Planetary Radio: Space Exploration, Astronomy and Science - Rosetta Swoops Past Asteroid On Way To Comet

Episode Date: July 19, 2010

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Rosetta swoops past a big rock on its way to a comet, this week on Planetary Radio. Welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. Of all the asteroids and comets we visited, Lutetia is by far the biggest. We'll talk with the European Space Agency's Andrea Accomazzo about the July 10 flyby that resulted in spectacular images of this object. Bill Nye, the science and planetary guy, drops by with some thoughts about Hayabusa's apparent capture of some tiny bits of another

asteroid, and there will be soccer balls and hamburgers in space during this week's What's Up segment. Bruce Betts and I also have another special prize for the winner of our latest space trivia contest. We'll get underway by visiting once again with Emily Lakdawalla, Science and Technology Coordinator for the Planetary Society and the editor of its blog. Emily, as you know, we're about to have a more in-depth conversation about Rosetta, but I thought you might want to mention a terrific piece of work that you put up on the blog last week.

Well, thanks. I'm glad you liked it, Matt. I put together a montage of all of the best photos I could find of all of the asteroids and comets that have been visited by spacecraft. There's four comets and nine asteroid systems, including 10 separate bodies, because of course, when Galileo flew by Ida, it found that Ida had a moon called Dactyl. So there's two bodies in that one system. And I just thought it was kind of interesting to compare the sizes of all these different things. It can be kind of hard to get a sense for the relative sizes of things when you just see one photo. Lutetia is so big, it kind of dominates the whole diagram. It's a beautiful image, but I guess it's going to get messed up before too long when the next two big bodies are

flown by or actually orbited. That's right. Dawn is on its way to visit the two largest bodies in the asteroid belt, although there's some competition between what some people think that Vesta might be smaller than Pallas, which is not on Don's itinerary. But anyway, Don will be visiting Vesta and following that with a visit of Ceres. And both of those things are just many times larger than anything else on this montage. And you did include those to scale, at least the best available images, right? Where did those come from? those to scale at least the best available images, right? Where did those come from? Both of those came from Hubble. Hubble's made the best images we have so far, at least in visible wavelengths of those two bodies. But they're just going to be absolutely amazing to be seen up close. I really can't wait for dawn to arrive. And that's going to happen in about a year from now.

Not long. Yes. And we'll keep tracking that mission. Back to the moon now, where there is an object, a feature that you have a very interesting piece about. Well, yeah. Lunar Reconnaissance Orbiter has been mapping the moon for slightly over a year now. And, of course, it's returned lots of gorgeous high-resolution images and amazing shots of the Apollo landing sites where you can actually see astronaut tracks. One of the things that hasn't been publicized very much is what their wide-angle camera is doing. This one doesn't get very high resolution, but it covers the entire moon, and it's going to produce this astonishing base map

that covers the whole moon and will be the basis for all other kinds of mapping for years to come. A year into the mission, they're making very good progress on that project, and I just posted an image of one of the larger basins on the moon, a place called Oriental.

It's also the youngest large basin on the moon. And because it's youngest, it's beautifully preserved. You see all of its concentric rings, three or four or more concentric rings. And it's just really gorgeous to examine at high resolution. It really is pretty stunning, and there's much more to be said about it. And we will put up the links to both of these blog entries at planetary.org, actually the page where you can catch this radio show as well. Emily, thanks again. Thank you, Matt.

Emily Lakdawalla is the science and technology coordinator for the Planetary Society, also a contributing editor to Sky and Telescope magazine. Here's Bill. Hey, hey, Bill Nye, the planetary guy here, soon to be executive director of the Planetary Society. And this week for me, the exciting news has once again to do with the Hayabusa spacecraft. This is the Japanese Aerospace Exploration Agency, JAXA's spacecraft. And it rendezvoused with a distant, distant asteroid, Itokawa. It opened up a little capsule and apparently captured some particles from this asteroid. To get it back to the Earth, all you got to do is return it to Earth orbit and have it

land in the outback of Australia a few weeks ago. Then you take it to Japan to a clean room where there's no dust. You open it up and you look very, very carefully, and they found some particles that are a hundredth of a millimeter. That's about the thickness of a human hair. And these particles would be made of the most primordial stuff you could find in our solar system. This is to say, every rock tells a story, no matter how small. So the story that these tiny particles of asteroid are going to tell

has something to do with where we all came from, with the origin of the solar system. And it's another very exciting thing being done by a space agency in Japan. It's fantastic. They just deployed a solar sail on their way to Venus. They brought back a piece of asteroid, which could change the way we know where we came from. It could change the world. It's a very exciting week. Way to go, JAXA. I got to fly. Bill Nye, the planetary guy. Bill Nye, the Planetary Guy. You heard Emily and me talking about the beautiful images of asteroid Lutetia captured by Rosetta on July 10th. The European Space Agency probe is now on its way to comet Churyumov-Gerasimenko,

not just for a quick flyby, but to become the first ever mission to rendezvous with and even land on a comet. Andrea Accomazzo is the mission's operations manager. Late last week, he joined me for a virtual conversation from ESA's European Space Operations Center in Darmstadt, Germany. Andrea, thank you so much for taking time to join us on Planetary Radio, so much for taking time to join us on Planetary Radio, and congratulations on what appears to have been a flawless flyby of the biggest asteroid that we've visited so far, we humans. Am I right? Was this pretty much perfect?

Yes, yes. The operation went very smoothly. Everything worked flawlessly, and we are super happy with the way it went. Now, as we speak, it has only been about a week since the flyby took place on July 10. How much has your science team been able to say so far about what has been learned about this big and apparently very old rock? Well, there are several levels of science. It's clear that the images that we have all seen are part of the scientific return

of this mission phase. And there it's relatively straightforward to start working on the science that is in there. Actually, our PIs, our investigators, our scientists have already said that there's so much science in the images that we have published that now they could be reluctant to publish

more. Other kinds of science requires much more calibration, much more analysis to derive, and so far we haven't heard very much from the scientists. We are assuming, of course, that they are working full-time on processing their data. I'm sure they are. Those images are really quite spectacular. I was actually surprised. They seem so sharp and so beautiful that then when I read that the spacecraft was still over 3,000 kilometers from the asteroid, from Lutetia, I was even more impressed. comet, which is our target. We will approach the comet down to a few kilometers, and we want to have a very high resolution of the surface, also because we have to deploy a lander there. So the accuracy we'll have on the surface of the comet will

be much, much higher than what we've seen so far on the asteroid. We'll come back to that ultimate goal in a few minutes, that orbiting of this comet, which is still about four years away. Tell us a little bit more about the spacecraft itself, and in particular, the fact that from what I read on the Rosetta website, which we'll put up a link for where people can hear this show at planetary.org, but apparently you were out of touch with the spacecraft as this flyby took place. That's correct.

Unfortunately, we couldn't maintain the radio link throughout the flyby phase, mainly during the close approach phase. You have to imagine that the spacecraft is flying next to the asteroid, and we want to observe it when approaching it and when leaving it, when going away from it. So basically, we had to turn the spacecraft 180 degrees along its axis and with this turn our antenna couldn't follow the earth moving, if you want, relative to the spacecraft. That's why we have this interruption of the link and there was no other way to fly the spacecraft to observe continuously the asteroid through the flyby. So it was either we tracked the asteroid or we had maintained the radio link.

Since we can store data on board, we decided for the option to track the asteroid throughout. Now, I imagine with Rosetta and Letitia half a billion kilometers away as the flyby took place, you wouldn't have had active control over the spacecraft. Was the spacecraft acting autonomously during this flyby? Absolutely, absolutely. This is a mission which is designed for deep space operation. As you correctly said, the spacecraft is so far away from the Earth that all the data we see or all the instructions we send to the spacecraft

have a delay in this specific phase of 25 minutes, so it would be impossible to control in real time the spacecraft. Therefore, everything is pre-programmed on board. We have a queue of telecommands, of instructions of the spacecraft. Therefore, everything is pre-programmed on board. We have a queue of telecommands, of instructions of the spacecraft, which are time-tested, and they execute at the time we have specified. So all the work for us turns out to be a planning exercise. We plan all these instructions on board the spacecraft, and the spacecraft acts autonomously according to these instructions.

How did the spacecraft manage to direct itself and keep Lutetia centered in the camera field? Well, this is one of the most challenging points of the flyby. We know orbits of asteroids with a limited accuracy. We are talking about a few hundred kilometers, and we wanted to fly at 3,000 kilometers from this asteroid. So you can understand that with an uncertainty of a few hundred kilometers and we wanted to fly at 3 000 kilometers from disaster so you can understand that with an uncertainty of few hundred kilometers we might mispoint the spacecraft to the asteroid therefore the spacecraft has been equipped with a special unit is what we call navigation camera

and a special software that is able to use this camera is able to image the asteroid determine its photometric center, pass this information to the attitude control of the spacecraft, and this system can actually use this information to keep tracking the asteroid. So it maintains the asteroid in the field of view of the camera, right in the middle. So the moment we activate this mode of the spacecraft, the spacecraft tracks continuously in what we call closed-loop the asteroid and can follow it during this phase.

Tell us about Rosetta. This is a big spacecraft. When you include its pretty large solar wings, you're talking about something that is more than 30 meters across and really loaded up with instruments. That's absolutely correct. Rosetta, in my opinion, has three parts which are big and give an idea of its mission of the environment it's going toward. You mentioned the solar arrays. The solar arrays are huge. They are tip to tip 32 meters. We have 64 square meters of solar panels on board the spacecraft. When the spacecraft is at one AU, so at Earth distance from the sun, can produce eight kilowatts with these arrays. When we are in deep space, at the largest Sun distance we will achieve, we'll be able to produce 440 watts.

You can see the difference. The second large part on the spacecraft is the fuel tank. More than half of the weight of the spacecraft is propellant, we need to accomplish the mission. And the third huge part is the antenna, the eigen antenna. It's two and a half meters diameter antenna to transmit data from those huge distances from the Earth. So these three elements give you an idea of the peculiarity of this mission. More to come from the Rosetta Mission Operations Manager, Andrea Accomazzo, when Planetary Radio continues.

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Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio t-shirt. Members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Rosetta shot past asteroid Lutetia last week. The European Space Agency probe has four more years in the void before it catches up with comet Churyumov-Gerasimenko. Then it will spend another two years carefully examining that icy body as it swings past our sun.

Andrea Comazzo is the mission operations manager. If you could say something about the instrument package that it carries as well, because I think that also says a lot about the international involvement in this mission. Yes, we have on board 11 instruments, one of which is a lander, which is composed in itself by several other instruments. Instruments on board Rosetta are remote sensing instruments, so cameras or instruments able to monitor the comet from far away. So when we are far away, we can image the comet, do spectrometry, infrared spectrometry, ultraviolet spectrometry. We have in situ instruments, instruments that

will sniff, will sample the dust that is around the comet, the gases which are around the comet, so they will be able to determine the chemical and physical composition of the tail of the comet. Then we have other instruments which are more to monitor the environment like magnetometer, plasma measurements instruments. So it's a very wide set of instruments. They've been developed for a large part in Europe. Several of them have been fully developed in the States. Some of them have parts developed in the States.

And we have a very strong collaboration with the colleagues also from the States. You mentioned the coma of the comet. Can you explain that? Well, the comet, we know comets with all this tail. This tail is actually material that is being released by the comet itself. And this is what we call coma. So we can call it dust or coma. It's still the tail of the comets which we are used to see. Once we are there, once we have achieved our mission target,

which is to reach the comet, then we will have to fly through this coma, through this dust, and we'll have to navigate the spacecraft in this environment. This will be one of the challenges. And the instrument will want to go into the tail of the comet, will want to measure what is in there, because it's their science, it's exactly what they want to do. That would seem to be kind of a nervous, a frightening portion of this mission plan.

Are you at all concerned about flying through that mass of gas and particles when you reach the comet? Well, definitely it's very challenging. We do have concern. We will have to face several decision points, whether we go for operation in this sense or not, how close we go to the comet. It's clear that the density of this coma is higher the closer we go to the comet.

Most of the tail is in the anti-solar direction, so we will have to decide exactly. Most of the tail is in the anti-solar direction, so we will have to decide exactly which kind of orbits we will be able, we will feel safe to fly around the comet. I guess it will last a bit until we have decided exactly what the spacecraft can do, what we can trust the spacecraft doing. There could be dust that is covering the solar rays, so we could have a power reduction. The dust could affect the optics of our instruments, our star trackers, which are the instruments that tell the spacecraft the orientation in space. So we will be posed several questions where we'll be confronted with a scientist that

wants to measure, and we will have to balance this against the safety of the spacecraft and the mission itself. How long after Rosetta reaches the comet will it release this little 100-kilogram, not really that small, 100-kilogram lander that will actually touch down, or would you call it rendezvous with the comet? Well, it's in relatively early mission phases. We plan to reach the comet, or if you want to start the close approach to the comet, in June 2014. We have to release the lander before November 2014, because at that distance is 3 AU from the Sun, so 450 million kilometers from the Sun.

Then the comet starts being active. Then we are pretty sure we will not be able to fly so close to the comet as required for the lander delivery. So it's relatively early in the mission phase. In between the arrival and the delivery, we have to have the mapping phase. And this is fundamental. There we are time constrained. We have to map very carefully the surface of the comet, map its gravity field, such that we can design a safe landing trajectory. So you have a lot ahead of you, at least at the end of this 10-year trip to the comet. What will be happening over the next four years or so as you approach it? If we forget for a second the comet phase, we go towards one of the most challenging, if not the most challenging, mission phase. We are flying far out in the solar system. We are flying

now around 3 AU from the Sun. We will be approaching 5 AU from the Sun, so Jupiter distance from the Sun. So the spacecraft will be facing a completely different thermal environment and environment to produce power for the spacecraft itself. So in the next year we will prepare the spacecraft for this delicate mission phase. Unfortunately, we come to a point where the distance from the Sun is such that we don't have enough power generated by the arrays to maintain the full spacecraft active. The main problem would be to maintain a benign thermal

environment for the instrument. So in order to guarantee this, otherwise we would damage them, we have to switch off some other subsystems. And in doing this, we configure the spacecraft in a mode which we call hibernation mode. Basically, we switch off two main subsystems, the radio link subsystem, the TTLC subsystem, the telecommunication subsystem, and the attitude control subsystem. Switching off the telecommunication subsystem means we'll have no contact with the spacecraft for two and a half years. Switching off the attitude means that we cannot control the attitude, so we spin up the spacecraft, we stabilize by spinning it like a gyroscope,

and in this mode the spacecraft will survive the deep space phase of the mission, which lasts two and a half years. Wow. Do you know the term we use here in the States, nail-biter? Never heard, but... A nail-biting experience, one that will be another anxious moment, I'm sure, for all of you on the Rosetta team when that happens. I hope that we can speak to you again when it's time to wake up Rosetta for this final approach to the comet. It will be my pleasure as well.

We've been talking with Andrea Accomazzo, the spacecraft operations manager for the extremely successful Rosetta mission that has just completed this fantastic flyby of Lutetia, the biggest asteroid that humanity has so far visited. Out there almost half a billion kilometers from Earth. It now continues on its way to accompany a comet. That rendezvous is still about four years away. Andrea, by the way, the former spacecraft operations manager for yet another very successful European space agency program, the Venus Express mission.

We'll be doing some exploring of the night sky with Bruce Betts in just a few moments when he joins us for What's Up on Planetary Radio. The director of projects for the Planetary Society is Bruce Betts. He joins us every week for this segment to tell us about the night sky. I think, by the way, and I didn't clear this with you, I think we should do another special prize this week. Maybe another weather station. All right. Sounds good.

We'll talk. Okay. How are things up there? Okay. Yeah. I think what people really want to know is what things are up there. By up there, you don't mean in my head. Up there.

Up there. Oh, up in the sky. Bird, a plane, Saturn, Mars, Venus, Regulus, Mercury. It's that complicated, wonderful planet thing going on in the evening sky. I have to tell people about. Things are dancing around, making it hard to discuss. But Venus, find Venus first. Super bright, star-like object in the west after sunset.

And to its upper left, you'll find Mars, reddish, Saturn, yellowish. To its lower right, you'll find Regulus, star of Leo, and Mercury. You're going to have to have a pretty good view to the horizon. Mars and Saturn are snuggling all around July 30th, but a few days before and after, very close together in the sky. This is the upper left of Venus, and they'll be swapping places in the sky. July 27th, roughly, a day or two before or after, if you've got that clear view to the western horizon, you can see Mercury and Regulus very close together.

Don't often mention our own star, the Sun, starting to get more active these days after a long lull and rest. So you can actually see sunspots fairly regularly and prominences. But don't go staring at it. Use proper information. I really hoped you were going to add that disclaimer. Let's be safe out there. Sun's safe, but go on the web and check out live solar telescope shots or use appropriate

filters. But it's uh it's going there this week in space history uh nothing much happened week of july 20th all right 1969 first human landing on the moon uh also 1976 seven years later viking one first successful landing on Mars. Just tons of stuff. You also had the last U.S. splashdown after Apollo-Soyuz, 1975.

And greetings to a friend of the show, Buzz Aldrin, who is heard on this program every once in a while. Happy anniversary, Buzz. Happy anniversary. Let us move on to random space for goal goal goal a bit of football appropriate to football or as i like to call it soccer. That whole pesky World Cup thing some people were paying attention to. Here's your World Cup analogy. If Earth were the size of a professional soccer ball,

ooh, ooh, ooh, then Jupiter's diameter would be about the height of a professional soccer goal. So picture a ball sitting there underneath the goal, and about the height of the goal would be Jupiter relative to Earth, the soccer ball. That's great. Okay, you world football fans, you can write your letters of praise because Bruce managed to work this into the show. I'm very pleased. We move on to the trivia contest.

And we asked you how much total lunar material was returned by the Soviet Luna Robotic Sample Return Program. There were three lunas that successfully returned samples. How did we do, Matt? Interesting. Lindsay Dawson, who as usual gave us a wonderful treatise on this topic, he said there were maybe as many as 11 attempts, but only the three successful that you mentioned. I'm going to go right to the winner and say that it was Jamie Cox. Jamie Cox in Melbourne, Florida, who said that it was about a third of a kilogram, to be precise. And we had answers, by the way, ranging from 301 to almost 400 milligrams, excuse me, grams of material. But they all seem to center on this 326 grams or 0.326 kilograms returned by those three.

Very cool. Lindsay had some cool shots of the drill that was on this spacecraft that could drill down like two and a half meters. But as Jamie himself points out, only about a thousandth of the mass that was brought back by the Apollo missions. Yes. Although they did sample some other areas, which does add some interest, additional interest to that small bunch of samples. Well, we're going to send Jamie a T-shirt. And we will send the winner of this next contest a weather station, a beautiful Celestron weather station.

It's very cool. I want to own one, actually, but we're going to give it away instead. Well, since we didn't discuss this, I have nothing thematic to weather stations. In fact, I've really gone fairly random in the trivia portion this time. I just ran across this and was so amused by it. Who was the first person born in Italy to fly in space? First person born in Italy to fly in space. Wasn't Leonardo. Go to planetary.org slash radio and find out

how to enter. If you do enter people like Leonardo, you'll need to provide some type of proof. It's all in the manuscripts. It's all written backwards. Anyway, you have until the 26th of July, July 26th, Monday at 2 p.m. Pacific time to get us your answer. And the winner will get a really very nice Celestron weather station with a little remote outdoor thermometer but all kinds of other cool stuff like a barometer. And it is really nice. Did you mean Leonardo da Vinci? I did. I thought you meant the Ninja Turtle. I meant DiCaprio. Can I mention this? I wasn't going to do it because I

didn't think we had time. Mark Detweiler, he also came up with the 0.326 kilograms worth of material brought back by the Soviet lunar missions. He said it's pretty much precisely the mass of two all-beef patties, special sauce, lettuce, cheese, pickles, and onions on a sesame seed bun. That's really cool. And for those of you who weren't around for that ad campaign, that's a Big Mac. You know what it would be if they took it back to the moon, don't you? No, what? Bun, seed, sesame, ah, no,

and sprinkles, cheese, lettuce, sauce, special patties, beef all two. Oh, that's so good. All right, everybody, go out there, look up at the night sky, and think about burgers. I know I am now. Thank you, and good night. Hey, backwards or forwards, he's Bruce Betts, the director of projects for the Planetary Society.

He joins us every week here for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California and made possible in part by a grant from the Kenneth T. and Eileen L. Norris Foundation. Keep looking up! Редактор субтитров А.Семкин Корректор А.Егорова