The Heliosphere: Our Laboratory in Space - John Simpson

>> Thank you very much. We'll reconvene once again. Everyone's had their refreshments. It's more convenient not to have them here but that's the rules of the house. Our next speaker is a principal investigator of the charged particle instrument on Pioneer 10. He has been the principal investigator on 31 successful space missions and he pointed out to me, this is -- just as I was walking into the room, he was on Pioneer 2, 5, 6, 7 in addition, so in addition to 10 and 11 that we're talking about here, there were 4 outer other Pioneers he was on in addition to his 31 other successful space missions. His current research includes the study of the heliosphere of the laboratories where charged particle acceleration by shock and he's currently the Arthur H. Compton distinguished service Professor Emeritus of the Enrico Fermi Institute in Chicago. I'd like you to welcome Dr. John Simpson.

>> John: Thank you for having invited me to talk here with you today. I'm especially interested in the, what we've learned in the educational mode of what we've discovered and getting at the fundamentals.

Now, even 25 years ago, when we were preparing for this mission, it was clear already that we were asking big questions. Some of those questions were related to what you've already heard, namely, the magnetospheres of the planet, the solar winds impact on the planetary magnetospheres and so forth.

But there are also some very large questions, questions like: Where do the cosmic rays come from? How did they gain these high energies?

And to emphasize this point, what I'd like to show is first a slide that wouldn't have been possible 25 years ago because if you looked at the galaxy and asked the question: Where does the energy of the galaxy come from, you would have been dependent upon what you could see with the human eye. And in more recent years, we've learned that at the Compton Observatory, that high-energy gamma rays generated by the cosmic radiation appear in the sky that you see here. You see the Edgeon galaxy in the light of 100 million volt gamma rays. That is, radiation which is over 2,000 times that of the typical X-ray machine that you find in the laboratory. And you see the sky is completely filled with this radiation. But this radiation has its energy source is mostly in the cosmic rays. And these cosmic rays then come into our earth and we've been measuring them ever since their discovery by Victor Hess about 1911 and we're still studying them.

Now, the reason I bring all of this up is that on that scale, we'll never be able to get there. We can't go there and do the physics in detail of what goes on. So we then turn an aspect over, why don't we do some of these simple experiments on earth to tell us owl all about this. But the scale of the earth is too small. All of these phenomena are so large in scale that you'd have to build walls that are a fraction of the distance between the sun and the earth in order for them to have a meaning and been able to carry out experiments like that. How does an electron gain energy and so forth.

And so we turn, then, with Pioneer 10 and the follow-on missions to an intermediate region discovered in 1966 and this is the heliosphere, this is the region you've heard from previous speakers expands outwards as a bubble in which the solar winds essentially meet the interstellar medium and where the two meet then they form a boundary. Of which you'll hear more from the next speaker.

So this regime which, on the next slide, illustrates the, in an artist's drawing, see, here's the solar system as you know it. And with the planets rotating. Here you see the Voyager I and Voyager II traveling outward and upward. And here also you see similarly here Pioneer 10 extending down the tail. Now, this whole regime that you see here is called the heliosphere.

The dynamical region of such a scale that we can emulate and study in detail many of the phenomena that are associated on the much larger scale with our galaxy.

All right? Now, let us go back to very simple principles and it may be a little overly simple for some of us but I trust it's satisfactory.

The next slide show what some of these simple principles are. Let's begin with the upper one. Let's assume that we've taken in our laboratory a south pole and a north pole, two magnets, and we've, with a uniform field shown as a dashed line, we now inject a charged particle with a given energy and that charged particle, if it's inserted perpendicular to the direction of the field, will circle in the field and be called a cyclotron motion in the field.

We'll continue that motion indefinitely.

If, however, we then tilt the particle so then -- the reason we know that it will stay within the field which is normal is that the forces acting upon the particle are perpendicular to both the velocity of the particle and the magnetic field. That's very simple physics.

But now suppose we tip the orbit, we find that the particles spirals but there's now a side-wise force in addition so that the particle with follow as we tilt it in one direction it will spiral itself until it hits the South Pole, all right?

Now, finally, we come to the point view there was mention by Dr. Smith, namely that the North Pole and the South Pole now I have taken a machine and melted down the size of the pole pieces so they're very small but the fuel is there, okay, because the higher intensity field now on the north and south poles. And now the field lines bulge out between the two poles and now if I start the particles spiraling in the field, I find it spirals in here until the field gets too strong, it were not go any farther and the spiral works itself right back again and it remains as a trapped particle.

So now you know that there are particles that are within converging fields that are trapped. But the particle hasn't gained any energy.

All right? So in the next slide, I want to show you what may happen. Let's assume now that in the upper drawing that now I'm going to move minority and South Pole inward as the particle moves back and forth.

All right? It's squeezing in and as its moving, it's imparting energy because you're putting energy into the system, right? And that in turn is putting energy into the particles as they try to turn around and move back and forth.

And so you're energizing the particles now. Now for the first time you've got energized particles in the system, all right?

It's still trapped, they're energized and they're there. Okay?

And so you then see as we move in, the example B then up above that I sketched then illustrates then the compression of this field.

All right. Now you've got some of the elements of what we're talking about. You know how particles can be energized, the basic physics, and now let's look a little bit further.

You may remember from Dr. Smith's talk that there's the solar wind, plasma, moving outward and this plasma can travel with a supersonic velocity. And if it does, it will overtake the regime ahead of it and build up a shock front. It's very similar to what you have in your elementary textbook. You almost always have this little picture of a bullet being fired in a gas or in the atmosphere and you see this little shock appearing out in front of the bullet tip.

Okay? And so this is what I represented here due to my limited drawing ability, I just drew this as a sheet. Here is a vast region of space in which solar wind is moving out, supersonic, it's a shock.

All right. Now we have a shock and we have the particles moving back and forth in the magnetic field. In this case the magnetic field has its origin as the sun, spread out as this shock wave advances, it provides the motion in we saw in the previous slide being due to the magnetic. Now, it's the shock wave that is advancing against the trapped particles in the interplanetary space, okay?

What I've tried to illustrate here, in an overly simplistic way is we're looking at the basic physics that's going on. We want to apply that and go out and see how these processes occur as we go into space.

So let's take an example of fundamental discovery made by -- and I want to mention the fact that it's no single experiment that solves the problems. It's a combination in our areas of physics of the plasma measurements, the magnetic field measurements that you heard about, and the particles, the high-energy particles. And I'm emphasizing the energizing of these high-energy particles.

So now in the next slide, we show an example, a real set of data. I notice that in our talks so far we haven't really showed you any real data. So here it is. [ Laughter ] If you look at the very top, you'll see a circle that with a black, can't quite reach that point up there, but you see inside h, which is the earth's orbit, a satellite is traveling in earth's orbit around the sun. At the center you see the sun and now, there's an interesting phenomenon. If you imagine that the solar wind has a stream going straight out with the sun, that as the sun rotates, what happens to the stream?

What you see is a stream like your hose as you rotate your hose, you see the water droplets going straight out but the net effect, the envelope is a curved distribution, a stream, okay? And this stream going on out into space carrying magnetic fields and producing the phenomenon that you see at earth; namely, when the stream crosses the earth, you see a magnetic storm and you see one with every solar rotation.

You remember the sun as the equator rotates at around 25 days -- rotates around 25-day period so every period it rotates this curved spiral, this structure called the core rotating interaction region --

And to prove it now, you see there's an 8 which is around the earth. There's Pioneer 10 and Pioneer 11 and you see at earth, at solar astronomical unit at four times the earth sun's distance and five to six times the earth sun distance, you see that there's the appropriate -- at the appropriate time and position, each of this spacecraft sees this phenomenon going on. And I've marked in heavy lines on either side of the stream of the fact that they are shocks discovered in this process.

All right? So the -- what you see here, the results of the shock accelerating charged particles. These particles are -- play a very important role in their acceleration, the -- you're seal them up to five to 10,000 times intensity every time the sun goes around so we discovered in space now the power of 10 we can say all right, here's how nature follows the charged particles and of course there are many, many other mechanisms that I've tried to give you, very simple ones.

I'm going to skip the last -- the next slide that -- but please go to the last one. Number 7 I think.

All right.

Well, in any case, what I wanted to say finally was that all of this data is based upon a wide range of physics and mathematics On a very classical level. We want to know some electromagnetics, electromagnetic field, you want to know the nuclear physics. We you want to know how, you want to know some solid state physics.

And if you're able to do that you're able to designed some of the smaller experiments.

This is one of them. This is a duplicate -- of what produces the events that you saw on that last slide.

And the -- if it's terribly important -- it's terribly important that you understand that the physics and the learning that comes is with -- that is required is no more really than what you would obtain in a good college education. And I hope that that leaves you with some sense of the simplicity of it all.

Thank you.

>> Thank you, John.

I'm going to defer questions for John Simpson until our question and answer session since we want to keep on schedule and we do that sometime for that later on in the afternoon.

The Heliosphere: The Barrier to Interstellar Space - Frank McDonald

Our next speaker is the principal investigator of the cosmic ray systems cope instrument on Pioneer 10. He was the first ever project scientist at NASA Goddard Space Flight Center.

He is currently a senior research scientist at the University of Maryland studying the outer heliosphere utilizing data from the Pioneer and Voyager missions. I'd like you to welcome Dr. Frank McDonald.

>> Frank: It certainly has been one of the great experiences of my life. And the experiment -- I'd like to start off with the first slide, please. Just to say, you know, it's worked wonderfully well for 25 years. We finally didn't have any power to support us in our experiment alone and we got our last data last July and we wrote up this sort of montage of pictures right after it that experiments all people and these are some of the 13 or 14 groups that worked on our small three kilogram, three-watt experiment that has returned us really a great deal of data.

I think each of the people there, each of the groups, was dedicated more so than we were, Jim Turner who sort of headed up the effort.

And all of the other people there, Don Law who sort of helped the experiment how to talk to computers and so and gave us access to the data.

And the cast has changed somewhat. This started out as the Goddard University of New Hampshire experiment. It would today be the University of Maryland, New Mexico State experiment and Bill Weber New Hampshire's moved there. But we're all still just as involved with it today as we were 25 years ago.

And it's been a great experience. And the next slide this is just to show you John Simpson introduced the idea of heliosphere.

It actually really resonates very strongly with what Ed Smith. This is just a great big earth magnetosphere blown up. You have the three spacecraft going out in this direction, Pioneer 10 going back in the aft direction. The shape and whole configuration is shaped by two factors, one, the factor you have an outgoing solar wind.

>> Creates a shock wave, slows down, there's a heliopause at this point and this further out may or may not have a bad shock.

Interstellar medium solar wind and one other fact, the fact that the solar system is moving through its local environment with a velocity of about 25 kilometers a second. We found people found that out -- back in the early 1970s and so there is a gas moving through the neutral gas. In the next slide, I show you how you can go home tonight and do an experiment in your kitchen sink.

And I used it in the "Scientific American" articles and I -- out flowing water here and sort of runs into the -- water there and that's your termination shock that you can create and make your own termination shock right at home. And so in the next slide, when we started out this experiment when we designed it, the object was really to look at the cosmic rays.

All that huge heliosphere excludes them, we don't get in and we thought we could get out to 10 astronomical units, we could see it all.

Two or three years we could go back to earning and honest living and so it's kept us off the streets for 25 years. [ Laughter ] So we knew there were two energetic particle populations. Galactic cosmic rays which range over a huge energy range. We wanted to study the low-energy properties. The solar energetic particle events which happened, and then one of the things that Pioneer and which I want to talk about today is sort of tells the story, the story of the anomalous of cosmic rays.

I hope it doesn't put you to sleep. But it turns out at the time of the -- when solar activity like right now is at its lowest level, then the energy is below 100 MEV or so, this becomes the dominant component and it increases as you go up.

The next slide gives a series discoveries, John and his co-workers felt the M 5 -- instead of the energy spectrum, it remained flat, it didn't fall off if you went to lower energies as one expected from conventional theory. Either homostat from the University of Maryland found there was a huge energy in velocity below -- we pounds as we went out both oxygen increased, nitrogen increased, and totally unlike solar energetic particles and galactic cosmic rays and the carbon didn't increase.

And this sort of composition was anomalous. It also turned out the intensity of each particle got larger the further out you went. And so this we call -- and it really rests on those three observations.

And the next slide -- this caused an enormous amount of difficulty. The "empire strikes back" because of this, the theoretical establishment felt endangered, you know. How did -- they had beautiful modulation theories that had been worked out but how do you get these low-energy particles? This sort of destroyed their theory. So then the person who did do useful work before he became social service administrator down here, in Goddard and New Hampshire, he and Vic Kozlowski, came up with the idea to have these interstellar neutrals going through and they took the very fragment of top -- information that we'd given them on the composition, namely, you have -- you were enriched in nitrogen, oxygen, and helium, these are all elements that will be predominately neutral in the interstellar space. They'll flow through us and then there are -- these will somewhere along the line become ionized. You will lose an electron.

The solar wind with tail them out and they will get reaccelerated and they will enter very high rigidity because they will be singly charged and they can come back into the solar system even if they have this relatively low energy. And this what I would call a Rube Goldberg explanation, you know, something very complex is you don't necessarily have the beauty and elegance that one expects with a physical theory but what it has a beautiful element is we've gone along and what I hope to have time to tell you about today, the way all the pieces have slowly fitted into places and indeed, this explanation -- they made two predictions. One, that the should be similarly charged, two, that if we looked we would see neon, so that would be in 7 and 8. In the next slide I show two other developments. John had stressed that it became obvious, the shocks and it appeared '77 '78 shocks were the one thing that accelerated particles. That became the thought and that in 1981, termination shock for that.

But other before, immediately after 1977, Blake and Friesen said all right, if these things are similarly charged, then, and the way that I'll talk about later, you can trap them in the earth's magnetosphere. It will be a process and show it and calculated and said, if you look at the earth's magnetometer, you will see these things greatly enhanced in the trapped radiation belt. And it took 10 years to sort of do that.

In the next slide, this sort of -- this illustrates the idea that Kozlowski and Ramadi had, particles come in, can be ionized, can be sort of either the charge exchange, sort of like a purse snatching with the solar wind where you simply snatch an electron away and you'll then have a neutral solar wind atom or you can get mugged by a UV photon from the sun which happens mainly with helium and neon -- the charge exchange occurs mainly with hydrogen and both of these processes are imported in oxygen.

In the next slide, I simply show anything that is charged, will simply flow around the helium balls. The fact it has a charge on it means it can't come into our heliosphere. Some of the hydrogen atoms likely would be ionized out here close to the heliopause and others will just simply flow in, ionize and then they will be convected right outward. They'll be taken radially on out and they form a very distinctive pattern in the solar wind which has just been seen on Ulysses. It will sort of form the outward solar wind going straight out and you will have then sort of a spherical pattern around that, produced by this pick-up irons that have twice the velocity of the solar wind.

And then in the next slide, I it has the next few graphs -- this shows you, one hand -- on the one hand, what actually looks like carbon, there's a very slight enhancement of carbon about 1% of oxygen which is just what you expect. This is really one of the clinchers of the origin of this is and this yellow you see the way you expect oxygen to behave and this huge increase which is what we actually see as we go on out of Pioneer and then helium, this is a very large piece. So these areas are the anomalous components that are superimposed on the galactic component and in effect, become a valuable tool for understanding actually what's going on in the outer heliosphere and also constitute unfortunate background for trying to understand the properties of the galactic particle. This is to show you how you have helium, very small -- this is a large scale so you have oxygen, hydrogen, carbon, neon and the Cal Tech group has seen argon and the galactic cosmic ray and solar energetic particles, you see essentially all the elements now and the composition here is very, very different. People have just seen -- at very little levels and this is because the ionization potential of sulphur is such that you do expect a small neutral component and -- should have seen this.

The next new graph, this shows the earth's magnetosphere. I think John talked about particles coming in and sort of spiral around. If they make a small a angle with the magnetic field, they will either -- if they've got rigidity, they will come in and go at a large angle and then lure down close in this region, they be what you will see and then what -- then what you will see and then what Blake and Friesen said they will be stripped. They will enter as this big rigidity oxygen ion, it only takes 10 microns or some very small fraction, the thickness of this paper, in micrograms and you take away all of its electrons. So now it's just an order oxygen atom instead of having a big spiral, it will be reduced by a factor of 8 or so. And now it will be trapped and this is where your radiation belt comes from.

It's shown in the next slide. Actually, the trapped particles we're first seeing -- further off Jim Adams using a hose, 15 sort of Russian cosmos brief flight and seen this in much greater detail so what you have is in that orange sector is a region of trapped interstellar materials that's been accelerated, been through all this procedure, come back, hit the earth, and the composition there is exactly like the composition of the anomalous component. Jim Adams showed that the intensity over a three or four-week period followed exactly what one saw in the outside because -- is about a month or so and so you are trapping interstellar Islands.

In the next slide, this is just the things have added to our knowledge and sort of confirming, namely, Ulysses is measured very precisely our velocity with respect to -- of helium and so of neutral helium coming in 2626 kilometers, also of the Hubble Telescope has also looked at nearby sources and seen absorptions in the local interstellar mediums and that. One is seeing now with the Ulysses, one seeing the freshly-ionized pick-up ions. The neutrals that have come in, been ionized and so. Then -- confirmed that these are indeed singly charged. And one is seeing sulphur and then the combination of Pioneer 10, 4, 1 and 2 is using the latest observations of 1993 and '94 to estimate, they came up with a number of 84.2. I prefer to think about sort of 1 AU these days plus or minus 15 or so.

So this is really sort of saying sometime in the next 10 or 11 years we should see the termination shock. And in the last slide, simply we should see anomalous cosmic rays in the other magnetospheres of other planets. It would be interesting to study what happens in other interstellar systems. You see lots of sterile and lots a data on sterile winds, like our solar winds.

There should be termination shocks and depending on the -- what the temperature of the local interstellar medium, one may get anomalous components there. And finally, we hope to see directly observe the acceleration going on at the termination shock when Voyager I will get there in 2010 or something of that order. But Pioneer 10 really led the way particularly with John Simpson's experiment and our experiment ensuring that a crucial factor this new component has been in telling us about this region of the outer heliosphere, telling us it's the best -- heliosphere and it's the best evidence we have that there's a termination shock and we look forward to a great deal of data from a different variety of missions. Thank you.

>> We have time for one question before we go into the next speaker.

>> Frank: Knowing that I would have talked longer.

>> Have a question. Okay, yes.

>> We would expect to see a big increase in whether the low energy particles would sort of pop up to much, much higher and then as you go beyond that, then you would expect to see the intensity start to fall off and so on so. Yeah. But you'd expect to see a very large increase there and so, you know, by quite a large amount.

Future Exploration of Outer Space - Dave Morrison

We do have a question-and-answer period after the next speaker. Our next speaker is the director of the space directory at the NASA Ames Research Center where he manages basic and applied research programs in the space life and earth sciences. He's also a distinguished astronomer who has a celestial object asteroid 2410 named for him. And hopefully that asteroid isn't going to come visit him soon. Please welcome Dr. David Morrison.

Dr. David Morrison >> Dave: This is a wonderful opportunity, both to honor the past and to look forward to what should be an exciting program of basic space exploration in the next few years, a much revitalized program. But let me begin as everyone has by looking to the past and saying what an honor it is to be part of a program that honored Pioneer. Truly this was a Pioneering effort and one way of calibrating that is to note that in all of its glorious space history, Russia or the USSR before it never spent a spacecraft in the outer solar system. They spent more spacecraft to Mars or Venus but they never did send a spacecraft through the -- Pioneer 10 and 11 did this within 100% success and paved the way for the two Voyagers and Ulysses and now Galileo which is in orbit around Jupiter today. But my job is to talk about the future of space exploration. Far too big topics to deal with in a few minutes but let me touch on a few highlights.

First to note historically, that the Pioneers came at the peak of the first great wave of planetary exploration. We launched many spacecraft, most of them relatively small and achieved the first solar system. We talk about Pioneers 10, 11, 12 and 13, there were Mariners, 7, 8, 9, you notice none of the spacecraft since then have had these sort of high numbers. We slow down. We sent Viking 1 and 2, we sent Voyager 1 and 2 but only a single Ulysses, a single Magellan, a single Galileo spacecraft.

As we built larger and more capable spacecraft which were inevitably more expensive, we ran into the declining curve of funding. And ultimately found ourselves almost out of business. Hence, the shift today of return to the past in many ways through the construction of many smaller spacecraft with much more frequent launches.

The concept of better, faster and cheaper spacecraft which is really just reinventing what the Pioneers knew 25 and 30 years ago.

There are three kinds of space exploration that we might think of one is the in situ measurements, the direct sensing of atmosphere, magnetic fields, plasmas. Much of the Pioneer of science was directed at this sort of in situ observations, and in the magnetosphere of Jupiter and Saturn. I won't say much about that today except to note that there is today in space a constellation, an international constellation of spacecraft of unprecedented capability to monitor the solar wind and its interactions with the earth's magnetosphere. The second approach to space exploration is that of the astronomer.

To build spacecraft, place them above the atmosphere, and let them look at the universe. The heroic era of big spacecraft brought us the Hubble space telescope and the Compton Gamma Ray Observatory and the European spacecraft. We are now moving beyond even as we continue to reach the fruits of those superbly capable machines still in earth's orbit. The access spacecraft, an X-ray telescope which will be launched in a year or so is substantially smaller than the Hubble or the Compton.

And the next infrared observatory in space, the space infrared telescope observatory will be launched at the turn of the decade, is again a much smaller and more focused approach for infrared observation than we might have thought of in the period of large spacecraft. Let me not say anymore about either the in situ observations observations or the astronomical explorations but turn to our solar system by sending spacecraft out to the object they wish to observing. In some cases these are fly-by spacecrafts as were Pioneer 10 and 11. In some cases they orbit. In some cases their atmospheric probes, surface landers, rovers. We are at the beginning of a second glorious age of solar system exploration with such spacecraft. Let me talk about this in terms of the object visited and start with our own familiar Moon. For a long time, after the last Apollo footprints, we sent no spacecraft to the Moon.

Although we all recognized that there was much undone and that in particular, the Apollo observations had concentrated on the equatorial regions of the Moon a had left the polar parts of the Moon and much of the far side relatively unobserved. We are now returning to the Moon. The Japanese are focusing much of their planetary space program on lunar orbiting craft.

The Department of defense sent its Clementine 1 spacecraft to the Moon and achieved unprecedented photography, motor spectral imaging, geology, measurement of lunar topography. And now, in about seven months from now, NASA will send its first spacecraft to the Moon since the Apollo era with a prospector, a small spacecraft that actually looks a lot like Pioneer 6 which is still in operation in space after more than 31 years which well measure the elemental composition of the lunar surface, the gravity field and the details of the remnant magnetic field, of magnet fields trapped in the surface material.

So the combination of Department of Defense, Japanese and American spacecraft will go back and do what many people thought we should have done for the last 25 years and give a global map of the Moon, in particular with the capability to look for that most exciting possibility of water ice in the lunar poles. The Moon is a very desiccated object. That's its main drawback. There's no water, no way to manufacture fuel. No way to manufacture oxygen to breathe. If we could find evidence of water, ice, trapped in the lunar poles, the Moon would be become a much more attractive space station as a stepping off point for the rest of the solar system.

Beyond the Moon, we sort of lump together the small bodies. Asteroids and comets. We had a wonderful, although very brief look at the nucleus of Haley's comet in 1986. Through the Russians and European and Japanese spacecraft. And especially, the European which flew within about 500 kilometers of the nucleus of Haley. We had a first look of the main asteroid belt from Galileo as it crossed the asteroid belt following the path Pioneered by Pioneer and now we are for the first time going to send dedicated missions to these objects.

The Mir spacecraft launched just a year ago, February 17 of 1996 is the first of the NASA discovery missions, the small planetary mission and its objective is the nearest asteroid on a usually we try not to call it an erotic mission but it will go into orbitor around Eros and spend a year in detailed study of an Eros asteroid.

There is the star dust mission, another discovery class, small planetary mission. Which will fly to a comet late in this decade, fly through the inner atmosphere of the comet, collecting gas and dust and then return with that gas and dust to the earth so that we can analyze these fragments of planetary material in our own laboratory.

The Department of Defense is planning a Clementine 2 mission. And the Europeans are well along in planning a mission which way actually land on the surface of a comet. We should see a major increase in our understanding of these small bodies.

Then we come to the rest of the planets. The emphasis on smaller spacecraft makes it harder to go to the outer solar system. It takes bigger radio antennas and more power to send the information back. You want to build in a great deal of redundancy into the spacecraft. So they can operate in spite of the hours-long gap in communication with the earth. So far we don't really know how to build small spacecraft for the outer solar system. Indeed, the last of the large planetary spacecraft, Cassini, is now in preparation for launch this year to Saturn. Cassini, like Galileo which now is in orbit around Jupiter, is a multi-instrumented, highly comprehensive platform for studying the planets, its rings, its satellites and especially its giant satellite Titan. As part of the Cassini mission, there's the European-built Higen's probe which will go into the atmosphere of Titan and major directly this enigmatic place rich in or back compounds which has often been compared to the conditions chemically of the early earth and of the time when the precursors for life accumulating on our own planet.

Coming up we hope sometime shortly after the beginning of the next decade will be the final Pioneering mission to finish off our exploration, that is our initial exploration, of the major planets; namely, a Pluto-class flyby. We certainly have the capability to send a spacecraft to Pluto. Indeed, the Voyager had been slightly different aimed, one of them could have gone on to Pluto, but we didn't choose to do that. The problem is it takes so long to get there.

So the emphasis today is on how to build a spacecraft and select a trajectory so that we can get there fast. And getting there fast with existing launch vehicles means choosing a small, lightweight, highly efficient spacecraft. Probably not quite as small as that model of Pioneer 10, but I've seen some effort that seem to be pushing the state-of-the-art towards very, very tiny spacecraft. In any case, there is the prospect that we could get to Pluto within just six to seven years of launch. And thereby complete our first look at the major planets. Beyond that, let me point out that there is a second major change that is taking place in our philosophy towards spacecraft exploration.

The first is the move toward smaller spacecraft. Smaller, lighter spacecraft that are less expensive to build and significantly are much less expensive to launch. The rule of thumb, you don't want to spend as much on a launch vehicle as you do in building the scientific instruments in the spacecraft itself. So we are -- we have a great advantage if we can launch on smaller and much less expensive commercial launch vehicles. The second change in emphasis is encompassed in the program administrator Van Golden have spoken so much about lately of studying origins. We are at a point in our scientific development when we can seriously address many of the most fundamental questions about our origins. With ice in it even.

Questions about the origin of the universe, the origin of galaxies, of stars, of planets, and most important, of life itself. And we will see an increasing evidence throughout NASA and other funding agency and I think into academia in the multi-disciplinary studies that are focused on origin and on life. This brings our focus very much toward Mars.

Mars is the one other planet in the solar system that we believe have conditions similar to the conditions on earth at the time life formed here 4 billion years ago. It's the one other planet in the solar system on which we can imagine humans setting up self-sustaining colonies that can live off the land and are not dependent upon the expensive ferrying of materials from the earth. Mars also happens to be one of the easiest planets to reach in the solar system. It's exciting as a scientific destination and it's exciting as a destination for human occupation. But Mars is not alone in its biological interest. Before talking about the Mars exploration program in any detail, let me mention the Titan, the giant planet of Saturn which is the target of the Higen Probe is also of great interest biologically because of the organic chemistry that happens naturally in its atmosphere and the history of this organic chemistry that may be available on the surface through the slow accumulation of organic materials over the last 4 billion years. I must also mention Europa.

How many of you saw the movie "2010." You all then remember the importance of Europa. Perhaps a bit of a reach for Marcia Clark, but not an impossibility because Europa appears to have an icy crust that is so smooth, it hints that it may be floating on a liquid ocean beneath. There's nothing particularly special about ice. The outer solar system is full of ice. But it's special because the ice on Europa may be floating above a global ocean and if there is a liquid water ocean on Europa, then that is the only other place in the solar system with such an environment exists. We know that liquid water is the most important, the most critical ingredient for life as we know it. It used to be that we would have thought it required a lot more than liquid water. Photosynthesis, for example.

But some of the remarkable discoveries about life have taken place on our own earth where we have found biological ecosystems of tremendous vitality and diversity in the deep ocean where no sunlight penetrates -- off the chemical energy released at mid-ocean vents and where even more recently we've found microbial communities, again a vast expanse living kilometers below the surface in the aquifers and the rock beneath our feet. Ecosystems that are completely disconnected from the surface and not dependent in any way on photosynthesis or the production of biological material in the life that we see around us.

If such ecosystems can thrive on earth, then why not on Europa and why not on Mars? We know the surface of Mars is a sterile place. Viking spacecraft taught us that. Most people after Viking thought of Mars as a planet without life, a planet which probably could have sustained life early in its history but which is no longer capable of doing that. But now we have the possibility that life once formed on Mars and it might continue to exist beneath the surface in aquifers in the same way that ecosystems exist beneath the surface of our own planet.

So we come to the end to Mars, and let me spend a couple of minutes on that even though you're about to pull me off, okay. We are planning to send two spacecraft to Mars at every opportunity, the opportunities that come about every two years, for at least the next decade and probably beyond. A fleet of robotic spacecraft relatively small to explore the atmosphere and the surface. En route today we have two such spacecraft. The Mars pathfinder, which will land on July 4th, and which carries a small rover called Sojourner which will lead the spacecraft and travel for some tens of meters exploring the surroundings.

A Mars Global Surveyor which is and Orbiter and will go into orbit around the planet and continue to do detailed studies of the planet. And continued pair of orbiters will land two years after that, two years after that. And a system that continually builds on what we already know. I can not tell you what instruments will be carried on those subsequent missions. Think of yesterday to be selected. They will be selected from the best that the academic scientific community can bring to bear on the competitive community process. What has invigorated this system even more is that we are now considering not just the scientific exploration of Mars, but an integrated program that answers scientific questions and also paves the way for humans to travel to Mars. We are not in a position today to plan more human trips to Mars. We are in a position to ask and answer the critical questions to find out the information we would have to have where to land on Mars.

Where are the scientifically interesting locales? What is the nature of the surface? To answer the engineering questions. Is the Martian soil toxic and interfere with the machinery we might want? Can we convert the Martian atmosphere into rocket fuel and thereby create the rocket fuel we need on the surface rather than having to carry it there? Can we learn a technological problem again to enter the Mars atmosphere, decelerate and land on the surface without using rockets, by using air braking and air maneuvering in the atmosphere?

We will be asking these questions as well as the scientific questions in the next few years so that with luck, if the answers turn out positive, and if public support continues for the space program, perhaps a decade from now, we can truly be discussing human trips to Mars to carry out that ultimately search for life on Mars. Life in fossil form that may have existed in the past and even possibly life existing today beneath the surface of the planet. Thank you.

>> Okay. At this point, if you take a look at our schedule, we're scheduled to do some questions and answers. And we've got virtually everybody who was here today and I suppose that what we're going to do is open up the floor to any questions and then we'll let different people field them. And if they don't pass, they don't get out of the room. Do we have any questions? We have one here to start you us off. It's like being back in school again. Have to get one brave soul. Yes.

>> What's the next step I'd like to ask Dr. Morrison for a probe?

>> Okay for the next step exploring Europa, Dr. Morrison.

>> Dave: Even as we speak, the Galileo spacecraft is taking pictures of unprecedented quality of the surface of Europa. And I have to tell you as someone who has been looking at those I can't tell if they increase the likelihood of there being lick-week-old water underneath that surface or not. It's an extremely complicated place. The next step is an extended mission for Galileo called GEM. The Galileo Europa mission which will concentrate after the end of the nominal mission on a series of six close fly-bys of Europa to obtain much higher resolution pictures of the surface. Beyond that, dedicated missions are more of a problem. But there have been some proposed. Including a mission called the Europa ice clipper which would send a small projectile down to the surface ahead of the spacecraft, blast off some of the ice and have the spacecraft fly through the plume and correct it. Beyond that, we had love to have rovers on the surface drill -- rovers on the surface, drill through, go underneath and that is something that is truly beyond our present horizon could so I don't want to speculate any more on that.

>> Any more questions?

Back all the way up there.

Can I have you come down to one of the mikes? I really can't hear you, I'm sorry. The fan up here makes enough noise it's really difficult to hear.

Questions and Answers

Probably get that question, maybe we could get a, just an Internet question. If it won't take too long. This is one from, where does this come from? Anonymous?

>> We're not sure.

>> We're not sure where it comes from. The question was: How much computer does the Pioneer have? And that's one of the amazing things about the Pioneer. We did not have a computer on Pioneer. This is the old days when we didn't have and we didn't want to have a computer on Pioneer.

Okay? Your question, please?

>> Yeah, you mentioned that Voyager could have been programmed to go by Pluto. I wondered if you knew why they made the decision not to do that with one of the Voyagers.

>> Okay, Dr. Morrison again.

>> Dave: Yes, the decision was made to concentrate on observations of Titan in the Saturn system. And you had to make a choice. You either flew past Titan or you tried to go on to Pluto. Since the Voyager spacecraft was not designed to survive beyond Saturn, it was originally just a Jupiter-Saturn mission, it would have been probably a poor decision to take the chance on another 10 years through space to get to Pluto, so the decision was made on both scientific and practical grounds to go for Titan instead.

>> Okay, any more questions? We have one up here. >> Some questions that refer to Pioneer 6. Do we have anyone who can tell us a little bit about Pioneer 6 here?

>> Where is Pioneer 6?

>> Pioneer six is in heliospheric orbitor and we're still in contact with it, it's still orbiting. Pardon me?

>> It's in the inner solar system?

>> Pioneer, the series Pioneer 6 through 9 were inner solar system, some were outside the orbit of earth and I'm not sure which, we have to look it up, some of them within a million miles inside of the orbit of earth and somewhere couple million miles outside the orbitor of earth.

>> I have some other information here. It's in an orbit which from the point of view of and earth-centered system looks like a rose et progressively moving around the solar system going in about .3 of an AU and going out of the earth's orbit and going back in again. More questions.

>> Right down front.

>> the question is whether the Voyager could either of the voyagers could have later been sent to Pluto and the answer is no because once you have started on a trajectory, you stay with it. You can't change. And the only way that the Voyager II was able to get four planets was by a fortuitous alignment. Pluto was not along that alignment for that trajectory. Once it had gone out to Uranus and Neptune that was the end.

>> Another question? Maybe we can get an Internet question. I've got a few of these. Also anonymous. Anonymous means the person hasn't signed in, hasn't used a handle of some sort.

How hard was it for Pioneer to pass through the asteroid belt? That's an interesting question. Actually, it was easy as could be. The question was. Whether that it did pass through with very, very good, very fortunate situation.

>> How hard was it for Pioneer to pass through the atmosphere?

>> Well, I think I put the question a little differently. The only significant hazard encountered what in the asteroid belt and the answer is no in that of course the position of all the major asteroids was well known or at least a few thousands of them were well known at the time so the chance of an encounter with one of the asteroids that was known was infinitesimally small. I don't think at any time that was considered to be a constraint on the orbitor. The question was whether there was enough ground up small gravel and debris from collisions among asteroids which has been previously been undetected by telescope and would that present a significant hazard.

One of the principal experiments on Pioneer 10 and 11 was a micrometeorite detector, called interplanetary dust detector, that shows detailed measurements of the number of impacts per day on this particular body of detectors during the whole mission out through and about the orbit of Saturn and there's no significant increase in the asteroid belt which shows as far as flying debris is there was no significant hazard. We had five spacecraft fly through the asteroid belts without adverse episodes, first Pioneer 10, then 11, Voyager and Voyager II and Ulysses passed through the belt without any incidents. So there appears to be a somewhat overexaggerated anticipation.

>> I'd like to add one thing to that. If you want to see asteroid dust, the moral is don't go to the asteroid belt, look up at night and see the meteor.

>> That's a good one. That's a question I think you might like to field. I'll give it to you but let me read it first and then I'll give it to you. It says, I'm trying to see where it came from. E-mail. Sender H. Shank. On earth the inner Van Allen belt is composed of eastward moving electrons and the outer belt of westward moving photons. On Jupiter where the polarity is reversed of the earth the respective particles should move in the opposite direction. Were the Pioneers sensitive enough to verify this?

>> Well, I think I understand the question. I think it's part of this is an incorrect statement that it is correct that the polarity of Jupiter is reverse of that of the earth. In the case of the earth, the north magnetic pole is at the south geographic pole and vice-versa. Jupiter is the other way around. And there's no known reason why that should be so and shouldn't be so on and since the earth's field reverses every some hundreds of thousands of years, it's obviously kind of a quirk of nature as to which way the polarity is for any given planet. But the question asked which way particles drift, and it's not true that the radiation belts have a different drift pattern. That's not true. The drift and longitude is the same in either radiation belt? Electrons always drift east around the earth and protons always drift west around the earth. And Jupiter it's the reverse.

>> I have to see if we have any more questions here in our audience.

>> Why should it be one result of our greater knowledge of the solar wind that at some time we can use it as an energy source to help navigation in space?

>> Okay, who would like to take this one dealing with using the solar wind to help for energy and navigation in space?

>> Quite a number of years ago, there was an effort, and I don't know the names of the originators of this, to have solar wind sailing expedition and that would mean having very large areas exposed to this very dilute solar wind so there would be a very, very gentle nudge given to a spacecraft as it moved outward. This never materialized, there were obvious technical and practical difficulties with that.

>> Okay. We have a question here from someone who we recognize.

>> I want to add to that answer because it is an important distinction. In solar sailing, it's not the solar wind, that's actually about three orders of magnitude less than the photons which provide the propulsive force so in the solar sailing, it's a photon pressure reflecting off a highly reflective surface like an aluminized solar sail sheet which provides the momentum transfer which provides the solar sailing force. Solar wind would be about three orders of magnitude less so it would be a different thing. Solar sailing has been applied for attitude control of spacecraft, and has yet to be used for a propulsive technique although we hope sometime in the future it might be.

>> We should note that Dr. Friedman led the last major NASA study of solar sailing as a technique for -- solar sailing as a technique for getting spacecraft from one place to another in the solar system.

>> Could we have do we have any other questions? [ question being asked inaudible ]

>> If I repeat your question correctly, in our quest to explore space, fit for exploration or commercialization or military? Who would like to address that one?

>> Different people have different motivations, I expect all three of those, exploration for understanding, commercial anticipation that markets will be created as we move into space, and military issues are at play. And perhaps the great virtue of a frontier like space is that it can be many things to many people and provide many ways to enrich our lives through understanding but also through commercial opportunities.

>> Okay.

>> Very difficult question, what are we going to do about the debris in earth orbit? And I think that is one of the biggest challenges we've had. We've done a great deal to reduce the production of debris, but we haven't figured out a way to clean it up. It's sort of like the pollution along the roadside for people who are throwing away beer bottles, we've stopped throwing away the beer bottles but we haven't picked up the ones that are already out there and some day we're going to have to face that.

>> And it certainly is a valid question because early on in the space program, that was something that people didn't think too much about and I think we were kind of regretting that now. Okay?

An Internet question?

>> No, actually it's an Internet report. I just saw on the board it's exciting because here we have the Pioneer mission's operating center at the Ames Research Center. And this is from Rick Eagle, one of our controllers who has been following it on the Internet. And I'll read it. I'll read it for the people on Internet and those who can't read it here, it says good afternoon. Just a note from Pioneer mission operations now tracking over DSS 63 in Spain. By the way, I think we mentioned that there are three different areas that we track from Spain and the Mohave Desert and Australia. So this is from Spain. This is a one-way non-coherent downlink only track ending at 000 which corresponds to 7:00 P.M. eastern standard time. The signal is nominal. The deletion rate is under 10% which is good for one-way tracking. We've been following along here via the Internet and virtual conference. Best wishes to all from Pioneer Mission Center. J. R. Eagle. That's Rick Eagle.

>> So they're watching us, huh?

This is incidental I don't know if it's mentioned before but this is going worldwide. 10 different countries? Is that it, 10 different countries aside. We don't know how many others might be watching.

>> I have a question down in front. [ question being asked inaudible ] The spacecraft that has gone out of the plane of the orbitor of all the planets is Ulysses?

>> Maybe Ed could answer that.

>> And do we have someone who could make some comments about Ulysses?

>> The answer is that Ulysses as I said is the only spacecraft that has gone perpendicular basically the plane is ecliptic. The maximum distance when we're right over and under the poles of the sun was about 2.2 astronomical units so about twice the distance from the sun to the earth. We don't know how far it is to the heliosphere over the poles. There's some suggestions in the data that is at least as far away as it is going out along the equator so we don't really gain anything by going in that direction in terms of getting there early.

>> Very good. May I add to that?

That not all four of the Pioneer and Voyager stayed strictly in the plane of the ecliptic. The Voyager that flew past Titan went out of the plane quite aways which is why it couldn't go to Pluto and I believe Voyager 11 enough gone out of the plane a fair amount also, 16 degrees.

>> Okay. I guess we have time for maybe one more question in-house. Do we have one?

>> No problems, it's a wonderful opportunity. Space is opening us to us and I think we're accelerating our efforts to explore space.

>> There is clearly a premium on resources. We know that everywhere. And that's true in the private sector and the government sector. So we have to learn to do things in an economical way. But I think the public support and the government support for the space program has been wonderful lately. And I look forward to an expanding program, not a shrinking one. [ Applause ]

>> Okay. Maybe one Internet question. If you've got one. You don't have one right this second?

>> I think probably be a good point to end this but I want to make a comment. I have this, you know, thrilling feeling in my heart here to realize that do we realize what kind of world-leading experts we have here answering questions? And it's just amazing.

And I wasn't even talking about the scientists. No, just joking.

The scientists and of course we are probably know about Pioneer 10 best, the project people. It's been a thrilling experience for all of us.

Closing Comments - Bob Hillenbrand

>> Okay, we have one last thing we're going to do today. We have kind of a nice surprise for those of you who have stayed with us. You may have seen it over here huddled in the corner and people writing away like crazy. And what we've been doing is we've got all of the presenters today to go through and autograph a copy of the Pioneer book and we're going to give 10 of these away. And the fair way is we'll just put all the names of the registrants in and you have to be here to win and we'll call out names. If you're one of the lucky people and you can prove that you're who you are, we will be very happy to give you one of these. Picture I.D., 13 different kinds of verification and you've got it made. Worse than going through the airport. So David Morrison will be our puller. The first pullee is David Eberhart. Okay.

>> He's actually going to show me his I.D. [ Laughter ]

>> Second winner oh, this is one I can read. Suzanne Linda. Congratulations.

Our third is Conner Marsden Conner Marsden twice, Conner is not here. Okay. Terry -- Kerrey Siesker. That's you, okay.

You have to pronounce it for me. Oh, so sorry. I don't have my reading glasses on. I should have them here. Louise Kelstra. There's Louise up there. This one is going to be a toughee because I think it's Tim or Ted, it didn't copy very well. Tim or Ted. Very good.

And Leonard Cogan. Okay, William -- it looks like Owenings. Yeah, I really can't read. Lorna. Okay.

Let's see, we've got, we've got one up here. And Catherine looks like Ashford. Something in front of had that, DY it almost looks like. Catherine I guess Catherine is not here. Okay. Well, we certainly gave her plenty of chance. Amy Wyatt. Amy Wyatt. No Amy Wyatt here. Paul -- no, no, The something so I've been out of the classroom too long I don't have the codes -- Paul Thies. Very good. And one more. William Barnet. Barnet, William?

Okay. As you leave today, we have this bag of goodies that we've told you about waiting outside the door and we have copies of the Pioneer plaque just like the ones you saw on the display out there.

And those will be available to you and if you'd like to stick around and ask more questions, I'm sure there will be people who will be glad to help you out. We've enjoyed you being here today and hope you've enjoyed the Pioneer conference. Thank you very much.