Planetary Radio: Space Exploration, Astronomy and Science - Emily Lakdawalla on the Last Orbits of Cassini

Episode Date: July 19, 2017

The Cassini Mission has less than two months to go before it ends with a spectacular plunge into the beautiful ringed world. Planetary Society Senior Editor Emily Lakdawalla has prepared a guide to the last orbits by the historic spacecraft. Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Emily Lakdawalla and the last orbits of Cassini, this week on Planetary Radio. Welcome, I'm Matt Kaplan of the Planetary Society with more of the human adventure across our solar system and beyond. Less than two months now till the Cassini spacecraft ends its nearly 20 years at Saturn by plunging down into that ringed world. My colleague Emily Lottweiler is back with a preview of what to expect as the school bus-sized robot grazes the planet, passing inside its magnificent rings. Bruce Betts puts on his best Shatner for this week's Random Space Fact. Lucky for him, we pay him to do science and projects, not impressions. But he'll still give you another chance to win the new Planetary Radio T-shirt

and a pair of eclipse glasses. Up first is the CEO of the Planetary Society, Bill Nye, the very much a science guy. Bill, we missed you last week because you were on the road promoting your brand new book. Tell us about that, and I suspect it has a space angle. Yes. Everything all at once. How nerds solve problems. Yes, everyone. There's 20 in a carton. They make great gifts. No, it's everybody. This is something near and dear to me. I was I've been

a nerd since I was in high school. I've been fascinated with how things work. And everybody is passionate about something, Matt. Everybody's got something they want to accomplish, they want to do. And I just encourage everybody to unleash that, to embrace that about yourself and do something cool to leave the world better than you found it. So along this line, there's three things that I think we want for everyone on earth. We want clean water, renewably produced, reliable electricity, and access to the internet. Now to provide access to the internet or whatever the future of

electronic information is called, we're almost certainly going to have to have space assets. These will be satellites in low Earth orbit, a constellation, so-called, of several hundred, maybe fewer than a thousand, but more than 500. And I'm not kidding. And these things would hand the internet contact from one satellite to another in the same way we hand mobile phone calls from one cell to another. And this is an extraordinary idea, but it's doable. We have the technology right now if we just decided it was a worthy thing to do. And by doing that, Matt, we could provide education to everyone on earth and this specifically provide education to

girls. Because when you raise the standard of living of girls and women, they have fewer children. The children they have have more resources. They are healthier. They live longer. They're more productive. Everything is better in every way. So this is a visionary idea that would not even be possible without the promise of space exploration, or even, let's say, the routine nature of space exploration. Meanwhile, Matt, there's a meanwhile. We are living at a time when we may discover life on another world. And if we do that, it will change the course of human history. Is that a big deal?

Kind of. Yeah, kind of. So the promise of space exploration is greater than ever. I just wrote a foreword for John Logsdon's new book. For those of you who don't know, John Logsdon is considered the dean of space history. And it's called A Few Small Steps. And he points out that as extraordinary as landing on the moon, as sending rovers to Mars, as all that, as a spacecraft that left the solar system is all that is amazing. It's really small compared to what's ahead.

It's quite an insight. It's a very cool idea. You know, we have been telling John that we've got to get him back on as soon as that book comes out. And I guess that must not be far away. So, John Logsdon, we'll return to Planetary Radio, as will you, I hope. Yes, thank you, Matt. Hey, it's the anniversary of the moon landing this week. Oh, you bet. We're going to celebrate with a live show here in Pasadena talking about Mars, and it'll be on that evening, July 20th. So happy Apollo 11 moon day. Thank you, Matt. Carry on.

Bill Nye, he's the CEO of the Planetary Society and the author of Everything All at Once, his brand new book for grown-ups and others. And it's in all the usual places right now. We are building toward one of the greatest climaxes in the history of space exploration. On September 15th, the Cassini spacecraft, nearly out of fuel, will plunge to its death. It will happen after nearly 20 years in orbit, revealing Saturn, its many moons, and beautiful rings. We don't know when another spacecraft will pass that way again.

Planetary Radio and the Planetary Society will join the world in celebrating this spectacular mission, and the Planetary Society will join the world in celebrating this spectacular mission and the hundreds or thousands of human beings who had a hand in it. But there's still much science to do, as we're about to hear from Planetary Society's Senior Editor, Emily Lakdawalla. Emily, join me via Skype. Emily, so good to get you back, especially for an extended conversation about this mission that you and I and millions of others are going to miss so much. I will miss Cassini a lot, but I'll be able to stave off

some of my longing for the mission by diving into its archives and looking at its beautiful images. It's just all this use in your July 5th review of what we can look forward to of words like last and final. Yeah. Yeah, there's a lot of that. I mean, we've already had a lot of the lasts and finals of the Cassini mission because it's already in a very unusual orbit that makes it unable to do the kinds of moon flybys that it used to do. So those are basically over, but we're getting such great science now. Oh, man. And even since you published this piece, this is just the first chance we've had to talk about it, a lot more has happened. There have been at least a couple of more passes through the ring plane. That's right. Cassini is on a very short orbit right now. Earlier in the mission, its orbits often lasted months. And right now, the orbits last less than a week apiece.

So every week, pretty much, Cassini is flying through the gap between the D-ring and the top of the clouds. In fact, we're getting close to the time that it'll be dipping just barely into the uppermost reaches of Saturn's atmosphere so that its particle-tasting instruments can actually directly sample the uppermost reaches of the atmosphere, which is just amazing. We haven't done anything like that on a giant planet before. So it's like a whole new mission. I saw in your piece that this was coming up. Is there any potential danger in dipping that low? You know, there's really no danger in dipping that low,

because we know Saturn's atmospheric properties well enough to know where it's safe. Cassini has actually been flying quite close to an atmosphere all throughout its mission. It's been flying close to Titan. Early on in the mission, they tried several different distances away from Titan to try to figure out the right balance between going deep enough to get really good science and staying far up enough above the planet's atmosphere that they'd be able to manage the turning of the spacecraft, keep its orientation straight without relying on thrusters. And so they settled on an altitude for Titan that worked well, and now they're tasting this region between the rings and Saturn and have settled on an altitude that they know is going to

be safe for the spacecraft. Another big relief, which Linda Spilker, project scientist, was able to talk about the last time she was on the show, and she will be on again in mid-August with one more update before the grand finale, which we'll also talk about in a moment. There was another fear that, thank goodness, proved unfounded, which was that flying through that ring plane might also be hazardous for the spacecraft just because of the ring particles. You know, it was an entirely unknown region. Well, I suppose not entirely unknown, but it was not a directly sampled region before. They've been studying the D-ring for many, many years.

They have a very good sense of what the particle size distribution is. It is how big the particles get. And Cassini has a lot of experience flying through other ring gaps. In fact, in order to enter orbit at Saturn, they pass through a very narrow ring gap. And so they've been playing at ring gaps for quite a while. They've got a good sense of understanding of their spacecraft. They have ways to keep the spacecraft safe, including pointing the spacecraft's antenna along its direction of motion to act as sort of an umbrella. And so they were really very confident that the spacecraft was going to be quite safe passing through this region. Still, there was a moment of drama.

It just felt dramatic because it was flying into a region of unexplored space. Well, speaking of drama, all anybody has to do is look at this first image of the rings that you've put in this July 5th piece. It is breathtaking. It is my imagination, isn't it, that I'm looking at individual particles here? That just can't be in this image, which you took a hand in processing from the mission. That's right. We're talking about an image that shows fine-scale structure in Saturn's rings, and the structures are not individual particles. Cassini really can't

see individual particles. In fact, anytime that they think they see an individual particle, it's big enough for them to name it as a moon. So these things are not individual particles. We're looking at wave-like structures created in the rings by the gravitational tugs of the planet's moons, mostly Mimas and Prometheus, you know, the moons that are very close in, but there are other moons that have an influence on the shape. And these wave-like structures get sheared out because all the particles in the rings are, they're particles on separate orbits, and things that are closer to Saturn pass around the planet faster than the things that are farther away. So it's not like a record spinning on a turntable. It's kind of like the middle of a blender. Anything that made a lump

or a shape in the rings gets stretched out over time where the inner part moves ahead of the outer part. And so an individual wave can get wrapped around the planet many, many, many times after it's formed. And so many of these things that you're looking at in this weird image are in fact a single wave that is just wrapped many times around Saturn. It is just a gorgeous bit of natural phenomena. Images, you make an interesting statement in the blog about how you could go on publishing these images almost forever if you did it at a slow pace. Absolutely. You know, the spacecraft has returned hundreds of thousands of images, millions of pieces of data from different

instruments. The images are, of course, what the public regards as being the most important, because they're generally fairly easy to understand. The fact of the matter is that there simply isn't time for a scientist to sit down and write out a careful caption for every image and process every image to make it pretty and post it to the web. So there have only been some thousands, couple thousands of these images that have been captioned and posted on the internet. So anybody who wants to can just dive into those archives and pull out something that, you know, maybe a few dozen, couple hundred people have ever really looked at before. And they can dust it off, clean it up and post it, talk about

it and educate the world with images that are months and years old. And we'll probably be doing that for decades. My conversation with senior editor Emily Lakdawalla about the last weeks of the Cassini mission will continue after a break. This is Planetary Radio. Hey, Planetary Radio listeners. The Planetary Society now has an official online store. We've teamed up with Chop Shop, known for their space mission posters, to bring you space-inspired art and merchandise. You can find exclusive Planetary Society T-shirts, posters, and more.

Visit planetly.com to learn more. That's planet.ly forward slash space shop. Hi, I'm Kalisa with the Planetary Society. We've joined with the U.S. National Park Service to make sure everyone is ready for the 2017 North American Total Solar Eclipse. Together, we've created the new Junior Ranger Eclipse Explorer Activity Book. It helps kids learn about the science, history, and fun of eclipses. Call your nearest national park and ask if they have the Eclipse Explorer Book, or you can download it from mps.gov slash kids or at planetary.org slash eclipse.

Welcome back to Planetary Radio. I'm Matt Kaplan, visiting again with my colleague, Planetary Society Senior Editor, Emily Lakdawalla. Emily's July 5th blog at planetary.org looked forward to the remaining days of the Cassini mission as it nears its inevitable end. Emily has done so much more than write about Cassini, its science, and its people. She has worked on hundreds of images captured by that spacecraft. Some of her

work has made valuable contributions to both the public and scientific legacy of the mission. But Cassini has delivered much more than images. Talk about some of the other science that is underway now as the spacecraft makes these close passes. that the Juno spacecraft is performing at Jupiter. Both of the two spacecraft are on highly polar orbits that are very elliptical. They get close to the planet, very close to the planet at closest approach, and they swing out much farther away at its farthest approach. Because of that, their fields and particles instruments, the ones that taste different molecules that are in space or the ones that sense the magnetic fields,

they're getting a really good survey of the very close-in structure of the planet's upper atmosphere, of the ion and neutral atom environment around the planet, about the way that its magnetic field is structured. And they're also probing very carefully the mass of the planet, the way that the mass is distributed in the interior of the planet. And for Saturn especially, this is the first time that the spacecraft is able to separate the mass of the rings from the mass of the planet. And we'll get the mass of the rings for the very first time. So it's great to have both of these capable spacecraft doing similar missions at the two largest planets in the solar system at the same time. spacecraft doing similar missions at the two largest planets in the solar system at the same time. And the science from one mission is going to multiply the quality of the science from the

other mission over time. But it's going to be years. It's going to take years for that kind of analysis to be complete. What else are you looking forward to in these final days? I'm thinking of one attempt to image another planet that you mentioned. They're making an attempt to image Neptune and Triton, which they have done before. They're also taking just some last Kodak moment shots. They're going to do an image from inside the rings, as Juno has done at Jupiter, taking an image looking at the rings from the interior perspective. They're taking images of very high-resolution features in the clouds. Honestly, though, there's no particular piece of data

that I think is more favorite than any other. It's just great to be in a new region of space with this trusty spacecraft. And I love the fact that they're taking as much advantage of it as they possibly can down to the last possible moment. I'm looking now at this table, which, as I said, we're already partway through since we're a little past the July 5th publication date. Can you review a little bit of what we have to look forward to just in the next few weeks? As we talk, it's the 18th of July, and we've actually just completed the very last radio

science observations of the mission, which is this gravity experiment that I was talking about. It's really going to lead to important insights about the interior structure of Saturn and the mass of the rings, and the mass of the rings is going to help tell us how old the rings are. This is the sort of Doppler-based work that is based on the change in frequency, right, as the spacecraft is dragged back and forth in those gravity fields? Yes, they can measure extremely tiny differences in the acceleration and speed and direction of the spacecraft by just maintaining a strong signal from the spacecraft, a carrier signal between the spacecraft and the giant radio dishes of the deep space network. And they can use that after a lot of work with supercomputers to model the gravitational field around Saturn, which is mostly dominated by Saturn.

Saturn's a little odd. It's not spherical. It's very oblate. It's squashed because it spins so fast. And so it's got an interestingly shaped gravitational field. And then there's the whole business of having the ring system outside of where the spacecraft is orbiting. So that adds a whole different kind of gravitational tug. It's going to be some fun modeling for those scientists.

Any other highlights coming up? I mean, I realize now that I've already gotten a whole bunch from you, but there's anything else that we've missed that's going to be just in the next even just three or four weeks? that's going to be just in the next, even just three or four weeks? Well, one of the things that they're really focusing on with their opportunity to be very close to the planet over the poles is to study the aurora at both poles. So the star there is the UVIS instrument, which is an ultraviolet imaging instrument, not the regular camera.

But of course, they'll be taking observations with all of the different optical instruments. And so I anticipate seeing some really pretty pictures showing how Saturn's aurora has fine structures that we haven't been able to appreciate from more distant observations. And some more study of that mysterious hexagon? You know, it's not so mysterious to atmospheric scientists, but every time you look at the planet, it looks really cool. It's just a standing wave in the atmosphere, but a hexagon, wow, it's a geometric shape on a spherical planet. It does look really awesome. All right, let's look forward, sadly, to September 15th. Where will you be?

I will, of course, be at the Jet Propulsion Laboratory with all of my colleagues and friends in the space reporting business. Space journalists are, it's a small group of people, and we're always happy to get together again for even for a sad event like this one, there's still going to be, I think, something of a party atmosphere and, and a general fond looking back on how wonderful it has been to get all of the beautiful pictures and science from this mission. And I look forward to joining you there. That, unless I am too busy preparing for something else that I think you will be part of, more details soon about a public event. If you're in Southern California, you might be able to attend it in person. If not, I'm sure it will be streamed live.

A celebration of the grand finale of the Cassini mission, the final weeks of which is what we've been talking with Emily about. Thank you so much, Emily. It's a great pleasure to talk as always. I hope you bring cake to that event, Matt. We better. We better do that with rings around it. She is the Planetary Society's senior editor, Emily Lakdawalla.

And we'll be talking to her again soon. Up next, it's What's Up with Bruce Fetz. Next, it's What's Up with Bruce Betts. Time for What's Up on Planetary Radio. Bruce Betts is the Director of Science and Technology for the Planetary Society and my cohort for this segment, as he has been for 14 and a half years. Welcome back. Thank you. Good to be back. You have an exciting sky for us, and we have an exciting event to tell people about.

I've already mentioned it, actually, but I know you're going to join us for a live What's Up segment at the end of our little Mars event that's taking place at KPCC here in town, Southern California Public Radio. Glad you'll be joining me. Yeah, it's always exciting. Anyway, people can find that at kpcc.org. Just go to the events area there, and that's where it will be embedded. It's going to be at planetary.org as well, and we'd love to have you visit our site. Just a little harder to find there. In the meantime, what should people look forward to in the sky?

Well, they should, of course, check out Jupiter looking bright in the early evening in the west. And then Saturn. Saturn is a little tougher to find, but out Jupiter looking bright in the early evening in the west. And then Saturn. Saturn is a little tougher to find, but it's still bright. It's up there in the south in the early evening. To its lower right, 13 degrees away, is Antares, the reddish star of Scorpius. And it is a little bit dimmer than Saturn. Then the pre-dawn east, we've got super bright Venus. We move on to this week in space history.

I don't know that you can come up with anything that happened this week in space history, Matt. Is there a reason we're doing planetary radio on the 20th? I can't remember. It was actually what I had in mind when we had to pick a date for this live show, that why not do it on what I think is maybe the greatest space anniversary of all. Oh yeah. 1969, Apollo 11 lands on the moon and humans visit another world.

That's not what I was thinking, but okay, I'll go with that. Oh, okay. Viking one landed on Mars in 1976. No, not that either.

No, it's Apollo 11. What can I say? It was a glorious day for all of humanity. Indeed it was. You got anything special for what's coming up next? No, no, nothing special. You're on your own. Actually, wait.

We did have a request for an impression by you, and now I can't remember what it was. Did I show it to you? Yes, you did. It was William Shatner as Kirk. Oh, that's absolutely right. And I think it was Chris Oldroyd in the UK who wanted to hear your chat. Go ahead, lay it on us, so to speak. I'll try, but it's always a little embarrassing,

because I know it's not great, but hopefully we'll try. Random. Space. The final fun fact. These are the voyages of the starship Matt. It's your customization that makes it. So in the random space fact department, the escape velocity from the sun's surface equivalent, the photosphere, is 55 times faster than the escape velocity from the Earth's surface. So, if you're on the surface to get away and not to be pulled back by gravity, you'd have to be going 55 times faster because that sun, it's really massive. Bring an air conditioner.

I know. I think that's the least you're worried when you're there. But I thought it was an interesting fact nonetheless. Do you know anything about this mission that NASA is now working on, which is going to get up close and personal with the sun? I do. It will get seven times closer than we've ever gotten to the sun. It's still not exactly dipping through

hitting the surface or anything, but it is going through what you could kind of consider outer layers. Yeah, it's pretty groovy. They've got quite the heat shield. Well, that's something we'll have to talk about with somebody aligned with that mission at some point on the show, but now you can go on. We asked you who submitted the name Sojourner Truth for the Mars Pathfinder rover. How'd we do, Matt? We did well. And we have, chosenbyrandom.org, someone who has not won in three and a half years. And last time when he won, it was a funny answer to one of your periodic quizzes where we demand that people get creative. It's Kamil Stefaniak in Lubin, Poland.

He said that Sojourner Truth was submitted by a 12-year-old girl named Valerie Ambroise. Is he correct? That is correct. It was part of a Planetary Society-run contest. And that we had something like 3,500 essays submitted for that? There were a lot. That actually predates even me at the Planetary Society. Yeah, and definitely me as well. But Valerie won out. Camille, you've won. Congratulations.

You're getting that brand-new design Planetary Radio t-shirt, which mine is going to arrive any moment now. Could even be in today's mail. I hope, I hope, I hope. And a 200-point itelescope.net astronomy account. iTelescope is that nonprofit international network of telescopes that anybody can use remotely. We have some others, of course. Joe Murray from Hoboken, New Jersey, hometown of Frank Sinatra.

We have some others, of course. Joe Murray from Hoboken, New Jersey, hometown of Frank Sinatra. He said the second place prize went to Deepti Rahatgi, who at the time was 18, of Rockville, Maryland, who proposed Marie Curie. I mean, I thought that was interesting. Jordan Tickton in Westlake Village, California. He says, interestingly, in the following years, Valerie and her family became kind of annoyed by the constant media attention, and even sent a New York Times article to back that up. I don't know. Is she? I wonder if she's still mad at the Planetary Society 20 years later.

Mel Powell, Sherman Oaks, California. He had to get together with Jordan. They're not too far apart. He says that he would have suggested, if he'd been in the contest, he'd have suggested Matt or Bruce or Emily, maybe Bill, but Sojourner's okay. Finally, from our poet laureate, Dave Fairchild in Kansas. And people have to remember that Lou Friedman, our founding executive director, was the guy in charge back when this happened. She sent in her essay for Friedman to read. He gave it a score of five stars. And so when the Delta took off from the pad, her sojourner truth went to Mars. Nice.

Thank you, Dave. You get to retain your position. We're ready to go on. All right. Here's your new question. By mass, what is the fourth most common element in the sun after hydrogen, helium, and oxygen? Go to planetary.org slash radio contest. It's not unobtainium, is it?

Oh, dang it. Now I need a new question. That is the question you have for this time. And if you get it right and you're chosen by random.org, you're going to get a really cool pair of Bill Nye eclipse glasses that are certified to be a safe way to watch the coming eclipse on the 21st of August. And that is if you're in the path of the eclipse. But you can look at the sun anyway, even if you're not with the glasses, that is if you're in the path of the eclipse, but you can look at the sun anyway, even if you're not, with the glasses, that is. That brand-new T-shirt from Chop Shop,

which is part of the Planetary Society store at chopshop.com, and, of course, a 200-point itelescope.net account for doing astronomy wherever you are. And you'll need to get it to us. I don't think I said, did I? You'll need to get it to us. I don't think I said, did I? You'll need to get it to us by the 26th, Wednesday, July 26th, at 8 a.m. Pacific time. All right, everybody. Go out there, look up at the night sky, and think of what it would be like to have horns.

Go think about it. Thank you, and good night. I'm sorry. I was thinking about it so seriously. It's like, wow, that would be weird. It really kind of blew your mind, didn't it? It sure did. I loved my bicycle horn.

Not that kind of whatever. That's Bruce Betts. He's the Director of Science and Technology for the Planetary Society, who joins us every week here for What's Up. And if you hear it in time, well, it's going to be archived if you miss the live show, which is going to begin Thursday, the 20th, at 7 p.m. Pacific time. If you miss that, it will still be archived, and you can hear us talk about living on Mars. It was 48 years ago this week that humans made landfall on another world.

Neil Armstrong is gone, but Buzz Aldrin is still with us, and so is Michael Collins, their colleague who waited in the Apollo 11 command module for Buzz and Neil to return. It made him the most isolated human being in history. We salute them and everyone else who made that miracle happen half a century ago. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its members. Daniel Gunn is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. I'm Matt Kaplan. Clear skies.