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5年18亿英里,朱诺号下周飞抵木星

更新时间:2016-6-30 18:47:32 来源:纽约时报中文网 作者:佚名

NASA’s Juno Spacecraft Will Soon Be in Jupiter’s Grip
5年18亿英里,朱诺号下周飞抵木星

After traveling for five years and nearly 1.8 billion miles, NASA’s Juno spacecraft will announce its arrival at Jupiter with the simplest of radio signals: a three-second beep.

经过五年、将近18亿英里的飞行,美国宇航局(NASA)的“朱诺号”(Juno)探测器将以最简单的无线电信号——3秒钟的哔哔声——宣告抵达木星。

The long-awaited beep will also mark the end of a 35-minute engine burn to slow the spacecraft down and allow it to be captured by Jupiter’s gravity. NASA expects the beep to arrive at Earth at 11:53 p.m. Eastern time Monday.

人们期待已久的哔哔声,还标志着为了让朱诺号放慢速度,以便被木星引力捕获而持续了35分钟的发动机工作过程告一段落。NASA预计,哔哔声将于美国东部时间下周一晚上11点53分抵达地球。

“I can tell you when that completes, you’re going to see a lot of celebration,” said Rick Nybakken, Juno’s project manager, “because that means we’ll be in orbit around Jupiter, and that’ll be really cool.”

“我可以告诉你,哔哔声过后,你会看到很多庆祝活动。”朱诺号项目经理瑞克·尼巴肯(Rick Nybakken)说,“因为这意味着我们的探测器进入了木星的轨道,这实在是太酷了。”

Juno’s mission is to explore the enigmas beneath the cloud tops of Jupiter. How far down does the Great Red Spot storm that has swirled for centuries extend? What is inside the solar system’s largest planet?

朱诺号的任务是探索木星表面云层之下的谜团。已经肆虐了好几个世纪的大红斑(Great Red Spot)风暴向下延伸了多少?太阳系最大行星内部都有什么?

“We still have questions, and Juno is poised to begin answering them,” Diane Brown, Juno’s program executive, said during a news conference this month.

“我们仍有很多疑问,而朱诺号做好了着手回答这些问题的准备,”朱诺号项目主管黛安·布朗(Diane Brown)在本月的一场新闻发布会上表示。

Juno will be the first craft to orbit Jupiter in more than a decade. NASA’s earlier robotic explorer, Galileo, spent eight years there and sent back astounding images of the planet and its many moons. It revealed features like a large ocean under the icy crust of the moon Europa, now considered one of the most promising places to look for life elsewhere in the solar system.

朱诺号将成为十多年来第一个进入木星轨道的航天器。NASA此前的探测器“伽利略号”(Galileo)在那边逗留了八年,发回了一些令人惊叹的关于木星及其诸多卫星的图片。它发现在其卫星欧罗巴(Europa)的冰壳下,有着大片的海洋,目前,那里被视为太阳系中除地球之外最有可能发现生命的地方之一。

This time, the focus will be on Jupiter itself, and in particular what cannot be seen beneath its colorful cloud stripes.

这一次的重点将是木星本身,尤其是它那多彩的云纹下人们无法看到的东西。

“One of the primary goals of Juno is to learn the recipe for solar systems,” said Scott Bolton, a scientist at the Southwest Research Institute in San Antonio who is the principal investigator for the $1.1 billion mission. “How do you make the solar system? How do you make the planets in our solar system?”

“朱诺号的一个主要目标是研究组成太阳系的基本元素,”耗资11亿美元的朱诺号项目的首席研究员、圣安东尼奥西南研究所(Southwest Research Institute)的科学家斯科特·博尔顿(Scott Bolton)说。“太阳系是由什么组成的?太阳系内的行星又是由什么组成的?”

Jupiter is the titan among planets called the “gas giants,” with more than three times the mass of Saturn, the next largest. But it is far more than a bland ball of hydrogen and helium.

木星是“气态巨行星”中的巨人,其质量比第二大的土星大出两倍多。但它绝不仅仅是一个由氢和氦组成的平淡星球。

What particularly piques scientists’ interest are the small amounts of heavier elements like lithium, carbon and nitrogen.

尤其让科学家感兴趣的是少量的锂、碳、氮等较重元素。

“Jupiter is enriched with these elements compared to the sun,” Bolton said. “We don’t know exactly how that happened. But we know it’s really important. And the reason it’s important is the stuff that Jupiter has more of is what we’re all made out of. It’s what the Earth is made out of. It is what life comes from.”

“与太阳相比,这些元素让木星的成分相当丰富,”博尔顿说。“我们目前并不确切地知道这是怎么回事。但我们知道这非常重要。其原因是,在木星上有着更多的构成我们所有人的元素,是地球的构成元素,它们带来了生命。”

On Monday, as the main engine on the spacecraft fires, in the control room at NASA’s Jet Propulsion Laboratory in Pasadena, California, there will be nothing to control, and all anyone there will be able to do is wait and watch.

下周一,当朱诺号的主发动机启动时,在加州帕萨迪纳市的NASA喷气推进实验室(Jet Propulsion Laboratory)里,将没有什么好控制的,那里的每一个人都只能等待和观望。

If anything goes wrong, there is no way for anyone to intercede. The radio signals take 48 minutes to travel from Jupiter to Earth. By the time engineers receive word the engine firing has begun, the engine should have already switched off, with the spacecraft in orbit.

即便出了任何岔子,也没有谁能够介入。无线电信号要用48分钟时间才能从木星抵达地球。等到工程师收到发动机开始启动的消息时,发动机应该已经熄火了,而朱诺号应该也应进入轨道。

If the engine shuts off prematurely, Juno might still end up in orbit, albeit in the wrong orbit. If the engine fails, “we don’t end up in a very exciting spot,” Nybakken said.

如果发动机过早熄火,朱诺号或许仍将进入轨道,只不过是错误的轨道。如果发动机出现异常,“我们也就没什么可激动的了,”尼巴肯说。

“We haven’t studied that too much in terms of where we end up, because we’re focused on success and not failure.”

“我们并未过多地研究那样一来结局如何,因为我们专注于如何取得成功,而非如何应对失败。”

In other words, Juno would zip right past Jupiter and end up in a useless orbit around the sun.

换句话说,朱诺号将迅速掠过木星,进入一个环绕太阳的无用轨道。

Through Monday evening, mission control will receive only a series of radio “tones” — three-second bursts at different frequencies — telling the sequence of operations the spacecraft is performing. To point the engine in the correct direction, the main antenna will not be pointed at Earth, preventing more detailed telemetry. The spacecraft will also not send back any photographs or data from the instruments, which will be shut down Wednesday, five days before its arrival, and will not be turned back on until a couple of days after its arrival.

周一整晚,任务控制组只会收到一系列的无线电“声音信号”——以不同频率发出的持续三秒的信号——告知太空船正在执行的一系列任务。为了把发动机对准正确的方向,主天线不会对准地球,从而无法传输更精细的数据。“朱诺号”也不会从相关仪器上发回任何照片或数据。仪器在太空船抵达目的地的五天前,即周三被关闭,直到它到达两天后才会再次打开。

Juno is to make a series of 37 highly elliptical orbits passing over Jupiter’s north and south poles over 20 months.

在20个月时间里,“朱诺号”将沿高椭圆轨道绕木星的南北两极运行37圈。

At its farthest, it will be about 2 million miles from Jupiter. For each orbit, it will accelerate inward, passing within 3,100 miles of Jupiter’s cloud tops. The slight fluctuations in Jupiter’s gravitational pull, measured by shifts in the frequency of Juno’s radio signals, will tell the density of the planet’s interior and whether there is a rocky core within, where pressures might reach half a billion pounds per square inch.

“朱诺号”与木星的距离最远时将达到大约200万英里。每一圈,“朱诺号”都会向内加速,穿过离木星云层顶端3100英里以内的范围。木星引力的微弱波动可用“朱诺号”发出的无线电信号的频率变化来测量。它们将表明这颗行星内部的密度,以及里面是否存在一个岩石内核。木星内核的压强可能会达到五亿磅每平方英寸。

“We don’t really know if there is a core in the middle of Jupiter,” Bolton said. “If there is, it tells you sort of when and how and a little bit of where Jupiter must have formed.”

“我们其实并不知道木星中心是否有一个核,”博尔顿说。“如果有,它会让我们在一定程度上知道木星一定是在何时以何种方式形成的,对地点也会有一些提示。”

Juno’s science instruments include one to measure Jupiter’s powerful magnetic fields and an infrared camera to observe the glowing auroras around the poles. At depth, increasing pressures transform hydrogen from a gas into a liquid. At even greater depths, the hydrogen is squeezed so tightly that the electrons squirt out, changing it into a metal. It is probably the churning of liquid metallic hydrogen that generates the magnetic fields.

“朱诺号”携带的科学仪器中,有一台用来测量木星强大的磁场的仪器,还有一部红外摄像机,用来观察木星两极周围的极光。在深处,不断增加的压力会把氢气从气体变成液体。更深处,氢气受到严重挤压,导致电子溢出,氢气变成金属。可能正是液态金属氢的翻滚产生了磁场。

After the first two orbits, during which engineers will check if the spacecraft and instruments are working properly, Juno is to fire its engine again to move into the orbit for making its scientific measurements.

运行头两圈期间,工程师会检查太空船和仪器是否正常工作。之后,“朱诺号”的发动机将再次点火,以便进入轨道进行科学测量。

Although the craft are very different in appearance, much of Juno’s electronics and programming are based on the design of Mars Reconnaissance Orbiter, an earlier spacecraft also built by Lockheed Martin. “It’s just configured in a different format,” Guy Beutelschies, the director of interplanetary missions at Lockheed Martin, said in an interview.

尽管在外形上有很大的不同,但“朱诺号”的大量电子器件和程序都是基于火星勘测轨道飞行器(Mars Reconnaissance Orbiter)的设计。后者是早前的一款太空飞行器,同样由洛克希德·马丁公司建造。“只是采用了不同的配置形式,”该公司负责星际任务的总监盖伊·博伊特尔席斯(Guy Beutelschies)接受采访时说。

Instead of developing electronic circuits that could operate in Jupiter’s intense radiation, Lockheed Martin used the same circuitry as Mars Reconnaissance Orbiter but shielded it within the half-inch-thick walls of a 400-pound titanium vault measuring about 1 yard on each side.

洛克希德·马丁公司没有开发可在木星的强辐射中工作的电子电路,而是使用了和火星勘测轨道飞行器一样的电路系统。不过,他们把电路系统放进了一个可承受400磅重量的钛保护箱里,箱体边长约一码,壁厚半英寸。

Unlike earlier missions to the outer solar system, Juno is powered by sunlight, not plutonium. Three solar panels 30 feet long with a total of 18,698 solar cells gather the dim sunlight to produce about 500 watts.

不同于早前探索外太阳系的任务,“朱诺号”的动力来自太阳光,而非钚。飞行器上有三块30英尺长的太阳能电池板,上面总计有18698块太阳能电池。它们将微弱的太阳光收集在一起,产生大约500瓦电能。

Even if everything goes better than planned, the mission will not last much beyond the planned 20 months. Despite the titanium armoring, “we know the radiation is going to kill us,” Beutelschies said.

即便一切都比计划的更顺利,此次任务持续的时间也不会超出原计划的20个月太久。尽管有钛做的盔甲,“我们知道辐射会要了我们的命,”博伊特尔席斯说。

Juno is expected to receive a radiation dose equivalent to more than 100 million dental X-rays.

“朱诺号”预计会受到的辐射,相当于照超过一亿次口腔X光。

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