Juno: Mission to Jupiter The Sky at Night

Jupiter.

The monster of the solar system.

Huge,

violent,

and unforgiving.

We have always been fascinated by it,

and that is why, over the past 40 years,

we've sent eight spacecraft to investigate this massive world.

But its swirling cloud-tops still conceal many mysteries.

And that is why we have now sent a ninth mission - Juno.

CHEERING

There it is! Juno's right on time, into orbit exactly as planned.

Last Monday, Nasa's Juno probe arrived in orbit around Jupiter.

The Sky At Night has been embedded here at mission control,

and so tonight we bring you all the action

as Juno completed the most dangerous and complex phase of its mission.

We'll also be looking forward to what Juno does next,

and how it's set to transform our understanding of the solar system.

Welcome to The Sky At Night.

This is the Jet Propulsion Laboratory in Pasadena, California,

one of the iconic sights of the Space Age,

home base for our exploration of the solar system.

It was from right here that the world watched

as the Voyagers and the Pioneer spacecraft

made their first reconnaissance of the giant planets,

and now, with Juno, we're going back to Jupiter.

In Roman mythology, Juno was Jupiter's wife -

the only person who could see through the clouds

that concealed her husband.

Juno the spacecraft's mission is exactly the same.

Its aim is to pierce through the clouds to reveal what's going on

inside the planet.

The mission has three main objectives.

To understand what drives Jupiter's violent atmosphere.

To discover how the planet was formed,

shedding light on the formation of the entire solar system.

And to find out why it has such intense and spectacular aurorae.

But first, it had to enter an orbit

that would take it within 5,000km of the giant planet.

The crucial manoeuvre was called Jupiter Orbit Insertion.

And with a certain sense of theatre,

it was set for the evening of the of 4th July.

That morning, Juno's scientists and the world's media

gathered at JPL to watch events unfold.

This was to be one of the most crucial days in the whole mission.

And the greatest fear was that the spacecraft might not make it through

the hostile environment close to the planet.

Can you say what we know about the ring particles

you were worried about?

We believe the probability's very low that we're going to hit one,

but it's not zero.

It's the same thing if I go through the asteroid belt, you know,

so as we fly by very, very close,

we look at the signal from the radio

and can tell how it's been changed...

I've just come out of the briefing

with a quite nervous-looking Juno team. They're excited,

but they're clearly worried about whether the spacecraft

will survive the next 24 hours. But I have to show you this.

It's the first movie we've seen from JunoCam,

it's about two days' worth of an approach to Jupiter.

What I love about it is you can see the main moons,

the four Galilean moons dancing around the planet.

You can see Jupiter growing

as it approaches over the course of this movie.

That means it's crunch time.

Juno is entering the most dangerous phase of its mission,

and what the team in the briefing there are worried about

is dust from the rings. A single collision could end the mission.

And the team are also worried about the radiation environment.

That could stop Juno working and put a very premature end to the mission.

To get into orbit, Juno had to fire its main engine,

slowing the probe down just enough to be captured by Jupiter's gravity.

Its trajectory had been carefully planned

to avoid the worst of the planet's radiation belts.

It would approach over the north pole

before falling into an orbit that would repeatedly squeeze Juno

between the radiation belt and the planet itself.

No spacecraft had ever attempted such a daredevil manoeuvre.

I spoke to Juno scientist Fran Bagenal about the dangers.

So we're not far now from the critical moment,

the engine burn that will deliver Juno, with any luck,

to its desired orbit. How are the team feeling? How nervous are you?

We're all worried and nervous and...

I'm sure everything will go fine and I trust the engineers,

but, yes, I've got all my fingers and toes crossed.

We've been to Jupiter before, we had the fly-bys,

but also the Galileo mission that went into orbit

and explored the Jovian system. What's different about this time?

-What is it that's dangerous?

-Usually when we go to Jupiter,

we're either getting a gravity assist

or we stay away from the inner region.

Or we're going in orbit and we stay on the equator.

Now for Juno's science, we really want to get up close.

Right around the belly of Jupiter

there is a doughnut of very energetic charged particles -

-ten million volt electrons whizzing around...

-Which is a lot?

Which is a lot, right? And so you're really worried

that the electronics will be zapped by these energetic particles

and damage the sensitive electronics you've got inside, in detectors.

It's like taking your computer and giving it a gazillion X-rays,

you know, you wouldn't want to do that.

So what we're going to do is very clever.

We're going to fly over the top of the pole,

we're going to fly through the slot between the radiation belts

and the clouds, through that region,

and then out again below. And that, we hope,

will protect us from those energetic radiation belts.

And how small a slot is that?

How much of a precision manoeuvre does this have to be?

We don't really know,

because we don't really know how far the atmosphere extends out,

and we don't really know what the radiation belts are.

We can map them from the ground using radio observations,

but they're not that accurate,

so it's not so much an issue of precision as uncertainty,

and we don't really know what it's like. This is terra incognita.

The other thing that makes this a little safer

is that because of Jupiter's strong gravity

we're moving really quickly.

So we go in through there and get out really quickly.

And so the spacecraft will be moving at about 165,000 miles an hour,

and so this allows us to go from pole to pole in two hours.

And since Jupiter is ten times the size of the Earth,

that's equivalent to going around the Earth

-five times in two hours.

-Wow.

It's a dangerous mission nearly two decades in the making,

and it could end in disaster before it starts.

So what is it that we want to know about Jupiter

that justifies these risks?

Jupiter dominates our solar system.

It's 140,000km across,

and two and a half times more massive

than the rest of the planets put together.

On this scale, if Jupiter were the size it appears on the screen,

about two and a half metres across,

then the Earth would appear the size of this basketball.

And it would fit into Jupiter

about a thousand times over.

We think that Jupiter was the first planet to be formed.

It sort of hoovered up most of the stuff left behind

after the sun's formation.

And like the sun, it's mostly made up of hydrogen and helium -

about 95%.

The other 5% is made up of heavier elements.

And it's all spinning incredibly fast.

This vast planet rotates on its axis

once every ten hours.

As it spins, the clouds of its atmosphere

are driven into thick banks

by the powerful winds that orbit the planet.

Those swirling forces create giant storms

like the famous Red Spot.

Even though we've been studying the planet for over 400 years,

there's still much that is quite mysterious about Jupiter.

One of the first things Juno is aiming to discover...

..is what powers those giant storm systems.

To find out how it's going to do that, I went to talk to

Jupiter expert and Juno collaborator Leigh Fletcher.

So, Leigh, what are we seeing here?

This is a beautiful movie that was taken by the Cassini spacecraft

when it flew by Jupiter back in the year 2000, 16 years ago.

You can see in this image just how dynamic the Jovian atmosphere is.

Things are changing all of the time

as we have these jets of wind whizzing east and west

and separating the beautiful banded structure.

And we think that these bright white clouds at the equator

are regions where air is welling up from the deeper interior

and it's dredging with it particles, or molecules, of ammonia gas,

and those ammonia gas molecules condense and it forms ice crystals.

Those ice crystals create these white colours

within the equatorial zone.

OK. What about these darker bands?

That's an even harder question to answer.

But what comes up must ultimately come down.

What we believe is happening is the air that's rising over the equator

is then sinking over the northern equatorial belt

and the southern equatorial belt.

Those ice crystals evaporate away

and they reveal the natural colours of Jupiter

deeper down within the planet. Unfortunately we still don't know

what is actually causing the brown colour.

What you can see here as well is that the belts look much more active

and much more dynamic than the white regions.

We think that all of that activity is being driven by the same molecule

that drives atmospheric weather here on Planet Earth,

and that's water vapour.

You're familiar with, if you have a humid atmosphere,

-it's more prone to thunderstorms...

-Or tropical, yes...

-Tropical storms.

-Hurricanes and things. Yeah.

Well, the same phenomena could be occurring within Jupiter.

But if water is part of the story

for what's driving this incredibly dynamic atmosphere,

then we'd have to understand where the water is located

within Jupiter and, crucially, how much is there within the planet.

So how can we do that? Can we go any deeper?

So Juno has got a very clever instrument

called a microwave radiometer on board.

And what we can see in microwave light

is modulated by the amount of ammonia that's there

and the amount of water that is there.

So by building up this map - and it will take a while to build it up,

many months of the Juno mission going over various longitudes

to paint a complete picture of the planet -

we'll then be able to map where the water is located

-and where ammonia is located.

-So that might give you

-an understanding of what's driving those weather systems.

-Absolutely.

It's going to be a step-change in our understanding of

how much water is present within the Jovian atmosphere.

But Juno's mission is about more than

just studying Jupiter's upper atmosphere.

By probing the deep interior, it hopes to reveal

how both the planet and the solar system formed.

One of the great mysteries of Jupiter

is understanding how it formed in the first place.

One possibility is that it began life as a star does,

as a collapsing cloud of gas, before becoming the planet we see today.

Another option is that, big though it is,

Jupiter began life in the same way that the Earth did,

starting as nothing more than a pile of rubble,

planetesimals that could stick together

to eventually form a core that was maybe then times the mass of Earth.

Big enough to grab and to hold on to a thick hydrogen atmosphere.

Juno will tell us which of these two possibilities is the correct one.

As it orbits the planet, Juno's path is not completely uniform.

It's affected by tiny variations in Jupiter's gravitational field.

By tracking these tiny wobbles over the months that it's in orbit,

Juno will build up an incredibly detailed map

of the planet's gravitational field.

And that should tell us whether or not

there's a rocky core at the heart of Jupiter.

Either way, it's a discovery that will have profound implications

for our understanding of how giant planets form,

not just in our solar system,

but also in other solar systems around other stars.

Juno has amazing scientific potential,

but before it could start its observations,

the spacecraft first had to complete its orbit insertion manoeuvre.

Back in mission control,

while the rest of America was out celebrating the 4th of July,

we waited for news.

So just a few minutes ago out near Jupiter

Juno should have started firing its main engine.

It's the critical manoeuvre required

to take it into orbit around Jupiter.

The only problem is, because it's so far away,

it'll take 48 minutes for that signal to reach us

here at mission control.

And only when it arrives will people start to breathe a little easier.

We're expecting a signal from the spacecraft to say all is well,

and then two minutes later,

confirmation that the burn has started.

I think it was quite jovial, but it's all gone very quiet

and very tense. People know if this doesn't come in on time,

something is seriously wrong.

-Everything's looking good.

-Standing by.

We're right on the time we expected the signal.

INDISTINCT

Good, now?

-Yeah, we see the expected...

-Got it! They've got it.

It's changed its velocity,

the burn has started,

and Juno is starting to put itself in orbit.

-CHEERING

-That's wonderful news.

The fact that the burn has started means the engine

is working as expected.

But the really difficult bit is keeping it working

as Juno travels through this most dangerous region.

They need a burn of 35 minutes to put themselves in the desired orbit,

so people will be keeping things crossed for a long time yet.

In order to make all its measurements

and probe beneath Jupiter's clouds,

Juno has been equipped as no spacecraft ever before.

I used to build instrumentation for spacecraft,

but I've never been involved with anything like Juno.

For one thing, it's huge - about 20 metres across.

That's about the width of this hangar.

Most of that width is made up of these huge solar panels,

each one nine metres long.

Now, the reason we need such large solar panels

is cos Juno is going to sit a long, long way away from the sun.

Out around Jupiter, the sun's intensity

is just one 25th of what we receive here on Earth.

It's the first time we're sending a solar-powered spacecraft

so far into the solar system.

The 18,700 solar cells

will only produce around 450 watts.

It's not much - not even enough to boil a kettle.

But Juno's instruments have been designed to operate at low power.

The spacecraft's brain and most of the instrument electronics

are housed in this titanium bolt to protect it from radiation.

But the instruments themselves

are based on the outside of the spacecraft.

The first instrument is Jedi,

used to measure high-energy particles

in Jupiter's magnetic field.

These are the microwave detectors.

They'll analyse water in Jupiter's atmosphere.

And this is the only optical camera onboard, JunoCam.

And as it was leaving the Earth, it took this magnificent picture.

It really is quite beautiful.

But the images JunoCam will take of Jupiter

will be far more spectacular.

At its closest approach to the planet,

it will be only 4,200km above the cloud tops.

That might sound like a lot.

So let's use our basketball again, only this time, it's Jupiter.

On this scale, Juno will fly less than a centimetre

above the surface, and from that location,

it will be able to take the highest resolution images of Jupiter

that have ever been seen.

This is the part of the mission we can all take part in,

because Nasa have asked for the public's help

in choosing the features that JunoCam will photograph.

And as Peter's been discovering, the first step

is that they want people to submit their own photos of Jupiter.

Right, I'm nicely lined up on Jupiter now,

and it's actually a pretty good view.

The planet is getting lower in the sky,

and it'll get even lower throughout July

as it gets closer towards the sun.

So what I'd say is, sort of wait 20, maybe 30 minutes after sunset,

and then look for the brightest star-like object

which is low down in the western part of the sky,

and that should be Jupiter.

OK, the view is a little bit wobbly tonight,

but you can still make out the main features.

You've got the two main belts running across the planet's disc,

and you can see the gaps in between them.

And if you look very carefully, you can see the undulations

and other features which are along those belts.

So what you need to do once you've got your image

is send it up to the Juno website.

They are processed into a composite map of Jupiter

that's constantly updated to give the most accurate view

of the planet's atmosphere.

And then everyone, even those who haven't got a telescope,

can take part.

When Juno goes into its secure orbit,

it will be possible to vote for the most interesting features,

and the most popular ones will then be the target for JunoCam.

The first really detailed images will be taken

as Juno sweeps past Jupiter's atmosphere on August 27,

and the first raw data will be released soon after that.

This will give us the most detailed view we've ever had

of Jupiter's clouds, so who knows what surprises

and 3-D structures we're going to see?

It's really going to be an exciting few months.

But there's one more mystery that Juno will hope to solve,

and that is the mystery of Jupiter's aurora,

that blaze in ultraviolet light

or in high-energy x-rays.

They are like the Earth's northern lights on steroids.

But our current understanding of the physics

cannot explain why they are so extensive.

Part of Juno's mission

is to find out exactly how these aurora are generated.

On Earth, the aurora are caused by the interaction

of the magnetic field with the solar wind,

the flow of particles that stream from the sun.

Something similar must be happening on Jupiter.

But there's a problem.

At this distance from the sun, the solar wind is much too weak

to generate such a bright display on its own.

Chris tracked down planetary scientist Jon Nichols

to find out how Juno is going to help decode

Jupiter's remarkable aurora.

So these are amazing images, but what exactly are we seeing?

So we're seeing Hubble observations of Jupiter's ultraviolet auroras.

These are the auroras here.

Now, auroras are formed when charged particles

trapped on a planet's magnetic field travel down the magnetic field

and hit the atmosphere, and make it glow.

I'm trying to imagine what it would be like looking at these aurora,

if you could somehow stand and look up on Jupiter.

How strong are they compared to Earth's aurora?

So typically the auroras are about 100 times brighter

than they are on the Earth.

In fact, during our campaign, we've seen auroral brightness

really increase dramatically to about 1,000 times

what you'd see on the Earth. Now, if you could see these -

these are obviously ultraviolet,

taken with the Hubble Space Telescope -

but if you could float in a balloon in Jupiter's atmosphere

and look up at these, you'd see a curtain of red.

It would be bright red, and it's 1,000km high,

and it would extend from one horizon to the other.

But auroral display of this magnitude

requires a constant and plentiful supply of charged particles

which can become entangled with Jupiter's magnetic field.

Scientists think they've identified that source.

It is Jupiter's moon, Io.

Io is the closest large moon to Jupiter,

and it's highly volcanic.

Every hour, its volcanoes spew tonnes of material

into the magnetic field that surrounds the giant planet.

That material becomes electrically charged,

interacting with Jupiter's magnetic field lines,

and creating the aurora where they intersect the planet's atmosphere.

It's an extraordinary idea,

but it's backed up by some remarkable evidence.

As Io orbits, it leaves its footprint

drawn brightly in the aurora.

I love the fact this is due to volcanoes on a moon,

and we see it on the planet. That's quite cool.

What about the rest of this structure?

There's an awful lot going on here.

Yeah, so this is the Io footprint here,

and then we've got the main auroral oval,

which is also driven by material from Io.

But then we've got all this stuff in the middle,

and we really have no idea what drives that.

We think that it might be due to something to do with the solar wind.

The solar wind drives the Earth's auroras.

But we have no theories in our magnetospheric physics

that tells us that we should see something like this.

So we really have no idea what's causing it.

And to understand that, you need to know what's coming in,

you need to understand the magnetic field,

and you need to know what's going on in the planet itself.

-It's sort of a really complex problem.

-That's right.

And that's why Juno is the perfect spacecraft to tell us

exactly what is going on here.

Juno is going to fly over this region for the first time,

and it's going to tell us what the magnetic field and the plasma

is doing in this region,

and it's going to reveal what's causing this.

And if there was one thing that you could find out about Jupiter,

you only get one answer to a question from the Juno mission,

-what would it be?

-I want to know what is causing this.

I really want to find the answer -

what is giving us all these sparkles and flashes and pops going off here?

As the end of the Jupiter orbit insertion approached,

things at mission control were increasingly tense.

We're into the last few minutes of the burn,

and so far everything's gone perfectly.

Now we're waiting to hear for news that it's shut off successfully.

If that doesn't happen, Juno only has about 10 minutes

to recover before it plummets into Jupiter itself.

INDISTINCT

Almost there.

That's the warning that the end of burn is imminent.

Should be seconds away

from having a spacecraft in orbit around Jupiter.

CHEERING AND APPLAUSE

There it is! There we go.

Juno right on time, into orbit, exactly as planned.

We have a spacecraft in orbit around Jupiter.

I think people are rather pleased.

CHEERING

A very, very relieved team.

I think they began to believe it was going to happen,

but for it to happen exactly on cue

is an astounding feat of engineering.

Burn time was 21.02 seconds,

only differing one second off of the pre-burn predictions.

They were one second off their planned burn.

To fly a spacecraft that far

and have it work that well is an incredible feat.

But now it's in orbit,

it's time for the real mission to start.

Juno's first two orbits are very long,

allowing it time to turn its instruments back on

and calibrate them in the hostile environment around Jupiter.

But then the engines will burn again,

putting it into a shorter orbit,

just 14 days long,

an eccentric orbit that will take it

from over 2 million kilometres from the planet

to less than 5,000.

Around the middle of August, the serious science will begin.

-Yaaaaay!

-Welcome to Jupiter!

-Congratulations!

-Yaaaaaay!

-So it went well, then?

-It went great!

It just... I mean, what were they? Like, one second off

-or something ridiculous.

-Perfect.

It's perfect. So now the work is going to start.

We get the data, we've got to do the work.

But it's great. It's... Oh.

Did you believe? Were you just sitting there relaxed,

-or was there a...

-No! I was like...

-SHE BABBLES ANXIOUSLY

-You know?

HE LAUGHS

-Anyway, it went well.

-But the next time you fly past Jupiter,

in less than two months' time, the instruments are on.

So the 27th of August is the key date,

when we do this first - all science on, engines off,

so no distractions, and we get the data.

And that's going to be really key,

because we go through the aurora, we get up close,

we look at the microwave, we try and find out the first set of water.

We're not going to be mapping, but at least getting the first taste,

the taste of Jupiter.

-And we'll see what it's like.

-Yeah. Well, we're looking forward to it.

-It's going to be great.

-Congratulations.

-Sure.

-Enjoy.

-Come and tell us about it.

-OK, I will.

-Take care, well done.

-OK.

Thank you.

What a wonderful night.

I can hear 4th of July fireworks going off all around me,

but up there in the sky is Jupiter,

and we now know that there's a space probe

orbiting that tiny point of light.

Juno performed perfectly,

placing itself in prime position

to solve the mysteries of this giant planet

and tell us lots more about the history of the solar system.

We'll be reporting on Juno's discoveries in the coming months.

But that's it for now, and there's no programme next month.

We'll be back in September.

In the meantime, go to our website to see Pete's star guide,

and to find out more about Jupiter,

including what we can learn about the planet

by examining it in the infrared,

and the strange physics at work in its core.

But as always, get outside and get looking up.