Planetary Radio: Space Exploration, Astronomy and Science - Huygens Probe Sets Off On Its Own for Saturn's Moon Titan

Episode Date: December 27, 2004

Huygens Probe Sets Off On Its Own for Saturn's Moon TitanLearn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

The Huygens Probe says goodbye Cassini, hello Titan, this week on Planetary Radio. Hello again everyone and Happy New Year. Welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. This is the last video's travel show that takes you to the final frontier. I'm Matt Kaplan. After seven years as the close companion of Cassini, Huygens has finally set off on its own for Saturn's moon Titan.

Our guests are the project scientist and the mission operations manager for the small but instrument-packed European spacecraft. Speaking of moons, stay tuned for Emily Lakdawalla's Q&A. She'll tell us where to find the biggest ones in our corner of the sky. Bruce Betts drops in with good wishes for the new year and the gift of five planets visible in the early morning. We'll begin with a quick review of space headlines. There was no Christmas break for Spirit and Opportunity. Mars Exploration Rover Project scientist Joy Crisp says the little robots will keep working right through the holidays. No word on whether she added a bah humbug or two. Opportunity is now closing in on its own heat shield, discarded as it descended to the surface months ago.

High above the rovers, the European Space Agency's Mars Express orbiter is finding increasing evidence of relatively recent volcanic activity on the red planet. This may have created regions that are somewhat more hospitable to life, if any exists or existed. And from Moscow, we get a good progress report on Cosmos 1. The solar sail remains on track for a March 1st boost into orbit on the tip of a submarine-launched Russian rocket. Want more? You can get the lowdown on these and other stories

at planetary.org. Stick around. I'll be back with our Huygens update right after Emily. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, What is the largest moon in the solar system? The largest moon in the solar system orbits the largest planet in the solar system. It is Jupiter's moon Ganymede.

For a long time, Saturn's moon Titan was thought to be the largest. As seen through a telescope, Titan's disk appears larger, once you have corrected for Titan's greater distance from the Earth, than Ganymede's does. So Titan was thought to be the king of the moons until 1980, when the Voyager spacecraft flew past Titan and used their powerful radio antennae to send signals through Titan's atmosphere back to the Earth. The radio signals penetrated through the edge of Titan's disk until they were blocked by Titan's solid surface. These radio occultation measurements proved that Titan was 600 kilometers

smaller than previously thought, knocking it below Ganymede in size. Titan is still big as moons go. In fact, both Titan and Ganymede are larger than some of the planets. Stay tuned to Planetary Radio to find out more. With a gentle spring-loaded push, the Huygens probe bid farewell to Cassini on Christmas Eve. The bigger spacecraft will continue to explore Saturn and its moons, possibly for many years to come. But Huygens has its rendezvous with destiny on January 14.

That's when it will plunge into the thick and hazy atmosphere of Titan, eventually coming to rest on the big moon's surface. Huygens' team members from the European Space Agency have been regular visitors at the Jet Propulsion Lab in California ever since planning for Cassini-Huygens began two decades ago. We met with two of their leaders just hours before the two spacecraft went their separate ways. Jean-Pierre Le Breton is Huygens' mission manager and project scientist. His colleague, Claudio Solazzo, is the mission operations manager.

Gentlemen, thank you so much for joining us here at Planetary Society headquarters. Our pleasure. We are really very pleased to be here. And we are especially pleased to have you because we are a very, very short time away from something that you have been looking forward to in your lives for, Claudia, how many years have you been part of the project? I've been part of this project since 15 years. And so these are essentially the last moments before the thing really becomes reality. I always thought about it as something very far in the future, and suddenly here it is.

Jean-Pierre, what about your tenure with the Huygens project? Well, I've been working on Huygens, well, on Cassini, in fact, because at the time we started more than 20 years ago, it was called the Cassini mission. And it became the Cassini-Huygens mission when the contribution of the European Space Agency, Huygens, the Titan probe was selected in 1988. So since then, it's the Cassini-Huygens mission. But I'm really working on this mission for more than 20 years. Huygens will travel on a ballistic trajectory, so without any active control. So that moment of separation is absolutely critical

because you cannot make any course corrections. Well, before we do separation, we still have to do a little bit of adjustment of the trajectory. And once separation takes place, it's about a three-week trip to Titan? It's indeed about, it's 20, 21 days on its own, slowly to titan yeah well i don't know about slowly well uh slowly i mean okay it will go out about six kilometers per second that's very fast i mean it's 20 000 kilometers per hour i say slowly because i think those three weeks are going to be to be a bit special i mean we are going to wait for the 11th, the entry of the 14th of January. And after how many years in space, mated to the Cassini spacecraft?

Well, Cassini was launched in October 1997, so more than seven years in space. Again, this moment of separation is so critical because you cannot make course corrections, and you are going directly, as soon as the probe reaches Titan, it's into the atmosphere, correct? Yes. I mean, the separation is actually, it happens with Cassini being itself on a collision course with Titan. At the moment of separation, the probe is imparted a small differential velocity, something like 30 centimeters per second, with respect to Cassini. And from that point on, it slowly separates and slowly goes away.

And about four days later, Cassini itself will go through a very big maneuver to take, first of all, it away from collision course. And the second thing is that it will go and configure the trajectory in such a way to support the radio link during the probe mission under the right conditions. I'm so glad that you brought up that radio link because, of course, it brings up one of the biggest challenges that you and the rest of the team needed to overcome, and that was this great, let's call it the Doppler dilemma, which I guess you've now solved. Can you describe what happened?

Oh, well, this is a long story, of course. It all started in early 2000 when we did a special test to verify the functionality of the link between the probe and the orbital. Because Huygens will depend on Cassini to communicate with Earth. Absolutely. Huygens is going to send its data via radio signal to Cassini. We found a problem. Cassini, well, in fact, it's the Huygens radio receivers on board Cassini, were not able to receive the Huygens signal. And this was because of what would be the difference in velocity between Huygens and Cassini. It's the Doppler effect, which is going to shift the frequency of the radio signal.

Yeah. In fact, the signal, I mean, the link, the radio link between Huygens and Cassini was working very well when the two are attached because there is no velocity between the two. Yeah. that the receivers, the radio receivers on board Cassini, were not properly tuned to receive the signal with a small Doppler shift, which would be due to the different velocity between Huygens and Cassini during the relay. And we had to live with it. We could not really correct it. There was no way we could repair it. So we had to find workaround solutions, and we found one. And you did that, I'm told, by changing the trajectory.

Well, in the end, we arrived to this solution, but we explored a lot of different paths. And so we went through a lot of, let's say, electronics and radio acrobatics to try to understand it. I must say we have a very good tool, which is located at the Huygens Operations Center in Essock, in Darmstadt. Darmstadt, Germany. In Darmstadt, Germany. And this is the Huygens engineering model. The engineering model is essentially a twin sister of the Huygens probe. It works the same way as the Huygens probe from an electrical and functional software.

Everything is the same. We emulated some of the tests we did in flight on the engineering model. We could duplicate the same behavior, and that gave us hints of what really was going on. So you were able to model the problem and also model the solution, I'm guessing. Right. So that gave us a lot of confidence that we could essentially solve the problem. So the end result was a discussion, a very open discussion between us and the Cassini team at NASA, JPL, and we came up with this very simple solution, change Cassini trajectory enough to reduce the Doppler effect. You both look reasonably

relaxed tonight for two gentlemen who are reaching the climax of an experience covering many, many years. You must have solved it to your satisfaction. And really, other than that, Huygens has been a remarkably problem-free spacecraft. Well, indeed. I mean, Huygens has been working very well. In fact, Cassini, the whole Cassini-Huygens mission, the spacecraft, is really fantastic. scrap is really fantastic. Each time we have been switching on Huygens to maintain our equipment, to do some regular activation help checks, it has been working very well. So we are very confident that Huygens is ready for the big job in January. Gentlemen, that's a good place for us to take a break for a moment. And then I hope when we come back, we can talk about what Huygens will be up to when it reaches this, I've said it before, I'll say it again, this mysterious moon called

Titan, circling the great planet of Saturn. Our very special guests this week on Planetary Radio are Jean-Pierre Le Breton. He is the mission manager and project scientist for the Huygens probe. And with him is Claudio Salazzo, who is the mission operations manager for Huygens. We'll be right back after this. This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system.

That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets. The Planetary Report is the society's full-color magazine. It's just one of many member benefits. You can learn more by calling 1-877-PLANETS. That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments at our exciting and informative website, planetarysociety.org.

The Planetary Society, exploring new worlds. Our subject this week, as it will be again soon on Planetary Radio, is the Huygens probe, which, if all has gone well, has already separated from the Cassini spacecraft, madly circling Saturn. Cassini saying goodbye to its companion of many years, and Huygens headed across 4 million kilometers of space toward the hazy atmosphere of Titan. Our guest, Jean-Pierre Le Breton, is the mission manager and project scientist for Huygens,

and he is joined by Claudio Salazzo, who is the mission operations manager. The big day is January 14, right, Jean-Pierre? Absolutely, the big day is on January 14. I mean, the probe is going to wake up by itself. A small alarm clock has been activated, and about four hours before we get to Titan, the probe is going to wake up. And then this will activate a number of units,

the onboard computers, and slowly the probe will wake up and will be ready for the entry, for the hot entry in the atmosphere of Titan. And at the end of the entry, parachutes will deploy, instruments will be activated, and the radio link between the probe and the orbiter will be activated, and we will receive data. So Cassini will receive data. We are not going to receive data directly ourselves.

We have to wait for a few more hours while Cassini has finished receiving the data. It's turning back to the Earth and then sending the data at the end of the day. And you said a hot entry. And Claudio, he's not kidding there, is he? Yes. I mean, actually, we could talk about a very fiery entry. Huygens is approaching Titan at a speed of a little bit over 20,000 kilometers an hour. That's pretty fast.

Yes, I'd say so. Turn around. And within about three minutes, it will slow down to a leisurely speed of only about 1,200 kilometers per hour, like a little sun going through Titan's atmosphere for a few seconds. And yet inside that fireball is a package, a very compact package of instruments, which you are hoping moments later are going to start returning data, at least to Cassini, about the atmosphere of Titan. Yeah, this package is very well protected inside the shell. The shell has been designed such that the package is going to stay at the normal ambient temperature, as we say, around zero degrees Celsius. temperature, as we say, around zero degrees Celsius.

And once the parachute, the first parachute is deployed, the instruments will be exposed and we'll start their measurement. And they will not have seen the hot phase. I mean, they have been protected from this by the heat shield. You have really crowded a lot of stuff in that little probe. We have packed a lot in this little probe. I mean, we have six instruments, but if I count all the various functions in the instrument, we have more than 30 different functions. Look at the camera, for example, which has been provided by the University of Arizona. And this camera itself has more than 10 sensors. So altogether, we are doing more than 30 various measurements.

So we are really going to return a lot from Titan with the descent. I know, Claudio, that in addition to those cameras, Titan is even bringing its own little flashlight to light up the surface just before it touches down. light to light up the surface just before it touches down. Yes, we will switch on a fairly powerful light about 200 meters above the surface of Titan and this will illuminate the ground where the probe is going to land and will allow the instrument, in particular the spectrometers on the DISR instrument, the imager, to provide information about the nature and the composition of the surface, whatever it will be. How long will it actually take from the time of entry into the atmosphere to touchdown on the surface?

It's about two hours and 15 minutes, plus or minus 15 minutes, as we say. And we really want to get down to the surface before the batteries are emptied or before the radio link between the probe and the orbiter is terminated. So we really want to get down rather fast. That's why we deploy a very small parachute for the last part of the descent. And I know that no one is saying that Huygens will survive on the surface, but you're hoping, aren't you?

Yes, we do. I mean, we even have a specific instrument whose main objectives are to do measurements at impact and once on the surface. He's going to make simple measurements like measuring the density of the ocean. If we do land in an ocean, it will measure the composition of the ocean, if we do land in an ocean it will measure the composition of the ocean, it will measure the index of refraction so very simple measurement, sound speed

another simple measurement, the conductivity even the depth of this lake, yeah we have a small sonar so an acoustic sounder which may measure which is designed to measure the depth of a lake down to one kilometer. Titan deserves to be fully explored. So I think we have the right equipment to reveal the mysterious surface of Titan.

So, Claudio, even when they are millions of kilometers apart, Cassini, Huygens, still very much a team. What about the team here on Earth that has been working for so many years on this collaborative project? The joint Cassini-Huygens team, and let me say it's really joint. People from NASA, people from ESA have worked together for, as Jean-Pierre was saying, at least 20 years in the development. But in particular, in the past three to four years, this cooperation has been even tighter because after the discovery of the radio anomaly on Huygens, both NASA and ESA decided that in order to make sure that the new mission would be implemented

to the best co-located team be formed here at JPL. So ISA contributed with a very small team. There are three people working at JPL since about three and a half years. And you're one of those who's been here all that time. I'm actually leading the small team here. So the whole cooperation is not only at agency level, but also, I would say, at different countries level. When I was at JPL last summer for orbital insertion, some of the slides they were showing were showing the instruments on Cassini and Huygens and where they originated. We tend to think of it, I guess, as an ESA-NASA mission,

but it's even more than that. Yes, it is truly an international mission. In fact, there are almost 20 countries, I mean, 19 or 20 countries, which are really involved directly doing the science. I mean, we have an ambitious mission, and I think it's really the way to go. If we want to explore, you know, the outer planets, really to make the best out of our sources.

So let's hope that Kathleen Huygens is going to show the way for the future exploration of the other planets. I very much hope that we'll have the chance to talk once again, either just prior to or perhaps after January 14th. Once again, gentlemen, thanks so much for joining us on Planetary Radio. Thank you very much. Our guests have been Jean-Pierre Le Breton. He is the mission manager and project scientist for Huygens and the mission operations manager, Claudio Salazzo, a transplanted resident of California for the last three and a half years,

going home soon. And we will be coming back with Bruce Betts and What's Up right after this return visit from Emily. I'm Emily Lakdawalla back with Q&A. Many of the solar system's moons would have no trouble qualifying as planets if they orbited the Sun by themselves. The two largest moons in the solar system, Jupiter's Ganymede and Saturn's Titan, are larger than the planet Mercury. Along with Ganymede and Titan, there are a total of seven moons in the solar system that are larger than the planet Pluto. Three more of Jupiter's moons make this list, Callisto, Europa, and Io, along with Neptune's

moon Triton and the Earth's own moon. Below that, there are another 10 objects that are larger than the largest asteroid. Saturn's moons Rhea, Iapetus, Dione, and Tethys, Uranus's moons Titania, Oberon, Umbriel, and Ariel, Neptune's moon Nereid, and Pluto's moon Charon are all bigger than Ceres, the biggest asteroid. All of the objects that I've mentioned are spherical globes. Even though they orbit other bodies, they are worlds unto themselves, each of them worth exploring.

Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Time for What's Up on Planetary Radio, the last What's Up of the year 2004. We are joined as always by Bruce Betts, the Director of Projects for the Planetary Society. Bruce, Happy New Year.

Happy Old Year, Matt. Well, it is still the old year. Most of our listeners will be hearing this as 2004 draws to a close. It's been a good year for What's Up, hasn't it? It has. It's been fabulous, but then, you know, we're biased. So, yeah, but the show's getting out there on more and more radio stations. So we're excited.

We're getting more listeners, more entries to our trivia contest. Always makes us happy. It's good stuff. And now we're ending the year with five naked eye planets visible in that pre-dawn sky. Pretty exciting stuff. Won't happen again for several years that you'll be able to see five so easily. so go out there if you can crawl out of bed or just stay up through the night go out and see look for venus first brightest object in the sky over there in the east looks like an extremely bright star-like object and if you look near venus you'll see mercury they're doing a little dance right now mercury is a little lower left but they're very very close

together mercury also pretty bright jupiter is to the upper right of Venus and also looking extremely bright, but not quite as bright as Venus. And in between the two, dimmer, not quite as bright, but let's not pick on it for that. Mars looking a little reddish. Go way to the other side of the sky. Over in the west, you'll see Saturn. If you're not a pre-dawn person, then go seeurn in the evening sky you can see it rising right around sunset or shortly thereafter hanging out near two bright stars looking like three stars in a line castor pollux and saturn being the brightest of the three have you heard anything about a comet coming into view we may have to talk more about this next week so we will come back to comments okay uh yes there is uh there is a

comment which of course can't remember the name of, but I think it's one of those survey names that are so exciting, that is coming around. It is a tough thing to see, however. Not exactly sure how bright it's supposed to get, but we'll get you more information on that in the coming weeks. So stay tuned. What else do you have for us? We've got... Red Bull Space Fact!

Sorry, it was a boring week in space history, so I decided to skip it. We need to do something exciting this week to make it. Anyway, Random Space Fact. Baltus Vellus, a sinuous channel on the lava plains of Venus, is at least 6,800 kilometers long. We're talking stretching across North America kind of thing here. It is the longest channel, longest single channel of any kind in the entire solar system, with the Nile River coming in a close second at 6,700 kilometers. Wow, Mars has got a whole bunch of these.

Mars has a big giant Valles Marineris thing, so if you count all the networks connecting together, then you can achieve these lengths. And so it's kind of for the single channel kind of thing. But this one cut by lava as opposed to the Nile by water. And as opposed to Valles Marineris having this ridiculously complex history we don't have time for right now. And sinuous, man. That sounds so sensual. Why, yes.

Yes, it does. Baltus, Vallas. I don't know what to do with that, Matt. I think we've done enough. I think we have. Let's move on to the trivia contest, shall we? What did we ask you? We asked you what asteroid will the Japanese Hayabusa mission, formerly known as Musa C, try to sample in 2005?

It's already on its way out there. How do we do, Matt? We continue to get lots more entries than we used to back in the early days of this program. We're talking simply months ago. And it happens that our winner this week was one of our first listeners. I think he may have been one of the first people to enter, maybe to win the contest. He hasn't won a T-shirt from us in a long time. Bill Magnuson, Bill Magnuson, Jr. from Malden, Massachusetts.

He said, hey, Matt, and Bruce, in 2005, the Japanese Hayabusa will attempt to return a sample from the asteroid Itokawa, which for bonus points, which he's awarding himself apparently, is named after the late Dr. Hideo Itokawa, the father of Japan's space development program. There you have it. Yes, indeed he do. Congratulations. We'll get a t-shirt out to him. If you want to win the Glorious Planetary Radio t-shirt, answer the following question.

What is the name of Mercury's largest, at least largest known, impact crater? Mercury's largest impact crater. Yeah, so darn big it's called an impact basin. Oh, okay. What is the name of that? Go to planetary.org slash radio. Find out how to email Matt. Fun and festive answers and win your t-shirt., Bruce, they need to get us those entries this time around by January 3rd. Monday, January 3rd at noon Pacific time. And you can be a part of this contest. Is that 2005? It is.

Did I say four? No. It is 2005. I'm being obnoxious. January 3, 2005. Isn't that exciting? It is. It's so exciting.

We're looking forward to a great year of planetary radio. You talked about all the new stations that we're on. Stay tuned, folks, because there's going to be more news. Yep, and a lot of great planetary stuff coming up in 2005. Huygens encounter a Titan. We've got Deep Impact both launching and getting to a comet, slamming into it. Hayabusa trying to sample an asteroid. All sorts of good stuff.

Cassini still cranking around at Saturn. Five tons of Mars missions still working. Five spacecraft still working on Mars. Matt, did you know that? That's amazing. Isn't it amazing? It's a real community, you know. It's actually crowded out there.

I don't know about crowded, but they are close. They have formed a close-knit community. They're not going to unionize, I hope. Shh. All right, everybody. I think we're about done here. We are definitely done here. We were probably done a few minutes ago.

Thank you, everybody. Go out there. Look up in the night sky and think about cheese. Thank you, and good night. I don't know if he means green or not, folks, but that was Bruce Betts, the Director of Projects for the Planetary Society. He is here every week as part of What's Up. Join us next time as we celebrate Mars Exploration Rover Spirit's one-year anniversary on the Red Planet. That's one Earth year, by the way.

Have a great week, everyone.