Planetary Radio: Space Exploration, Astronomy and Science - Big Eye in the Martian Sky: Mars Reconnaissance Orbiter Project Scientist Rich Zurek

Episode Date: May 29, 2006

Mars Reconnaissance Orbiter Project Scientist Rich Zurek returns with an update on the craft now orbiting Mars.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

A big eye in the Martian sky, 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. The Mars Reconnaissance Orbiter is slowly settling into an orbit that will put its big camera just 300 kilometers above the surface. Project scientist Rich Zurek returns to our microphones with an update on the spacecraft's

health and the great gobs of data it has already begun to send us. Later, it's giant stars and interstellar dryer lint on What's Up with Bruce Betts, along with the new space trivia contest. Here's some space headlines. Columbus arrives in the new world this week, this time setting out not from Spain, but Germany. It's the European Space Agency's laboratory module for the International Space Station. After the space

shuttle carries Columbus to orbit, ISS astronauts will use it to conduct research in the life, physical, and material sciences. Here's a heads-up about a couple of stories on Emily Lakdawalla's blog. It happens that they're both Mars-based and both have gorgeous pictures. First is a Mars Odyssey image of Gale Crater that will knock your socks off. It's not just beautiful, it's loaded with evidence of past surface water. Then, from the European Space Agency, come artist renderings of ESA's own Mars rover. ExoMars is on track for a 2011 launch.

It resembles Spirit and Opportunity, but whoa, is Chrome making a comeback? Check it out at planetary.org. Now, we haven't quite been taken over by the Martians. Here's Emily to explain just how miraculous the Huygens probe was. I'll be right back with Rich Zurek. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, why didn't they send a better camera on Huygens to Titan,

and why didn't they plan to take more than one picture of the surface? It's very important to remember that Huygens was the first probe ever sent to the surface of anything in the outer solar system, a surface about which we knew very little. Before the mission, there just wasn't enough known about Titan to predict whether Huygens could survive the entire descent, and if it did, whether it could survive landing. Any number of unknowns could have killed Huygens. Colder than expected temperatures, unexpected wind patterns, a landing on a steep slope, or an excessively rocky surface.

Therefore, mission planners had to make sure that all the data from six instruments was returned live as it was captured, so that the mysteries of Titan would pose the least possible danger to the volume of data that the little probe returned. Given those constraints, Huygens performed spectacularly. No other spacecraft sent beyond the moon has returned more than three images during a descent to the surface. Huygens returned hundreds, and the images from the surface were an unexpected bonus. What can we learn from those? Stay tuned to Planetary Radio to find out. Rich Zurek arrived at the Jet Propulsion Laboratory in the year Viking 1 and 2 landed on Mars.

Three decades later, he is the project scientist for the biggest eye ever sent to another celestial body. The so-called high-rise instrument on the Mars Reconnaissance Orbiter would be able to pick out a good-sized beach ball anywhere on the red planet's surface. And the pictures have already begun arriving. Which I found it hard to believe when I checked that we haven't talked since September of 2005, and a heck of a lot has happened with MRO since then. First of all, congratulations. Well, thank you.

Yes, back in September, we had just launched. We were only 30 days out. We had just turned on our instruments, and since then, a whole lot of things have happened. Yeah, the primary one, I would think, being you're in orbit around Mars. And that's not a small thing. We've had difficulty with our past attempts. You know, we've had many successes, but we've also lost a couple at that very critical junction. Yeah. But you're there. It's not the orbit that you're going to end up in. In spite of this, you're already getting great images.

That's right. When we went into orbit around Mars, we used our six thrusters to break it slowly enough that we could go into orbit. However, we went into a very elliptical, egg-shaped orbit where we're 40,000 kilometers away at the farthest point and only 400 kilometers away at the closer point. That's not a very good orbit to do our imaging from eventually at Mars. And what we have to do is to turn that very elliptical orbit into a nice circular orbit. And the way we do that is something we call aerobraking. Aerobraking, not that many years ago, was such a controversial thing.

Will, can we even control a spacecraft and make this work? Now, you guys are doing it for hundreds of orbits? That's correct. In fact, this will be the third time that we are aerobraking a spacecraft in the atmosphere of Mars. So we've had a lot of experience from our previous ones. Each spacecraft's a little different, though. What you do in aerobraking is you dip your spacecraft into the atmosphere at the closest approach point and the friction

with the solar arrays and with the high gain antenna, we use the backside so we don't know, slows you down just enough that when you climb back out, you don't go as far away from the planet as you had been on the previous pass. You do that 540 times

and you get down to where that farthest approach is now at 400 kilometers, and now you're ready to let your propulsion system go the rest of the way. So now, then you fire your engine, and you go into, what, about a 300-mile orbit? That's correct. And so what we'll do is we'll go into that 300-kilometer orbit, and someone could ask, well, you know, why take all this time and go to all this trouble to aerobrake? It saves us over 500 kilograms of fuel. That's over 1,000 pounds. And by comparison, our payload is less than 200 kilograms.

So you get a tremendous advantage by doing aerobraking, but it takes time. Is that going to be used at all for station keeping or steering the spacecraft in the future, or is that done by smaller thrusters? Right now, we'll use the small thrusters to do what we call orbit trim maneuvers or maintenance maneuvers once we're in orbit close down around the planet. Right now, we only use a very small amount of fuel on each of these 540 aero passes, only about 10 grams on each pass. And that is just to orient it, make sure we go in with the solar arrays protected, 540 aero pass is only about 10 grams on each pass.

And that is just to orient it, make sure we go in with the solar arrays protected, with the good side pointed out away from the flow, and to make sure our spacecraft's kind of aimed right as it goes into and has friction with the atmosphere. That's the closest approach to the planet, of course. And so you do end up, though, in a pretty much circular orbit eventually and, of course, a polar orbit, as you will want in any spacecraft that's going to take lots of pictures. The reason for a polar orbit, of course, is so we can see any place on the planet. If you're in a polar orbit, then the planet turning under you lets you see any place on the planet.

Our altitude for this orbit is lower than our present two orbiters there, the Mars Global Surveyor and Odyssey spacecraft. And that's because we want to increase the resolution, our ability to see detail down on the surface of the planet. The closer you are, the better that detail. Sure. And yet you've already got, by far, the best camera that has ever been on a spacecraft,

in addition to all the other instruments. But, you know, remind us, talk a little bit about HiRISE for those who don't remember. What we're trying to do is to see things at Mars at greater detail than we've ever seen before. That means you've got to have a camera that can zoom in, so to speak, and give you that detail. HiRISE is actually 14 digital cameras spread across the focal plane. We put them all together so that it sort of forms a line array 20,000 pixels across. Now, each of those pixels projected onto Mars once we're in that final polar low-altitude orbit is only 30 centimeters across.

That's a foot. So each pixel projected on the planet, about a foot across. That means you can start to resolve things that are about a yard across because you need two or three pixels to do that. And because we have so many of those pixels in the camera, though, we're still seeing across six kilometers of Mars as we move along in any given picture. The biggest picture it can take, by the way, is 28 gigabits worth of information. And that's when all 14 of those CCDs, those little digital cameras, are pumping away.

How does that compare with what is already there? Well, essentially, that's a factor of five better than the resolutions that we're able to achieve with our current best cameras at the planet. Now, we've also learned with some of the older missions to use them in a little more clever way. In fact, we do something where we actually pitch the spacecraft over some of the older planets, our spacecraft, and that slows down the ground track so that you can get more resolution as you fly. But unfortunately, it only improves it in that down track direction. Your cross track is still the same as it was before. That's five times more coarse than what we'll be able to do with

high rise. The other thing about high rise is it can take a large area. And that's important because you don't want a high resolution kind of postage stamp out there on the surface that you go, what's that at the edge? What is this thing? Is this part of a bigger system? Is it a crater wall? Is it a mountain range? What am I looking at? And HiRISE helps us do that with that 6-kilometer swath as we fly along. It's not quite enough, though, so we have another camera. And that other camera has a swath that's 5 times that, 30 kilometers across, 6 meters per pixel.

Now, that's 20 times more coarse than the high-rise, but it gives you that context. And then you can take the high-rise image right in the center of it, and you know what's around it, but you're looking at this great detail at that one place. And that's why you call it the context camera? That's why we call it the context camera, and that's why it's the high-resolution science imaging experiment. You were presenting some slides at the recent ISDC conference where you were comparing some images taken by Mars Reconnaissance Orbiter at this orbit,

which is not even close to where you're going to be, and comparing them to Mars Global Surveyor, and you're already getting some very comparable resolutions, I guess. We took advantage of the fact that we had a little time after we got into orbit around Mars, but before we started aerobraking, and we wanted to check out. We want to see if our cameras are working. And we also wanted to get a head start on the kind of processing that we'd have to do in the images. Spacecraft motion, can we point the spacecraft the way we want?

So we did this little experiment right there at the images. Spacecraft motion, can we point the spacecraft the way we want? So we did this little experiment right there at the beginning. Now, because we're in a very elliptical orbit, not our nice, low-altitude, circular orbit, we had to take those images when we were ten times further away from the planet than we will be once we're in our science orbit. So the resolution, naturally, is ten times

worse than it is, and we already were seeing great things. The cameras are in focus. They're working very well. And that was great to see all of that information and that data. We're working out a couple of problems that we did see. We are at such high resolution that our spacecraft has to turn the instruments ever so slightly to compensate

for the rotation of the planet, even while we're taking them in just over short periods, a few seconds. And what that means is, we were testing out that algorithm for the first time. We need a little fine-tuning, but no problems there. That's why you do it early. Learning to use your camera. That's right. A little bit like anybody has to when they take snapshots.

It's like when you get that new one and you want to take it out in the field and you want to take a couple of shots, make sure you know how to set the controls, how to take the images, how to use the information that you get back. Yeah, especially moving subjects. We all know that's maybe the toughest thing to do. Exactly. Back with more from Mars Reconnaissance Orbiter Project Scientist Rich Zurek right after this quick break. Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets.

We sponsor the search for life on other worlds. And we're building the first ever solar sail. We didn't just build it. We attempted to put that first solar sail in orbit. And we're going to try again. You can read about all our exciting projects and get the latest space exploration news in depth at the Society's exciting and informative website, planetary.org.

You can also preview our full-color magazine, The Planetary Report. It's just one of our many member benefits. Want to learn more? Call us at 1-877-PLANETS. That's toll-free, 1-877-752-6387. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Rich Zurek is project scientist for the Mars Reconnaissance Orbiter.

That spacecraft is very gradually moving into a circular orbit above the red planet, from which it will grab ultra-high-res images, showing us objects just a meter across. But MRO has much more in store. You've got a lot of other instruments. You're starting to get data back from those as well. That's right. One of the things we did is with an instrument that we actually used to take the temperature of the atmosphere, tell us how hot or how cold it is and how dusty.

We did this at this point because if the other spacecraft that are currently at Mars, they're monitoring the atmosphere for us so that as we aerobrake, we know what's going on down at the lower altitudes. The upper atmosphere is kind of the tail that gets wagged by this much lower atmosphere.

That's where all the mass is, just like on Earth. So when we're aerobraking at altitudes that are up over 60 miles above the surface of the planet, you have to watch what's going down below. Mars has these marvelous things, dust storms and other things. Sometimes that heats the atmosphere up. The atmosphere expands. The density at any given altitude gets bigger.

If we didn't know that, we might overheat the spacecraft as we were flying through at an altitude. So we wanted to keep an eye on it. It's fascinating to think that it is already so important for us to be able to monitor Martian weather. That's right. It's part of, you have to define the environment so that you can design the vehicle and make sure it's safe. And yes, you can always over-design a vehicle and make sure it's safe no matter what happens. That's a very expensive proposition. We take advantage of our knowledge here, and our spacecraft's trying to add to that. However, just to be safe, we wanted to check out that in case those other orbiters weren't able to support us, we could use our own instrument

to take a look at Mars and see what was happening down there below. What other kinds of data are you getting back in this very early phase? Well, right now our instruments are off. We did take images with all three of our cameras, the context camera that we talked about, high rise, and also our weather camera.