missions like this. to me, everyone who's ever looked up at the night sky and wondered, anyone who has any curiosity at all about earth and how it fits in, anybody who feels that longing to know the cosmos, or who wants to understand the nature of nature, and for that matter, anybody who's just ever felt that drive for bold adventure, right, a noble undertaking to go beyond the next horizon and see what's there. everybody participates in a mission like this. and that, to me, is what's most exciting about this kind of thing, because i think dawn and the other spacecraft around here truly as human kind's robotic ambassadors to the cosmos -- and

i think we all share in that -- and that's what i think is really rewarding about this. so that leaves the question, how do we do this? well, we start by putting the spacecraft on top of a huge bomb and hoping that it blows up in a controlled fashion, and it usually does. [laughter] >> and we've got dawn off to a quite a beautiful launch. in fact, dawn launched at dawn -- i don't know how well you can see it here. the sun is rising in the background. we left cape canaveral at dawn in 2007 and when we got into space, this is our trajectory and once again, it's this conventional view with the sun in the center. here's the orbit of earth and the orbit of other bodies and as

we follow the trajectory for dawn along when it's this nice xenon camillion blue color is where it's thrusting with the ion engine and where it's dark is where we're coasting. we launched in september 2007 when earth was here and you can see we coasted a little bit, and we had some thrusting and coasting as we were checking out the ion engines and others as we were getting the spacecraft ready for its interplanetary journey. then we got into a regular pattern of ion thrusting most of the time and as a subtle technical detail, the durations of these coast periods here, that is where we're not thrusting and exaggerated in this, because the software used to generate these trajectory samples just once a day, so we're really thrusting more than

it looks like here. you see thrusting most of the time and then we have this long coast period during which we flew by mars in order to speed up the spacecraft and slow mars down, but we continued spiralling gradually farther and farther and farther from the sun sun until july of 2011 when we got to vesta, went into orbit around vesta, accompanied it 14 months, making our comprehensive set of measurements and maneuvering extensively from one orbit to another around vesta. one of the benefits of the ion propulsion system is not only do we get into orbit, but once we're there, we can fly to different orbits in order to optimize our scientific investigations. but we use the ion propulsion system to break out a vesta orbit, undertake this 2 1/2 year climb through the main asteroid belt until we got to ceres just a little bit more than a year ago, went into orbit around ceres and the spacecraft is staying there and will stay there essentially forever and, in fact, where this line turns from bold to light represents the end of dawn's prime mission, which was june 30. so we successfully completed this 8.8-year 3.5-billion mile journey just a couple of weeks ago, but we're very grateful that nasa has decided to extend the mission because it's going so well and there's still more

neat things we can do at ceres, so we're continuing our exploration there. so we can zoom in right now and see where dawn is today. so we can see we've progressed a little bit beyond the end of the the primary mission. and on this scale, you can't see see the difference between where where dawn is and where ceres are, but basically in the same \are but basically in the same place on the scale of the solar system, but we can also zoom in and see where vesta is today. and so one thing that's sort of interesting is we departed vesta from here, so that was a little bit more than one vesta year ago. and actually, dawn is now farther from vesta than the earth is from the sun. again, to me, this is cool. this is a reminder that this is an interplanetary spaceship, right. we go to distant bodies. we orbit them. then we can travel from there huge distances to go elsewhere to explore as well. and so since i mentioned earth, we can zoom in and see where earth is today and that's actually where it is right now and, in fact, those of who you came here drove in through the guard facility here, went in here, parked up here, and we're in here right now and actually

unfortunately, i can see that gentleman back there, you left your lights on. [laughter] >> you might want to go out and take care of that. so that's the overview of the trajectory. but when you look at a picture like this, it's flat and it's static, and it's easy to forget the solar system is in motion. the way i think of it is, the solar system has this big beautiful complex choreography. so let's take a look at an animation of what's going on here. we want to get oriented first so that as the animation progresses you can follow it. once again, the standard view, the sun is in the center, blue is the orbit of earth, red is the orbit of the red planet mars. this is the orbit of vesta and this is the orbit of ceres. and starting out by showing you the locations of these things, where they were in march 2007 so

that you can sort of synchronize your watching of it in preparation of the september 2007 launch, and what you'll see is that vesta is going to go all the way around the sun before we get to it and ceres is going to go around almost two full times before we get to it. it's much more complicated than just going to -- out to a certain distance from the sun. you have to get to the right place at the right time. here in september 2007, the spacecraft leaves earth, lights up its ion propulsion system. we're now aiming to fly by mars. remember that occurred while we were coasting. so here, we've flown by mars, turn on the ion propulsion system again. we're aiming for vesta but won't get there until here and ceres is going to go all the way around the sun for another full revolution before we get there. but finally, as we get into 2011, dawn gets to vesta, goes into orbit around it. once again, spends 14 months there, making extensive measurements. in september 2012, fires up the ion engine heading for ceres. it looks like it's not that far away, but that's a long, arduous

climb through the asteroid belt, 2 1/2 years to get there. but as we get into early 2015 it did, indeed, go into orbit and that's where the spacecraft is right now and once again that's where it will be effectively forever orbiting the sun with the largest body between mars and jupiter. and it's continuing now its exploration of this strange alien world. so that's a broad overview of the mission. i can tell you that we have lots of things going on. we're very busy. there's all kinds of things going on all the time. i'm not going to bore you with every imaginable detail with what's happening. instead, i will thank you very much for your attention. i appreciate you letting me tell you about the dawn mission, so thank you very much. [applause] marc: so i'm happy to take questions for a little while. i'll remind you, if you'd like to ask a question, please come

up to the microphone. and while people are doing that, i'll just tell if you you're interested in the dawn mission, you can go to our web site, dawn.jpl.nasa.gov. you can see all kinds of cool things about the mission. we release a new picture every day, sometimes more, but at least every work day, we release a new picture of ceres. we have lots of educational activities there for students and teachers and, of course, we're all students, so there are a lot of neat things to learn. if you enjoy the way i talked about it, i have sort of a blog called the dawn journal and write about the mission in kind of the same way i talk about it here. we also have more frequent status reports and other things as well. so questions? audience: thank you very much. the lecture was fascinating. you spoke a little bit about the

formation of jupiter and how that stopped the formation of these protoplanets and i was wondering if you could say a little bit more about how that happened. marc: sure. so first, can somebody verify that the microphone works so everybody can hear? so i won't repeat the question for you. when jupiter formed, it did several things. one of them is that its gravity tugged and pulled on all this other material that was orbiting orbiting the sun and sort of stirred it up. and the consequence of that is when things hit, they wouldn't necessarily come together with these gentle approaches like this and stick together. but rather, they would tend to hit at higher velocities and so stick together and not break apart. in addition, it actually ejected a lot of that material from that

region, that is, scattered it to elsewhere in the solar system. and so not only were collisions that occurred less effective in building larger bodies, but there were many fewer collisions. there was much less material to work with. and so what was there didn't get the opportunity to continue growing. did that answer your question? yes, sir? audience: this is a fascinating presentation. thank you. so you stated one of the main mission points was to measure the gravitational field. what kind of challenge is there between the gravitational field as you understand it when the mission starts and when you actually arrive. how do you account for fluctuations in fuel consumption? marc: you're saying how do we account for the fact that we didn't know the gravitational field when we got there?

that's an insightful question. that's another one of the many unique aspects of the dawn mission, is this is the only mission ever that's gone to a massive solar system body to orbit it, which had not previously been visited by a fly-by spacecraft. so mercury, venus, the earth, mars, jupiter, saturn, these other massive bodies that spacecraft have orbited all have have been visited by fly-by spacecraft so we had measurements of the gravitational fields before we got there. dawn did not. so there were a number of ways that we accounted for it. but thanks to the flexibility of the ion propulsion system, essentially what we would do is, is, here is our massive body, here's the spacecraft flying in. we would fly toward it and measure the gravitational pull, if you will, as we got in, determine with the extraordinary and exquisite accuracy that interplanetary navigation is able to achieve, measure that gravitational pull, and then update our flight plan, our thrust profile, that is the

aiming of the ion engine and the throttle level that we use, update it to account for our improving accuracy in the gravitational field as we got closer and closer. so essentially, you fly in a little, measure the gravity field. fly in a little closer, measure it more accurately. fly in still closer and measure it still more accurately. does that make sense? audience: thank you. marc: yes, sir? audience: hello, and congratulations on this extraordinary accomplishment. i was wondering as i was looking at those amazing photographs of ceres, that, wow, it's -- the surface of ceres is like a record of a record of every piece of whatever from space that's slammed into it. i was wondering is there -- do you think any of the surface of an object like ceres is the result of any kind of internal forces, and is there any way to

know that? marc: that's a good question, and i'll start with the short answer, yes. there is good reason to believe -- in fact, excellent reason to believe that there are internal geological processes operating on ceres which directly affect the surface. and we can see that in several ways. one of them is that i showed you you the cator crater, in a moment you'll see it rotating into view in this picture. it will be the bright thing. i don't know when it will come around. but as i said, that's measured to be only about 80 million years old. and the bright material there has to be even younger than that. there are current geological processes. but more to the point, you started with the reasonable comment that it's recorded everything that's hit it throughout the -- more than 4.5 billion years of the solar system. but, in fact, a number of areas on ceres -- you can't see it very well in this picture, which

actually are relatively smooth, that is, don't show many craters. and we have mathematical methods that i could describe if you're interested, for predicting how many craters of certain sizes should occur on ceres. and partly as many craters as we see on vesta and there aren't as as many large craters there as there should be. that's a suggestion that, perhaps, there are geological processes over time erase those craters. and so one of the things that planetary geologists are working working on now is understanding the nature of these processes. there's other geological evidence as well of the effect of ceres' internal activity much more recently than -- occurring

much more recently than the 4.5 billion years since it formed. does that make sense? audience: yes, thank you. audience: good evening. just two questions on the design of the spacecraft. first of all, you mentioned, i think, that it had another ion engine. marc: we have three. the star wars pathfighters only have two. we have three. [laughter] marc: our lasers aren't as powerful as theirs, but you can't have everything audience: it was a military project.

[laughter] audience: is that strictly for to actually use those to eliminate the need to turn the craft around? marc: that's a good question. before i answer, let me explain to other people what redundancy is, do we have more than one in case one fails. that's what you mean by that term, right? so it turns out there's a mechanism that we understand very well about which twin engines wear out in space, because of use. just like lots of physical devices get consumed by their use. and so given the amount of xenon propellant that we had to expend in order to accomplish the dawn mission, you had to have triad engines. that is if one wears out too soon, or we didn't have sufficient confidence that we could do it with one. so we carried two in order to have sufficient lifetime. and then the third is for exactly what you raised. so that was an insightful observation. the third is in case one fails. however, as it turns out, all three are still healthy. so we didn't have any problems with the ion engines. and we don't pick them on the basis of what direction we want to thrust, because you can even

see in this picture -- and i'm going to turn this picture off in a moment only because my computer doesn't like staying on one picture for too long. but see there's one engine here, one here and one on the back side. so that's not enough to cover all the directions anyway. if you wanted to point an engine up in this way. so we don't use it for that purpose. if we want to point an ion engine in that direction, we rotate the entire spacecraft and point the ion engine in that direction and go there. audience: thank you, and it seems to be -- this is an ambitious size of solar array to have worked and unfold perfectly and everything.

did you have a trade-off between thinking and using like a radio isotope power supply? what was your thinking on that? i'll thank you for the answer. marc: you might want to wait until after i've answered it, but that's your call. for other people's benefits, this radio isotope thing he referred to -- in fact, you can see them, for the people in the room, i don't know if you can see the laser pointer here, but this black structure sticking out of the side of voyager here is what's called a radio isotope thermo electric generator. this scale model of the spacecraft here has them, if you go into the museum, which i think is open this evening. i'm not sure. you can see models of them on

the galileo spacecraft as well. these are devices which contain radio active materials which when they decay produce heat and that heat is used to produce electricity. and it's not a nuclear reactor, but it uses nuclear energy. and we did not consider using them on dawn for several reasons. one is they are very, very expensive and so you only use them if you really have are to. they were well worth the investment for the fabulous return of voyager and cassini here and gallileo and many other missions. but also, they don't produce enough electrical power. devices like that only can produce 100 or a few 100 watts and the ion engine itself, just to turn on the ion engine takes well over 500 watts just to turn it on. and normally -- in fact, we've never actually operated it at that low power level. when we started, we were thrusting with more than 2 kilowatts. so the mass of these devices would completely overwhelm the benefit of the ion propulsion system, because we would have to propel that mass through the solar system. so having these large solar arrays for us was the better trade. but every mission makes its own trades on what the most effective way is to accomplish whatever its objectives are. so i lost track of where that gentleman is but i hope that answered his question. yes, ma'am? audience: hi, thank you so much.

i was wondering how we know the asteroid debris on earth came from vesta and why the north part of it is much more densely cratered than the south. marc: so the first part, how do we know that these meteorites -- and i forgot to say if you want to come up and take a look at this afterwards, you're welcomed to. how do we know these meteorites came from earth? there are a number of lines of evidence, but it started with a method that i need to explain to you called infrared reflectant spectrum. let's break that down. infrared, a wavelength of light that we can't see but we know is there, just as there are wavelengths of sound that we can't hear, but your dog can confirm for you that there are wavelengths of sound that we can't hear but that are detectable. so there are wavelengths of light we can't see, infrared. reflectants, that just means the

infrared light from the sun bounces off vesta and goes elsewhere just like the visible light does, and the spectrum is where you break up the light into its constituent colors. think of using a prism on white light and you see, quite literally, all the colors of the rainbow. you break it up into its constituents. we can do that with infrared light as well. it turns out when you do that that the infrared reflection contains sort of the finger print or the signature of the material that reflected it. some infrared wavelengths are reflected very strongly, so it's bright at those infrared wavelengths. some are not reflected very well, so it's dark. and so this produces a distinctive pattern for different materials. and so around 1970, astronomers started using infrared detectors to look at astronomical bodies. they looked at vesta, measured this now infrared reflectant spectrum, and found that it was a wonderful match for this large class of minerals that occurred

in these meteorites. for experts, the minerals are called howardites, udites, so the meteorites if you want to get them, they're not that expensive because they're so common. i bought this myself before i even heard of the dawn mission because i thought it would be cool to own a piece of vesta. they're called heds, howardite, ueuchrite and diodronite. i could tell you other things about it, if you care, i'm giving a long answer, but it wasn't until dawn got there and made much more detailed measurements that we were able to clench the story. the other question you asked, why is the northern hemisphere more cratered than the southern hemisphere, and the reason is because that impact that excavated this material just happened to occur deep in the southern hemisphere near the

south pole. so some of that material was thrown out with so much energy that it left the vicinity of vesta and went elsewhere, including to here on earth. but some of it, just like if you had a big impact on earth, some of the stuff would fly up and come down some place else. so it landed elsewhere in the southern hemisphere and erased the craters it already formed there. it resurfaced it. so you can think of it as the northern hemisphere records 4.5 billion years of stuff falling on it, whereas the southern hemisphere had its record wiped clean, and so it only records 1 billion years. does that make sense? audience: yes. thank you. marc: you're welcome. i apologize for my wordiness. audience: hi, i have a pretty good intuition for a chemical rocket engine. i've watched a lot of videos and heard the audio and seen some

live. marc: heard what? audience: heard the audio, heard heard it live. i don't have a good intuition for what an ion engine is like. marc: nobody does. darth vader, right, because he flies the knight riders. audience: sort of what it would sound like, what would happen if i put my hand a foot away from it or stood 10 feet away from it. marc: for all intents and purposes, the ion engine can only work in a vacuum chamber. so in space -- somebody can't hear me? okay, so in space, in space nobody can hear you.

you can't hear an ion engine in space. it doesn't make a sound. what would it feel like if you put your hand in front of it? there's a lot of energy in these very high-velocity xenon ions, kilowatts. this is a highly-efficient system. so of course it's not perfectly efficient, so not all of the electrical energy goes into that that beam, but it is very high energy. and so if putting your hand in the vacuum of space was tolerable, you would not appreciate the effect of these high-energy xenon ions impinging on your skin. it would just -- it would be very damaging. it's very energetic. and what was the third -- oh, what if you stood 10 feet away from it? standing 10 feet away from it is no problem because they operate in vacuum chambers and as long as the vacuum chamber is less than 20 feet across, it's easy to be within 10 feet of it but we're in the safety of the laboratory outside. i don't know, does that -- maybe that's so really get it, but

>> hi. ion engine, how long to makectually take you it? >> like most of the components these things aft, take, actually, i don't know long.ly how but around a year or so. months to atake six couple of years to make. produce ou have to hese things to very high -- very strict standards, right?

because you don't want them to to operate them correctly in space. and they go through extensive testing. so the total time to -- from with the raw materials until you have the ion engine on the spacecraft ready go is years because you test you ndividual engine, then put it on the spacecraft and test it on the spacecraft, then spacecraft whole with the engine on it. started building the spacecraft in 2005 and until even launch it 2007. use xeono asid you a repellant? ion engines ts of

repellants.erent zeon has a number of advantages. mentioned it is one of the noble gases. reactive.chemically so that means that when onto cians are loading it the spacecraft, there's no risk to their health. they don't have to wear special rotective gear in case there's a leak. another benefit of it is there's that we understand well by which a little bit of out of the aks engine at low velocity. so the spacecraft ends up almost a sort of cloud of xenon it.nd because it's inert that doesn't chemicallyisk from a reactive compound that could obstacle surfaces like

damage the camera say or the solar rays or interfere with the electronics or even affect the temperature of surfaces. everything on the spacecraft is designed with xenon won't d interfere with that. proven i'm wordy, so i need to tell you a couple more things. store. is very easy to we launched with 937 pounds gallons. in just 71 so a tank about this big, about yard across and about that tall. so we need to be able to store this very effectively because premium in the spacecraft. >> okay. thank you. >> you're welcome. >> hi. talk.you for the i was curious, as the end of the there approached, were any particular like last things that you wanted to see there? about like the end of

ife planned would just float off into space? >> i'm not sure i heard you. did you ask whether there were things we wanted to see near tend of the mission? did that evolve? a funt's actually kind of question. as it turns out, there weren't. even e reason is because before the end of the prime mission -- i should take you back. all nasa missions, has a well defined set of objectives. personally, you, and i, and all other taxpayers have in what nasa ment does. and so we have to make sure that investment is done responsibly. we have to build a spacecraft, it, tell it to go do good things. we agree tpha it's worth this a estment to accomplish certain set of objectives. of e had a well defined set objectives that we wanted to

accomplish in the mission. not just that, but surpassed all of those bjectives i think by either february or march. i think it was february of this year. but the end of the prime mission wasn't until june. so by the time the mission ended, we were already just ecstatic with this rich trove of returning.e sure, the cosmos is endlessly and there will always be interesting things to look at. but we were in the very of not e position needing sort of urgently to just see one more thing. we would like s to see and that's why it's so onderful that nasa had chosen to extend the mission to continued its operations. by there was nothing that the end of the prime mission we felt we were sort of rushing to see. that answer that question? >> yes. >> i think the second question asked is sort of what's going to happen to the

spacecraft. stay in orbit. just as surely as the moon stays in orbit around the earth, the orbit around the sun. right? siri. moon of we will continue operating it as things -- important two important criteria are met. as long as the spacecraft healthy and productive. criteria, elf is two and the third, as long as nasa continues to choose to invest and limited funding into dawn. but in any case, when the pacecraft completes its operational lifetime and i could explain if people are interested occur, it will just become the way i like to will become anit inert select field monument to creativity and ingenuity

in orbit around siri. it's not going to go anywhere else. remain in orbit. >> thank you. sure. >> thank you very much. our dreams about true. >> if i could just interrupt you. it's not just your dreams. all our dreams. it's so cool. >> yes. it's exciting. and the question is what was the biggest problems spacecraft had ofpened during the ten years the mission and how did you solve these problems? >> okay. did somebody tell you to ask that question? did, i know. the question was, what's the happened tolem that the spacecraft during the mission? anybody associated

with the mission you'd get exactly the same answer. problem.t have a big i'll jump to the end and tell you the mission was successful. the spacecraft has devices called reaction wheels. these are disks about this big electrically spun. gyroscopes.like and there's a phenomenon that remember from high school physics, some of you, where you take a spinning wheel and hold it on a shaft like this. the whole spins like this. like maybe nobody went to the same high school i did. you sit on a bar stool. rotate the wheel, you spin on the stool. what expertso with call anning hrar momentum. the point is with these disks, the speed at which hey spin, we can turn, rotate the spacecraft. because in the zero gravity frictionless space, there's no to turn it. so if you have a wheel like this

and you change its speed, the around it.will turn so that's how we orient the spacecraft. nd these other spacecraft as well around the room. not all of them but many of them are oriented the same way. you need three of those because there's three dimensions. left, right, front, back. we need three along the lines of the earlier question. we have four. because we couldn't -- didn't want the mission to fail because of just some random failure. however, two have failed. we didn't build the spacecraft to be able to tolerate two failures. failures like that could be catastrophic for the mission. june of 2010.in one failed in august 2012 as we in the process of breaking out of orbit from vesta begin the journey to siri.

there's no especially good should hat the mission ave been successful following that second failure. one of the things that's so cool bout these missions is that we found a way. is if it our mottos isn't impossible, it isn't worth doing. hat's what makes nasa so neat, right? and so we found ways to control to fly the ft, spacecraft in ways we had truly never thought of. when the considered spacecraft was on earth or even in the vicinity. just give you one aspect of that. much longer story. it i'll mention one because comes back to one of the earlier questions. e have a very small supply of conventional rocket propellant. 12 gallons of that on board. it was not meant for the purpose we're using it, but we have these thrusters on the

spacecraft. little thruster here. thruster here. if you squirt some out of this thruster, that makes the spacecraft turn like this. if you squirt some south of this thruster, makes the spacecraft that.like we hadn't intended to fly the spacecraft that way, but that's ways we're doing it. we didn't have enough of this hydrozene to fly the mission this way. a very very ook ambitious campaign. of work a huge amount by very dedicated and creative and apable team of men women here at jpl and with our orbital atk and came up with ways to use this ydrozene much more efficiently than we ever thought. it never occurred to us that we would be in the position to extended mission.

hydrozene was so tight, we didn't think it would last until now. there's another wordy answer for you. > it sounds like this problem with the periscopes. spacecrafts.ith internationalthat space station lot of times. why -- what is the root cause program? >> so the question is, it sounds ike these devices like gyroscopes, failures of them are common. of your fair summary question? >> yeah. very common problem. does it happen every time to spacecrafts? >> that's a good question. of a k it's somewhat misperception. satellites myriad of and spacecrafts with these devices that operate just essentially endlessly

decades.ust years, but the ones -- told you that was happen.o visual ite the audio else. to show something thank you. let's see. truly, most satellites, they andate flawlessly for years years and years. truly many, many billions of revolutions. the ones that don't operate are the ones who make the news that you've heard about. really, they generally do work very, very well. happens to be a number of spacecraft like dawn that used one particular we all found out reliable for t endless years of operation after

rigors of a launch, the rature changes, forbidding environment of space. and so those have not worked successfully on a number of spacecraft. satellites, they do. of bashing one. i should point out, here you've a device that's spinning, right? it's not like an electrical circuit. movement.o mechanical but this constant motion for years without stopping. that's a pretty challenging for people to make them so they work reliably. the truly overwhelming majority do work beautifully. unfortunately some don't. >> thank you very much. welcome.e >> i'd like to make a comment

bout -- before i ask my question. >> i will say on behalf of the -- nizers here >> quick. spacecraft, venus, use the ction and it worked for 40 years successfully. used control ion -- >> which are different. changing. same momentum. worked successfully. no problem. y question is about the electric propulsion and ion propulsion. how much work on the development propulsion being that we see.t as nd how much -- particularly hughes aircraft would develop

propulsion. i recall that in the mid 1970s jpl young engineers came to to work on electric propulsion. short time everyone went to do something else. >> okay. i don't want to interrupt you. is the uestion what history of the development of ion propulsion? >> that's right. > an the term electric propulsion that he's using is terms for it.er that.s well back before the first recorded thoughts bout ion propulsion were by robert goddard in 1906. rocketry.american arkovski published a paper on it. in the 1950s they did very important work on ion propulsion. you're making the entirely

accurate point that engineers at aircraft and elsewhere id was worked on by people in nasa and private industry from the '50s up to the present. o i mean, there's a rich history here of many very people and talented contributing to the development of it. that jpl was sted the organization that developed thought of it or was the only one to work on it, i didn't mean to suggest that. raised the that i question of how could we travel around the solar system more expensively, it was that we could turn to the propulsion that people, brilliant people had been nearly a century. very important. did jpl not forward -- it

was such importance. i'd be happy to talk with you about this more elsewhere. some y have perhaps incomplete perceptions of jpl's role in the development. solely responsible for the development of ion propulsion. nasa industry t development. and we've taken advantage of the brilliant work that was done by people to have the success. i think rather than get into the details of the technical history, i think there are probably broader questions that would be of interest. ut come up afterwards and we can talk about it. thank you. used for ion is station keeping. people are terms most don't know about station keeping. you're right. here are many spacecraft satellites that use ion propulsion. i didn't say dawn was the only one. first not the

mission to use it. i'm glad you're so interested. i would be delighted to talk to afterwards. you obviously have some good knowledge of the history. >> how's it going. jupiter in one of the first orbits ou showed of the around the sun, jupiter showed through these asteroid.f the i'm wondering why it didn't clear that material. >> are you referring to the that showed all the steroid belt and that both leading jupiter and following it? >> yeah. >> right. that's a good question. so it doesn't go through those because those are going around as jupiter is going around the sun. ut just so everybody else is following here, remember that belt.re of the asteroid

he was observant enough to see that there's two groups of asteroids sort of ahead of and jupiter. and those are called trojan asteroids. orbit ies, things that the sun. doesn't have to be orbiting the sun. body is orbiting another, they turn out to be laces in its orbit that are relatively stable for other bodies to orbit. ahead of and behind jupiter are two such places. asteroids that happen to have wandered through this place kind get trapped there. for experts, that's a little bit simply tpeu kaeugs. it's not that jupiter is plowing them, but they're orbiting the sun with jupiter and they're relatively stable. there are places that are

like that for earth's orbit even the sun and earth. orbit around the >> the same plane? >> they're close. you.ank >> sure. there are people who are -- oh, okay. we were gonna answer questions that came from the web but another one first. > is there ever going to be a into raft that travels space to refill dawn? refill dawn? the question was is there ever spacecraft to refuel it? good question. and i guess i could answer that question by asking you a question. hen you grow up, would you be willing to make a spacecraft that will travel into space to refuel dawn?

the answer's yes. so nasa doesn't plan to do that, but we're waiting for smart energetic enthusiastic people like you to come up with that.missions like but right now dawn, as i said, times over 1 million farther away than the space station. that's a pretty long way even robotic that is spacecraft on board to nauts go to refuel another one rather if we were gonna send a spacecraft out there hat is carrying fuel, it could carry advanced instruments, more cameras, things we haven't even thought of. nevertheless, a great idea. it, i'm old and retired, things, send me the future

communication vessel will be and tell me how dawn is doing. okay? does that answer your question? >> yes. >> good. thank you. [ applause ] >> so we got a couple questions people who are watching right now in the live stream. thank you for that. so, i'm not very good at pronouncing some of these things. kyanite asks. was there ever any plan for dawn visit a third body in the asteroid belt? large is another very body comparable in size to as a, although not quite large. and the answer to that is no. there was never such a plan. i presume the background for the question is, for those space about these o read things on the internet, i have been reading for years that dawn

has actually done -- the dawn team has done studies going to other body pallas. i genuinely don't know what the is, but i that rumor can tell you we've never looked it. i have read it many places. looked at it. the argets were vesta from time we conceived them. we never had any intent to go else.re however, as you may know from in ing news recently, just the last few months, we gave sending the on of spacecraft to another body for mission possibility. so extended mission after the of the primary mission. we told nasa that if they would the mission, ding we could continue to stay in orbit around siri or we could go

to a different body. scientific red the merit of remaining in orbit, lingering, continuing to make observation at siri or flying to a different body concluded that the best use of this precious resource that taxpayers have funded is to continue with siri of ake more measurements this, the only dwarf planet in the intersolar system. hope that answers your question. and the other question i'll tell one, is will be the last is from arpotu who asks, are we determine the mass or other properties of the object with vesta?ed apologize for stumbling over that. remember, the big crater, this 00 mile diameter crater near the south pole of vesta which is s e source of these meteorite

crashed into it. that that body that crashed into it is around or so miles in diameter. that's pretty big. imagine that crashing into your back yard, that be appreciated't by you or your neighbors. that's a big thing. it's large compared to the object which crashed into earth primarily responsible for the extinction of the dinosaurs species 66 million years ago. big at was a big object, a impact. and that's the estimated size of it. so once again, thank you very coming to jpl and hearing about this. [ applause ]

>> today i'm at the central high school museum in little rock, a of the civil rights

trail around the south. ere in 1957, was the biggest school integration crisis following the brown versus board of education decision. park service has this memorial right here at central high school, one of the schools in ul high our country. i'm an avid outdoorsman, so the arkansas ark site in that has the most meaning to me is the first national river in country, the buffalo national river. i have been going there 55 years.for about so i have many, many miles on happy er and wonderful memories of america's national river, the buffalo national river. teddy roosevelt led the charge to protect america's wild places places.cial he believed in the strenuous life. youngw more than ever our people, our families, need to get outdoors and enjoy america. that's why if you're watching this show, i'm up in maine national park up

there in the northeast, participating in the 100 mile challenge. urge everybody in america this fall support our centennial for the national parks and get outside america. > coverage of the centennial begins thursday with washington journal at 7 a.m. eastern here on cspan. history tv marks the centennial from arlington cemetery. that's live at 7:00 p.m. eastern on cspan 3. uesday president obama visited parts of louisiana affected by floods. n the town of zachary north of baton rouge, he spoke about the affected communities and efforts to provide disaster relief. this is a half hour.

>> what's going on, man?

>> what's going on, guys? what's your name? good to see you. how long you been living here? since '78? [ inaudible conversation ]

[ inaudible conversation ] >> thanks a lot.

>> all right everybody. line up here. let's get this done. tell me when everybody is all lined up. of congress. to begin with, i just want to to the rpblg you outstanding officials behind me on the ground working 24/7 since this flood happened. begins with outstanding leadership from the top, with governor edwards. we very much appreciate all the done.nding work he's his better half, the first lady by ouisiana i know has been his side every step of the way. we are grateful for her. they've got their own

cleaning up to do because the flooded s mansion was as well. in addition, i want to cknowledge senator bill cassidy, senator david bitter, grays, ntative gary representative richmond, the baton rouge. and somebody who i can't brag nough about, one of the best hires i made as president, the has istrator of fema, who done such an outstanding job, dealing with this particular incident, but has fema so that culture. change of and everybody knows that when the disaster happens, fema's there on the ground cooperating with state and local with als rapidly and attention to detail and keeping the families who have been most in their

mind. so we very much appreciate everything craig's done. to be here r craig because he's a florida gator and he's been seeing a lot of lsu tee-shirts as we've been passing by. i just had a chance to see some of the damage from the historic here in louisiana. i come here first and foremost prayers of the entire nation are with everybody who lost loved ones. we are heart broken by the loss of life. there are also people who are desperately trying to track down friends and family. helping themeep on every way that we can. who can see ybody just the streets, much less the inside of the homes here, been up lives have ended by this flood. suffered nesses have terrible damage. families have, in some cases, homes.

certainly lost possessions. keep sakes. i was just speaking to a young husband died shortly birth of her second child. she was talking about how her aughter was trying to gather all the keepsakes that she had reminded her and of her father. and that gives you some sense is not just about property damage. roots.s about people's you also have a situation where there are a lot of kids who are schoold to start the new year, and they're gonna need some special help and support awhile. sometimes when these kinds of things happen, it can seem too bear.o what i want the people of louisiana to know is you're not alone in this. the tv cameras leave, the whole country is gonna support you and help

you until we get folks back in and lives are rebuilt. he reason i can say that with confidence is because that's what americans do in times like this. this it when i visited place, louisiana, when i came senator after katrina. i saw it when i visited new rleans for the tenth anniversary last year. i know how resilient the people are, and i know that you will rebuild again. and what i have seen today proves it. i want to thank all the first the national guard, who were od neighbors in a boat going around making safe, showing e extraordinary heroism in some cases risking their own lives. governor edwards, state of louisiana, the city, the parish they've all stepped

up under incredibly difficult circumstances. thank the people on this block. womanas walking down, one at the end, elderly, she was on her own. daughter.st lost her she had a young man next door who was helping out his father, offered to help out that neighbor so that she could alvage as much as she could, start the process of rebuilding. respect to the federal response, over a week ago i directed the federal government to mobilize and do everything we could to help. fugate ministrator craig arrived here a week ago to help lead that effort. homeland security jay johnson visited last week to make sure state and local getting what they need. to give you a sense of the here,tude of the situation more than 100,000 people have applied for federal assistance so far. federal support has reached $127 million.

help like temporary rental assistance, essential insurancers and flood payments. fema's also working with louisiana around the clock to who were displaced by the floods find temporary housing. family that needs help, you can find your nearest center by covery visiting fema.gov or calling 1800-621-fema. i'm going to repeat that tpp fema.gov or 1800-621-fema. now, federal assistance alone is not going to be enough to make people's lives whole again. american to every do what you can to help get amilies and local businesses back on their feet. if you want to help, if you want to help, governor edwards put ways to start at volunteerlouisiana.gov. volunteerlouisiana.gov.

is though federal money moving out, volunteer help helps the state because it can offset some of its costs. obviously, private donations are gonna be extremely important as well. red cross thank the for everything they're doing. ut there are a lot of private organizations, churches, parishes around the state and around the country who want to help as well. and that's how we're gonna make is able to erybody get back on their feet. just remind folks, the floodwaters ass, people's attention spans pass. this is not a one off. issue. not a photo op this is how do you make sure that a month from now, three months fromnow, six now, people still are getting the help that they need?

americans to stay focused on this. f you're watching this today, make sure that you find out how you can help. volunteerlouisiana.gov. or you can go to fema.gov. you. direct you can go to white house.gov and we'll direct you how you can help. all right? we're gonna need to stay on this. these are some good people down here. we're glad the families i had a to meet are safe. they got a lot of work to do and shouldn't have to do it alone. all right? thank you very much, everybody. god bless. you know, we discussed that on here.ay what you have is, the stafford provides a certain match, a lot of the homes had flood homes ce, but a lot of don't. and what craig fugate is doing,

to do fromructed him the start, is let's get money out as fast as we can, because that there's gonna be a certain amount of assistance that will be forthcoming. in waiting.oint we have to make initial estimates and start pushing stuff out. that helps us and helps the these officials here do their jobs. and then what we have to do, as exactly what's needed, when we know for example how much permanent housing's built.o have to be when we have a better sense of how much infrastructure's been what more we need to do in terms of mitigation strategy, hat's when congress, i think, maybe called upon to do some more. now, the good news is that you four members of congress right here. number of them happen to be in the majority. they may be that able to talk to the speaker and mcconnell.ch

ut in part because of the stewardship at fema and, frankly, because we've been lucky so far. i'm gonna knock on some wood, in amount of money that's gone out this year. fema has enough money for now to can be e cost that absorbed. the issue will be less what we do in terms of paying for the short term. it's going to be the medium term term rebuilding. congress should be back in session right after labor day. that time we'll probably have a better assessment. n the mean time, lawyers at fema will be examining what statutory flexibility we've got. know the governor's been right on top of making sure that louisiana gets everything that to help t in order rebuild. [ inaudible question ] >> no, i don't. one of the , benefits of being five months short of leaving here is i don't

politics.much about the second thing i ask, is that when disaster strikes, that's probably one of the few times not to shington tends get political. guarantee you nobody on this block, none of those first hoot ders, nobody gives a whether you're democrat or republican. what they care about is making getting the drywall up and car pent out, there's not mold building, they get contractors in here and start rebuilding as quick as possible. they care about. that's what i care about. so we want to make sure we do it right. we do it make sure system attically. want to hing i just i am of fema proud the se if you think about number of significant natural disasters that have occurred

began, you'dsidency e hard pressed to find a local official anywhere in the country, including those in the other parties, who wouldn't say fugate and his team ave been anything less than exemplary and professional. and one of the things i did when of these hrough each omes, was asked, have you con tacked fema? have you filed? uniformly they said they've been fema, they had acted professionally. some had already been out here inspection. and i think that does indicate it's important for us to government eral seriously, federal workers seriously. there's a tendency sometimes for us to bash them and to think they're these faceless bureaucrats. get into trouble, you want somebody who knows what they're doing, who's on the

outstanding g with officials. and that's true whatever party. be prouder of the work that fema's done. hat doesn't mean there aren't going to still be folks that need more help, that we're not constraints some statutorily. but it does mean the basic ackbone, the basic infrastructure and architecture we have in terms of disaster high se i think has been quality. and i'm very proud of them for that. i want to publicly acknowledge the moment. all right? thank you guys. >> what's your name? >> here. come on. got to have the podium. we got to have the podium.

here. you get on one side. on the other. that way, we can look like we're press conference together. come on. how you all doing? all right. [ inaudible conversation ] >> do you have video? a happy i can wish her birthday.

she's the one with the birthday. what's her first name? tell me when you're ready. you happy nt to wish birthday. everything is going to be okay. mom and dad, they got this covered. all right? all right. god bless you. all right. thank you. all right. all right.

[ inaudible conversation ]

[ inaudible conversation ]

>> wash journa"washington journ. police and gun violence from the national institute of justice. and a discussion about what's britain. now that voters there have the europeanve union. we have live coverage from the foundation. american civil libertieamericann on the justic justice department decision to stop federal use of private prisons. the commerce department about how to apply trademark.t or a washington bureau chief

reporting about whether hillary nigerias policies in were influenced by nigerian donors to the clinton foundation. >> good morning, it's wednesday august 24. yesterday president obama toured rouge, louisiana to bring attention to the recovery efforts in the area in the wake worst flooding to hit the state in year. president obama's visit comes in trump's visitnald to the region and after criticism that the president was crisis.the during his visit yesterday, president obama was asked about timingticism, about the of his visit. with that in mind, we're asking think the roleu of the president should be during