VOA常速英语:NASA to Launch Telescope That Will See Into the Past

Light from distant galaxies, billions of light years away from us, is so faint that it shifts from the visible spectrum ino the infrared segment and becomes heat. It can be detected only by instruments cooled to almost absolute zero. The U.S. space agency NASA is building a new space telescope that will be cool in both senses of the word.

In the "clean room" of  NASA's Goddard Space Center, outside Washington, engineers are building the new infrared space telescope named after NASA's second director James Webb.  They hope that when deployed in 2014. it will help them look many billions of light years into the past.

The deputy senior project scientist for the telescope, Jonathan Gardner, says its 6.5-meter-wide (21-foot-wide) mirror will be able to detect extremely faint infrared signals, because it will be kept at a very cold temperature, close to absolute zero (minus 459 degrees F).  A large radiator screen, the size of a tennis court, will shield it from the warmth of the sun and earth.

But how will the scientists be able to look into the past? 

"We can see back in time because light takes time to get from there to here.  So, as we look further and further away, it takes longer and longer for the light to get from where it's emitted to here and we can actually see backwards in time.  And if we look far enough away, we're actually looking back to when the universe was much younger than it is today, when the light was emitted from these galaxies.  We're looking at the universe when it was younger and we're looking back most of the way to the Big Bang," Gardner explained.

Gardner says scientists want to know when the first galaxies were formed.  What did they look like?  What were their features?  How were the stars born?  Many are also hoping to find something we don't yet even know exists.

The telescope will be equipped with three infrared cameras, more sensitive than ever before.  But its most interesting parts are the special gold-coated mirrors that form the big primary mirror.

"The primary mirror is made up of 18 hexagonal segments, as you can see on the model.  Each of these segments is supported by actuators which can move.  So, during the lifetime of the mission, when it's in orbit, we can send the commands to move these mirrors and that way we can constantly keep them in alignment, in a common focus," he said.

Jonathan Gardner says the new telescope will be available to scientists around the world, whose projects will be chosen according to their scientific value.

"We will ask for proposals from astronomers.  Any astronomer, at any university, in any country can write a proposal for what they want to do with the telescope.  The committee, probably about a hundred astronomers, will consider these proposals, and they will read all the proposals and choose the very best science that will be done that year," Gardner stated.

Gardner says the process makes sure that the telescope is doing the best science it can, answering the most important, relevant, current questions.

The new telescope is scheduled to be launched in 2014 and is expected to function around 10 years.  The life expectancy is limited by the quantity of fuel in its booster jets, used for periodical adjustment of its position in space.  The telescope will be stationed a million-and-a-half kilometers, or 932,000 miles, from earth, so astronauts will not be able to visit and replenish its fuel.