Translator: Iris Klotz Reviewer: Denise RQ
Hello, thank you.
Comets have always intrigued men, made us dream.
Many years ago, we considered them divine omens.
The name comet comes directly from ancient Greece
from the Greek "kometes", which means long-haired,
referring to the comet's tail or halo.
Actually, they're small celestial bodies made of ice and dust
and as they approach the Sun,
the ice that they're made of melts,
leaving part of their substance behind in space
and creating this tail of gas and dust
tens of thousands of miles long,
which makes them so visible from Earth.
Undoubtedly most famous comet is Halley's comet.
Halley's comet returns every 76 years
to our planetary neighborhood.
And the last time that it came by, in 1986,
this comet provoked the interest
of the general public, certainly,
but also of space agencies
because for the first time in history, thanks to space flight technology,
we could go and see this famous comet close up.
Several unmanned spacecrafts,
called space probes,
several space probes were sent to meet the comet,
to study it.
among them the European space probe, Giotto, in 1986.
Comets: where do they come from?
and, above all,
why are they so interesting from a scientific point of view?
They come from two regions of outer space that we call
the Kuiper belt and the Oort cloud.
Outer space, because the Kuiper belt, for example,
begins about 3 billion miles away from the Earth, around Pluto,
and the Oort cloud is more than 10,000 billion miles
away from Earth.
At these distances, to give you an idea of scale,
we're already at a quarter
of the distance that separates us from the closest star,
Proxima Centauri.
There would be billions of comets
in these spaces and, from time to time,
under the gravitational pull
of one of the giant planets in the Solar System,
Jupiter, for example,
or even the stars closest to our Sun,
some of them are propelled towards our Sun
and pass close by our planet.
Some only pass by once,
and others come back more regularly,
like Halley's comet, for example.
The comets are so fascinating because, due to their small size
and distance from the Sun, they've never changed
the way the planets in our solar system have.
So they're wonderful proof of the origins of our Solar System,
and what's more, since they bombarded the Earth a long time ago,
they might have contributed
to bringing the water that makes up our oceans or even the organic compounds
that might have allowed the development of life on our planet.
So now we understand the scientific interest of these comets,
and that's why the ESA, the European Space Agency,
after the success of the Giotto mission decided to launch
the Rosetta mission in the early 1990s.
So the Rosetta mission was challenging for several reasons:
a time challenge, you see, because from the early 1990s to 2016,
that's more than 25 years of this mission, with about a dozen countries
participating or collaborating closely or otherwise on this project.
The mission, at the beginning, was meant
to be a collaborative mission with the Americans, with NASA,
an even more ambitious mission in true American style
because it was going to collect samples from the comet's surface
and bring them back to Earth to study them in a laboratory.
Due to budget restrictions,
in 1993, NASA more or less threw in the towel
and Europe had the idea to continue the adventure on its own,
nevertheless setting its sights a bit lower
because it would have the Rosetta mission follow the comet for several months
to study its evolution as it approached the Sun
and to land a little laboratory robot,
that you can see behind me,
the robot Philae,
that would then, for the first time,
do evaluations on the comet's surface.
Slightly less ambitious, but nonetheless a huge challenge
because all the probes that had studied comets up until that point
hadn't done more than pass close by.
So it was really a first.
As you can imagine, during that whole time, 25 years,
thousands of people across Europe
have worked on this mission.
Some have been there since the beginning,
not me,
but some of the ones that started with the mission are still there.
Many others have moved on, passed the torch.
In the end, the Rosetta mission
and the scientific community are like a big family in flux
with people coming and going.
I won't hide from you that, like in all families,
after a certain amount of time relationships can sometimes be tense,
there are ups and downs,
and the family reunions are sometimes
a bit agitated, strained at times,
but that's the human challenge of this mission,
to have people work together
for such a long time,
coming from such different backgrounds
and to make sure their skills are shared and not lost.
When you talk about challenges you're also talking about adventure and,
of course, the unexpected, right from the start.
The original target of our mission
Wasn't the Churyumov-Gerasimenko,
nicknamed Chury,
but a comet called Wirtanen.
Rosetta was supposed to be launched in 2003 with an Ariane rocket
and a couple months earlier, so in 2003,
rocket failure during Ariane's flight, an explosion,
all flights were suspended for several months, obviously.
There was an inquiry; we wanted to know why.
So the Rosetta flight was delayed.
For a comet, you can't be late.
If you miss the window,
the comet passes,
and won't come back for several years, even several dozen years later.
So, we missed the window, Wirtanen was no longer accessible.
So we had to chose a new window within a few months,
recalculate a trajectory.
We chose the Churyumov-Gerasimenko comet,
named for its Russian co-discoverers, Mr. Churyumov and Mrs. Gerasimenko.
This comet was discovered at the end of the 1960s.
It returns to Earth every 6.5 years,
so we know it well.
And, importantly,
it had the distinct advantage of being more or less similar to Wirtanen,
which is important
because our robot was supposed to land on Wirtanen.
So we had to find a new target that was similar.
It would be the Churyumov-Gerasimenko comet, that we call Chury now.
On March 2, 2004, Rosetta finally enters space,
for a ten year journey destination:
the Churyumov-Gerasimenko comet.
Ten years of traveling
during which Rosetta passes near the Earth several times,
and Mars as well,
and propels itself towards the Churyumov-Gerasimenko comet.
During its long journey,
Rosetta will have to get very far away from the Sun,
five times the distance from the Earth to the Sun,
more than 500 million miles.
It's important to know that the satellites in orbit around Earth
get their energy
from solar panels that recharge their batteries,
like the solar panels
that you might have on the roof of your home.
However, at that distance, 500 million miles,
you only get 4% of the solar energy that we get on Earth.
That's why the probes that go so far into space
are generally loaded with small nuclear batteries,
like the famous Voyager space probe that was launched in the 1970s,
and that is now in the process of leaving the Solar System,
or the New Horizons probe,
which passed by Pluto this summer,
if you've been following space news.
However, in Europe, we don't have that technology.
We therefore had to equip Rosetta with enormous solar panels,
two by 32 meters,
two solar panels 32 meters long,
and despite its 64 square meters of solar panels,
when it was at its farthest from the Sun,
Rosetta didn't have enough power to function normally.
So again, a new challenge: for 30 months,
from June 2011 to January 2014, almost 31 months,
we had to keep it on a sort of sleep mode,
minimum power consumption,
with its wakeup scheduled for January 20th, 2014 at 11am.
It was terribly difficult: during that entire time,
No communication was possible with the probe,
We didn't know how it was doing.
And then on January 20th, 2014
Rosetta's awakening gave us cold sweats.
The awakening was set for 11am, the probe should have turned on,
turned on its apparatus, recover its power,
turn its antenna towards the Earth and send us a signal.
The signal should take 45 minutes to arrive
and we should receive it between 5:30 and 6 pm.
At 5 o'clock we were all there to wait for Rosetta's signal.
5:30, no signal.
6 o'clock, still no signal.
Well, up to that point, no worries, it was still within the normal range.
6:30, the minutes pass.
7 o'clock, we were really starting to get worried, to say to ourselves..
maybe the adventure is over before it even started.
The minutes kept passing, and happily, at 7:18,
we got the signal that you see on the screen,
really not impressive,
but still it was a huge relief
because that was the proof that Rosetta had reestablished contact,
that the operators in Germany, on Earth,
could once again send commands and that the adventure could continue.
And it really is an adventure,
because flying around a comet is really quite dangerous,
exactly because of that dust and that gas
that are propelled through space as the comet approaches the Sun.
You might be thinking of
the film Armageddon, if you've seen it,
with Bruce Willis who's landing his space shuttle
I don't know if you remember, with a bunch of gas jets,
on a comet with a rough surface.
The reality is a lot less dramatic,
but nonetheless, it's true the surface of a comet is really dangerous.
In the photo behind me,
you can clearly see the gas expulsions,
and the white points that you see are definitely not stars,
but dust that's all around the comet
that disrupts the probe's navigational instruments
at the risk of Earth losing control of Rosetta.
We've even seen rocks several yards long
flying around the comet.
You can see that it's a dangerous environment,
and that's why the probe was unable to reach the surface,
not even to drop our little robot Philae.
The probe stayed at a height of 12 miles, 12 miles above the surface,
for a comet that's 2.5 miles at its largest,
12 miles to land on a comet 2.5 miles wide,
we really had to aim well.
And that was a huge gamble.
And that's what we were all waiting for,
on November 12th, 2015, we were pretty anxious.
We weren't sure how it would go.
The probe dropped the robot at 9:35am, landing at 4:35pm,
the contact signal should come to us around 5pm.
We had seven long hours to wait for the signal.
Thankfully, we quickly received the first pictures
of our little robot on its descent towards the surface of the comet
that showed us that things seemed to be going well,
the legs were extended, and if we were able to take the photo,
that meant that generally it was going in the right direction.
The descent continued.
It's good to know that no real-time intervention was possible,
because the signal took 25 minutes to arrive on Earth,
and to send a signal back,
another 25 minutes for Rosetta to receive it.
so it wasn't possible to give any orders in real time.
During that whole time, we were following it, receiving information,
but we weren't too sure of the robot's direction.
We didn't know if we would really land on the comet
or if we were going to miss it.
Luckily, again,
several minutes before the landing,
we had our first reassurance:
we received the first photos
taken by our little robot's camera
of the comet's surface,
about 2 miles up, and then at 100 feet up.
Then we knew that everything was going right.
Finally, at almost the exact moment we were expecting,
the contact signal, touchdown,
it was there.
For the first time, we had landed on a comet.
As you can imagine, it was an explosion of joy.
Unfortunately, the tension quickly mounted again
the data showed
that our little robot was still moving.
The first photos were blurry.
We paced.
And then, for two hours,
we watched,
still without being able to do anything, as our robot bounces
and bounces all over the surface of the comet
until, at 7pm, two hours later
we get confirmation that our robot has stabilized somewhere
and that it's stopped.
In the end, we had had a little bit of bad luck
and lot of good luck.
A bit of bad luck because we found that the hooks
that should have anchored Philae to the surface of the comet didn't launch;
and a lot of good luck nonetheless,
because despite a rather ungraceful landing,
in a rocky area with bad lighting,
we succeeded, during the following 3 days,
at making almost all Philae's instruments work,
and collected the first data about the surface of the comet.
Rosetta and Philae will likely allow us
to revolutionize comet science.
For example, we can say that Philae
has confirmed the presence of complex organic compounds
in comet dust.
and I would say
that this mission is a symbol of space exploration
because it requires us to reflect over long periods, to look to the future,
to take risks,
to put all possible skills at work in common,
and to prepare for the unexpected,
because, by definition,
we really don't know what we're getting into.
We may be rewarded, for example,
by the photos that are behind me,
that our team loves very much, because they are photos
taken by an object built by man twenty years ago,
on or near an object that's several millions of years old,
several hundred million miles away.
Thank you.
(Applause)
Thank you so much.
(Applause)