The thing is left open whether the child is that child we all have inside us who gets left behind, who is ourself.
But it is also a real child on whom the poet in that book is projecting both the child in himself and that imaginary child.
There are high risks in this enterprise. If it had failed it would have been diabolically awful.
But it didn't fail. It's an exciting and moving piece of theatre. A re-education in just what can be done when people shut up.
It looks fantastic doesn't it? It's on in Sydney for another week but so far there's no interstate tour. Perhaps someone will organise one.
Okay that's just about all we have tonight but before we go some video art. The AFI has just launched a national tour of short films and music videos.
One of those featured is by Lucinda Clutterbuck. It's called Flotsam and Jetsam. The post-impressionist painters would have loved it. Good night.
This edition of State of the Arts can be seen again tomorrow at 20 past one in all states except South Australia where there will be highlights of the Royal Jubilee visit.
In a few moments Halley's Comet, The Encounter and at 10 past nine tonight's feature movie Woody Allen's Broadway Danny Rose.
On ABC the beautiful and exotic ballet based on the epic poem by Nizami, The Seven Beauties.
Featuring the dancers of the Baku Opera and Ballet Theatre with the State Cinemagraphic Symphony Orchestra of the USSR.
Simulcast on ABC FM, The Seven Beauties, our next Sunday stereo special 9.15 Sunday night on ABC.
Australia has one of the highest doctor patient ratios in the world. Our medical school produce 1400 new doctors every year.
The oversupply of doctors is felt most in the capital cities of Australia. Yet there's often a shortage of medical skills in the country and the rural community can be poorly serviced.
Medical incomes are falling and they're falling quite substantially. If you ask a plumber or a television repairman to come to your home on a weekend then they will charge you 30 maybe 40 dollars before they even walk in the door.
Today doctors are losing business to alternative practitioners. Alternative medical therapies have been steadily increasing in popularity and are now an important component of health care for an ever growing proportion of the population.
I worry a little bit sometimes that if we're going to lose the status and prestige of being a doctor that the commitment will also go.
A fractured fantasy next in Focal Points 8 o'clock Tuesday on ABC.
Music
Music
Music
To introduce this program on Halley's Comet I'm out here on the western plains of New South Wales out near parks. The sun's just up and it's been a bit chilly.
I'm out here for two reasons really. The first is that this part of New South Wales west of the Great Divide with wide flat horizons and dark clear skies is really ideal comet watching territory.
The local tourist industry, the motels and souvenir shops are hoping to make quite a nice profit over the next month or two serving the tourists who come here in droves hoping to get a glimpse of the comet.
But I must say that even out here it's not easy to see the most famous comet of all. I was out about three hours ago when it was still fully dark and I looked in the east and to be sure I could see the comet hanging there against the stars rising before the dawn.
But it was pretty close to the limit of visibility and certainly was not the spectacular sight that it was last time. Halley's Comet came by in 1910.
But even though this visitation will be a disappointment for you and me with just our eyes or perhaps a pair of binoculars it'll be a bonanza for the boffins.
They're really ready. This time around Halley's will be the most intensely studied comet in history.
Over the last month or so a whole armada of spacecraft from a number of nations have rendezvoused with the comet in space gathering scientific information, taking pictures, sending them back, harvesting a whole cornucopia of data on what makes a comet tick.
Now one of those probes was Giotto launched by the European Space Agency and programmed to fly right through the head of the comet.
And that's the second reason that I'm here because this great radio telescope run by the CSIRO out here at Parks is the ear of Giotto.
It's the point of contact between the spacecraft in the depths of space and its handlers here on Earth.
Without this telescope there would really have been no mission.
On the morning of the encounter the telescope swung over well before dawn to acquire the signal from Giotto as it rose above the eastern horizon.
The signal was then processed through the control rooms here and sent on to Damstart in West Germany where the nerve center for the entire operation is.
As the encounter developed throughout that morning, Friday the 14th, our time, the BBC was on hand in force.
At Damstart itself the well-known broadcaster and writer on things astronomical Patrick Moore.
And at the old observatory buildings at Greenwich, James Burke. Let's join them now.
The object of tonight's mission is to follow Giotto all the way in.
At the present moment it's something like a quarter of a million kilometers away from the nucleus of the comet.
At closest approach in just over an hour's time it will only be 540 kilometers away.
And it's then, if at all, that we're going to see the nucleus. We've simply got to wait and see.
Halley's Comet is named in honor of the second astronomer royal, Edmund Halley.
His headquarters was at Greenwich at the Royal Greenwich Observatory where James Burke now is.
James.
Thank you Patrick. Well I'm here on what is a bitterly cold night at Greenwich
because it was here in a sense where the original scientific interest in the comet Halley really got going.
And I'm here especially to look at the technology behind tonight's literally once-in-a-lifetime encounter.
The encounter between the spacecraft Giotto and the comet called Halley.
That we are able at all to rendezvous with a comet traveling 68 kilometers a second,
230 million kilometers out in space, is mainly due to the original predictions by Edmund Halley,
England's second astronomer royal here some 300 years ago.
The latest of his successes is with us tonight here in the Octagon Room where the earliest observations were made.
Professor Sir Francis Graham Smith, the 13th astronomer royal, is watching these events with his guests
who include Professor Alec Boxenberg, director of the Royal Greenwich Observatory at Hurst-Monseau,
and other experts in what we'll loosely call tonight cometary. We'll be talking to them later.
As Giotto races towards the encounter at about 70 times the speed of a bullet,
I will be taking a look at the onboard instruments and in particular at the camera
that we hope will answer fundamental questions not just about Halley,
but perhaps about the origins of the solar system and even the origin of life on Earth.
I say we hope for two good reasons.
One, Giotto may not survive the journey to the heart of the comet to take those first ever pictures of its nucleus,
and two, even if it does, the pictures that the two Russian spacecraft that went past the other day
made it all look pretty dicey.
The situation as they saw it makes us feel that tonight the encounter may turn out to be a more dangerous event
than was perhaps foreseen, but more of those problems later on,
because right now the spacecraft is heading into the comet's coma,
a giant cloud of gas and dust surrounding the nucleus,
and since Giotto's encounter speed is about 240,000 kilometers an hour,
every tiny dust particle will hit Giotto like a bullet.
This is what the spacecraft looks like as it heads for Halley like this with its dust shield forward,
and as we go through the evening I hope we will be able to see the buildup of computer generated data
showing that dust impacts actually hitting the shield at the time.
The point is, will that dust shield work?
Well, you'll be able to see the answer to that as I said here,
as the onboard impact sensors feedback second by second data on the kind of punishment that Giotto's taking,
if the sensors themselves aren't destroyed, that is.
Initially that data and all the rest is coming in from space to a huge radio telescope in Australia
and then to the European Space Operations Centre, PATRICK,
which is where I am now at the headquarters of the European Space Agency.
This is where the information from the comet is being received,
but the real action is taking place over 90 million miles away.
Here's the science area. We'll be meeting some of the principal investigators during the course of the night,
and of course there's the control room,
which recently had the job of directing the spacecraft to its precise distance from the nucleus.
But since the Russian and Japanese encounters,
there's been a great deal of controversial discussion among the scientists here as to what that distance should be.
We know that at the moment Giotto is inside the coma but outside the main dust area.
What exactly is a comet?
Basically it has a nucleus described as a dirty ice ball, which is the only reasonably massive part.
When the ice is warm, they start to evaporate and the nucleus hides itself inside the head or coma,
which is why we've never yet seen a cometary nucleus, something we'd like to rectify before this program's over.
There are two types of tails.
The plasma, or gas tail, is caused by the solar wind striking the comet's coma,
the solar wind being a stream of electrified particles being sent out by the sun all the time in all directions.
The dust tail is produced by the sun's light striking the coma and driving the dust particles outwards,
and that's why comet tails always point more or less away from the sun.
At the moment Halley's comet is moving outwards and so it's traveling tail first.
The solar wind interacts with the cometary dust, and the solar wind is variable, gusty if you like,
and this causes marked changes in the comet's tail.
Giotto has already passed through the bow shock set up by the traveling comet,
and we're getting ready for the main encounter, so let's consult the experts. What do they feel?
Well, I think this is the most exciting part of the mission.
The spacecraft, of course, is now going to start seeing the dust.
The instruments are now really going to start earning their money.
The dust will start to increase significantly now, and it will be starting to make the spacecraft wobble,
so we hope we can maintain the signal, but at the same time we're hoping we can see the nucleus of the comet with the camera.
I'm hoping to see what the comet really looks like so far.
We've never seen, we've never really seen a comet.
We've seen the dust cloud that envelops comets, and even those from a great distance.
We have preconceived ideas about the nature of comets.
We believe that there's a comet nucleus in the center.
We have some ideas about the origin of comets.
We have worked for years on the composition of the gas and dusty atmosphere.
We have pretty good ideas how much dust and gas to expect, but I'm sure there will be major surprises.
I am truly excited because it was 36 years ago that I first published my conclusions that the comet, the real comet, the nucleus,
was made of ices and dust, and now we will be able to see what such a nucleus looks like.
Quite apart from the camera, Giotto carries many other experiments.
Most of them are arranged on a necklace around the spacecraft.
At the present moment, we can only speculate as to what a comet's made of.
Giotto ought to tell us.
We've been studying the dust and the magnetic fields that are so important in tail production.
We've been looking at the chemistry and composition of the comet.
It's atoms, molecules, and ions, which are incomplete atoms.
And then there are plasma studies.
Plasma has been defined as the fourth state of matter, the other being solid, liquid, and gaseous.
This made of broken-up pieces of atoms.
But to demonstrate just what plasma is, let's go over to James Burke,
or rather see what James was doing in the courtyard of the old Royal Observatory a few hours ago when it was still daylight.
I'm doing it here in the freezing courtyard because, as you'll see, they didn't want to risk burning Greenwich down.
Plasma, those broken-up pieces of atoms that Patrick was talking about, make up about 90% of the universe.
In this case, the plasma in question is caused by the solar wind,
a cloud of superheated gas exploding at a million kilometers an hour out from the sun all the time.
Now, the tremendous temperature of the sun strips the electrons from the gas atoms
and atoms without electrons are called ions.
On board Jotto, the energy levels of those ions is being measured by a British experiment from the Mullard Space Science Laboratory.
In essence, this is how the experiment works.
This flame represents the hot gas plasma.
And if you use this generator to send a charge through these plates and then through the ions in the flame,
you can deflect the ions like this.
Watch it being deflected to the left. It looks like wind, but in fact it's an electrical charge.
Look, I'll do it again. And it's deflected.
Now, if you measure how much charge causes how much deflection, you know how much energy the ions have,
and you've measured the energy of the plasma.
Now, that is basically how the plasma instrument on board Jotto works.
This is where the plasma experiment sits on the spacecraft, and in fact it was switched on out in space some time back.
The leader of the plasma analyzer experiment from Mullard is Alan Johnston.
At his lab, he prepared his standby instrument for Jotto.
This is the voltage generator.
And these are the plates across which the electrical charge is applied.
They are mounted on the particle detector itself.
The plasma particles stream into the instrument and get bent towards the detector.
Change the voltage, and you tune the instrument to measure the energy of different particles.
Well, some time ago, Jotto was hit by a huge shock wave.
This is what it looked like on the computer printer.
Let me stress that it didn't cause any damage, because the density of the material is so low.
Since then, within the last few hours, we've had some new information.
Alan, what are your results so far?
Well, we've now been detecting the comet for more than 30 hours.
We first found it at four o'clock yesterday afternoon, and it's gradually been increasing in intensity ever since then.
And at about eight o'clock this evening, we saw the first signs of the bow shock,
and the bow shock turned out to be about 100,000 kilometers thick.
And once we passed through the bow shock, we found, in fact, that instead of being more turbulent as I had expected,
so far it's been quite a bit smoother, but hotter.
Well, you've been using plenty of graphs. What exactly do they mean?
Well, we've got two to show on the screen here.
This first one shows some of the different masses of ions that we're detecting in the comet.
There's four frames there, each one taken successively, one after the other, in time.
And each one shows hydrogen ions and alpha particles from the solar wind in the bottom left-hand corner, where it's red and green,
and cometary ions in the top, where it's blue.
And one of the interesting things is that we're seeing particles at a mass of eight where we didn't expect to see them.
How do you assess your results?
Well, they're very interesting. They're going to take a lot of analyzing, but they're extremely interesting.
Can I imagine you expect better results from this as you close again to all the comets?
Yes, we're expecting things to change very rapidly in the next hour, and especially in the last two or three minutes just past midnight.
Patrick Moore was talking there with British scientist Dr. Alan Johnson.
The object of all this attention has been ploughing through the darkness of interplanetary space for most of the last 76 years.
The comet's fame comes from a fortunate combination of circumstances.
It's bright enough to be easily seen, and it comes back regularly to the vicinity of the Earth.
No other comets do both.
The bright ones don't return. The ones that come back are faint.
It's time, I think, to take a look at the known history of the comet and at how it came to be called Halley's Comet.
Sightings of Halley's Comet go back nearly 2,000 years, though only since the 17th century did we know that they were successive sightings of the same comet.
The Chinese were assiduous watchers of the heavens and carefully recorded everything they saw, even if they were more interested in astrology than astronomy.
It's to them we owe the earliest known sighting.
本类星波类晦,孝者苏传,成晦,精天。 This is the first searching record of Halley's Comet.
That was in 240 B.C. For many years, astronomers believed they had no record of the next visit in 164 B.C.
Then, just last year, some ancient clay tablets from Babylonian times were deciphered at the British Museum.
上海,在海南,在海南,在海南,在海南,在海南。 And it tells us that the comet appeared for the first time in the northern part of the sky in the area of Taurus in the Pleiades.
When the comet appeared in 1910, the whole world seemed to know and most of them were trying to turn a fast quid out of the event.
This produced a rash of forgettable songs and the comet emblazoned on every conceivable product.
Future archaeologists will have little trouble finding evidence of just when the comet came by.
This is a negative of the first sighting of the comet that time round as seen on September 11th, 1909.
Over the months, it waxed into a most impressive sight, remembered vividly by many people still living.
These pictures were taken at Sydney Observatory.
The brilliance of the sight resulted from the comet being quite close to the earth as it rounded the sun.
We actually passed through the tenuous tail of the comet.
After a few months of glory, the comet faded again, dwindling once more to a speck among the stars and was soon lost to human knowledge for another seven decades.
Its next visit was destined to be less spectacular but far more important.
Nowadays, comets are a matter of wonder and scientific curiosity, but in the past they brought terror and superstition.
The Chinese called them broom stars and believed they brought change, mostly for the worse with war and pestilence.
In medieval times, the unexpected arrival of comets, the word actually means hairy star, in their often awesome appearance led to belief that when a comet was seen, some disaster would follow.
Civil strife, panic in the streets, plague and cataclysmic events, the deaths of kings and emperors.
When Halley's Comet appeared in 1066, it was taken as an omen.
A flaming star was recorded on the Bayeux Tapestry.
The inscription says in Latin, they are wondering at the star. The omen was certainly bad for King Harold.
He lost the battle, his kingdom and his life.
The Florentine painter Giotto saw the comet in 1301 and put it into his painting about the three wise men visiting the infant Jesus.
Giotto made the comet the star of Bethlehem, announcing good news to the world.
Comets were feared because they seemed unpredictable. No one understood them.
The learned men of old argued about their true nature and motion.
The great Aristotle thought they were phenomena within our own atmosphere, like clouds.
Two thousand years later, Johannes Kepler knew that they lay far out in space beyond the moon, but he had them travelling in straight lines.
Avelius gave comets curved paths like the other heavenly bodies, but thought they spiralled out of planets.
The honour of determining the true cause of comets goes to the Englishman Edmund Halley, the second astronomer royal.
It's appropriate, therefore, he should have the most famous comet named after him, though he did not actually discover it.
It was in this slim volume published late in the seventeenth century that Halley summarised his own comet observations.
He then proceeded to examine the data on 24 known comets and to fit their motions through the solar system to the laws of gravity and motion recently discovered by his friend Isaac Newton.
He saw that under the influence of gravity, the comets followed curved and apparently parabolic paths.
Pushing on, Halley found something most remarkable and unexpected.
A comet seen in 1682 proved to have a very similar orbit to one seen 75 years earlier in 1607 and to another seen 76 years earlier again in 1531.
Halley's hunch was that those three comets were in fact the same comet returning to the vicinity of the earth each 75 or 76 years.
If that was so, comets were not wild bringers of ill fate, but well-mannered celestial objects circling the sun in predictable orbits.
Halley confidently predicted the return of the comet in 1758, another 76 years ahead.
Throughout 1758, astronomers sought the predicted comet, but it was almost gone before anything was seen.
Then just before Christmas, a comet was sighted by a German farmer and Halley's immortality was assured.
The comet has been called Halley's comet ever since.
The last 30 returns of the comet are now on record, some much more spectacular than others.
In 837 AD, the comet could be seen in the daytime and its tail stretched halfway across the sky.
But scientifically, the current visit of 1986 will be the most memorable, being the date of the first encounter.
That first encounter with Halley's comet took place yesterday, centered on the Giotto spacecraft.
So let's go back to James Burke and Patrick Moore, first to James and the threat posed to the spacecraft by grains of dust.
Well, there's now less than an hour to go and 231,700 kilometers to go to closest approach.
As you can see on the left, there's time to go to the closest point, and on the right the distance.
And from here on, from this distance out, to the problem of dust becomes the major test of the mission.
The first impact from the dust cloud in the coma around Halley were predicted to start just a few minutes ago,
and we've heard that that's exactly what's happened.
Let me remind you of what's happening out there in space.
Giotto is heading in towards Halley like this, with its protective dust shield forward,
and I'll get back to that particular shield in a second.
There you can see it spinning around with the dust shield leading.
Now, the theory is that the dust I'm talking about happens as a result of the sunlight evaporating the icy surface of the nucleus of the comet
and the explosion of superheated gas pockets in that surface,
sending the dust shooting out in great fountains to spread perhaps as far as, oh, 100,000 kilometers out round Halley.
I say it's all theory because nobody knows. That's one of the things we're hoping to find out tonight.
But the size of the dust particles in that maelstrom are known.
They're anywhere from this size, the size of a dried pea, right down through sand grain size,
to tiny particles this size, so small that they almost smudge when you move them around,
and beyond that to the size of the particles in the smoke from a cigarette.
Now, those dust particles are killers for two reasons.
The first is communication. You see, the main spacecraft antenna, this dish here,
is sending all the data and the pictures back to the receiving dish in Australia, back on Earth, oh, 130 million kilometers away.
Now, the distance involved in that communications link is so great that it needs pinpoint accuracy for the antenna to make and maintain contact.
One degree off, that much, and we lose contact.
And an impact from one particle this size hitting the edge of the spacecraft could knock Jotto off-center enough for the signal beam to miss the Earth.
The second danger to the spacecraft is less, shall we say, subtle. Particle impact could just destroy Jotto.
That's why there is a dust shield, or rather two of them.
An outer shield here, one millimeter thick, made of aluminum alloy, like this,
and an inner sheet 25 millimeters behind it, itself 12 and a half millimeters thick,
a backup shield made mostly of bulletproof plastic laminate to take the force of the particles that are big enough to smash through the outer shield
and hit this inner shield in the form of a jet of high-temperature vaporized material.
And they're expecting plenty of that kind of activity.
In fact, at worst, all the spacecraft has to do is just survive through that dust storm,
long enough to get in really close to the nucleus to snatch its pictures and scientific data before it is possibly destroyed.
And if you think I'm overdoing the drama a bit, take a look at this.
This is a piece of test material looking at the conditions that that forward shield would encounter, the thin aluminum shield.
It's been scaled up because they can't shoot a pellet as fast as the spacecraft is going, so the whole thing is scaled up.
This was made by a pea-sized object fired at five kilometers a second at this aluminum, eight centimeters thick.
That is the same scaled-up effect of one pea-sized object hitting the forward shield, that thin one millimeter thick shield.
Now, they're expecting many, many of these impacts, perhaps as many as 10,000 a second.
The second test they ran was on the Kevlar, as it's called, the Kevlar backup shield.
And here they used a laser to produce the kind of effect that the jet of high-temperature plasma coming from the result of a particle having smashed through the front shield,
the effect it would have on the Kevlar.
And as a matter of interest, over here on the edge, there are tiny, there's a tiny detector, there are several of them around as you'll see soon,
that actually detect those impacts happening, and that was I was talking about when you were looking at the screen on which we will be able to show you the effect of those impacts as they happen because of computer generation.
The key point, encounter, as you can see on the countdown, will happen in 51 minutes, just under 51 minutes, and 213,000 kilometers from now.
There are, as you would expect from what I've said about the dust, several experiments on board measuring those impacts.
Two experiments registering impacts by the very small particles, and one run by the University of Kent for the bits large enough to call what they're expecting to make real trouble.
Tony MacDonald leads this British experiment. It's called the Dust Impact Detector, or DID.
Jotto's leading surface carries three tiny sensors. The inner shield carries one more. The sensors are miniature microphones to record the impact of particles hitting Jotto faster than a bullet.
MacDonald's main problem is that he doesn't know just how big the particles will be, and will the twin shields be enough to protect Jotto?
He tests the system with tiny glass beads.
The mini microphones record the impacts, telling MacDonald the size and position of Halley's dusty missiles.
At the moment, the experiment's going very well. We're getting a high-level activity on the front dust shield, and this is showing that some of the particles are going through to the rear.
And it does show that the meteorite protection system is working. Looking at the next few minutes, we're going to find activity increasing, and several thousand per second later.
What's important is that we get through the point of closest approach and come out of the comet on the other side.
So you see there, from what Tony MacDonald was saying, they're already getting impacts that are going through that front shield. By the way, it's called the sacrificial shield, and now you know why.
Because even this far out, what, 206,000 kilometers with 50 minutes to go, they're beginning to get impacts going clear through that front shield.
Well, the predictions are, in fact, that they will hit a fair amount of these medium-sized particles early on, and then, hopefully, the impact rates ought to drop off a bit,
or those rates start to rise inexorably towards maximum density as we move towards encounter.
Question is, will Jotto survive long enough to get close enough to learn something about what that nucleus is made of? Patrick?
The nucleus is, after all, the heart of the comet, and that's what the scientists here are trying to study above all else.
Up to now, we've been with you for little more than guesswork. Some years ago, it was thought that a comet might be a flying gravel bank,
but now there's good circumstantial evidence that a nucleus is an icy mass, about six kilometers in diameter, spinning round in something like 54 hours.
If we knew the size of the nucleus, we could work out its mass and its volume, and we could then estimate how long Halley's Comet will last before all its ices are used up,
and present estimates range between 50,000 and 200,000 years.
The camera was switched on again for the encounter five hours ago, and this is the best picture it's sent back so far.
Well, dust or no dust, the camera is certainly sending back results, and there's quite a difference between this picture and the last one you saw.
Now remember, Jotto was approaching the comet at something like 68 kilometers per second, and that makes a tremendous difference even over short periods,
and now we can actually start to see structure in the comet. Once again, let me remind you that these colors are not real.
They indicate differences in brightness and therefore differences in density, and there's no doubt that the densest and brightest part of the comet is that white blob you can see at the bottom,
and that is where the nucleus is, even though we can't actually see the nucleus itself at the present moment.
And then red, blue, green, and purple indicate lower and lower light levels.
So at the present moment, the camera is sending back good results, and of course, as it goes in closer and closer, we shall get better and better results.
And one thing we know, though, for certain now, the camera itself is working really well. James?
Well, this is where the camera sits, with its mirror poking out from behind the dust shield.
That camera's job, of course, is to detect the nucleus and then take as many color pictures of it as it can.
The delicate camera is Jotto's most immediately dramatic experiment, already it's sending back a continuous stream of pictures.
This is Jotto's eye, giving scientists the chance to see a comet's nucleus.
The camera can be rotated to take pictures both ahead and behind Jotto as the spacecraft skims close to Halley.
The hope is that the camera will survive the dust storm mounted as it is behind the bumper shield.
Its pictures in four colors allow scientists to establish the size and shape of Halley's nucleus.
From 500 kilometers away, the camera can pinpoint an object a mere 30 meters across on the comet's surface.
All this while Jotto itself is spinning four times a second.
Incoming light, and maybe dust, bounces off a steel mirror into a telescope.
The image is then focused onto two charge-coupled devices, or CCDs, which take the picture.
This is what the charge-coupled device looks like, hundreds of lines of light-sensitive spots.
As the spacecraft rolls, I'll use my finger to imitate that, and the image moves across the camera mirror.
One thin cross-section of the image at a time is stored on here for a few microseconds, and the data sent back to Earth.
And then the next line, and so on. It's hairy stuff, but that's quite a camera.
It could, for instance, get a clear shot, they say, of a mole on the face of the pilot of a Concorde going by a mile away at the speed of sound.
Which is great if the Concorde isn't in the middle of a cloud, which according to last week's Russian pictures, Halley is.
Out from 8,000 or 9,000 kilometers, the Russians weren't expected to see the nucleus.
Even so, the cloud they did see looked very small and very dense.
When all the Darmstadt scientists got together to discuss that particular matter, all hell let loose.
Some wanted to send Jotto very much closer than the planned 500 kilometers.
But the camera team naturally wanted to play it safe and steer clear to over 1,000 kilometers away from anything that would sandblast the motor of their camera.
With two or three times as many camera scientists occupying far more space than any other experiment,
it would have made it a waste of money to build a spacecraft that could go to half that distance to 500 kilometers.
So in the best European tradition, they compromised.
They chose a target distance the other day of 540 kilometers, almost exactly what had been originally intended.
Just now, as you can see, the distance to go is 185,000 kilometers with just under 45 minutes and closing.
What are the pictures like from this distance? Patrick?
Well, they're pretty good and the camera is working very well.
But one thing we have got to remember, as Jotto goes into closer to approach, he makes a very, very rapid pass of the nucleus, only about 10 seconds or so.
And altogether, Jotto spends only about four minutes closer into the nucleus than Vega did.
So it's got to be a very fast business altogether.
All the same, they seem fairly confident that they will get better pictures than Vega obtained.
The procedure, by the way, is for Jotto to send back a raw picture and then after a few minutes, it's enhanced.
So you get a bigger and better view of it.
And that's the way it is done. And all the pictures you're going to get tonight will be on this false color principle.
Now, say again, the colors are not genuine.
But already, the comet is showing structure and as we get closer and closer to the nucleus,
there's no doubt at all that these pictures will gradually improve.
So is the nucleus really a dirty snowball?
That was the theory put forward by Dr. Fred Whipple over 30 years ago.
You're still confident about it?
I certainly am. I think we have a great deal of evidence to prove that it is true.
Particularly radar observations, radio reflections from the nuclei of four comets,
showing that there is a discrete body in each one of them.
What evidence are you looking for from Jotto?
Well, particularly the shape and the surface characteristics of the nucleus,
because so far this has been entirely a matter of imagination.
Now we will see the real thing.
You're really hoping to see the nucleus tonight?
I'm really expecting to see it tonight.
Well, some people suggested that we won't because it will be hidden by dust.
Well, there will be some loss of visibility due to dust.
There's no doubt of that.
But I think that because of the detection that the camera has in Jotto,
there's a good chance that we shall see at least some details of the nucleus.
If we're going to make really close-range studies of the nucleus,
the first thing we have to decide is exactly where the nucleus is.
And remember, it's well and truly hidden by the dust.
There's another complication also, the jet problem.
Gases escaping from the nucleus which push it around and may also be a hazard to Jotto.
Dr. Ludwig Reinhardt, couldn't they possibly endanger the Jotto mission?
They could very well endanger the Jotto mission,
although one has to say that the dust jets as we see them
consist of dust particles in the range of one to ten microns.
These particles are of no danger to the Jotto spacecraft.
However, associated with these visible jets are regions of dust particles
which are not visible, large dust particles,
and these could endanger the Jotto mission.
Could they put it off course?
Not off course, but they could disturb the spacecraft attitude
and then telecommunications linked to the Earth could no longer be maintained.
Patrick Moore there with Dr. Rudiko Reinhardt and before that with Dr. Fred Whipple,
patriarch of comet lovers and inventor of the dirty snowball.
Jotto is not alone in space in its probing of Halley's Comet.
While the United States has not sent a probe to meet the comet,
it has turned the cameras of a spacecraft currently in orbit around Venus onto it
and another American probe will scout the general vicinity of the comet in a month or so.
But a far more active role in the Halley watch is being played by Japan and the Soviet Union.
Their probes launched last year joined Jotto to form the biggest and best equipped welcoming committee
the comet has ever had.
The Russians launched their Vega 1 space probe in mid-December 1984 and Vega 2 six days later.
The start of a 14-month journey to take the Vegas to within 9,000 kilometers of Halley.
The slim solid fuel rocket carrying Japan's second Halley mission stood ready for liftoff last August.
For the Japanese, Project Halley is the first venture into interplanetary space.
Their main spacecraft was aimed to pass 150,000 kilometers from the comet's nucleus.
The Japanese Planet A spacecraft's mission to monitor the comet's vast ultraviolet Coroda.
The European spacecraft Jotto is by far the most ambitious of the multinational group.
Tonight's encounter comes at the end of a journey that started last July in Kourou, French Guiana.
Sighted near the equator for maximum benefit from the Earth's rotation at liftoff,
the Kourou launch pad is the home of ESA's Ariane rockets.
Jotto was to be carried on the first stage of her 700 million kilometer space journey by Ariane flight number 14.
July the 1st, launch day minus one, halfway through the long countdown procedure, Ariane is ready to go.
For Jotto's scientists, five years' work now rests with the Ariane launch engineers,
and Ariane rockets had been known to fail in the past.
Plus 3.4 seconds, the opening of the hooks, followed by the takeoff.
The parameters as measured are currently correct.
The final armament is taking place at the moment.
9, 8, 7, 6, 5, 4, 3, 2, 1, go!
Ignition. Ariane first stage ignition and takeoff.
Takeoff, bay end.
Takeoff.
First stage flight.
Beginning of the rolling maneuvers.
Safely on course.
The Japanese Planet A arrived five days ago, closing with the comet at over 70 kilometers a second,
and successfully measuring Halley's ultraviolet output.
The Russian Vegas moved in last Thursday and Sunday, sending back pictures and pinpointing Halley's precise position.
The Vegas narrowed down the path of Halley's orbit by a factor of three.
So, Jotto is being guided with amazing accuracy for the closest encounter.
Tonight sees the culmination of that mission as the small spacecraft spins the last kilometers towards the comet's very heart.
Just a few moments from now, Jotto meets Halley.
So, how did the pathfinders get on?
The Russian Vegas spacecraft are vital to the success of the International Halley mission as a whole, and of course for Jotto in particular.
Patrick.
Both the Russian probes, the Vegas, have been very successful.
They're also of tremendous value in the Jotto mission, because now we have at least some idea of what to expect.
Both the Vegas bypass the comet between 8,000 and 9,000 kilometers.
The instruments recorded strong electric fields and electron currents.
The plasma density was measured, and there were indications of a tight inner dust shell.
Vega, too, took some fascinating pictures.
Look at this. It seems rather like a double nucleus, although there must presumably be some sort of connection between them if it really is a double nucleus.
Let's hope Jotto will tell us more.
But there's always the dust striking the spacecraft at 68 kilometers per second, and it did do some damage.
Remember, though, that the Vegas weren't equipped with dust shields, anything like so efficient as Jotto's, so they were much more vulnerable.
Now, the Japanese have been getting a great deal less publicity for their encounters, but they, too, have been getting some extremely interesting results.
At the Institute for Space and Aeronautical Science in Tokyo, results from the twin Japanese spacecraft have been coming in since mid-December.
Spacecraft Sakigake has been measuring Halley's interaction with the solar wind from a distance of 7 million kilometers,
while spacecraft Planet A has been taking ultraviolet pictures of the comet's hydrogen corona.
The UV pictures confirm that Halley's hydrogen cloud is over 2 million kilometers across, and that the comet rotates once every 53 hours.
The Japanese have been busy not only in space but on the ground as well.
For some time, a team has been camped up at Siding Spring Observatory in upcountry New South Wales, where the skies are reputedly the darkest in the world.
Siding Spring Mountain is home to a number of telescopes, including the great Anglo-Australian telescope.
The Japanese technicians have coupled together telescopes, image intensifiers, and TV cameras to produce the best pictures of the comet taken from the surface of the Earth.
Music
Well, what did you think of that? It's time we were back in Darmstadt.
Throughout the morning, Giotto continued ahead for its target at blinding speed.
So let's find out from Patrick Moore how things were progressing.
Well, in point of fact, we're now within a very few minutes of supposed encounter.
By entering the most exciting time of all, let me show you how they enhance the pictures.
The picture comes through, and then it can be jacked up like this.
And you bring out the details, you can see.
So the raw picture that comes in bears only a little resemblance to what you finally get.
The picture can be improved by all, out of all recognition.
And that is in fact how it's done.
And another picture has just come in. Look at that.
Once again, this is a false color picture, and that red blob must indicate the position of the nucleus.
And before very long now, we shall know exactly what that nucleus is.
And Giotto at the moment is still going.
It's still going, and we're very close now to the vital moment as it speeds inside and makes its closest pass of the nucleus.
Most of the action in this encounter was to be crammed into the last few minutes.
As the probe neared its objective, data would be streaming back much faster than it could be analyzed.
There was also the underlying uncertainty about the fate of the craft.
Would it reach the target still in full working order?
Well, no one knew quite what to expect, and that added to the mounting excitement.
So it's back once more to Darmstadt and to Greenwich.
The countdown clock has still just under ten minutes to run.
The point of closest approach is 41,000 kilometers away and closing fast.
We're getting this, finally getting this computer of generated data coming back in about the amount of damage that's going on here.
And Tony McDonald, I gather you're out there talking to Wood Patrick right now.
Are things hotting up for you? Are you still as happy as you were?
Well, very much so. We're now within a minute or so of closest approach,
and we're very glad that Tony McDonald has taken time off at this particular moment to come and join us.
Tony, then in the other crisis now, what's the situation?
Well, we're a little bit behind in terms of information coming back, of course.
The probe is actually at its probably worst position now, but in fact the data's filming behind it, the data's building up.
We know that the shield is lasting. In fact, it's going to survive, and I think the chances for getting past and getting data on the way out are very, very good.
You are, in fact, you think, on our over the worst period?
I think we are indeed, yes.
So in fact the shield has really done all and more than was expected of it.
Superb indeed, yes. The dust cloud is though very much smaller than we'd anticipated.
Very much smaller or just in margin, marginally, sir?
Perhaps a factor of two smaller.
And what about the actual distance of the dust from the nucleus? Is that smaller as well?
Yes indeed, yes. It took us indeed at least an hour before we got our first impact, so very much smaller.
Have you had any major impacts at all on the spacecraft?
Not any which have rocked the spacecraft in any way, and therefore the stability of the spacecraft is good.
It's going on the same course, good pointing direction, the camera will get good images.
As we know, you know better than I do, the bumper shield was designed in two parts, a thin one to break the emitter particles up and produce them into a kind of a spray, and that principle really paid off.
We've got to evaluate the data before we can really confirm it, but yes indeed it looks as if it's doing very well at the moment.
What about the numbers of really large particles? In view of the fact that the Yachto has escaped so far, do you think they really are much rarer than was expected?
Well at this time the largest particle probably has indeed struck the comet, the space probe indeed, but we don't know yet. We've got to wait six minutes for that information.
We have indeed, and of course you're not quite out of the wood yet, rather out of the dust storm, because you may be just about passing closer to Perch now, but then there's the outward journey.
Do you think there's any danger of being struck on the outward journey?
That's supposed to be I think an easier ride than the inward journey. The comet is a bit shorter on that side because of our approach direction.
And in fact well, we know therefore it does seem that all is going to go well.
I think so.
Well Tony, thank you very much.
A pleasure.
And in fact we have here got pictures of the control room where everything at the moment is going on.
This after all is the nerve centre of the entire operation as you can see, and you can see there a picture on the control room screen coming in from Yachto.
At the moment it all seems to be going well, and I imagine there's rather a feeling of considerable relief down there at the moment, because if all the indications are as we believe,
then Yachto will in fact survive the encounter and will be able to pass on to possibly to other comets, which is probably something that most people, well everybody wished, but I don't think people were entirely confident about right up to the last moment.
So I imagine down there now that there's all kinds of discussions going on, and the revelation that the dust cloud is smaller than we expected really is I think very much of a surprise,
because after all, Hany's Comet is always regarded as a very active comet. It's a large comet, a very large comet, and we are now just about at closest approach.
That of course, remember, the distance of the comet and the probe from us at the present moment is something like 150 million kilometres,
and that's just about the same distance as the distance between the Earth and the Sun, and light and radio waves and messages take something just over eight minutes to cover that distance,
so eight minutes to cover that distance, and so it won't be for another seven or eight minutes if you don't know whether Yachto really has survived, but all the indications are that it has. James?
Yeah, well here in Greenwich we're about to see some of the pictures that have been coming in, and perhaps I could ask you, Alec, to start commenting on what you think they're telling us. Can you see enough at all?
Well, it's difficult to really appreciate what one sees in a picture of this nature. It's in false colour. The brightest bit is the red bit, and that looks quite small,
but I can't tell you exactly how big it is. That has to be really processed properly, but the pictures look of very high quality indeed.
Do you think that might be because of this business about their being, they're having gone through perhaps the sort of last major shell of dust, and got themselves into a clearer zone?
Well, they certainly look a lot clearer than they did before, and a lot more compact there in the middle, and if anything you'd expect it to be larger being closer,
so I guess that is what's happening, that the dust is clearing so to speak, and we're seeing further into the nucleus than before, maybe we are seeing the actual nucleus, but it's hard to say at the moment.
Yeah, the point is of course these pictures are pictures that have come in some minutes ago, they're not in fact, as we can see we're 21,000 kilometres to the point of closest encounter, in fact these pictures may have come from how far back,
how long do you think it would take to get these pictures processed to that stage and on this screen? Well, the light travel time is about eight minutes, and it will take a few more minutes perhaps to come out on the screen like that.
So those pictures you reckon could be ending about 15 minutes back? Yes.
The quality of those pictures, Jim, does that mean that you stand a better chance of getting the kind of analysis you need than there would have been if the dust had been higher than was expected?
Sorry, yes, there's been a lot of dust? It means that Jodo has a much better chance of getting right through, yes, than we would have said perhaps an hour ago.
What about this business of the Russians saying, Jack, that they thought that there might have been a very dense cloud of dust just above the surface of the nucleus? Did I not hear that claim?
You did indeed, yes. That's the interpretation. They produced slightly different interpretations from the two Vega spacecraft which went through a few days after each other, but about the same distance away.
But the interpretation they put forward after the second one was that there was a cloud, an egg-shaped nucleus, about six kilometres across, so a bit less than five miles.
But what they were seeing, they thought, was a dust cloud around a real solid nucleus which was perhaps two-thirds to a half that size.
Now, if that's the case, we really are in serious problems because one of the great things we expected to get out of this was a solid nucleus.
I'm sorry to interrupt you because these are live pictures coming down from Jodo now. Alec?
It's progressing, as far as one can really judge it from those pictures. They look like they've got more structure than they had before.
What does that mean, more structure?
Well, that means we're seeing more detail. We're getting closer and we'd expect to see more detail, but I think we can see a rather gross structure.
Of course, the nucleus would not be a uniformly white ice ball or something like that. It would be very murky and gray in places, and so on.
That's what it looks like we're seeing. If we're seeing the nucleus, I'm not suggesting we are.
Can I ask you, the general blob, presumably the blob to the top left there is a dust or some artificially created thing,
but the general blob that we're looking at, the orange-colored blob with the core, approximately how big a cross would that be
if you were saying seeing pictures that came in that were taken eight minutes ago and left, say, about 50,000 kilometres out?
Do you want to make a guess?
I can't make a guess, I'm afraid, and it's difficult anyway because those are contours we're seeing and we can't really make out which contours we see.
Maybe I should ask the question more clearly. Are we actually seeing well inside the head of the comet that we would normally see if we looked up on a clear night and saw it?
We're looking at it well inside, are we?
Yes, we're certainly looking well inside it. But just how far inside? It's very difficult to say.
Yes, right. Let me go back to Darmstadt with Patrick.
Well, with the life of Alan Johnstone, are you able to join us again? Well, Alan, this is the great moment. What do you make of it?
Well, it's been very exciting. We've got some very interesting data. We've just seen the ions disappear from the view of our instrument,
and so that means we're inside the contact surface very close to the comet. And we're now just seeing the final pictures from the nucleus.
We really are seeing the nucleus itself, you think?
I don't know. We'll have to wait until we see the pictures in more detail before we can tell exactly what part of it is the nucleus.
It seemed to be irregular in shape, and that could, I suppose, tie in with the results obtained earlier on by the Vegas.
Yes, I'd expect it to be irregular in shape. Certainly, it's always been thought of as probably irregular, and that's the picture that's coming through now.
Does that give you any clue as to why one side of the comet is so active and the other apparently passive?
Not yet, I think. If it's irregular, it certainly tells us it's not a uniform body.
But to tell exactly why the reasons are that one side is active and the other side is quiet is beyond us at the moment, I think.
Well, when we came on the air, we said that we hoped that just after midnight we would be able to see the actual nucleus of the comet.
All in all, do you think we've done that?
I don't know. We'll have to wait and see.
Can I interrupt because I hear that we're getting live pictures in from the dust detecting equipment from the experiment looking at what's happening to the shield at the moment.
And you can see there the impact actually being generated in real time.
Is that going to be a problem, do you think?
I'm waiting to see.
We're not sure what that picture is there. That obviously looks like something coming down from the camera, but why it's coming in that particular format.
Alec Boxenberg, do you want to guess about that?
I think there's some interference there that is making it very confusing.
And so, in quite dramatic fashion, the screen went black.
With only two seconds left on the countdown clock and with Giotto still some 140 kilometres short of its point of closest approach, the pictures simply stopped arriving.
For quite a few minutes confusion reigned at Dumshtart in parks in the BBC studios as people tried to work out what had gone wrong.
A vital clue came from the record of the dust detection experiment.
Whereas for most of the inbound flight, this had recorded fewer impacts than expected, there was a real surge in dust noise just prior to the screen going black.
It seemed that having got through the region where the dust was expected to be thickest, Giotto had run right into a hail of dust particles, all travelling at 70 kilometres a second relative to the spacecraft.
There were three possibilities. The first was that the spacecraft had been totally destroyed.
That was always a chance. And indeed, as one scientist said to me straight afterwards, that was Giotto's destiny.
It had been designed to go in very close to the action to collect the maximum data, and that meant almost certain destruction.
Secondly, perhaps the Giotto had merely been disabled in some way. Perhaps fatally, perhaps not.
And thirdly, this was the option everyone hoped for, there was a chance that the dust impacts had simply knocked Giotto out of alignment, so that its radio antenna was no longer pointing at the earth.
The transmitted signals would then not reach parks.
If this third possibility was the right one and all was not lost, Giotto had a self-writing program in its computers.
And after 10 or 15 minutes, it would trim its attitude, find the earth again with its antenna, and the signals would come through once more.
Well, those were the possibilities. But for the first few minutes after the loss of signal, nobody knew what was right. Confusion reigned.
In the Dam Start Studios, Patrick Moore cornered Fred Whipple to find out his thoughts on the outcome.
And after all, who better to join us at this critical juncture than Fred Whipple, the man who worked out the dirty snowball theory of the comet.
Well, Fred, you said earlier on that we were going to see the nucleus tonight, did we?
We did. I'm quite sure we did, yes.
It was, in fact, that red mass that we saw on the screen.
Well, it will have to be analyzed in more detail without all of those pretty colors,
which may mislead the public as to the nature of a comet nucleus, because it's really a very black, gray, like that black velvet or charcoal.
Well, we have emphasized all the way through this program that these colors are not genuine. You don't really see a comet like that.
But from those pictures, what can you tell about the composition of the nucleus?
Can you think it can definitely confirm finally your dirty snowball theory?
Well, I think that we have enough evidence that will come out of the spectroscopic evidence,
the nature of the gases, and the analysis of the dust to show it conclusively.
Of course, it's not only the camera. As we know, I mean, the camera did magnificently right up to the time of closest encounter.
Now, when I mentioned those last pictures that actually came back from Giotto were taken just about the time,
some may be something like 540 kilometers away from the nucleus itself.
Perhaps a little farther than that, but perhaps a thousand kilometers, something of that order.
But of course, it's not only the pictures. They're not only those pictures that will help to confirm your theories, all the other experiments as well.
Which do you think are the most important of those from your point of view?
Well, I don't know. There are several of them, of course.
But I think the one that tells the composition of the gas will be in the final, when the final story is told, will be the most important.
Well, now come back to the matter of the moment. We have lost all trace of Giotto.
What do you think has happened? Has the spacecraft been destroyed?
Is it the cameras being put out of action, or has the antenna being jolted so that the President and I are not receiving the signal?
Well, I don't think at this point I can answer that question. I think that will be a technical question.
But I'm sure that the dust in the neighborhood of the nucleus did it,
and shows that comets are very dangerous when you go through them at 70 kilometers per second.
The justly pleased Fred Whipple with Patrick Moore.
Well, as events in the next few minutes showed, Giotto is a tough little bird.
The word came through from parks quite quickly that they had picked up the signal once more.
Faint, but certain. Giotto was not, in fact, dead. It was still on air and collecting data as it plowed its way out of the comet.
It had survived a passage through the very heart of Halley's Comet, passing within a few hundred kilometers of the comet's icy core,
after a journey covering many millions of kilometers.
In the control room at Damstart, they stood up and applauded, as well they might. They had plenty to cheer about.
The very latest information, which has come from our friends at parks, has came in just this afternoon,
is that Giotto, although it has survived, is really in not very good shape. It's been pretty badly knocked about.
For example, it's still tumbling a little bit, and that's causing the signal to waver.
The spacecraft is covered with dust. This is causing it to heat up.
But the camera is functioning, but the main mirror has been pretty badly blasted.
Perhaps the most interesting piece of information of all is analysis has shown that the particle of dust,
which knocked Giotto off its orientation, weighed 8.5 grams and was big as a golf ball. It was a real biggie.
None of the particles seen before that moment was anything like that size.
Well, the park's dish stopped tracking the Giotto probe at 2.30 this afternoon.
So in that sense, the encounter is over at last.
Giotto has now fallen into an orbit around the sun, and in five years' time,
it will once more be back in the vicinity of the Earth.
Well, it's not easy to sum up the achievement of Giotto, other than mere survival, so soon after the event.
Many of the boffins are predicting quite cheerfully that it will take them years to work through the mountain of data that Giotto has provided.
Even those pictures, which look so impressive in their rainbow colours, have had only the most elementary processing as yet.
With the help of James Burke and one of his expert panel, let's take a closer look at one of the last images Giotto sent back before it fell briefly silent.
We've got now the first real enhanced picture available from the spacecraft.
There you can see it. And would you care to comment on that, Alec?
Yes, I think it's a remarkable picture. There's clearly a lot of irregularity in the nuclear region there,
and also a lot of surface structure that we saw before. It's much easier to see it in this picture that we're seeing now.
But of course, we still have to, as has been said by many others, massage it further,
and of course we can't really make out exactly where we are in the nucleus because the colour boundaries are a little bit confusing.
But sorry, you're saying where we are in the nucleus. You mean a large part of this picture could represent the nucleus itself?
Yes, most definitely.
In other words, we are looking at a partial view of the entire nucleus, you think?
No, no, I think we are seeing the nucleus within that picture, and it's probably in the area of the green part of the frame that you're seeing.
But just where it comes in depends very much on where the colour boundaries are placed, and that is a matter of massaging.
We'd see it more easily if it were black and white, but then we wouldn't see the whole depth of the image,
and that's why we're seeing it in this forced colour now.
It's worth remembering that Giotto, for all the prominence we've given it tonight, is only one element in a major international effort to uncover Halley's secrets.
A number of nations were involved. There were probes in deep space, satellites in orbit around the Earth and around Venus, and many detectors on the ground.
Through the joint efforts of all those observers, we know that as Comet Halley rounded the Sun,
the cloud of hydrogen that closed it grew to be nearly 20 million kilometres across, 15 times bigger than the Sun, a thousand times the diameter of the Earth,
that its hidden frozen core spun on its axis once every 15 hours, that water boiled off from the nucleus at a rate of 50 tonnes every second,
and that meant the loss of nearly half a metre thickness of ice and dust every day, that the core was a mere five to eight kilometres across,
chilled by its passage through deep space to a temperature nearly 250 degrees below zero, that one side of the comet was more active than the other,
suggesting a surface with clefts and chasms, a hidden landscape that the fully processed pictures may reveal.
Giotto, by flying through so close to the comet core, has given us a chance to taste the comet, to determine in detail its chemical composition.
The lure of that is that comets are widely held to be deeply frozen leftovers from the formation of the Sun and the rest of the solar system five billion years ago.
So comets are made of primeval stuff. The more we know of their make-up, the better we understand the history of the solar system and of our own planet.
So before we go, let's take a look at the question I think everybody is asking, just where to look in the sky to see the comet now, say over the next month.
We've prepared some star maps that I think should help. Right now you have to be up before dawn to see Halley's Comet while it's still dark,
and since daylight saving ends in about five hours, that means being up before half past four.
Look due east. This map shows you some of the stars you'll see, particularly the curved line of stars like a question mark reversed,
which is the constellation of the scorpion. Below that is Sagittarius, which I've called the teapot.
It does look a bit like a teapot on its side. And further down still the stars of Capricorn, another sign of the zodiac.
Another guide is the Milky Way, which cuts right through these stars as a dim band of light.
It's not much fainter than the comet, so if you can't see the Milky Way, you'll be struggling to see the comet with the naked eye.
Go somewhere darker and clearer, like out of town.
Tomorrow morning around 4.30, the comet will be hanging in the sky well below the Milky Way and the teapot, about 40 degrees up, looking due east.
The movements of the comet in the sky are a bit complicated. First of all, the comet is moving westward through the stars.
The stars themselves are rising about four minutes earlier each night, and the sun is rising later.
So on April the 1st, you can get up about five o'clock. Look due east, but much higher up, now 75 degrees,
and the constellation will be lying across Scorpio and the Milky Way.
It's then at its brightest, with the longest tail, but there's a last quarter moon not very far away.
Thereafter, the comet takes pity on all sleepy heads and begins to rise during the evening.
By April the 10th, the comet, still moving upwards through the stars, has almost cleared the Milky Way.
At eight in the evening, it's about 35 degrees up and to the south east.
The comet will be fading by then, but there's a new moon on April the 9th, so the sky should be dark.
With the comet above the Milky Way from now on, it's time to name some more star groups.
Over on the right, you can see the Southern Cross, and the star field through which the comet is ploughing is called Centaurus.
The Scorpion lies below. By eight p.m. on April the 17th, the comet has just about cleared Centaurus, still due east, about 50 degrees up.
By now, the moon is growing bright again, moving east through the stars.
On April the 24th, the comet is 60 degrees up at eight p.m. and fading fast.
The moon should be full that night, but it is in fact eclipsed, and so the resulting darker sky will give you your last real chance to see the comet before it departs for another 75 years.
By the time Halley's Comet comes round again in 2061, we may know all there is to know about comets,
and may be content to let it go by unmolested.
If that's so, our descendants may care to recall that the first big step in that growth of knowledge was taken this time round, with Giotto and all the other probes.
In summing up this mission, I put it with that other great close encounter that took place this year,
that between the spacecraft Voyager 2 and the planet Uranus in January.
That too carried cameras and scientific instruments into hostile and uncharted regions of space,
enhancing our knowledge of just where this planet stands in the scheme of things.
Well I hope you've enjoyed this coverage of the Giotto mission, the first ever encounter with the most famous of comets.
From all of us here, good night.
Next week in Discovery, anyone can be a genius. A fascinating story of Dr. Luis Alberto Marcado, charged with raising the IQ of the entire population of Venezuela.
Thanks for watching!