Planetary Radio: Space Exploration, Astronomy and Science - Closing In On An Interplanetary Mystery: The Pioneer Anomaly

Episode Date: February 6, 2006

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Closing in on an interplanetary mystery, this week on Planetary Radio. Hi everyone, I'm Matt Kaplan. Welcome to Public Radio's travel show that takes you to the final frontier, and sometimes where no physicist has gone before. Why aren't the Pioneer spacecraft where they're supposed to be? Is there an overlooked prosaic cause, or is something wrong with our understanding of the laws of the universe? An update this week on the Pioneer anomaly from JPL scientist John Anderson.

Later, Bruce Betts will provide another opportunity to win the new Explorer's Guide to Mars poster as he sizes up the current night sky and other happenings around the solar system. In our news this week, some astronomers are sizing down 2003 UB313, the Kuiper Belt object affectionately, though not officially, called Xena by some. You'll remember Mike Brown of Caltech telling us he believes the faraway sphere was substantially larger than Pluto. A lot more data has been gathered since then, enough to make Mike decide at one point that his planet or planetoid or object,

take your pick of terms, might be only barely larger than Pluto. But hold the phone. A German team says Xena is much larger than Pluto. But hold the phone. A German team says Zena is much larger than Pluto. There's an article at Planetary.org that may help sort out some of the confusion. And the absolute latest is in Emily Lakdawalla's blog, where she says Mike now accepts the German data. Also at Planetary.org is a detailed update on Spirit and Opportunity. They keep going and going and going.

Be sure to check out the bird's-eye self-portrait of Spirit, taken as it continues to make its way down Husband Hill, headed toward Home Plate. Love those Martian place names. Finally, a question. Where did your fourth or fifth grade class go on field trips? The zoo? Maybe a museum? How about Saturn? Kids from Shirley Avenue Elementary School in Reseda, California,

were given ten days to study three targeting options for the Cassini spacecraft's camera. They decided to go for an image of Saturn's rings. JPL engineers made it so, and now the young explorers have their snapshot from a billion miles away. Other schools will get similar opportunities soon. Your opportunity to explore the Kuiper Belt with Emily has just arrived. I'll be back with John Anderson of JPL in a minute. Hi, I'm Emily Lakdawalla with questions and answers.

A listener asked, Have they identified yet which Kuiper Belt objects New Horizons will fly by? Can they go to the 10th planet? No, they haven't, and no, they can't. New Horizons is intended to study both the Pluto system and perhaps two or three other Kuiper Belt objects, but New Horizons will not have a huge number to choose from. Once New Horizons passes Pluto, it will have only a very limited ability to change its course, which means that it can only study Kuiper Belt objects that happen to lie within a roughly one degree cone around its path. Unfortunately, none of the more famous Kuiper Belt objects that happen to lie within a roughly one-degree cone around its path.

Unfortunately, none of the more famous Kuiper Belt objects, including 2003 UB313, Quawar, Chaos, Ixion, or Varuna, will lie within that cone. The mission planners do want to visit a reasonably large object, bigger than 50 kilometers in diameter, and hope to find one that has a different color from Pluto, so that it may represent a different kind of evolutionary history. But no Kuiper Belt object has yet been identified that fits the mission's criteria. Why not? Stay tuned to Planetary Radio to find out. From the time of Isaac Newton, we've been able to predict the movements of stars, planets, and smaller bodies with a high degree of accuracy. An even higher degree came with the arrival of Albert Einstein and relativity. So why are a couple of ancient spacecraft bucking the system? Pioneers 10 and 11 were launched in 1972 and 1973.

Pioneers 10 and 11 were launched in 1972 and 1973. Over the following decades, as they headed toward interstellar space, they sent back gigabytes of data, our first on-the-scene reports from the outer reaches of the solar system. But that data also led to the mystery called the Pioneer Anomaly. A handful of engineers and scientists at the Jet Propulsion Lab decided to re-examine that data and try to figure out what was going on. First, though, they had to recover the data from obsolete computer tapes, some of which were originally thought to have been lost or destroyed. A lot of progress has been made since we talked to Slava Turashev and John Anderson

months ago. We decided to call on Anderson, a senior research scientist, for an update. John, it's been nearly half a year since we talked to you and Slava about the Pioneer anomaly, and I guess there have been some significant developments since then. We wanted to check in with you, get an update. I guess the biggest development is how much data has been recovered. Yeah, that's right. Time flies, but we have made a lot of progress in the last six months, and I'm very pleased with that.

You know, the Planetary Society, thanks to them and their membership and their generous donations, we were able to recover the data, and we basically have it all recovered at this point after this six-month interval. And when you say all the data, you're talking about, what is it, several years of data from both spacecraft. I think you have much more from one than the other. Yeah, that's right. It's Pioneer 10 that we analyzed from 1987 to 1998.

That was about 11 1⁄2 years of data. Now we've got about a 30-year time span for both missions, although Pioneer 11 ended earlier in 1990, and Pioneer 10 is still going as far as we know. We got some data from it in 2002. So there's a lot of years for Pioneer 10 and even Pioneer 11. You said Pioneer 10 is still going, and that's one of the most interesting things I read. It's at the end of an update by your colleagues Slava Turashev and Victor Toth, and they mentioned that I guess there's some consideration being given to getting the Deep Space Network

to make one more attempt to listen in for Pioneer 10? Yes. We're working with the DSN engineers to see if we can make that happen. You know, the antenna has to point at the Earth. It's a parabolic antenna, very much like the antennas that you use for satellite TV, only this one's larger. And that beams the radiation on a very narrow beam to the Earth. The larger the antenna, the narrower the beam.

So we've got a very narrow beam coming out of that antenna on the spacecraft, and the Earth has to be practically right in the center of that beam in order for us to be able to track it. And that happens. The geometry is just right about, oh, March 2nd, March 3rd, somewhere in there, where the antenna will be off point from the Earth, as we put it, by maybe three-tenths of a degree, which is about the best we can do. We can't get any closer than that. So this is our last chance to get one more track from Pioneer 10, and that would be a March 2006 track, if we can pull it off.

and that would be a March 2006 track if we can pull it off. Does the Deep Space Network, do you have to send a signal to Pioneer 10 to tell it to answer, or is it just pinging us on a continuous basis? No, absolutely. We have to send an uplink. We have to activate the radio on board the spacecraft with an uplink. It's not sending out anything otherwise. So the only way we can communicate with Pioneer now is with an uplink from, well, in this case we'd use Goldstone, and then we get the signal back a little over a day later, about 25 hours later.

So you uplink to the spacecraft one day, then you come back the next day, basically the same shift, and you listen to it. And then we see how much it's stopper shift to get our data. More than a light day away, as opposed, of course, to a light year. Do you have off the top of your head an idea of how far that is in miles or kilometers? Well, I know it's 90 AU. That's what we'd be able to get here in 2006. And AU is about 93 million miles, as I remember.

So we're talking about 9.3 billion miles, just doing it off the top of my head. Good calculation there. I think that's right. On AU being, I know I don't have to say this to most of our very sophisticated audience, but the mean distance between the Earth and the sun. of our very sophisticated audience, but the mean distance between the Earth and the Sun. The outermost planets now are 30 AU, Pluto, and some of the newly discovered planets that we have out there now,

they're all in that region around 30. Astronomical units are AU, which is the distance between the Earth and the Sun. And now the spacecraft, Pioneer 10, is at 90 AU, about three times the distance of Pluto and Neptune. At 90 AU, this thing was launched. I mean, Richard Nixon was president when it was launched. How much hope do you really have of being able to hear that still small voice of Pioneer 10? You know, it is really small. It transmits at 8 watts.

Imagine how much light that would give you in a room. 8 watts, but it's beamed. I would give it about a 50-50 chance. There's enough of a chance that we're encouraging the DSN to spend the money and pay the operators and give it a try, but it's iffy. So you do expect that that RTG that's generating electricity with that little bit of decaying plutonium in there, that it is still generating a little bit of power, a little bit of heat. It is.

It's delivering power to the bus, and we need about 23 watts to drive the radio transmitter, and then it's going to come out of the feed at about 8 watts. But there's still 23 watts of power there, or if there's a little less, we'll be transmitting a little less than 8 watts, which is also a possibility. But doing the link calculations, it's not hopeless. You wouldn't just give it up and say this year we shouldn't try. It's moving away, though, at about 2.5 AU a year. So a year from now when it's at 92, 93 AU, that's really too far.

We wouldn't try it next year. Wow. Well, I'm glad the RTG has come up since that is, well, I guess they're called systematic or possible systematic sources that you guys are looking at as possibly explaining this anomaly, if indeed it's not some basic misunderstanding about the physical laws of the universe. You know, it's the only thing we can think of that would work at all would be if we've done some miscalculations on the thermal budget of the spacecraft somehow. We think that's unlikely because we did it pretty carefully for the papers we published, and other people looked at it as well.

The RTGs are way out on booms, which is what makes this experiment possible. Couldn't do it with other spacecraft. For example, Cassini, they're tapped in underneath the antenna, and it's radiating like crazy. There's just no way you can detect the Pioneer anomaly with the Cassini spacecraft. But the fact that they're out on booms and they're radiating into space and they're not radiating to the spacecraft, a very small amount of the energy coming out of the RTGs goes to the spacecraft.

In the calculations they've done in the past, it doesn't work. But we can't think of any other so-called systematic on board the spacecraft that could produce an acceleration anywhere near the Pioneer anomaly, and we can't even get that. We're off by a factor of six at least. We'll be back with JPL's John Anderson with more on the Pioneer Anomaly in just a minute. This is Buzz Aldrin.

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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. We continue our conversation with JPL Senior Research Scientist John Anderson about investigation of the so-called Pioneer Anomaly. Just as critical to their work as the data received from the Pioneer probes, is knowledge of the exact positions of the giant radio antennas that make up the Deep Space Network, which spent three decades

communicating with the spacecraft. In a way, it's a statistic or a figure that is just as incredible as thinking of this eight-watt transmitter being received from so far away, and that is that you're now able to figure the locations of these deep space network antennas to within a centimeter at the time they receive signals from Pioneer 10? Yeah, that's right. We can do that now. We're using the Pioneer 10s to do that. It's just the interferometry systems we have, radio interferometry. We know the locations of those DSN stations,

each one of the stations within the complex, to the order of a centimeter. That's about a factor of 100 improvements since we launched the Pioneers. They were good to about a meter at that point. But that technology has really improved over the years. You're right. We've got it down to about a centimeter now. It sounds like science fiction. That's a small length, isn't it?

You can look at a metric ruler and see that centimeter, and imagine shifting the station back and forth by that amount. That's the kind of accuracy we have on the location. Well, I can see why that kind of accuracy would be extremely useful to you as you now begin to analyze this 30 years of data to figure out what's going on with Pioneer. It's very useful, and the data is in the JPL navigation system, so it's all there, those very accurate station locations. And the stations do move when you get into that level of accuracy. There's a number of factors that will cause them

to move. And we have all that. We have polynomial tables that tell us exactly where the stations are as a function of time. And all that will be filtered into our data analysis. that will be filtered into our data analysis. What do you hope to learn from the data? I mean, I read several points in this article at planetary.org. I guess there's some acceleration taking place. You want to know where that points. Yeah, we would like to know where it's pointing. And the analysis that we published, we couldn't distinguish, for example,

whether it was pointing at the Earth, that acceleration, or whether it was pointing at the Sun. We say toward the Sun because even if it's pointing at the Earth, it varies back and forth over a year. So on the average, it does point at the Sun. But if we can get enough accuracy in the pointing angle, and it's really pointing at the Earth, we should be able to track that now with all the data we have and all the accuracy and station locations, as you pointed out. We'd like to actually see if it's pointing right at the sun, which would indicate that it's probably new physics, or is it pointing at the Earth, which might indicate that it's some systematic that we haven't uncovered yet or something in the tracking link that we haven't uncovered.

It's very important. It's a very small angle between the Earth and the sun, and the fact is if we go farther back in time, which we can do now with the new recovered data, that angle gets larger because you're closer to the sun, so the angle between the Earth and the sun is larger. So if we're going back before the 1987 data that we originally analyzed, we'll be able to see if that pointing is really at the sun or if it's at the Earth.

What would it tell you, what would it indicate to you, if the change in acceleration was either increasing or decreasing, or if it was stable. Do those suggest things to you? Well, it does suggest things. If it's stable, it's pretty hard to think in terms of a systematic, because we've narrowed it down to thermal. I can't think of anything else.

Of course, maybe we haven't thought of it. But the only thing we can think of that could be causing it outside of some new physical principle would be that, the thermal. And the thermal, that's a smaller factor as time goes by, right? Yeah, that's right, because the RTGs, their plutonium, the plutonium decays, the junctions that convert the heat into electricity deteriorate with age, so that over time the power from the system should be going down, and we should see that in the Pioneer anomaly if it's being caused by the thermal. But you're not there yet. I mean, you now have the data. Now the analysis begins?

The analysis begins. We have the data all archived. We're not going to be able to find any more. the data all archived, we're not going to be able to find any more. It's on media of some sort that Slava is leading that with Yunus Lau on computer disks. And now it's just a matter of getting that organized and starting the data analysis. Do you have any idea, as we are almost out of time, how long it might take before you reach some conclusions, or is that totally unfair? Yeah, it is, because we're in an unknown region, aren't we, of data analysis. Nobody's ever done this before.

That's right. It's completely new. We don't know what we're getting into, so we're going to have to use a lot of ingenuity by the entire team to pull it off. But I would say that within six months to a year, we'll have something new to report. Well, John, we hope that even before that, that those big antennas that are part of the Deep Space Network will point one last time out to where we know Pioneer 10 is lurking,

and that you get that additional data point you'd like to have. Yeah, we'd like to get that one. So I hope so, too. We'll keep working with the engineers to see if we can make that happen. It's just about exactly a month from now. John, we will definitely check back with you if not then. Certainly when you have more to report as you begin to look at this, what, I guess it's about 35 gigabytes of data, but a lot of that you'll be able to compress. Yeah, it's an enormous amount of data in that region, 40 gigabytes of data, but a lot of that you'll be able to compress. Yeah, it's an enormous amount of data in that region,

you know, 40 gigabytes or so for one spacecraft. So, yeah, it's a lot of data, but we'll get into it, and hopefully we can compress it a bit so we can distribute it publicly, perhaps in a smaller storage capacity. Well, good luck to you, and please give our best wishes to your associates in this project, the Pioneer Anomaly Project. We look forward to those results, whether it turns out to be systematic or whether we need to rewrite the laws of the universe.

Yeah, thank you. John Anderson is a senior research scientist at the Jet Propulsion Laboratory, and he is one of this team that is painstakingly recovering data. Now it is recovered from Pioneers 10 and 11, and now we'll begin to analyze the Pioneer anomaly. We will be back with the always anomalous Bruce Betts in this week's edition of What's Up, right after a return visit from Emily.

I'm Emily Lakdawalla, back with Q&A. There are several excellent reasons for the New Horizons planners to delay their choice of Kuiper Belt targets. First of all, which bodies would be in reach of New Horizons depended to a great extent on the spacecraft's launch date. But the most important reason is that the Kuiper Belt objects that New Horizons will study have very likely not been discovered yet. Only about a thousand of them are now recognized and tracked. In fact, very few are known to lie in orbits near New Horizons' path, because New Horizons happens to be headed toward the galactic center. Astronomers have avoided searching for objects there

because the density of the star field in that part of the sky makes it challenging to find them. But several new observatories and experiments are being developed that will multiply the number of known objects by a factor of 10 or more by the time New Horizons arrives at Pluto. For example, the Pan-STARRS Observatory under construction by the University of Hawaii is a wide-field imager that will come online in 2009. It is estimated that Pan-STARRS could discover 20,000 Kuiper Belt objects over

its operational lifetime, giving New Horizons lots of options. 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. Dr. Bruce Betts is here, the Director of Projects for the Planetary Society, and our cohort on this wonderful examination of the night sky and other things going on in our universe. How's that? Right off the top of my head. That was really impressive. I'm looking forward to cohorting with you today. Well, cohort. Cohort away.

All right, I'll cohort. Oh, yeah, yeah, yeah. Or I'll just tell people what's up in the night sky. Do it by yourself. Are you hoarding? Up in the night sky, we've got Saturn in the evening looking very nice, rising a little before sunset. So you can see it already up in the east at sunset and appearing high in the east by the early to mid-evening, looking like kind of yellowish if you're trying to pick it out, and below Castor and Pollux, the bright twin stars of Gemini. You can still pick up Mars in the early evening, high in the south or southwest.

It continues to fade but looking orangish, so look for Saturn yellow, Mars orange, and Jupiter just looking bright white in the pre-dawn sky, very high, continues to fade, but looking orangish. So look for Saturn yellow, Mars orange. And Jupiter just looking bright white in the pre-dawn sky, very high in the sky, the brightest star-like object up there. So there you go. There's your sky. Let's move on to this week in space history. It is the fifth anniversary. The fifth anniversary.

Someone was eviscerated? By a cohort. The fifth anniversary of the near landing on the asteroid Eros. This was the spacecraft that was designed and successfully orbited for the first time an asteroid, in this case the asteroid Eros. And at the end of its lifetime, they decided to try to set it down on the surface, even though it was by no means designed as a lander, and darn if it didn't work. So they actually landed on the surface, and I have a picture from down on the surface,

and they got all sorts of great data from some of the other instruments, like the gamma ray spectrometer, that really do well being up close and personal. So an amazing accomplishment accomplishment five years ago. On to random space facts! This one's basic, but I like it. Venus has the slowest rotation rate of any planet in the solar system. And since these are kind of basic, I'm going to give three of them. And it rotates retrograde.

And the third one, which is really a corollary of the second one, it means the sun rises in the west. And slower than Mercury? Really, really slowly. Slower than Mercury. Incredibly slow. Which for a long time, they didn't think rotated at all, right? I mean, when I was a kid, they said Mercury didn't rotate.

Yeah, they were wrong. Yes, no, that was the common belief was that Mercury was in a synchronous locked rotation around the Sun, just like our Moon is around the Earth, always facing the same side, and it wasn't until some, I believe, radar observations in the 60s, I think, you're testing my planetary history, where people realized, no, it's actually in this other funky resonance, a two to three resonance between its orbital period and the length of its day, basically. Which leaves unasked why Venus is rotating retrograde. We don't have time for that.

I'll have to ask you another time about that. We'll wait a year. All right. We'll check back. A Venusian year? Maybe it'll be shorter. It'll be shorter that way. All right.

Moving right along to our trivia contest. We asked you about the, what were the names, what are the names, of the two strange Saturnian moons that actually switch orbits about every four years, and they've just completed doing that. One goes closer in to Saturn while the other goes farther apart, and then they switch again, doing a strange gravitational dance. How'd we do, Matt? A lot of entries this time around.

Almost everybody got it right. I guess they might have checked the website, planetary.org, where there was a nice article about this. I think Emily, Emily Laktawalla, wrote that. That is indeed true, and if you go there, you can see all sorts of pretty pictures and learn all about it. Want to know about our winner? Oh, desperately.

Our winner is a listener to KIOS-FM in Omaha, Nebraska, one of our, I think, one of our newer affiliates out there. You know, we have about 60 radio stations now that are running planetary radio at one time or another, but that's where he hears us. He is Mick Mesbarger, or Mesbarger, don't know which. And he lives, what a coincidence, in Omaha. Really? And Mick indeed got it right. He said that those two moons are Janus and Epimetheus. Did I get it right? I was letting you pronounce it, so I didn't have to.

Epimetheus. Epimetheus, there you go. It's kind of fun to say. Yeah. Epimetheus. Epimetheus. There you go. It's kind of fun to say. Yeah. Epimetheus. Epimetheus. So Mick is going to get not a T-shirt, but a poster. A beautiful Explorer's Guide to Mars poster to hang on his wall in Omaha, Nebraska.

Yep. Coolness. And if you want to win a beautiful Explorer's Guide to Mars poster, recently produced, giving all sorts of pretty pictures and information and map about Mars. Then answer the following question. This one is a fairly simple one. If you remember it, you don't even have to look it up. What was the giant storm half the size of Jupiter's red spot on Neptune called that was discovered at the same time of Voyager 2?

Or at the time of Voyager 2, basically. That might take a little digging. Okay, that's good. It depends on what other people remember. What was that storm called? And let us know. What's been interesting about it is it vanished over time once we were able to actually see Neptune again with Hubble

as opposed to the red spot on Jupiter that's been around for 400 years. How did they enter? Go to planetary.org slash radio and find out how to enter our beautiful contest. And do so by Monday, February 13 at 2 p.m. Pacific time. Monday the 13th, 2 p.m. Pacific time. Be there or be square. So everybody go out there, look up in the night sky, and think about balls flying around and hitting things.

Thank you, and good night. I think one just fell, if you heard that. It's Bruce Fetz. He's the Director of Projects for the Planetary Society, and he joins us every week here for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California. Join us again next time, and have a great week, everyone. Thank you.