Original subtitles

Pluto, an icy dwarf planet three billion miles from Earth.

Our most powerful telescopes see only a blur, until now.

We have lift-off.

A space probe called New Horizons is on its way.

This is an epic journey.

To the far reaches of our solar system.

It's going farther

than any exploration by human beings ever has.

To capture images of a mysterious world

that may hold the secret to the origins of our solar system.

Are there going to be surprises?

Absolutely.

But not all the surprises are good.

About 1:55 p.m. local,

we've lost signal with the spacecraft.

Could it be we hit something?

But a last-minute rescue saves the day...

as Pluto comes into focus, revealing a world stranger

than we ever imagined.

Wow!

There's a heart on it!

"Chasing Pluto," right now on NOVA.

Major funding for NOVA is provided by the following:

We love science.

Supporting NOVA and promoting public understanding of science.

And the Corporation for Public Broadcasting,

and by PBS viewers like you.

Thank you.

And Millicent Bell,

through the Millicent and Eugene Bell Foundation.

Additional funding from Roger and Vicki Sant.

January 19, 2006.

An Atlas 5 rocket, a 212-foot powerhouse,

is prepped for launch at Cape Canaveral.

It was one of those days where you say to yourself:

This is it.

Project succeeds or fails today.

Because when things go bad on launch,

they usually go bad in a spectacular way.

T minus five, four, three, two, one...

We have ignition and liftoff

of NASA's New Horizons spacecraft

on a voyage to visit the planet Pluto and beyond.

It's the fastest launch ever recorded...

36,000 miles per hour.

New Horizons needs all the speed it can muster,

on a journey that will take it clear across the solar system,

to attempt something unique in the history of spaceflight:

get an up-close and personal look at Pluto,

a mysterious, distant world

unlike anything we've explored before.

Back on Earth,

at the Johns Hopkins Applied Physics Laboratory,

the mission operations team for New Horizons

is not quite ready to celebrate.

Once the rocket took off,

there was a great feeling of joy

and then you hold your breath for a while

because you're not done until you get the signal back

from the spacecraft that everything's okay.

We don't have a mission

until we know that spacecraft is communicating with us.

And so they wait.

Everything is a concern.

Things we've thought about we know we've solved.

To try and anticipate so many eventualities,

it's the challenge of spaceflight.

Almost an hour passes.

And then, Mission Ops receives the first signal

from New Horizons.

Scientists turn to each other and go,

"I love you, man!"

It was an astonishingly happy time.

And that's the greatest feeling,

because now we know we have a mission to Pluto.

This is just the first of many challenges to come

on a journey that will take almost a decade.

Just nine hours after leaving the launch pad,

it was already crossing the orbit of the moon.

A trip that took Apollo astronauts three days.

But even traveling tens of thousands of miles an hour,

it will take over nine years for New Horizons

to reach its destination, to explore the far reaches

of our solar system, more than three billion miles from Earth.

Beyond the planets we've come to know...

Mars with its rocky red surface,

the gas giant Jupiter with its raging storm,

and Saturn with its stunning rings.

Uranus, where turbulent winds blow over 500 miles an hour,

and Neptune, a planet so far from the Sun,

it takes 165 years to complete just one orbit.

Finally New Horizons will arrive at Pluto,

a world we can only picture

with the help of artwork like this, at least for now.

Who can tell us more about the planets?

Back in the 1950s, every grade schooler

was taught there were nine planets,

Pluto being the last and loneliest.

Everybody loved Pluto because it was this funny oddball

sitting out there at the very edge.

You don't find that kind of name recognition

and emotional connection and interest level for Uranus,

or Mercury, or going down the list,

but somehow Pluto just naturally attracts people's attention.

What makes Pluto so popular?

It may have something to do with a playful bloodhound

named Pluto the pup.

It turns out the Disney character made its debut

around the same time the planet was discovered.

Over the years we've gotten to know this beloved little pup.

The same can't be said for this mysterious little world.

The truth is, Pluto and its moons

have only been observed from billions of miles away.

Our best images, nothing more than a blur.

In fact, one of the biggest, baddest space telescopes

in our arsenal, the Hubble,

which takes stunning images of enormous distant galaxies,

can only capture these pixelated images of Pluto,

because not only is it far away, it's really small.

But even at this resolution,

they suggest something intriguing.

Using these precious pixels,

a computer-generated image reveals Pluto has

a surprisingly varied surface.

The light areas could be miles and miles of ice.

The ices are the most obvious signature that you see,

but you can discern that there's other components there as well.

We just don't know exactly what they're made of.

But here's what we do know:

one of the few planets in the solar system

with such a varied surface is planet Earth.

We also know that Pluto has a rather bizarre atmosphere.

During its 248-year orbit, as Pluto gets closer to the Sun,

its frozen surface starts to thaw

and its atmosphere slowly emerges.

What we see in the atmosphere

is gases that are coming off the surface,

creating a temporary atmosphere, perhaps.

Pluto has a unique type of atmosphere

in this outer part of the solar system

that we've never studied before.

An area so distant and elusive

we knew almost nothing about it until the 1990s,

when powerful new telescopes discovered lonely little Pluto

wasn't so lonely after all.

It's part of a region in the outer solar system

beyond the orbit of Neptune called the Kuiper Belt.

And it is enormous.

Billions of miles from the Sun,

the Kuiper Belt is filled with hundreds of thousands

of icy objects.

While they may look like asteroids,

which are made of rock and metal,

these objects, hidden in the solar system's deep freeze,

are made of a mixture of rock and ice.

These are basically frozen remnants

of the early part of the solar system

that are still in the freezer.

You can start to read this fossil record

of how the solar system evolved by looking at these objects.

You can't say for the New Horizons mission,

"Been there, done that," because it hasn't.

We've already explored the terrestrial planet region,

the giant planet region.

Now we're exploring

a completely new portion of the solar system

that's never been touched before.

We don't know what we're going to find, we really don't.

And I think that that's what really makes this so exciting.

How do you design a spacecraft that can survive

a three-billion-mile journey to parts unknown?

Any time you explore something new,

there's always a little risk.

The New Horizons mission

faced a huge number of challenges.

We're going to the outskirts of the solar system, you know,

30 times farther from the Sun than the Earth.

And so in order to get there in a reasonable amount of time

we had to build the lightest possible spacecraft

that we could,

put it on the largest rocket we could.

There was no opportunity to fly big solar arrays

because the sunlight is just too faint,

so we carry a nuclear-powered source.

We have a suite of instruments, seven instruments

to do very different things.

And they weigh less than about 70 pounds, all of them together.

Seven scientific instruments

not much bigger than a grand piano

with whimsical names like Pepsi, Swap,

and an antenna named Rex.

Two are named after the lead characters

in the 1950s television show The Honeymooners,

Ralph and Alice.

All of these instruments will analyze Pluto's surface

and geology, and reveal secrets about its mysterious atmosphere.

Back in the 1980s, one of the best ways

to observe Pluto's atmosphere was with this,

a C-141 cargo plane

with a makeshift observatory on its side.

The Kuiper Airborne Observatory

was not what you'd call a first-class ride.

The Kuiper Airborne Observatory is not built for comfort.

You're on headsets the whole time.

It's very loud, it's very cold.

The telescope, it's in the middle of an airplane.

It bounces around.

But by flying a telescope above the weather,

they had a chance to capture a rare event

called a stellar occultation.

During this event, an object, like Pluto,

passes in front of a bright star blocking its light.

If the object has an atmosphere, the light gradually fades out,

then slowly fades back up again.

But if it doesn't, the light abruptly disappears,

and then quickly reappears.

This is a recording of what happened

onboard the Kuiper Airborne Observatory

the night of June 9, 1988, when a group of researchers

were determined to find out if Pluto has an atmosphere.

The light behind Pluto slowly faded,

and the crew made history.

I was fortunate enough to be involved.

I would call that the beginning of my being an astronomer,

and it's a pretty good beginning.

One of the instruments onboard New Horizons

that's designed to study Pluto's elusive atmosphere is Alice.

This model is an actual size model of Alice.

Alice is an ultraviolet spectrometer.

It's a telescope that breaks up light into a rainbow.

Every chemical element reflects and absorbs light

in a unique way,

creating a pattern as distinct as a fingerprint.

Hydrogen's fingerprint looks like this,

while nitrogen's looks like this.

Powerful Earth-based telescopes have already detected molecules

of nitrogen, methane and carbon monoxide on Pluto's surface

and in its atmosphere.

We suspect it has

a number of others that we simply can't detect.

As the spacecraft flies just a few thousand miles

above Pluto, Alice will search for those fingerprints.

Then, at the end of the flyby, the spacecraft will turn around

to give Alice a one-of-a-kind view of Pluto's atmosphere,

as seen through the light of the Sun.

We can use the Sun as our light source

to probe the atmosphere

and look for those fingerprints of certain types

of atoms and molecules.

While Alice probes Pluto's atmosphere,

her partner, Ralph, an infrared spectrometer,

will be hard at work searching for those chemical fingerprints

of molecules on Pluto's surface.

We want to know what's causing

the very bright surfaces on Pluto, which we think

is exotic snowflakes of molecular nitrogen and methane.

But there are other regions that seem to be devoid

of those snowflakes and are probably much redder,

darker hydrocarbon deposits.

Ralph will finally reveal what these strange,

dark regions are made of.

But to get up-close and personal images of Pluto

requires an instrument with a one-of-a-kind telephoto lens.

The largest imager on board New Horizons, named LORRI,

will capture extraordinary images of Pluto's surface.

LORRI will take pictures so detailed

that if it was flying over New York City,

you could see the Hudson River, the East River,

even Central Park.

To put this in perspective, this image of the Big Apple

was taken by a satellite

traveling about 400 miles above Earth.

LORRI is so powerful,

it could capture the same amount of detail

from more than 7,000 miles above Earth.

But sending a telescope with a lens like this

into the grueling subzero temperatures of the Kuiper Belt

is risky business.

When you have a telescope,

it's opened to space,

and so it's cooling through that opening.

The result is that you're putting part of camera cold,

part of it warm,

and that changes the shape of the telescope

and that tends to put it out of focus.

And you can end up with pictures that look like this.

To solve this problem...

...they turn to a material found in bulletproof vests.

What makes vests like this so strong

is a compound called silicon carbide.

LORRI is made out of a special version of it

which is able to tolerate temperature gradients

without distorting its shape.

But it's also very strong and very light.

There's a lot of things that might go wrong,

and we've tried to anticipate all those things

and work out contingency plans,

and contingency plans for those contingency plans.

We've been working for years to get the spacecraft ready,

prepare for everything you could think of.

In the end, it just...

You know, you just have to sit there and wait,

and it just either works or it doesn't.

For the New Horizons team, waiting to find out

if all their hard work will pay off

just may be the toughest challenge of all.

During the Pluto encounter,

the spacecraft's basically pre-programmed

to do everything on its own.

If it gets into trouble, we can't help.

We can't give it a call and say,

"Whoops, you're looking at the wrong thing.

Adjust your sights a little bit to the left."

That's because when the spacecraft flies by Pluto,

it will take four-and-a-half hours

for a radio signal to reach Earth

and another four-and-a-half hours

for instructions to get back to the spacecraft.

If something went wrong, it would be more than nine hours

before we could tell it to do something.

The most important science

is happening really only over about a 12-hour period.

The timing has to be precise because the onboard commands

all have a predetermined time that this is supposed to happen.

If that time changes too much,

we'll get a lot of pictures of black space

and we'll miss the science.

February 28, 2007.

New Horizons has been en route for a little over a year.

Back at mission operations

at the Johns Hopkins Applied Physics Laboratory,

the team prepares for the spacecraft's

first real test since launch.

As New Horizons nears Jupiter,

it must hit a mark just 500 miles wide,

where it will get pulled into the gas giant's gravity

and get flung out.

At that point, it will be traveling a lot faster.

Think of it like a clever maneuver used in roller derby

called "the whip."

One skater pulls another,

propelling her forward with greater velocity.

That's what Jupiter's gravity will hopefully do

for New Horizons.

At mission operations, the tension is palpable,

especially for the mission operations manager,

Alice Bowman, also known as "MOM."

Status check.

She has spent years preparing for this moment,

and she knows all too well

what it means if this maneuver should fail.

It would take years longer

to get to Pluto if you did not have that flyby.

If you think nine years is a long time,

adding another couple years onto that,

that would have been intolerable.

The clock is ticking.

MOM, along with the Mission Ops team,

waits to receive telemetry from the spacecraft.

This data will reveal whether New Horizons

successfully pulled off the gravity assist or not.

Red is bad, green is good,

gray means you don't have any data.

Finally, they hear from the spacecraft.

PI, this is MOM on Pluto One.

Spacecraft telemetry for all subsystems is nominal.

Spacecraft is outward bound from Jupiter

and we're on our way to Pluto.

So far, so great.

This is good.

By stealing some momentum

from Jupiter along the way to Pluto,

we can actually increase the speed of the spacecraft

by about 20% and cut three years off the travel time.

And at the same time,

because in order to do the Jupiter flyby

you end up coming fairly close to it,

it gives you an opportunity to do some great science.

It was the only time we were going to have large objects

for the cameras to actually point to and say,

"Okay, are we doing this right?"

We used all the instruments on New Horizons,

but LORRI was prominent.

Okay, thar she blows.

Oh, wow!

Look at that!

And we got both of them, we got both of them.

It's beautiful!

From more than a million miles away,

LORRI captures a sequence of images

of the eruption of a volcano on Jupiter's moon Io.

It was the first time

that a time-lapse had ever been made

of any volcano anywhere in the universe off the Earth.

So it was really unique.

It's another plume!

Perfect image.

Yeah!

We were extremely lucky we got these fantastic movies.

It made all those sleepless nights and all that hard work

very much worth it.

After the gravity assist,

New Horizons goes into hibernation.

Only essential systems are up and running.

This limits the amount of wear and tear on the equipment.

For most of its nine-year journey, it will be asleep,

but once a week, the spacecraft phones home to MOM.

This is MOM on Pluto One, status check.

And MOM lets the whole team know

if all systems are in working order.

As New Horizons makes its way across the solar system

to the last and loneliest planet to be explored,

back on Earth, a revolution in astronomy is taking place.

After 75 years as the solar system's ninth planet,

Pluto is getting its walking papers.

Pluto was, since 1930, a planet.

He had stature, he had friends.

Could it be the final indignity

for the farthest and smallest planet in our solar system?

Size doesn't matter!

The public takes to the streets to fight for Pluto.

Go, Pluto!

Pluto forever!

It's been America's favorite planet

since it was discovered back in the 1930s

by the unlikeliest of planet hunters.

Clyde Tombaugh was a self-educated farm boy

who attended a one-room schoolhouse.

His first job in astronomy included cleaning telescopes

and sweeping up at the Lowell Observatory.

He spent the rest of his time searching for something

that could be causing disturbances in Neptune's orbit:

the mysterious "Planet X."

Every few nights,

he placed a photosensitive glass plate on the telescope,

securing it so it would not shift.

Then he exposed the plate for one hour

to the universe.

During that time, the motorized telescope slowly moved

to compensate for Earth's rotation.

Several days later, he'd retrace his steps,

taking pictures of the same sections of the sky

he had photographed earlier.

Then, using an ingenious device called a blink comparator,

Clyde aligned the two images

to carefully examine their differences.

The blink comparator enabled him to shift back and forth,

searching for the subtlest of changes.

Although the human eye is good at spotting differences,

finding a dim celestial object billions of miles away

was a daunting task.

Month after month,

he forged ahead through a harsh, cold winter.

He almost froze to death

one night because his fingers got so numb,

he couldn't get the trap door open

to get out of the dome.

They were having a lot of problems

with the photographic plates breaking in the cold weather,

and he invented a new plate holder

that would keep the plates from breaking,

and that's what led to the discovery.

After patiently searching for almost a year,

a determined Clyde finally found a tiny dot

slowly moving across the night sky.

Can you see it?

Here it is.

Two months later, the Lowell Observatory

proudly announced that a young assistant

had discovered the ninth planet in our solar system.

Because of the discovery,

my dad got his college education.

Otherwise, he probably would not have been able

to afford to go to college.

The discovery was, I would say,

the driver of our life in many ways.

After discovering Pluto, Clyde taught astronomy,

and for decades to come, he searched for another planet

in the far reaches of the solar system.

But as hard as he and other astronomers looked...

And they looked hard... Nobody found anything.

Until astronomers David Jewitt and Jane Luu

took on the challenge.

They started a search that would take a lot longer

than they could ever imagine.

Why did it take so long?

It was a matter of technology catching up with the problem.

While it's easy to see distant stars

because they radiate light,

other celestial bodies are much harder to see.

That's because light has to travel

all the way from our Sun to the object,

reflect off its surface,

and then make the long journey back to Earth.

By then, it's barely visible.

David and Jane hoped that advances in digital detectors,

now standard in today's smartphones,

would help them see a whole lot more.

After searching for five years, they finally found something.

Here is the set of discovery images

for the first object.

So you can see this object

drifting from this picture to this one to this one.

It's drifting slowly to the left.

When they found several more of these slow-moving objects,

David and Jane could finally declare Pluto is not alone.

In fact, it's got plenty of neighbors.

They named this new region of the solar system

the Kuiper Belt, after Gerard Kuiper,

the astronomer who proposed its existence back in the 1950s.

The discovery of the Kuiper Belt

expanded our understanding of the solar system

in a profound way,

but it also put Pluto's planetary status in jeopardy.

Is it a planet

or a Kuiper Belt object, one of many?

My Dad knew there were rumblings in the wind, and it upset him.

It certainly was not easy for my father.

But the final blow was yet to come.

A few years later, a young astronomer

decided to look for more objects in the outer solar system.

Mike Brown was determined to do something really big:

find a Kuiper Belt object larger than Pluto.

We even thought we might be finding things

the size of Mars, the size of the Earth.

We really had no idea.

So when we started off doing this back in 1997,

it was pretty exciting to think what might be out there.

At the Palomar Observatory in California,

Mike had access to the largest digital camera on earth.

The images were uploaded to his computer,

where he analyzed them every morning.

With technology on his side,

the discoveries just kept on coming.

We found Quaoar,

which is an object out in the Kuiper Belt

that's about half the size of Pluto.

The next year, we found something

about three-quarters the size of Pluto,

and in the following year, we found this thing,

and it was so bright and also moving so slowly,

moving so slowly because it was so far away.

After all this time, Mike couldn't believe

he might finally have found what he had been looking for.

I looked at it and I thought, "This can't be right."

If it's that bright and moving that slowly,

it's the furthest thing we've ever found

and it's the biggest thing we've ever found,

and it must be bigger than Pluto, and that's crazy.

It was the first object to be discovered

that could have been larger than Pluto.

That caused a ruckus because, well, if Pluto's a planet,

then this has got to be a planet, right?

And so what are we going to call these things?

Most people really didn't care that much

about this thing that we just discovered.

They wanted to know, "Well, what does it mean for Pluto?"

It's like, "Oh, yeah, you found something bigger than Pluto.

But what does it mean for Pluto?"

For the past century, the IAU...

The International Astronomical Union...

Has been in charge of naming celestial objects,

but it couldn't give Mike's discovery a name

without knowing if it was a Kuiper Belt object

or the tenth planet.

I think it started an interesting conversation

because we didn't really have a definition for planets, okay?

You know, it came from the Greek "wandering star,"

and we did need a better way of classifying things

as being planets or small bodies in the solar system.

At the IAU meeting in Prague, a vote was taken

on a new definition of the word "planet."

Pluto's fate came down to the phrasing of just one line:

"a planet has cleared the neighborhood around its orbit."

Pluto resides in a crowded neighborhood

filled with thousands of Kuiper Belt objects.

Unlike larger planets, tiny Pluto

doesn't have enough gravity to clear them out of its way.

It also has an extreme elliptical orbit

not on the same plane as the rest of the planets.

Eight major things which dominate the solar system

are planets.

They're all big.

They go in circular orbits in one disk around the Sun.

And everything else is much smaller.

Those are not planets.

So according to the IAU, Pluto is not a planet;

it's a "dwarf planet."

There has been a consensus developed

that Pluto is a dwarf planet,

and you know, I have no problem with that.

The controversy comes in when you try to say

a dwarf planet is not a planet.

Well, it seems a little ridiculous

to have "planet" in the word, the designation for an object,

and say somehow it's not a planet.

In a sense, this question

of how do you label certain objects

is less important than understanding

that objects like Pluto, the Earth, Jupiter, exoplanets

come in a remarkable variety

and in remarkably different configurations

across the universe.

While Pluto may no longer be the solar system's ninth planet,

it turns out it's got plenty of company.

Planetary scientists continue to discover more dwarf planets,

giving them temporary nicknames like "Santa" and "Easterbunny."

We've discovered that the outer solar system

is littered with small planets.

These are typically rocky and icy objects.

Many have atmospheres.

Many, possibly most, have moons.

All the things we're used to

in the planets we're familiar with,

but in miniature.

I think a decent analogy is

when you see a Chihuahua, it's still a dog

because it has the characteristics

of the canine species, just in miniature.

Not everyone agrees with Alan Stern's canine analogy,

and as more Kuiper Belt objects are discovered,

how did our outer solar system

end up with these pint-sized dwarfs?

To answer that, we may need to look back

at the birth of the solar system.

We think

that the solar system began to form

about 4.5 to 4.6 billion years ago

when a cloud of nebula, a cloud of gas and dust,

fell in on itself because of its own gravity.

As it fell together,

it began to turn into a great disc

of orbiting, swirling material.

It's that disc of gas and dust

that we think turns into planets.

You make a planet from material sticking together

and building larger and larger pieces.

Scientists theorize that planets form

when this material starts to stick together.

Pebbles turn into boulders,

boulders into mountain-sized comets.

Comets turn into protoplanets.

Protoplanets turn into planets.

After objects reach a certain threshold in their mass,

they can grow more rapidly than they could before

because they have substantial gravity.

Gas giants like Jupiter and Saturn

siphoned up massive amounts of hydrogen and helium,

sweeping up everything in sight.

It seems plausible that Pluto

originally formed somewhat closer in to the Sun,

but then as those major planets got larger and larger,

it got pushed to a more distant orbit.

We think that objects like Pluto and the other Kuiper Belt bodies

are really the remains of that process of planet formation.

They are sometimes called planetesimals,

celestial objects that somehow stopped growing.

Dwarf planets were arrested

in the mid-stage of planetary growth.

They are actually planetary embryos.

And to study those objects

rather than objects that grew to much larger scales

will give us a great window

into the process of planetary formation.

Perhaps we can find clues

in the surface of Pluto and its composition

that point towards that deep history

and in turn tell us about the architecture

of the solar system as it is now.

Where did that come from?

How did that happen?

Pluto may even hold clues

to unravel another great mystery.

As far as we know, the requirements for life

are water, energy, and organic matter.

A large number of dwarf planets

may have all of these ingredients.

There are very reputable models of Pluto

that suggest that there's a vast interior ocean

and that these may be common inside the dwarf planets.

Wherever you have water, then you have the potential...

And I want to stress that word, "potential"... for biology.

So it may be that the dwarf planets

are not only the most common kind of planet

in the solar system,

they may be the most common abode for life

in the solar system.

Clearly, organic chemistry, carbon chemistry

can take place on the surface of objects like comets

and probably Kuiper Belt objects too.

Whether or not that relates

to the existence of life on Earth

I think is a totally open question.

But just understanding the chemical richness

of our solar system and the universe

is a big piece of the puzzle,

and it's a piece of the puzzle that we need to solve.

June 8, 2008.

New Horizons has been soaring through space

for more than two years.

Today, it passes the orbit of Saturn.

In three more years, it passes Uranus.

It's spent half a decade traveling through space,

and it's still running like clockwork.

But then the unexpected happens,

putting the entire mission at risk.

Images taken by the Hubble Space Telescope

reveal Pluto has not one, not two, not three, not four,

but five moons.

All of these moons probably all formed

in the same big cosmic collision taking place

about 4.6 billion years ago,

where two Pluto-sized objects rammed into each other,

and now we're seeing the aftermath of that.

In the end, Pluto remained intact,

but the other object broke into pieces,

forming the five moons that we know of,

some very oddly shaped.

All of these small moons are debris generators,

creating the potential of millimeter-sized dust

forming a ring around Pluto.

The spacecraft is flying so fast through the Pluto system,

roughly 30,000 miles per hour,

that if it hit even a millimeter-sized particle,

it could blow a hole in the spacecraft

and it could destroy the mission.

Back in 1967,

this almost happened to the Mars probe Mariner 4.

It ran into a cloud of space dust.

And over the course of about 45 minutes,

they were seeing thousands

of impacts on the spacecraft, completely unexpected.

Clearly, there are particles out there that we can't detect

that could potentially cause a loss of mission.

How much of a beating can New Horizons take?

We're about to find out

at one of the most powerful shooting galleries in the world.

NASA's hypervelocity gun

can shoot the tiniest of pellets up to 17,000 miles per hour.

The dust particles New Horizons might run into

range from the size of the head of a pin

down to the size of a grain of sand.

These little objects may not look very dangerous,

but imagine a sandstorm with winds so strong

that just one grain of sand could kill you.

The gun is loaded.

The room is cleared.

This gun is so powerful,

metal is pulverized from the impact.

A pellet is propelled down this 120-foot-long barrel

to a target made of the materials

used in the construction of the spacecraft.

The first layer is the gold thermal blanket

that covers New Horizons.

The second layer is the spacecraft's wall.

The third layer, a thin metal plate,

represents the heart of the spacecraft:

the electronics and scientific instruments.

Test after test is conducted,

tiny pellets slammed into the target

at lightning speeds.

The results are mixed.

Most of the pellets penetrate the gold thermal blanket

but are stopped by the wall of the spacecraft.

But not all.

In fact, some, like this one, punch a hole right through it.

A few more holes like this

could put a quick and violent end to the mission.

The potential for a debris impact that came out

through the detection of the newer moons

does add another layer of complexity to the flyby.

The New Horizons team had to come up

with alternate flight plans, or trajectories,

for the spacecraft to travel.

This is the ideal trajectory they are hoping for.

There are actually four different trajectories

that we could potentially go on,

and we may not know until a couple of weeks out

which one we're going to be on.

The worst possible scenario is it comes into the system,

it starts taking images,

it gets destroyed by some impact,

and we'll never see the images,

which is pretty nerve-wracking.

I want to see the results.

I'm glad I'm not the person waiting for that data to come.

On the approach, we have planned observations

to look for any other debris,

or we're calling them hazard now... not moons, hazards.

It's funny how things change.

There'll always be a little nagging question,

you know, "Did we make it through?"

So that first beacon that says we made it through,

everybody is just going to...

They'll breathe a sigh of relief

and then they'll look at each other and go,

"Oh, I knew it all along."

August 25, 2014.

New Horizons reaches Neptune's orbit

on the 25th anniversary of Voyager 2's encounter.

The original mission was designed

to study only Jupiter, Saturn, and their moons,

but Voyager 2 went on to take stunning images

of Uranus, Neptune, and its moon Triton.

In the '60s and the '70s

and the '80s we were exploring new planets all the time.

First to Mars, first to Venus, first to Mercury,

first to Jupiter, first to Saturn.

That came to an end in 1989 with Voyager.

It's been 25 years,

and now we're doing the next first mission.

That's epic.

December 6, 2014.

After years in hibernation, the spacecraft is waking up.

The final leg of its journey is about to begin.

Tonight, we're ending hibernation.

We have been hibernating the spacecraft

for most of the three-billion-mile journey

across the solar system.

That's over now.

It's really quite a historic day.

Once the spacecraft has checked

that all systems are up and running,

it will send a report back to MOM.

So when we receive

a signal from the spacecraft,

it's data that the spacecraft sent

four-and-a-half hours earlier.

And it requires a special network of radio antennas

to receive it.

Theses enormous antennas are spaced across the globe

so as the Earth rotates,

the team can stay in touch with the spacecraft 24/7.

The spacecraft has a ten-watt transmitter.

That we can pick that signal up on Earth is incredible.

In comparison, your average radio station

uses 50,000 watts to transmit a signal.

It is an amazing accomplishment, and a lot of that's due

to the technology that's at the stations,

at the Deep Space Network, these amazing antennas.

Getting ready for showtime here.

A few members of the team have gathered

in the room next door, hoping to celebrate.

But that moment will only arrive when a very tense MOM

gets word from NASA's Deep Space Network

that they are starting to receive a signal

from New Horizons.

Data begins to show up on her screen.

Did we get it?

We got it.

But before she can breathe easy,

all members of the Mission Ops team

must verify that all systems are in working order.

RF, MOM on Pluto One.

Status Check?

RF is green.

Power status?

Power system is green.

Propulsion status?

Propulsion is green.

Oh, there we go!

We have a nominal wake-up

of the New Horizons spacecraft on our way to Pluto.

The team is ready for the next leg of our journey.

We've got an encounter coming.

Yeah!

Yeah, how about that?

Some days, it just goes like clockwork.

Here we go, cheers.

We're just gonna all take a big breath now.

To Pluto and beyond!

Hear, hear.

To history.

This has been a very long road.

For the MOM!

Thank you.

Well, it's just amazing.

We are on the other side of the solar system,

and where we were meant to be.

When we talk about the spacecraft,

we talk about it as if it's, you know, our child, our baby.

When it does something that we don't expect,

we relate it perhaps

to "terrible twos" or something like that,

so it really... it becomes part of us.

Over the years, hundreds of people

have dedicated themselves to this historic mission.

For many team members, revealing Pluto's secrets

is the challenge of a lifetime.

The New Horizons mission

has been a large part of my life,

and it's been the majority of my children's lives.

I think they can't even imagine what it'd be like

to have this data from Pluto,

because they've been looking forward to it

for their whole life.

As New Horizons gets closer and closer to Pluto,

the team determines there are no more moons

and little risk of the spacecraft being destroyed

by debris.

They looked and they looked and they looked,

but they couldn't find any new moons.

I think they were kind of disappointed

from a scientific standpoint, but from a hazard standpoint

it was really good news.

But the good news is short-lived.

About 1:55 p.m. local, we've lost signal with the spacecraft.

You just feel that pit in the bottom of your stomach.

You're thinking, "Oh, my God,

I can't believe this is happening."

Your pulse goes up a little bit.

Could it be these millions of miles away, we hit something?

Searching for a solution, mission ops tries to connect

with New Horizon's backup computer,

which transmits on a different radio frequency.

Right away, Deep Space Network locked up onto that signal

and it was such a great feeling because we found our spacecraft.

Turned out that the main processor had reset

and it had switched over to the backup processor.

That's sort of like your worst nightmare

a week before an encounter.

We knew that we could fix it.

The question was:

were we going to be able to do that in enough time?

Alice, I swear, didn't get any sleep.

But she said she slept on the floor

for a few minutes one night.

For a couple nights slept there.

You know, just like a child that's sick,

you want to be there to help it recover along the way.

The team fixes the problem

just seven days before New Horizons is set

to fly by Pluto.

We did it with four hours to spare, or something like that.

Yes, things are definitely back onto track.

And the pictures are flooding in.

Every day, it's been getting better and better.

We've been getting beautiful stuff for the last week.

We are drooling with anticipation.

The next picture from LORRI that we will see

is a full-frame image of Pluto.

And it's the one that we think is really going to tell us

what's happening.

I almost can't wait for it to come down.

Taken almost half a million miles away,

this is New Horizons last portrait of Pluto

before its closest approach.

Scientists speculate the light areas are ice;

the dark could be a dusting of organic molecules

that fall from the atmosphere.

Wow.

This is the heart, right?

This is the heart-shaped region,

being traced out here.

Clearly there's a lot of craters.

Boy!

It really is breathtaking and awe-inspiring.

I've never seen anything like this before.

But there's one more hurdle, and it's a big one.

The world watches

as the team tensely awaits a signal from New Horizons

that it has made its closest approach to Pluto

less than 8,000 miles above the surface

and survived with all systems intact.

Stand by for telemetry.

PI, MOM on Pluto 1.

We have a healthy spacecraft.

We've recorded data of the Pluto system,

and we're outbound for Pluto.

We did it.

Very relieved and happy, yes.

No, I mean, every polling that was done,

every subsystem that reported in was like music to my ears.

It's never sounded that good.

The next day, the tiny spacecraft,

three billion miles from home, starts beaming back...

The first close-up pictures of Pluto,

with icy mountains 11,000 feet high,

and Pluto's biggest moon, Charon,

with hardly any impact craters.

It will take about 16 months for New Horizons to send back

all the photos and data it has gathered...

and years for scientists to analyze it,

slowly revealing Pluto's secrets as New Horizons itself

heads out through the icy Kuiper belt and beyond.

At pbs.org/NOVA.

Get the latest updates

from New Horizon mission control,

and take a closer look at the surface

with the most recent images

from the probe's close encounter with Pluto.

You can also watch original video shorts,

explore in-depth reporting, and dive into interactives.

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