Planetary Radio: Space Exploration, Astronomy and Science - MESSENGER Sails by Mercury for a Second Flyby

Episode Date: October 20, 2008

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Hello again, podcast fans. It's your fellow space cadet here, Matt Kaplan, with another secret message for all of you. As you're about to hear, I really did run out of time in today's show, didn't get to run any headlines at all, although there is some news built into the show, including from Bruce Betts during the What's Up segment. I hope you don't mind that too much. There was just too much there that I didn't want to cut. I just thought there was a lot of good stuff in today's show. Hope you will agree. One note, you'll hear us talk at the end about OPT, Oceanside Photo and Telescope, the donor of the grand prize for the upcoming sixth anniversary contest that we hope you all will enter. And I did want to let you know that OPT is in the midst of its annual We Pay the Tax sale. It runs until October 27th, I believe.

You can check it out online with them, of course, at www.optcorp.com. I guess that's it for now. Here's this week's edition of Planetary Radio. Here's this week's edition of Planetary Radio. Solar sailing to another Mercury flyby, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan of the Planetary Society. We have so much show for you this week that I only have time to tell you that our guest is Sean Solomon,

the principal investigator for the Messenger mission to Mercury. The spacecraft gloriously completed its second flyby of First Rock on October 6. We've got Emily Lakdawalla and Bruce Betts, too, but let's jump right in with this news from Bill Nye. I'll be right back with Sean. Hey, Bill Nye, the planetary guy here, vice president of Planetary Society. And I just want you to know that I'm in Boston for a meeting of the Planetary Society board. And I can tell you that the society is getting younger. We just elected Dr. Jim Bell to be president of the board of the Planetary Society. And Jim Bell is the guy who did all the photography, or does all the photography, with the panoramic cameras on the Spirit and Opportunity rovers. He's a professor at Cornell University, sits very near to Carl Sagan's old office. And he's been a member of the Planetary Society since he was a teenager.

And now he's the president. You know, the Planetary Society was started by Carl Sagan, Pulitzer Prize winning professor at Cornell. Bruce Murray, once declared the admiral of the solar system, former director of the Jet Propulsion Laboratory. And Lou Friedman, who continues as our executive director, an honored planetary mechanician, a guy who computes orbits of spacecraft and so on. Well, these three original founders, Carl, of course, has passed on, but these guys are getting older. And there's always a concern in an organization like that when the whole organization gets older. But Jim became a member of the Planetary Society when he was a teenager. And now he wants to lead us, if I may, to new horizons.

And if you're not familiar with Jim, you can check out his book, Postcards from Mars. It's a must for the coffee table and everyone's observatory. And he's got two new books, Mars in 3D and the Moon in 3D, where you see three-dimensional pictures of Mars and the Moon, and the moon in 3D, where you see three-dimensional pictures of Mars and the moon, and the red and blue anaglyphic 3D glasses are built into the book. So we're hoping to take the society to a more international stage, engage more people in space-faring countries around the world, like India and China, engage more young people, like some of you who are listening, so that space exploration continues to be an important human endeavor that helps us learn our place in the universe, and dare I say it,

you can help change the world. Well, congratulations to Dr. Bell. Thanks for listening to Planetary Radio. I've got to fly. Bill Nye, the Planetary Guy. Sean, you've done it again. Congratulations. Thank you, Matt. Very, very exciting. Some beautiful images. One of them I'm going to refer right up front to my colleague, Emily Lakdawalla, who

had a really nice piece in her blog at Planetary.org on October 7, if anybody wants to check the archives, where she starts out with this global shot that you got of this pretty interesting planet. And she calls it the money shot, but I don't know. I'm guessing that there are a lot of other images there that you are sinking your teeth into. There are indeed. We took over 1,200. But that shot, which shows the hemisphere in sunlight as we departed the planet after closest approach,

that was the first image that we sent down from the spacecraft. We guessed that that one would be of interest to the team, and we pre-programmed that one to come down first. So at about 1.40 in the morning, or a week ago, Tuesday, that was the 7th of October, the science team was collected around various computer monitors at the Science Operations Center for the MESSENGER mission. This was the first image down, and we just enjoyed the moment. Seeing terrain for the first time, oohing and aahing over these spectacular rays, these bright streaks that emanate out from several of the youngest craters, and it was just a real thrill to be there with my colleagues

and watch that first image come down. I wish I could have been there. It would have been very exciting. One crater in particular, up there very close to the North Pole of Mercury, seems to have had influence all over the planet. Yes, we're a little surprised by how great a linear extent these rays have. Interestingly, that crater had been seen in Earth-based radar images as a radar bright feature. The radar astronomers called it feature B,

without being able to designate a crater name, although they suspected it was a crater on the basis of their highest resolution images. And the fact that it is bright at radar wavelengths and bright at visible wavelengths is going to be very helpful in sorting out everything we're seeing. But it was a surprise to us to see how long these ejector rays wrap around the planet, nearly to the opposite side. Well, we will have that shot up at our page on the planetary.org website, planetary.org slash radio.

But there are many more, many up close and personal with the planet. My gosh, you just about hit the bullseye on this, didn't you? We did. The area on Mercury that we viewed close up for the first time is bigger than the land area of South America. So there are lots of new features to see. We specifically targeted the very highest resolution color imaging that anyone, including Messenger at its first flyby, has done of Mercury's service. As we came away from closest approach, we crossed the Dawn Terminator, and we made a sequence of color images with our 11 color filters.

That would be a wonderful data set because we also took high-resolution spectra of the surface along that profile. And to the extent that we could, we took altimetry along that profile until we got out of range of our laser altimeter. So that combination of data, particularly the high-resolution components of those data, will be a real treasure for us as we take advantage of these observations to think, well, how do we get the most out of the next flyby? How do we get the most out of the time we're going to be in orbit a little over two years from now? We'll come back to that next flyby, of course. But with this altimetry, I assume you're going to be putting together some 3D views? Not yet. That is, well, yes and no. The altimeter itself is a profiler and gives us very high resolution, very precise measurements of topographic profiles. After the first flyby, we had one profile, but it was over an area that no spacecraft had ever seen

because it was taken on a night approach in a part of the planet that not even Mariner 10 imaged. But the second flyby, the altimeter profile was over an area that had been partly imaged by Mariner 10 and partly imaged by us in January. And we imaged the entire track of the profile that was taken in January. So now we go from having one altimeter profile with no ability to match two images to two profiles, both of which can be matched to high-resolution spacecraft images. So it will allow us for the first time to figure out exactly where we are on the surface and to use the altimeter to gain a better understanding of the impact craters, of the fault structures that we fly over, of all of the terrain that we've passed over.

But you asked about topographic maps. There are ways that our team is using to make topographic maps using different views of the surface, using stereo to prize out strictly short wavelength topography. And they're first doing it in areas where we have the laser altimetry just to calibrate the methods and to angulate the topographic results. You did some spectroscopy, too. Is it too soon to talk about what you've discovered about the composition of that surface?

The surface spectroscopy, it is still a little early. We did take a great deal of spectra along the track as we came out of the night side of Mercury. We took additional measurements in the ultraviolet. Those had given us quite an intriguing result from the first flyby. But we're still intercalibrating. We're still sorting out what we've seen there. If I can talk about other spectra we took with the same instrument.

Yeah, please. That instrument doubles as our tool for looking at Mercury's neutral atmosphere and tail, particularly in the ultraviolet. You had some results with that from the first flyby, too, right? We did have some interesting results. We took the first spacecraft observations of Mercury's neutral sodium tail, which Earth-based astronomy has now shown extends at least a thousand radii in the anti-sunward direction, and is a major mechanism for loss of atmospheric species from Mercury out of its very tenuous exosphere.

We took more measurements two weeks ago than we did in January, starting farther from the planet and looking for other species. For instance, we now have observations of calcium as well as sodium in this neutral tail. So what has been called for six years now, since it was discovered, the Mercury sodium tail, now it's going to need a new name because it's clearly a multi-species tail, and we'll be looking for other species as well. We also took observations of sodium, calcium, and hydrogen in the exosphere,

both the night side and the day side, and we looked for new species. In particular, we looked for magnesium, which is expected to be in Mercury's atmosphere. It has not been seen from Earth. We're working through the data now and hope to be able to report a result there. I'll be back with more from Sean Solomon, including how MESSENGER has become a solar sailor. This is Planetary Radio. I'm Sally Ride. a solar sail, informative publications like an award-winning magazine, and many other outreach efforts like this radio show. Help make space exploration and inspiration happen.

Here's how you can join us. You can learn more about the Planetary Society at our website, planetary.org slash radio, or by calling 1-800-9-WORLDS. 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. Sean Solomon is visiting with us once again. Sean is the principal investigator for the MESSENGER mission, which just completed the second of three

flybys of Mercury. I asked Sean if there was more flyby data he was prepared to talk about. Well, the magnetic field turned out to be quite interesting. Of course, we got a good measure of Mercury's internal field. We flew by the planet for the first time in the Western Hemisphere, so we got a measure of the internal field on the side of Mercury that we didn't see in January and Mariner 10 never saw. And so that gives us an important observation that the main internal field, the dipole field, the field of the North and South Pole, is pretty symmetric. It looks very similar on the two hemispheres of the planet.

And the tilt of the dipole is very, very small. It's smaller than we thought it was, almost aligned with the spin axis. But we saw some really interesting things in the magnetosphere as well, because of the solar wind, the plasma that streams out from the sun and interacts so strongly with Mercury's magnetospheric envelope that surrounds the planet and its internal field. The solar wind field was opposite in direction from what it was in January, and the behavior of Mercury's internal field was quite different. In January, it was a pretty quiet internal field. But on October 6th, it was a pulsating field.

It was interacting strongly with that solar wind field, and there were patches of magnetic flux that were apparently peeling off of magnetospheric influence, Mercury's influence, and being released down the tail. And you could see that in pulsations in the magnetic field, even near the planet. So it's a very interesting data set for us to look at magnetospheric phenomena. Well, you mentioned the solar wind, and I am, after all, with the Planetary Society. So how about the fact that your team managed to steer this spacecraft, in part, by solar sailing? Yes, well, I know the Planetary Society has long been an advocate of using solar sailing

as a major propulsion system for moving spacecraft around the solar system. solar sailing as a major propulsion system for moving spacecraft around the solar system. This was a wonderful opportunity for us that we discovered not quite a year ago, as we were getting ready for our first flyby of Mercury back in January, that we could tilt the solar panels and we could adjust the pointing, the attitude of our main spacecraft to take advantage of solar radiation pressure and use that pressure to make small but continuous changes in the direction that our spacecraft travel. And so we needed to make some corrections prior to that first flyby. The solar sailing allowed us to do so without use of propellant.

And we've been utilizing that method ever since. We had a major propulsive plan, propulsive maneuver back in March of this year that put us on the trajectory for the flyby on October 6th. We normally would have a sequence of very small propulsive maneuvers between March and October to line us up as precisely as we could manage for that flyby. But the solar sailing was so good, the navigation and guidance and control teams on Messenger became so skilled at using radiation pressure to gently nudge in a continuous fashion our spacecraft in the direction it wanted to go. Not only did we need no further corrective maneuvers between March and the flyby,

but we hit our endpoint more accurately than in any of our previous flybys. So it was a marvelous demonstration of how powerful a technique solar sailing is to achieve really pinpoint accuracy in flying through space. Yeah, I think I'm going to send Lou Friedman of the Society your way toward your guys for some driving lessons. Well, Lou, to his credit, has been a great advocate for solar ceiling for many years, but we would be happy to provide him with driving lessons whenever he's got the time. And we are almost out of time. Are you now set? I mean, one more flyby, but then the big event after that, you go into orbit. Is your trajectory so accurate now that that's, in a sense, inevitable, or are there more actions ahead?

There are more actions ahead. Between each flyby, there is a planned major propulsive event, and the next one for us comes up in December. Then our next flyby, and we'll be solar sailing after that propulsive event to target the next flyby, is at the end of September in 2009, 29 September 2009, we have another in-space propulsive event to then make sure we're heading toward Mercury. And then on the 18th of March 2011, that's the last nail-biter,

because that is the time we have to fire our large propulsion system for the longest time and insert our spacecraft into orbit permanently around Mercury. So those are the events to come. And we think we've got a team flying this spacecraft that knows how to steer and knows how to handle these propulsive events. But we'll still be doing a lot of practicing between now and then. Sure sounds like you're in good shape,

and you've got lots of science to chew on until then. Sean, once again, congratulations. It's a beautiful mission, and we look forward to your analysis of more of that data with, I think, a press conference scheduled for the end of this month. We do indeed. We are on track for a PRINCE conference on 29 October. We hope to report out some of the major findings that are coming from our analyses. But

you're right, Matt, we're going to be looking at these data for years to come. We have our first global view of Mercury's surface. We've now imaged about 95% of it, so it's really giving us a lot to chew on. Thanks so much, Sean. Okay, Matt, my pleasure. Sean Solomon is the director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington, and the principal investigator for the MESSENGER mission, which has just had this extremely successful second flyby of Mercury. Much more to come. Sean's also a past president of the American Geophysical Union.

We'll be right back with Bruce Betts for this week's Helping of the Night Sky. That'll be our What's Up segment right after we visit with Emily. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, what's the difference between the orbiters at Mars? It can be hard to keep all the Mars orbiters straight. Right now, there are three. NASA's Mars Odyssey and Mars Reconnaissance Orbiter, and ESA's Mars Express. All three carry cameras for taking images of the

surface. All three also have infrared mapping spectrometers. And both Mars Reconnaissance Orbiter and Mars Express have ground-penetrating radar instruments that they're using to search for subsurface layers and even ground ice. Even though there's some similarities in instrumentation, though, the spacecraft are quite different, both in details and in their mission goals. For instance, the camera on Odyssey is much lower resolution than the other two. That may sound like a bad thing, but it's actually good, because one of Odyssey's goals was to create a new global photo map of Mars, something that hadn't been done since the Viking missions of the 1970s,

and lower spatial resolution translates into wider spatial coverage. By contrast, Mars Reconnaissance Orbiter's wonderfully detailed images will only cover 1 or 2 percent of Mars. That team actually depends on the Odyssey map to select their targets. Another difference is the orbiter's paths around Mars. Unlike the other two, which are in circular orbits, Mars Express has a long elliptical orbit, which can give it unusual crescent views of Mars and also allow it to fly out to encounter Mars's moon Phobos. And while all three spacecraft can serve as communications relays for landers, Mars Reconnaissance Orbiter's

radio dish is bigger than the Odyssey and Express dishes combined, making it the relay satellite of choice. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. So here we are on Skype with Bruce Betts, the Director of Projects for the Planetary Society. It's time for What's Up? How are you? I'm doing pretty well. In the evening sky, Venus getting higher. Really bright star-like object over there in the west after sunset. And if you rotate yourself more to the left, you'll see another really bright

star-like object. That's Jupiter. And I always enjoy when you get two or three objects like this, in this case the sun, which, you know, presumably is below the horizon at this point. And then you rotate to Venus and then over to Jupiter. They're all in a nice line. And that's nice little proof that that's the ecliptic, the plane of, in that case, the Earth's orbit around the sun, but that all those things line up in a nice little line pretty much. Gosh, that's cool. Okay, good. Thanks. In the pre-dawn sky, we've got Saturn getting higher and higher in the pre-dawn sky over in the east. And below Saturn, low above the horizon in the east, is Mercury these days for a little bit, also looking like a bright star-like object.

We go on to this week in space history. It is the 10th anniversary of the launch of the Deep Space 1 spacecraft. This was primarily flown as a technology demonstration. Demonstrator demonstrated 12 different technologies, among them solar electric propulsion, which is now being used quite successfully in planetary exploration, including by the Dawn spacecraft. And they also encountered the comet Borelli.

We move on to Random Space Fact! Since Shondrayan-1 is scheduled to launch any day now, I wanted to tell you a little bit about it. It's the first mission by India to the moon, and literally means moon plus craft in Hindi. So together, kind of meaning trip to the moon. Indian Space Research Organization was founded in 69, launched its first satellite in 75,

but has not yet sent a spacecraft beyond Earth orbit, and so this will be the first attempt at that. Excellent, and we wish them well, of course. We have so much more going on. Tell us about last week's, or two weeks ago's, trivia contest. We asked you if you could squish them all up, how many mercuries or mercury-sized objects could fit into the volume of Earth? How'd we do, Matt? Yeah, well, the key

thing there, of course, being if you crush them all up. Rick Byers told us that you could do seven if you don't crush them, which seems, you know, terribly cruel in the first place. But he had the right answer, was not our winner. Just about everybody derived this. Everybody came up with it by figuring it out. Among them, Ed Lupin, Edward Lupin from San Diego, California. 17.88 mercuries would fit in the earth if you ground it finely. And if you put it in your mercury grinder and set it on frappe. You know what? He's got a coffee company in San Diego, Cafe Lisa.

Maybe just build the universe's largest coffee grinder and you can just sprinkle it inside the earth. That could do it. Oh, and I love the smell you get as you're grinding mercuries. It just gets you going. Yeah, it's the sodium. It never tastes quite as good, though, as it smells. It's a weird thing. Should we move on to the next trivia contest?

Let's do that. We're going to send Edward a t-shirt, of course. And guess what? We're going to add something to the next contest, which I don't know why we didn't think of this a long time ago. Not only are you going to win a t-shirt, you're going to get a one-year membership in the Planetary Society. Is that cool or what? That's really cool. So that's for this upcoming contest. And I assume

if people are already members, we'll add a year on. Makes sense. I didn't think about that. But, I mean, this is a great deal. You'll get the Planetary Report, all the other benefits of being part of the Society, and you won't have to pay a thing. And there are other ways you can actually join that have nothing to do with that. Oh, yeah. You can go to planetary.org and get a t-shirt for joining up, right? You sure can, as long as you go to planetary.org slash radio. That's what I meant to say. Click on the sign up from there, and then you get the spiffy planetary radio t-shirt. So for this next trivia contest, our question for you. How far will the Opportunity Rover have to drive to reach the 22-kilometer crater provisionally named Endeavor? This is the long-range goal that's now

been set for the Opportunity Rover. So how far, roughly, does it have to drive to get to the edge of that crater? Go to planetary.org slash radio, find out how to enter, and compete for the t-shirt and membership. And as you may have guessed, you've got until Monday, October 27, at 2 p.m. Pacific time, to get us that answer. I have other news, beginning with Ennia Culpa. I said that we had to have the 6th anniversary contest coming up at the end of this month. Wrong. As a surprising number of listeners pointed out, we started in late November, not late October. And so you're going to have a little bit more time and we'll have a little bit more time to come up with an appropriate contest.

But, Bruce, I can tell people about the great prizes we've already arranged. Oh, tell us. Tell us. All right. Now, a couple of these. We go back to people who provided prizes last time, beginning with Bill Mueller, who heads up Vision Video Games, their Space Station Sim game, which you can read all about at spacestationsim.com. I think we're going to have a copy of that for all of our winners this time around. Thanks to Bill. It is great fun.

He's got some other cool stuff going on. They have something called Mission Control that's multi-user for like a classroom or a challenger center, a museum sort of setting. And it's very cool. But Space Station Sim is something you can have fun with all by yourself, build and operate your own space station. Then from Florian Knoller, who was also... There's more?

There's more! Wow. then from Florian Knoller who was also there's more there's more wow Florian Knoller who provided our little fragment of a Mars meteorite last time came up with something this time he is something different I should say he's chosen a set of five commemorative covers made by the JPL stamp club these are from Mars Pathfinder Mars Global Surveyor and Lunar Prospector. And this is the best of all, and he sent a picture of it. It's a cover, an envelope, that flew on the helicopter, the recovery helicopter, that picked up the Apollo capsule or the Apollo astronauts that were on the Apollo-Soyuz mission in 1975. You can find Florian's great collection of stuff at spaceflory.com. That's one word, space, F-L-O-R-I.com.

You ready for the grand prize? It is. These have both been very cool. There's more? I can go beyond that. Are you ready for this? No, but go ahead. Craig Weatherwax, the boss, the man in charge at OPT, Oceanside Photo and Telescope, which is at optcorp.com.

This is just amazing. The Celestron SkyScout. The SkyScout Personal Planetarium. Have you seen these guys? I have, yes. Very, very cool. Over 50,000 objects in the database, GPS equipped. You hold them up to an object.

You push the button. It tells you what you're looking at. Or conversely, you tell it you want to find a particular object and it takes you right to the object. And in about 200 cases, tells you all about the object. Congratulations. These are all from personal experience. Really, really cool. Aren't these great? Yeah, we are so pleased. Now we should actually come up with a contest for people to enter to try to win them. Maybe by next week. Maybe by next week we will have something appropriately challenging. All right. All right. Anyway, at least we've whetted their appetites. Your appetite out there, folks. Stay tuned.

I think we're done. All right, everybody. Go out there, look up at the night sky, and think about what do dogs dream about. Thank you, and good night. Bruce Betts is the director of Projects for the Planetary Society. He joins us every week here for What's Up?, and I often wonder what my dog is thinking about as he perhaps looks up at the dog star.

Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week.