Today, I am going to talk to you about 
limits with a question mark.

Are there limits?

I am going to use two examples.

One is the orbiting and landing 
of an asteroid with NEAR spacecraft.

NEAR stands for 
Near-Earth-Asteroid-Rendezvous.

And the other is exiting 
the solar system with Voyager.

This is the kind of thing

that is very much in line with 
the theme of Uncharted Waters,

which, of course, is the theme 
of this conference.

You know that we don't know 
a lot about asteroids,

and we certainly did not 
fifteen years ago.

We didn't know 
if they were a solid body

or a rubble pile, a bunch of rocks.

Are they moving together in space?

So the idea is to leave Earth
and go and orbit an asteroid

which is typically not spherical, by the way.

And nobody had orbited 
a non-spherical body.

So, asteroids, there are lot of them

that go orbiting in the vicinity of Earth.

As you can see here is the orbit of Mars

and here is the orbit of Earth,

and these are a few of the asteroids

that cross the path of Earth.

And, of course, we have been lucky

that we haven't had too many collisions.

There have been collisions
as I am sure you have heard.

So the idea is to go to one of these,

orbit it and study it 
for a long period of time.

To do that you need the spacecraft.

We started the work two months 
before this picture was taken.

You see the spacecraft on top
of what we called a shake-table.

Which means that we take 
the spacecraft, once it is finished,

and then we vibrate it to a level

which it is going to experience

as it goes up on top of the rocket,

through the atmosphere 
and then into space.

And it better survive that, 
otherwise it will not work.

So, that's what we did.

The spacecraft and we moved 
on to Cape Canaveral.

We put it on top of the rocket, 
as you can see here,

and you can also see 
there is a protective shell

which is called the heat-seal

simply because it protects 
the spacecraft

as the rocket moves through 
the atmosphere at a very high rate.

(Buzzing sound)

This is sort of my last walk

through the tower 
that surrounds the rocket.

By the way, the young lady that you see
is the first program manager

that I appointed 
to a NASA planetary mission.

And I am very proud 
of having worked with ladies

who really know how to do it.

(Applause)

So this is the rocket and 
you can see the exhaust,

it's a little bigger 
than your car exhaust.

These are just the solid rockets

that surround 
the main body of the rocket.

And then, of course, when 
the fuel is exhausted from these,

they fall off and then we go on
to the next main tank of the rocket

and it goes up.

This lasted a long time

so I am not going to tell you a lot more
and spend time on it.

Finally we launched on February of 1996.

What you see in this ...

This is Eros, this is the asteroid.

We put the spacecraft around it into orbit,

and it rotated every 
about 6 1/2 hours, or so.

So the spacecraft is rotating

and watches the asteroid 
as it rotates around.

Getting there, of course, 
wasn't simple.

So we launched and then we went

by the asteroid Mathilde in 1997.

We came back to Earth 
to change the plane of the orbit

so that we could match 
the trajectory of the asteroid.

And then, something happened

just before we were 
ready to get into orbit.

That is, we fired the onboard rocket

and we lost the spacecraft.

No communication
for almost 24 hours.

It's the worst thing.

It can ruin your whole day
when you are in this business.

(Laughter)

But fortunately we had built 
enough redundancy into the system

that 24 hours later 
we got a weak signal

and we got the control 
of the spacecraft again.

We found out what happened,

and it turned out that the two computers 
on board had a disagreement.

The spacecraft computers couldn't 
agree with propulsion in engine computer

and we got in trouble.

We lost some fuel.

We went around the Sun once more 
and finally we got into orbit.

As we were approaching Eros, the asteroid,

on February 12, two days 
before Valentine's day, mind you.

Here was the picture,

it looked like a heart.

Of course we knew 
it was an optical illusion

and, of course, 
we never published the picture

because we would get 
into all kind of trouble.

And when we got close, 
as you will see,

what happened is that 
you had these three craters

that were arranged in a triangle,

and they looked with 
a kind of Sun angle and the shade,

it looked like a heart from a distance.

So, that is the kind of stuff 
that you see in the tabloids

that in the United States 
we pick out in supermarkets.

Supermarket counters.

You know ... "Heart on Eros" ...

So much for that.

It was big news that a NASA spacecraft 
orbited an asteroid on February 12.

CNN is very loud everywhere it goes,

including the United States.

(CNN Speaker): A close encounter

between a NASA satellite and an asteroid.

An unmanned spacecraft is now 
in orbit around an asteroid.

It's supposed to teach us 
about these giant rocks,

and perhaps help scientists to figure out

how to protect us from a possible collision.

That is our Trajectory Manager

who was making, he and his team, 
most of the calculation.

(CNN Video)

And this is the Senator of Maryland.

And now I am showing you 
the next episode,

after we were in orbit for a year.

We had charted the entire asteroid.

We were familiar 
with every little corner

and every little crater.

And we just had a little bit of fuel left.

And we said, "What are 
we going to do now?"

Because to maintain a spacecraft
in orbit around an asteroid

that has this kind of shape, 
like a potato,

it's very hard and you have 
to really keep pushing

and adjusting the orbit by using fuel.

And we were at the end of the fuel.

So what would happen is that 
the spacecraft would drift away.

So what we did is, I went to NASA

and persuaded the administrator that

we were going to try to easy down
on the surface of the asteroid.

He eventually agreed to let us do it.

So the day came, again it was 
as I mentioned the year later.

We had already calculated what 
the trajectory was going to be like.

What you see here is 
the calculated trajectory,

[it] is the black line.

And the points are the real-time data.

We had the laser altimeter 
that measured

the distance of the spacecraft 
from the ground

by signing a laser, 
getting the reflection

and measuring the distance with 
the precision of about a centimeter.

So we knew what was happening.

And we figured that it would take about 
45 minutes to get down to the ground.

It seemed like it was going very well.

I will show you a simulation
of what we had done

with the spacecraft as you see it.

And in fact, the spacecraft landed

with the solar panels pointing 
in the direction of the Sun,

with the antenna pointing 
in the direction of Earth,

and we kept getting data.

And it went on for a number of days.

What you see is the pictures 
that were taken by the spacecraft

as it was moving into closer 
and closer to the surface of Eros.

And at the end we had a resolution
which was actually quite good.

You can see here, 
this is the last image we had.

You can discriminate and see rocks

that were of the order 
of a few centimeters across.

Well, that wasn't all.

We had the opportunity 
to do other things.

This is the announcement 
that we had actually landed.

And Mr.Goldin, who was 
the NASA administrator at the time,

was exceptionally anxious because

NASA had just crashed 
a spacecraft on Mars a month before.

And he was very worried about 
what was going to happen,

if this happened again, 
to NASA's reputation.

But he was very happy.

Then, I wanted to show you 
another thing, here,

about the details of the surface.

There is a crater

that the International Astronomical Union

in its wisdom decided to name Hios,

which was the love child of 
Poseidon and the nymph Hiona.

So we have a crater on Eros 
by the name of Hios.

Nothing to do with the fact 
that I am from Chios, mind you.

(Laughter)

The most important thing, however, 
is that we finished the project

and we didn't spend all the money.

Which had never happened 
in the history of NASA.

We had a little ceremony,

the down payment to NASA of
the remainder of 3.6 million dollars.

In the end we gave them 
back about 30 million.

Needless to say, we got a lot of abuse
from my other colleagues at NASA centers

who said, "You never give back 
money to the government.

"Shame on you", and so and so .

But we overcame.

Now let me tell you about the other part

of the things that go 
on uncharted waters.

What you see here is 
a view of the solar system.

Each one of our planets 
of the solar system

has already been imaged by spacecrafts.

The four planets you see here,

Jupiter, Saturn, Uranus, Neptune

are all, of course, pictures 
from the Voyager mission.

The Voyager mission started 
in 1977, ladies and gentlemen.

It was 36 years ago, 
in a couple of months.

The original plan was to go 
to Jupiter and to Saturn.

It was going to be a four year mission.

But then it turned out that it was possible

using gravity assist 
from Jupiter to go on to Saturn,

but then also using gravity assist

from Saturn to go on to Uranus

and from Uranus to Neptune.

And that's exactly what 
we did with Voyager 2

while we sent Voyager 1 
away from the Sun

and towards the north ecliptic.

That was a very well planned program,

it worked well, it provided 
essentially all new information.

And I just want to show you

the spacecraft which 
is about this size.

This is the antenna,
it points in the direction of Earth.

It transmits information.

These here is the instrument 
from my team.

And I am pointing it out loud

because it did some other things 
that we were very proud of.

I am showing you this picture

with President Herbert Walker Bush.

Not the new one,
not the son, the father.

He had a lot of brains, the father.

(Laughter)

He invited us to the White House

as had done Mr. Reagan before him.

And I am showing you 
that simply because

to point out that the American 
government, the politicians,

really appreciate what science 
does for the country.

And it is not just NASA,

it's the National Institute of Health,

it's all kind of national science foundations.

And they show it. Effectively.

With this kind of things,

by inviting us to lunch, 
and things like that.

Anyway. This, after Voyager went 
past all these four planets.

This is a simulation, 
that I am showing you,

where it was moving away 
from the Sun

passed the last planet, 
the orbit of Pluto.

And we expected that someday

we were going to run into this boundary

and then eventually 
cross another boundary

that would lead us into the galaxy.

The problem was that nobody knew
how far these boundaries were.

We were sort of going in blind.

There were suggestions that it could be

a year away, five years away,
ten years away.

Nobody really knew.

So, how to find it out?

We had four instruments 
that were working.

This is the one that I pointed out 
before, our team had built.

And another thing that we did

is to put a little stepper motor

that rotated the entire platform 
back and forth.

I'll show you a very short video.

(Buzzing sound)

That is the kind of sound it made 
in the laboratory, when it rotated.

I did this little video for the press

right after the Neptune encounter.

I did have hair at one time, you noticed? 
(Laughter).

We had this little stepper motor

that was rotating the detectors.

Just like this simulation shows.

And you see the colors here.

You can't see them 
because of these lights.

But by rotating around 
it was possible for us

to measure the speed and the direction 
of the hot wind from the Sun,

which moves at the speed of about
1.5 million Km per hour.

Now, you say, "OK, you told us 
about these instruments,

what did you find by rotating this?"

What we found...

Here it is, we kept going 
and going and going.

The idea was that once 
we cross this boundary

we would be out in the galaxy.

What we found instead
is that we ran into a place

where the solar wind no longer
moved away from the Sun.

And we called that 
the Stagnation Region.

We published it in 2011.

It was not predicted by theory.

However some models were suggesting 
that what happens to this wind

is that it goes to the north direction
towards the ecliptic pole.

Our instrument, however, 
was only rotating in one plane

and we couldn't measure 
the speed up and down.

So, I asked the engineering team,

I said "Why don't we turn the spacecraft 
90 degrees, now and then?

And then we can measure 
the north-south direction."

Mind you, this is a spacecraft

that had been in space 
for 34 years already.

And it is just like getting 
a dog that's about to die

trying to teach him new tricks.

However, what happened is

that we were able 
to send the commands,

and by guiding the spacecraft

it executed every command perfectly.

And for two years we have been 
doing this every two months.

We rotated the spacecraft 
in this direction.

What we found out is that, in fact,

even this model was also wrong.

There was no flow of the wind 
in the north direction

or in the south direction 
for that matter.

So theory failed us again.

We actually wrote this up
and were publishing it

until we found something very strange
that happened last year.

What you see here,

and it is the only data that I will show you,

is the curve for cosmic rays, the intensity.

And you see that they started increasing
right about early May of 2012.

These are the so-called 
Galactic Cosmic Rays.

These are particles that were actually 
generated by explosions of Supernovae

millions of years ago
in the vicinity of the Sun,

and were coming from outside 
the galaxy into our solar system.

And they began to go up.

And then, eventually, 
at about the same time,

after two or three increases,

the material that was coming from the Sun,

never mind what these are, protons and 
heliums and what we have here, oxygen

dropped at the same time.

In other words, 
the solar material disappears

and the stuff that was supposed to be coming

from outside the galaxy 
-- that's what we believed --

appeared and increased.

So we said, "Aha! We actually got out of 
the solar system and into the galaxy!"

But we lacked some data.

This is a picture from a press event

at the Jet Propulsion 
Laboratory in Pasadena.

We were trying to interpret the data

a few days after 
we had made that observation.

Here we have the model 
of the spacecraft.

But we didn't have 
all the data that we needed.

Namely, we couldn't measure the density
of the atmosphere of the galaxy,

if I can put it that way.

Until April of this year.

I don't know if you can hear the sound,

maybe you can turn it up a little bit?

(Whistling sound)

OK. Now, what are these,

is, we have some antennas on the spacecraft.

And in the vicinity of the spacecraft
something happened

and all these electrons 
began to oscillate back and forth.

When the electrons oscillate 
in a magnetic field

they produce sounds.

And when they produce this sound

we are able to determine 
the density of the material

around the spacecraft.

What you see here is that 
we were able to determine

that it was 0.1 per cubic centimeter.

You would say, 
"What does that mean?"

Well, it was 50 times 
what we had before.

When we were in the solar wind,
inside our solar atmosphere.

And because most models predict

that the density in the galaxy is about 0.1,

we knew that we had actually arrived.

So, we had a meeting at my lab
back in Johns Hopkins in September.

We looked at all the data 
and we finally decided

that it was safe 
to issue a press release

that actually we had crossed

the boundary with the galaxy
on August 25 of 2012.

So, think about this:

a hundred and ten years ago,

it was when the Wright brothers

flew a... you could call it an airplane

-- that's what they called it --

at an altitude of few meters
for about 30 seconds.

And then about 50 years later

there was the launch 
of the first Earth satellite, Sputnik.

It went outside the Earth's 
atmosphere for the first time ever

in our history, in humanity's history.

And it got to an altitude 
of 946 km, to be exact.

And then another 55, or so, years later,

we had the exit of the first 
spacecraft, Voyager 1

from the atmosphere of the Sun
at an altitude of 18.2 billion kilometers.

To give you an idea:

the signal that we get from Voyager,

when it leaves Voyager, 
it travels with the speed of light,

and it takes 17 hours and 20 minutes
to get from there to Earth.

The light from the Sun to come to Earth
only takes 8 1/2 minutes.

So you can imagine 
how far this spacecraft is.

To give you the bottom line, so to speak.

Here we are. 
Voyager 1 is in the galaxy.

Voyager 2 is not there yet, 
it is a little slower,

so we expect it will go out at some point.

Finally, I can imagine that 
there was a rooster there

that said "People of Earth, 
welcome to the galaxy!",

(Laughter)

on August 25, 2012.

I posed the question in the beginning: 
"Are there limits?"

I think you can imagine that my answer 
to that is "No, of course no."

I think limits constrain our imagination

and retard progress, I think.

So, we don't need any limits.

And there are none.

Thank you very much.

(Applause)