this week to celebrate the 25th anniversary of the launch of the Hubble Space Telescope, workers in an airtight cleanroom at Goddard Space Flight Center in Greenbelt, Maryland, are looking ahead three years, to the launch of its successor, the James Webb Space Telescope.

The $8 billion Webb and the Hubble have a lot in common. Both operate in the vacuum of space, have mirrors that collect light from distant stars, use radio signals to transmit images and get power from the sun.

But the similarities end there, said Matt Greenhouse, a veteran project scientist for the James Webb Space Telescope.

“One of the biggest differences between the Webb and the Hubble is that the Webb is designed to be an infrared¹ telescope and will see very primordial² objects that are among the oldest objects in the universe,” he noted³.

Greenhouse said the infrared capability⁴ will allow astronomers⁵ using the Webb to peer through the clouds and dust in space that obscure the view.  

“With spectroscopy, which is spreading light out into component⁶ colors and observing one at a time, we can see features of individual atoms in molecules⁷ in space that will allow us to understand the chemistry that occurs in space. Many of those features only exist in the infrared,” he said.

Hubble can see a small segment of the infrared spectrum⁸, but primarily captures visible and ultraviolet light.  

Size matters

The Webb, named for the man who ran NASA from 1961-1968, will be sent 1.5 million kilometers above Earth's atmosphere, far beyond Hubble, which flies in low Earth orbit.

Its mirror is 6.25 times bigger than Hubble's, which will enable it to observe objects that are fainter and farther away. Made from lightweight beryllium and coated in gold for its reflective qualities, the segmented mirror was too large for the rocket that would carry it into orbit. So it had to be designed to unfold in space.

Its design also had to ensure that the instrument payload would be kept extremely cold, at approximately minus 200 degrees Celsius⁹. Greenhouse explained,“The reason for that is because anything above absolute zero emits infrared light. If we didn’t cool it, it would be blinded by its own infrared emission¹⁰.”

The Webb is shielded by a multi-layer sunscreen to keep light from the Sun and reflected light from the Earth and Moon from heating up the telescope and blocking any astronomical¹¹ signal. For that to work, Greenhouse said, the Webb must be in an orbit with those three bodies lined up in about the same direction. “When it’s in that shadow under the sunscreen, it will cool naturally to this cryogenic temperature."

All those cutting-edge technologies combine to make the Webb 100 times more powerful than Hubble.  

“We have some special capability in this instrument payload to observe as many as 100 galaxies¹² at a time and obtain their spectrum simultaneously,” Greenhouse said proudly.   

No second chances

As launch day approaches, Greenhouse said the assembly and testing now underway leave no room for error, like the mistake that sent Hubble into space with a flawed mirror.

“One of the big things we learned from the Hubble is the Hubble didn’t do something called an end-to-end optical test, where we take the entire observatory¹³ and shine light through it the way it will be done in space and make sure that everything works,” he said.

Unlike the Hubble, the Webb cannot be repaired in space, so the team has one chance to get it right.  

Greenhouse, who has been with the Webb for almost the entire life of the project, expects the new telescope to rewrite textbooks much in the same way that Hubble has.

“Like Hubble, it’s likely that after this mission is over, we will look back and find that the most important discoveries and the most important questions that were answered are not the questions that we had in mind when we designed and built it,” he said.

The Hubble has operated much longer than expected, and Greenhouse said he hopes for the same lifespan for the Webb, which could last 10 years or longer.

The James Webb Space Telescope is a project of the U.S., European and Canadian space agencies.

1 infrared   

adj./n.红外线(的)

参考例句：

• Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
• Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。

2 primordial   

adj.原始的；最初的

参考例句：

• It is the primordial force that propels us forward.它是推动我们前进的原始动力。
• The Neanderthal Man is one of our primordial ancestors.的尼安德特人是我们的原始祖先之一.

3 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

4 capability   

n.能力；才能；(pl)可发展的能力或特性等

参考例句：

• She has the capability to become a very fine actress.她有潜力成为杰出演员。
• Organizing a whole department is beyond his capability.组织整个部门是他能力以外的事。

5 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

6 component   

n.组成部分，成分，元件；adj.组成的，合成的

参考例句：

• Each component is carefully checked before assembly.每个零件在装配前都经过仔细检查。
• Blade and handle are the component parts of a knife.刀身和刀柄是一把刀的组成部分。

7 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

8 spectrum   

n.谱，光谱，频谱；范围，幅度，系列

参考例句：

• This is a kind of atomic spectrum.这是一种原子光谱。
• We have known much of the constitution of the solar spectrum.关于太阳光谱的构成，我们已了解不少。

9 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

10 emission   

n.发出物，散发物；发出，散发

参考例句：

• Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。
• Finally,the way to effectively control particulate emission is pointed out.最后，指出有效降低颗粒排放的方向。

11 astronomical   

adj.天文学的，（数字）极大的

参考例句：

• He was an expert on ancient Chinese astronomical literature.他是研究中国古代天文学文献的专家。
• Houses in the village are selling for astronomical prices.乡村的房价正在飙升。

12 galaxies   

星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）

参考例句：

• Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
• We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。

13 observatory   

n.天文台，气象台，瞭望台，观测台

参考例句：

• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。