Fred Jansen: How to land on a comet

翻译人员: chunhua zhang 校对人员: Alan Wang

I'd like to take you on the epic quest of the Rosetta spacecraft.

我想带你们进入罗塞塔号 史诗般的探险中去。

To escort and land the probe on a comet,

护送这个探测器在一颗彗星上着陆，

this has been my passion for the past two years.

是我过去两年以来的热情所在。

In order to do that,

为了实现这个目标，

I need to explain to you something about the origin of the solar system.

我需要向你们解释 关于太阳系起源的一些东西。

When we go back four and a half billion years,

让我们回到45亿年前，

there was a cloud of gas and dust.

有一个充满气体和灰尘的云团。

In the center of this cloud, our sun formed and ignited.

在这个云团的中心， 我们的太阳在那里形成并燃烧。

Along with that, what we now know as planets, comets and asteroids formed.

与此同时，那些现在被我们称为行星、 彗星和小行星的天体也形成了。

What then happened, according to theory,

随后，根据理论，

is that when the Earth had cooled down a bit after its formation,

在地球形成并且温度 开始降低了一些的时候，

comets massively impacted the Earth and delivered water to Earth.

彗星极大地影响了地球， 并向地球输送了水分。

They probably also delivered complex organic material to Earth,

它们可能还向地球输送了 复杂的有机物质，

and that may have bootstrapped the emergence of life.

而那有可能诱导了生命的出现。

You can compare this to having to solve a 250-piece puzzle

你们可以将这一过程与完成一个 250块的拼图相比，

and not a 2,000-piece puzzle.

而不是完成一个2000块的拼图。

Afterwards, the big planets like Jupiter and Saturn,

然后，像木星和土星这样的大行星，

they were not in their place where they are now,

它们当时并不在今天所处的位置，

and they interacted gravitationally,

它们会通过引力相互作用，

and they swept the whole interior of the solar system clean,

并将整个太阳系内部打扫干净了，

and what we now know as comets

而我们现在称为彗星的天体

ended up in something called the Kuiper Belt,

最终到了一个叫做“柯伊伯带”的地方，

which is a belt of objects beyond the orbit of Neptune.

这是一个海王星轨道以外的天体聚集带。

And sometimes these objects run into each other,

有时这些天体会相互碰撞，

and they gravitationally deflect,

并且发生了重力转移，

and then the gravity of Jupiter pulls them back into the solar system.

木星的引力随后将它们拉回了太阳系。

And they then become the comets as we see them in the sky.

然后它们就变成了 我们在天空中所见到的彗星。

The important thing here to note is that in the meantime,

需要注意的重点是，在此期间，

the four and a half billion years,

这45亿年间，

these comets have been sitting on the outside of the solar system,

这些彗星一直安坐在太阳系之外，

and haven't changed --

并且从没变过——

deep, frozen versions of our solar system.

深沉、冻结版的太阳系。

In the sky, they look like this.

在空中，它们看起来是这样的。

We know them for their tails.

我们通过它们的尾巴认识它们。

There are actually two tails.

这里事实上有两条尾巴。

One is a dust tail, which is blown away by the solar wind.

一条是尘埃尾，是被太阳风吹出来的。

The other one is an ion tail, which is charged particles,

另一条是离子尾，是带电粒子，

and they follow the magnetic field in the solar system.

它们受太阳系磁场的影响。

There's the coma,

可以看到慧发，

and then there is the nucleus, which here is too small to see,

还有慧核，小到几乎看不见，

and you have to remember that in the case of Rosetta,

但是你们要记住在罗塞塔号的案例中，

the spacecraft is in that center pixel.

航天器就在那个中心像素上。

We are only 20, 30, 40 kilometers away from the comet.

我们距离这颗彗星 只有20、30、40千米。

So what's important to remember?

那么需要记住哪些关键点呢？

Comets contain the original material from which our solar system was formed,

彗星中含有来自太阳系 形成时的原始物质，

so they're ideal to study the components

因此它们是用来研究

that were present at the time when Earth, and life, started.

地球和生命起源时 所出现的成份的理想对象。

Comets are also suspected

彗星还很可能

of having brought the elements which may have bootstrapped life.

带来了那些引发了生命起源的元素。

In 1983, ESA set up its long-term Horizon 2000 program,

1983年，欧洲航天局开始了 长期的地平线2000计划，

which contained one cornerstone, which would be a mission to a comet.

它包含了一个基础项目， 可能是一个造访彗星的任务。

In parallel, a small mission to a comet, what you see here, Giotto, was launched,

同时，一个小的造访彗星的任务， 就是你们在这里看到的乔托号，启动了，

and in 1986, flew by the comet of Halley with an armada of other spacecraft.

1986年，它与其它航天器组成的 舰队飞经了哈雷彗星。

From the results of that mission, it became immediately clear

那次任务的结果清晰地表明，

that comets were ideal bodies to study to understand our solar system.

彗星是用来研究太阳系的理想天体。

And thus, the Rosetta mission was approved in 1993,

因此，1993年，罗塞塔任务被批准，

and originally it was supposed to be launched in 2003,

最初它被设定在2003年发射，

but a problem arose with an Ariane rocket.

但是后来由于阿里亚娜火箭 出现问题而被取消。

However, our P.R. department, in its enthusiasm,

然而，我们的公关部门，充满热情，

had already made 1,000 Delft Blue plates

他们已经制作了1000个 代尔夫特蓝色瓷盘，

with the name of the wrong comets.

并印上了那些错误的彗星名字。

So I've never had to buy any china since. That's the positive part.

因此从那以后我没有买过任何的瓷器。 这是积极的一面。

(Laughter)

（笑声）

Once the whole problem was solved,

在所有的问题被解决之后，

we left Earth in 2004

罗塞塔在2004年离开了地球，

to the newly selected comet, Churyumov-Gerasimenko.

飞向重新被选定的彗星， 丘留莫夫·格拉西缅科彗星。

This comet had to be specially selected

这颗彗星是被特别选中的，

because A, you have to be able to get to it,

因为首先，你得能够到达它，

and B, it shouldn't have been in the solar system too long.

其次，它没有在太阳系待太长时间。

This particular comet has been in the solar system since 1959.

这颗特别的彗星在1959年进入太阳系。

That's the first time when it was deflected by Jupiter,

那是它被木星偏转后第一次来到太阳系，

and it got close enough to the sun to start changing.

并且它跟太阳的距离近到 足够让它发生变化。

So it's a very fresh comet.

所以这是一颗非常新的彗星。

Rosetta made a few historic firsts.

罗塞塔取得了很多历史性的突破。

It's the first satellite to orbit a comet,

它是首个进入彗星轨道的人造卫星，

and to escort it throughout its whole tour through the solar system --

并且伴随彗星走过了 它的整个太阳系之旅——

closest approach to the sun, as we will see in August,

到达了距离最短的近日点， 这个我们将会在8份看到，

and then away again to the exterior.

然后重新离开太阳系。

这是第一次有航天器在彗星上着陆。

It's the first ever landing on a comet.

We actually orbit the comet using something which is not

我们实际上在罗塞塔号上 使用了一些通常不会在其他航天器上

normally done with spacecraft.

使用的彗星轨道环绕技术。

Normally, you look at the sky and you know where you point and where you are.

通常，你们看看天空， 就会知道方位和坐标。

In this case, that's not enough.

但是在这个案例中，那还不够。

We navigated by looking at landmarks on the comet.

我们通过观察彗星上的地标来导航。

We recognized features -- boulders, craters --

我们辨别那些特征——卵石、环形山——

and that's how we know where we are respective to the comet.

然后我们就知道我们处在彗星上 哪个对应的区域。

And, of course, it's the first satellite to go beyond the orbit of Jupiter

当然，这也是第一次 使用太阳能电池飞跃

on solar cells.

木星轨道的航天器。

Now, this sounds more heroic than it actually is,

这听起来比事实更称得上是壮举，

because the technology to use radio isotope thermal generators

因为那时放射性同位素热电机的技术

wasn't available in Europe at that time, so there was no choice.

在欧洲尚未得到应用，所以当时别无选择。

But these solar arrays are big.

但是这些太阳能电池板很大。

This is one wing, and these are not specially selected small people.

这是它的一个侧翼， 下面这些可不是特意挑选的矮小的人。

They're just like you and me.

他们是跟你我一样的正常人。

(Laughter)

（笑声）

我们有两个这样的侧翼，65平米。

We have two of these wings, 65 square meters.

Now later on, of course, when we got to the comet,

随后，当然，当我们飞向这颗彗星时，

you find out that 65 square meters of sail

你们会发现扬着一个65平米的帆

close to a body which is outgassing is not always a very handy choice.

向一个正在排气的天体靠近， 并不总是一个便捷的选择。

Now, how did we get to the comet?

我们是怎么到达这颗彗星的呢？

Because we had to go there for the Rosetta scientific objectives

因为我们得去一个十分遥远的地方 去完成罗塞塔号的

very far away -- four times the distance of the Earth to the sun --

科学目标—— 是地球到太阳距离的4倍——

and also at a much higher velocity than we could achieve with fuel,

而且以一个我们用普通燃料 无法达到的速度。

because we'd have to take six times as much fuel as the whole spacecraft weighed.

因为我们得携带六倍于 航天器本身重量的燃料。

So what do you do?

那要怎么做呢？

You use gravitational flybys, slingshots,

在一个非常低的高度，大概几千公里，

where you pass by a planet at very low altitude,

经过一个行星时， 利用引力的拉扯效应和

a few thousand kilometers,

弹力作用，

and then you get the velocity of that planet around the sun for free.

你就会直接获得跟那颗行星同样的 绕日运行速度。

我们尝试过很多次。

We did that a few times.

在地球上，火星上 ， 然后又在地球上试过两次，

We did Earth, we did Mars, we did twice Earth again,

and we also flew by two asteroids, Lutetia and Steins.

我们还飞掠了两颗小行星， 鲁特西亚和斯坦斯。

Then in 2011, we got so far from the sun that if the spacecraft got into trouble,

到了2011年，我们已经距离太阳太远了， 如果这个航天器遇到问题，

we couldn't actually save the spacecraft anymore,

我们根本没办法挽救它了，

so we went into hibernation.

所以我们进入了冬眠状态。

Everything was switched off except for one clock.

除了一个计时器，所有的仪器都关掉了。

Here you see in white the trajectory, and the way this works.

这里你们看到白色的是它的轨道， 以及运动轨迹。

You see that from the circle where we started,

可以看到从一开始的这个圆，

the white line, actually you get more and more and more elliptical,

这条白线， 我们可以得到越来越多的椭圆，

and then finally we approached the comet

最终我们在2014年5月靠近了这颗彗星，

in May 2014, and we had to start doing the rendezvous maneuvers.

然后我们得开始做会合减速。

On the way there, we flew by Earth and we took a few pictures to test our cameras.

在途中，我们飞经地球并拍了一些照片 以测试我们的相机。

This is the moon rising over Earth,

这是月球在地球另一侧升起，

and this is what we now call a selfie,

这是我们现在所称的自拍，

which at that time, by the way, that word didn't exist. (Laughter)

顺便说一下，那个时候“自拍” 这个词还不存在。（笑声）

It's at Mars. It was taken by the CIVA camera.

这是在火星上， 由彗星红外与可见光分析仪 相机拍摄的。

That's one of the cameras on the lander,

那是着陆器上的一台相机，

and it just looks under the solar arrays,

它看起来处在太阳能电池板的下方，

and you see the planet Mars and the solar array in the distance.

你们能看到火星和太阳能电池板 出现在远处。

Now, when we got out of hibernation in January 2014,

当我们在2014年1月从冬眠中被唤醒后，

we started arriving at a distance

我们开始前进，并在5月份

of two million kilometers from the comet in May.

到达了距离这个彗星 200万公里的地方。

However, the velocity the spacecraft had was much too fast.

然而，这个航天器的速度太快了。

We were going 2,800 kilometers an hour faster than the comet, so we had to brake.

我们的时速要比这颗彗星快2800公里， 因此我们需要刹一刹车。

We had to do eight maneuvers,

我们得做8次减速，

and you see here, some of them were really big.

可以看到， 其中的一些减速幅度真的很大。

We had to brake the first one by a few hundred kilometers per hour,

我们的第一次减速需要 将速度每小时降低数百公里，

and actually, the duration of that was seven hours,

事实上这个过程花了7个小时，

and it used 218 kilos of fuel,

消耗了218公斤的燃料，

and those were seven nerve-wracking hours, because in 2007,

这也是令人心惊胆战的7小时， 因为在2007年，

there was a leak in the system of the propulsion of Rosetta,

罗塞塔号的推进系统出现了一处泄漏，

and we had to close off a branch,

我们不得不关掉了一个分路，

so the system was actually operating at a pressure

因此推进系统是在超出设计能力的

which it was never designed or qualified for.

压力下运行的。

Then we got in the vicinity of the comet, and these were the first pictures we saw.

然后我们到达了这颗彗星的附近， 这是我们看到的第一批照片。

The true comet rotation period is 12 and a half hours,

这颗彗星真实的自转周期是12.5个小时，

so this is accelerated,

所以这是加速播放的，

but you will understand that our flight dynamics engineers thought,

但是你们肯定能够理解我们的 飞行动力学工程师的想法，

this is not going to be an easy thing to land on.

这不是一个容易登陆的东西。

We had hoped for some kind of spud-like thing

我们曾经幻想过它是某种 形状像土豆一样的

where you could easily land.

容易登陆的东西。

But we had one hope: maybe it was smooth.

但我们扔抱着一线希望： 也许它比较平坦。

No. That didn't work either. (Laughter)

不，它的表面还很粗糙。（笑声）

So at that point in time, it was clearly unavoidable:

因此，当时我们迫不得已 做出了如下选择：

we had to map this body in all the detail you could get,

我们得利用收集到的所有细节 去绘制这个天体的地图，

because we had to find an area which is 500 meters in diameter and flat.

因为我们得找到一块直径500米的平地。

Why 500 meters? That's the error we have on landing the probe.

为什么是500米？ 这是我们让探测器着陆时的误差。

So we went through this process, and we mapped the comet.

于是我们立即采取行动 并绘制出了彗星表面的地图。

We used a technique called photoclinometry.

我们采用了一种叫做 照相测斜术的技术。

You use shadows thrown by the sun.

利用太阳拋下的阴影。

What you see here is a rock sitting on the surface of the comet,

你们现在看到的是一块 位于彗星表面的岩石，

and the sun shines from above.

而阳光从上面照下来。

From the shadow, we, with our brain,

透过阴影，我们用大脑，

can immediately determine roughly what the shape of that rock is.

可以立刻大致判断出这块岩石的形状。

You can program that in a computer,

你可以编一套那样的程序，

you then cover the whole comet, and you can map the comet.

然后覆盖整颗彗星， 就可以绘制出它表面的形貌图了。

For that, we flew special trajectories starting in August.

为此，我们从8月份开始沿着 一种特殊的轨迹飞行。

First, a triangle of 100 kilometers on a side

首先，在100公里外的地方沿着一个

at 100 kilometers' distance,

边长为100公里的三角形飞行，

and we repeated the whole thing at 50 kilometers.

然后将三角形的边长改为50公里， 再重复整个过程。

At that time, we had seen the comet at all kinds of angles,

那时候，我们已经通过所有的角度 观察过这颗彗星了，

and we could use this technique to map the whole thing.

我们也可以利用这一技术绘制出 整个彗星的表面形貌。

Now, this led to a selection of landing sites.

现在，到了选择登陆地点的时候了。

This whole process we had to do, to go from the mapping of the comet

我们要做的就是在60天内， 通过绘制这颗彗星的形貌图，

to actually finding the final landing site, was 60 days.

来找到一个最终的登陆地点。

We didn't have more.

我们没有更多的时间。

To give you an idea, the average Mars mission

对比一下，平均来说，火星上的任务

takes hundreds of scientists for years to meet

需要成百上千的科学家花数年的时间

about where shall we go?

去找到一个登陆地点。

We had 60 days, and that was it.

但我们只有60天，就那么多了。

We finally selected the final landing site

我们最终选定了一个登陆点，

and the commands were prepared for Rosetta to launch Philae.

并且让罗塞塔号发送菲莱号的 指令也准备好了。

The way this works is that Rosetta has to be at the right point in space,

不过前提条件是罗塞塔号 得处在空中的正确位置，

and aiming towards the comet, because the lander is passive.

并且瞄准这颗彗星，因为着陆器是被动的。

The lander is then pushed out and moves towards the comet.

它需要被推出并飞向彗星。

Rosetta had to turn around

罗塞塔号得转过身，

to get its cameras to actually look at Philae while it was departing

以便使它的相机在 菲莱飞离的过程中能对着它，

and to be able to communicate with it.

并且能与它进行交流。

Now, the landing duration of the whole trajectory was seven hours.

整个着陆过程花了7个小时。

Now do a simple calculation:

简单的计算一下：

if the velocity of Rosetta is off by one centimeter per second,

如果罗塞塔号的速度误差是1厘米每秒，

seven hours is 25,000 seconds.

7个小时就是25000秒，

That means 252 meters wrong on the comet.

那就意味着着陆器 登陆彗星时的误差是252米。

So we had to know the velocity of Rosetta

因此我们得将罗塞塔的速度误差

much better than one centimeter per second,

精确到小于1厘米每秒，

and its location in space better than 100 meters

而它在太空中远离地球5亿公里的位置，

at 500 million kilometers from Earth.

误差要精确到100米以内。

That's no mean feat.

那不是一件易事。

Let me quickly take you through some of the science and the instruments.

让我快速的介绍一下 其中的一些科学理论和仪器。

I won't bore you with all the details of all the instruments,

我不会介绍所有仪器的细节， 以免你们听得一头雾水，

but it's got everything.

但想帮助你们了解一些概念。

We can sniff gas, we can measure dust particles,

我们可以检测气体，测量粉尘，

the shape of them, the composition,

测它们的形状和成分，

there are magnetometers, everything.

这里有磁力仪等等我们需要的一切。

This is one of the results from an instrument which measures gas density

这是一部仪器所测到的 罗塞塔号所处位置的

at the position of Rosetta,

气体密度的结果，

so it's gas which has left the comet.

这是从彗星上释放出来的气体。

The bottom graph is September of last year.

下面的图是去年9月份的。

There is a long-term variation, which in itself is not surprising,

这是一个长期的变化， 对于它本身来说可能不算什么，

but you see the sharp peaks.

但是看看那些尖峰。

This is a comet day.

这就是彗星上的一天。

You can see the effect of the sun on the evaporation of gas

你们可以看到太阳对于气体蒸发的影响，

and the fact that the comet is rotating.

以及彗星是旋转的这一事实。

So there is one spot, apparently,

这里有一个点，很明显地，

where there is a lot of stuff coming from,

很多东西都出自那里，

it gets heated in the Sun, and then cools down on the back side.

它被太阳加热，然后在背面冷却。

And we can see the density variations of this.

我们可以看看这里的密度差异。

These are the gases and the organic compounds

这些是我们已经测量到的

that we already have measured.

气体和有机化合物。

You will see it's an impressive list,

看得出这是一份令人印象深刻的列表，

and there is much, much, much more to come,

并且还会有更多更多的东西出现在上面，

because there are more measurements.

因为我们还进行了更多的测量。

事实上，这会儿正有一个 在休斯顿举行的会议，

Actually, there is a conference going on in Houston at the moment

where many of these results are presented.

这些数据会在会上被展示出来。

Also, we measured dust particles.

我们还测量了尘粒。

Now, for you, this will not look very impressive,

对于你们来说，这可能没什么太大的意义，

but the scientists were thrilled when they saw this.

但是当科学家们 看到这个的时候都非常激动。

Two dust particles:

两颗尘粒：

the right one they call Boris, and they shot it with tantalum

右边的他们叫它鲍里斯， 他们用钽去射击它，

in order to be able to analyze it.

以便能够分析它。

Now, we found sodium and magnesium.

我们发现了钠和镁。

What this tells you is this is the concentration of these two materials

而这也说明了这就是当太阳系刚形成时

at the time the solar system was formed,

这两种物质的浓度，

so we learned things about which materials were there

因此我们知道了当行星形成时

when the planet was made.

存在着哪些物质。

Of course, one of the important elements is the imaging.

当然，最重要的因素之一就是成像。

This is one of the cameras of Rosetta, the OSIRIS camera,

这是罗塞塔号上的一个相机—— 奥西里斯相机——拍摄到的，

and this actually was the cover of Science magazine

而这实际上是《科学》杂志

on January 23 of this year.

今年1月23日那一期的封面。

Nobody had expected this body to look like this.

没有人想到它看起来会是这样的。

Boulders, rocks -- if anything, it looks more like the Half Dome in Yosemite

大卵石，岩石——相比于其它任何地方，

than anything else.

它看起来更像是约塞米蒂的半屏岩。

We also saw things like this:

我们还看到了这样的东西：

dunes, and what look to be, on the righthand side, wind-blown shadows.

沙丘，还有在右手边， 看起来像一些被风吹动的影子。

Now we know these from Mars, but this comet doesn't have an atmosphere,

我们在火星上发现过这些， 但是这颗彗星没有大气层，

so it's a bit difficult to create a wind-blown shadow.

所以要制造一个被风吹动的 影子是有点困难的。

It may be local outgassing,

这可能是局部的出气，

stuff which goes up and comes back.

有什么东西上升然后落下来。

We don't know, so there is a lot to investigate.

我们还不清楚， 所以还要进行很多调查。

Here, you see the same image twice.

这里有两张同一地点的图像。

On the left-hand side, you see in the middle a pit.

左手边这张，中间有一个坑。

On the right-hand side, if you carefully look,

右手边这张，如果你们仔细看，

there are three jets coming out of the bottom of that pit.

有三股气流从那个坑的底部喷出。

So this is the activity of the comet.

所以这就是这颗彗星的活动。

Apparently, at the bottom of these pits is where the active regions are,

显然，这些坑的底部就是活动区域，

and where the material evaporates into space.

也是物质蒸发到空中去的地方。

There is a very intriguing crack in the neck of the comet.

这颗彗星的脖子上 有一个非常有趣的裂缝。

You see it on the right-hand side.

就在右手边。

It's a kilometer long, and it's two and a half meters wide.

它有1公里长，2.5米宽。

Some people suggest that actually,

有些人提出，事实上

when we get close to the sun,

当我们向太阳靠近的时候，

the comet may split in two,

这颗彗星可能会一分为二，

and then we'll have to choose,

然后我们不得不做出选择，

我们要去跟踪哪一半的彗星？

which comet do we go for?

The lander -- again, lots of instruments,

这个着陆器—— 一样的，携带了很多仪器，

mostly comparable except for the things which hammer in the ground and drill, etc.

除了一些打钻用的装置， 其他大部分跟航天器上的差不多。

But much the same as Rosetta, and that is because you want to compare

与罗塞塔携带几乎一样的仪器是因为要把

what you find in space with what you find on the comet.

太空中发现的物质跟这颗彗星上的做比较。

These are called ground truth measurements.

这被称为“地面实况调查”。

These are the landing descent images

这些是奥西里斯相机拍摄的

that were taken by the OSIRIS camera.

着陆下降时的图像。

You see the lander getting further and further away from Rosetta.

可以看到着陆器离罗塞塔号越来越远。

On the top right, you see an image taken at 60 meters by the lander,

右上角，是着陆器在60米外拍的照片，

60 meters above the surface of the comet.

彗星表面60米以上。

The boulder there is some 10 meters.

那个大卵石直径大约10米。

So this is one of the last images we took before we landed on the comet.

这是我们在彗星上着陆之前 所拍的最后一张照片。

Here, you see the whole sequence again, but from a different perspective,

换个角度，再看一遍这整个过程，

and you see three blown-ups from the bottom-left to the middle

大家可以看到从图中的 左下角到中间有三幅

of the lander traveling over the surface of the comet.

着陆器飞过彗星表面时的放大照。

Then, at the top, there is a before and an after image of the landing.

然后，在顶部有 着陆之前和之后的对比照。

The only problem with the after image is, there is no lander.

唯一的问题就是在着陆后的照片中 没有出现着陆器。

But if you carefully look at the right-hand side of this image,

但是你们仔细观察这张图像的右手边，

we saw the lander still there, but it had bounced.

我们看到着陆器仍然在那， 但是它被反弹了。

It had departed again.

又离开了彗星表面。

Now, on a bit of a comical note here

现在，有点滑稽的是，

is that originally Rosetta was designed to have a lander which would bounce.

本来在罗塞塔号的设计中， 它会携带一个能反弹的着陆器。

That was discarded because it was way too expensive.

但是因为成本太高所以就放弃了。

Now, we forgot, but the lander knew.

我们已经忘记了这件事， 但是着陆器还记得。

(Laughter)

（笑声）

During the first bounce, in the magnetometers,

第一次反弹期间，在磁力仪上，

you see here the data from them, from the three axes, x, y and z.

你们可以看到来自X、Y、Z 三个坐标上的数据。

Halfway through, you see a red line.

半途中，你们可以看到一条红线。

At that red line, there is a change.

这条红线表示有变化产生。

What happened, apparently, is during the first bounce,

发生了什么呢？ 很显然是在第一次反弹期间，

somewhere, we hit the edge of a crater with one of the legs of the lander,

着陆器的一条腿在某个地方 碰到了一个坑的边缘，

and the rotation velocity of the lander changed.

然后着陆器的旋转速度被改变了。

So we've been rather lucky

所以我们很幸运

that we are where we are.

是处在当时的位置。

This is one of the iconic images of Rosetta.

这是罗塞塔号拍的标志性的图片之一。

It's a man-made object, a leg of the lander,

那是一个人造物体，着陆器的一条腿，

standing on a comet.

站在一颗彗星上。

This, for me, is one of the very best images of space science I have ever seen.

对我来说，这是我见过的 最棒的空间科学的照片之一。

(Applause)

（掌声）

One of the things we still have to do is to actually find the lander.

未来的任务之一就是要找到这个着陆器。

The blue area here is where we know it must be.

蓝色区域是我们知道的 它应该所处的位置。

We haven't been able to find it yet, but the search is continuing,

我们还没能找到它，但是搜索仍在继续，

as are our efforts to start getting the lander to work again.

同时我们也在努力让着陆器重新工作。

We listen every day,

我们每天都仔细监听，

希望从现在到4月份的某个时候，

and we hope that between now and somewhere in April,

the lander will wake up again.

这个着陆器会重新开始工作。

The findings of what we found on the comet:

我们在这颗彗星上的发现是：

This thing would float in water.

这颗彗星可以在水上漂浮。

It's half the density of water.

它的密度是水的一半。

So it looks like a very big rock, but it's not.

因此它虽然看起来像一块大岩石， 但实际上不是。

The activity increase we saw in June, July, August last year

去年6到8月间我们看到

was a four-fold activity increase.

它的活跃性提高了4倍。

By the time we will be at the sun,

当我们靠近太阳时，

there will be 100 kilos a second leaving this comet:

每秒种将会有100公斤的物质 离开这颗彗星：

gas, dust, whatever.

气体、灰尘等等。

That's 100 million kilos a day.

1天的话就是1亿公斤。

Then, finally, the landing day.

最终，到了着陆的那一天。

I will never forget -- absolute madness, 250 TV crews in Germany.

我将永生难忘——大家都疯狂了， 在德国有250名电视台工作人员争相报道。

The BBC was interviewing me,

在BBC采访我的同时，

and another TV crew who was following me all day

另一家电视台全天都在 跟踪报道我的工作人员

were filming me being interviewed,

也拍下了我的访问过程，

and it went on like that for the whole day.

那种状况持续了一整天。

The Discovery Channel crew

探索频道的工作人员

actually caught me when leaving the control room,

在我离开监控室时找到了我，

and they asked the right question,

并且提出了正确的问题，

and man, I got into tears, and I still feel this.

我当时激动得流下了眼泪， 而那种感觉依旧挥之不去。

For a month and a half,

此后的1个半月里，

I couldn't think about landing day without crying,

每次想到着陆日我都会热泪盈眶，

and I still have the emotion in me.

并到现在那种情绪在我心中仍然存在。

With this image of the comet, I would like to leave you.

我想用这张这颗彗星的照片 来结束今天的演讲。

Thank you.

谢谢。

(Applause)

（掌声）