美国国家公共电台 NPR NASA Probe Lands Safely On Martian Surface

 

MICHEL MARTIN, HOST:

Mars is about to get a new visitor from Earth tomorrow. If all goes well, a NASA probe called InSight will land near the Martian equator. Its mission is to study the interior of the planet. But, before it can carry out its mission, it has to land safely. That means slowing down from 12,300 mph as it enters the Martian atmosphere to a complete stop on the ground 6.5 minutes later. NPR science correspondent Joe Palca explains the steps involved in making that happen.

JOE PALCA, BYLINE¹: The person responsible for getting InSight safely to the Martian surface is Rob Grover. He's in charge of the team that designed the landing scheme.

ROB GROVER: The landing is all completely automatic and autonomous². We have no ability to actually kind of fly the lander to the surface.

PALCA: That's because it's a 6.5-minute ride to the surface, but it takes a radio signal longer than that to reach Mars, so real-time control is out of the question. So here's what's supposed to happen. First, the probe gets rid of what's called the cruise stage. That's a part of the spacecraft only needed while InSight is traveling from Earth to Mars.

GROVER: We eject that from the vehicle seven minutes before we're going to hit the top of the atmosphere.

PALCA: Next, the spacecraft turns so its heat shield is pointing in the right direction. As the probe drops towards the surface, air molecules³ in the Martian atmosphere strike the heat shield, causing it to heat up and the craft to slow down.

GROVER: Believe it or not, 99 percent of the energy that we have coming in from space is actually bled off by the atmosphere.

PALCA: The heat shield does its thing for about 3.5 minutes.

GROVER: The next big event is parachute deploy⁴.

PALCA: Grover says, at this point, the probe is still traveling faster than the speed of sound, so they have to use a special parachute designed for supersonic speeds. When the probe is about four miles above the surface, the radar⁵ comes on. It will help inform the onboard navigation how to steer⁶ the craft once it cuts loose the parachute and lands using rockets.

GROVER: The whole descent under rocket power takes about 40 seconds or so. We have 12 small descent engines grouped around the bottom of the lander. They're providing the thrust the slowest down the final kilometer.

PALCA: Even though they can't do anything to help InSight as it descends⁷, mission managers should be able to watch its progress.

GROVER: It'll be sending back data in real time, and the MarCO spacecraft will be helping⁸ with that, relaying the data.

PALCA: MarCO is a small spacecraft that's flying to Mars with InSight.

ANNE MARINAN: It's about the size of a cereal box

PALCA: A family-size cereal box, but still. Anne Marinan is systems engineer on MarCO. She says MarCO is one of a new generation of really small satellites called cubesats.

MARINAN: Cubesats were originally developed as a way to easily give students, essentially⁹, access to space.

PALCA: But Marinan says cubesats are now being used at NASA to test new technologies. In MarCO's case, the new technology is communications equipment that will relay InSight's telemetry data back to Earth. There are two nearly identical MarCO spacecraft that launched with InSight last May and have been trailing the probe on its flight to Mars.

MARINAN: To start out with, we're behind. But by the time InSight lands, we'll be beyond Mars.

PALCA: And you're not stopping

MARINAN: No.

PALCA: Marinan says the two MarCO spacecraft keep on going past Mars and into space. Their communications relay mission is over. With luck, InSight's mission on the Martian surface will just be beginning.

Joe Palca, NPR News.

1 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

2 autonomous   

adj.自治的；独立的

参考例句：

• They proudly declared themselves part of a new autonomous province.他们自豪地宣布成为新自治省的一部分。
• This is a matter that comes within the jurisdiction of the autonomous region.这件事是属于自治区权限以内的事务。

3 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。

4 deploy   

v.（军）散开成战斗队形，布置，展开

参考例句：

• The infantry began to deploy at dawn.步兵黎明时开始进入战斗位置。
• The president said he had no intention of deploying ground troops.总统称并不打算部署地面部队。

5 radar   

n.雷达，无线电探测器

参考例句：

• 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。

6 steer   

vt.驾驶，为…操舵；引导；vi.驾驶

参考例句：

• If you push the car, I'll steer it.如果你来推车，我就来驾车。
• It's no use trying to steer the boy into a course of action that suits you.想说服这孩子按你的方式行事是徒劳的。

7 descends   

v.下来( descend的第三人称单数 )；下去；下降；下斜

参考例句：

• This festival descends from a religious rite. 这个节日起源于宗教仪式。 来自《简明英汉词典》
• The path descends steeply to the village. 小路陡直而下直到村子。 来自《简明英汉词典》

8 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

9 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。