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IRA FLATOW, host:

For the rest of the hour, the anniversary of a pretty impressive achievement in the already impressive field of robotic space exploration with recent mission to Mars, Saturn, Jupiter, and even a comet. But the granddaddy of them all has to be a mission that turned 30 this week, the Voyager mission. I could to say Voyager missions because there are actually two Voyager spacecraft.

Thirty years ago, Voyager II was launched on its tour through the solar system with the destination of Jupiter and Saturn. And then two weeks later, Voyager I followed. I know, it's two and one. We'll talk about why did it that way. The Voyagers have been proven to be such successful missions, sending back such detailed photos of the storms of Jupiter, the rings of Saturn, that they set the standard for all planetary space missions that followed.

The missions have even been enshrined in popular culture, even in Hollywood as the star of the first "Star Trek" movie. And believe it or not, both Voyagers spacecraft are still going in the far reaches of the solar system, still sending back data to a team of scientists and engineers at NASA's Jet Propulsion Laboratory. In fact, Voyager I holds the record for the most distant human-made object. It's currently about 10 billion miles from the sun.

Joining us now are two of the engineers who made it possible. Voyager's project manager at the time of the launch and Voyager's project manager today. Also with us is a space historian who I'm sure will fix Voyager's place in the history of space exploration.

If you'd like to get in on the talk about Voyager, our number is 1-800-989-8255, 1-800-989-TALK.

John Casani was the project manager for Voyager from 1975 to 1977. Now, he's special assistant to the director of NASA's Jet Propulsion Laboratory in Pasadena. And he joins us today from his office there. Welcome to the program.

Dr. JOHN CASANI (Former Project Manager, Voyager Mission; Special Assistant to the Director, Jet Propulsion Laboratory): Thank you. It's a pleasure to be here.

FLATOW: You're welcome.

Ed Massey is the current project manager for the Voyager mission at NASA's Jet Propulsion Lab in Pasadena. And he joins today from his office there. Welcome to the program.

Mr. ED MASSEY (Project Manager, Voyager Mission): Thank you. I'm also glad to participate.

FLATOW: You're welcome.

Howard McCurdy is a space historian and co-author of "Robots in Space: Technology, Evolution, and Interplanetary Travel" due out later this year. He's a professor in the school of public affairs at the American University in Washington. And he joins us from WAMU right there on the campus. Welcome to SCIENCE FRIDAY, Dr. McCurdy.

Dr. HOWARD McCURDY (Space Historian; Co-Author, "Robots in Space: Technology, Evolution, and Interplanetary Travel"): It's an honor to participate. Thank you.

FLATOW: Ed, tell us about those days. What made that mission such an incredibly - such an incredible mission. I'll ask all of you. John, you could talk about it first, because you were right there also.

Dr. CASANI: Okay. Well, thank you. I think the thing that made it so incredible is that for the very first time in space exploration, we had images coming back from, you know, from the outer region of the solar system, from beyond Mars, from Jupiter and then ultimately Saturn, Uranus and Neptune.

And these pictures were of high - such high quality and they came in so fast, and they were so revealing in terms of showing us something about the moons of Jupiter that, I think, really not even a scientist had anticipated. I think most of us were thinking we're going to see more moon-like - Earth moon-like objects.

FLATOW: Right.

Dr. CASANI: But the color, the detail, the dynamics, the difference among them all was so tremendous, and then on to Saturn and likewise beyond. So it gave people not only a view of - or an image of what the far reaches of our own solar system were, but it wetted, I think, the appetites of both the lay people and the science communities to see even more.

FLATOW: Yeah.

Dr. CASANI: It opened up the whole solar system for exploration.

FLATOW: You know I remember being at JPL in the newsroom as those photos were coming in, and it reminded me - I didn't think any scientists or missions - project mission specialists or whatever could be as excited about the moon missions ever again, but these people were turning just as blue.

Dr. CASANI: Yeah, that was true. I remember that as well.

FLATOW: Ed Massey, you weren't there, but you're current project manager for the Voyager missions at NASA. It's hard to believe you still have a job. I mean, that Voyager is still working.

Mr. MASSEY: Yes, I guess we have to attribute that to the good work done by John and his people. You know, they built a very robust spacecraft with lots of backups. And even though some of those backups aren't used today now, these spacecraft is - are both still very healthy.

FLATOW: Where are they at the moment?

Mr. MASSEY: Voyager 1 is headed north toward interstellar space and is almost 10 billion miles away from the sun. Voyager 2 is headed south, and it's almost eight billion miles away.

FLATOW: How were you able to keep track - how were you able to listen in on them? I mean, don't they have tiny, little transmitters on them?

Mr. MASSEY: Yeah, the transmitter on the spacecraft is about 20 watts or so. And, of course, with the distance and the signal it - the signal strength diminishes as they get further away. But we have these huge antennas from the Deep Space Network, 70 meters and 34 meters, and very sensitive receivers that are able to capture even the smallest signal and basically give us very good data.

FLATOW: Are they - how many instruments on each one are still working?

Mr. MASSEY: Five on each…

FLATOW: Okay.

Mr. MASSEY: …even though they are slightly different on each spacecraft.

FLATOW: Did you - is the fact that the technology for listening has been upgraded over the years, is that what allows us to keep track of them?

Mr. MASSEY: That helps. For instance, when Voyagers were launched, the largest antenna was 64 meters and that was upgraded during the planetary encounters to 70 meters. And over the years, of course, the receivers have gotten more sensitive as well.

FLATOW: Talking about Voyager on the 30th anniversary of their launches this hour on TALK OF THE NATION: SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

Let's bring in Howard McCurdy, who's a space historian. How do you view this, Howard? What was the - set the stage for us, where does Voyager fit it into the larger picture of space exploration?

Dr. McCURDY: In many ways, Voyager defined the nature of the race between humans and robots in space in the latter part of the 20th century. What has to be remembered is that on Christmas Eve 1971, Voyager was cancelled. It was cancelled in the form of Grand Tour, a robotic mission that was designed to visit five planets.

Instead, later in 1972, NASA was given permission to proceed to Jupiter and Saturn with two spacecrafts. That became the Voyager project. They were given one-third of the budget that was designed for Grand Tour. And out of that budget, they fashioned two spacecraft and, in fact, accomplished four-fifths of the objective of the Grand Tour.

So it's a rather remarkable accomplishment that they were able to do so much with what, in effect, was so little after the mission that was - that became Voyager was actually canceled. So I think it defines the nature of the race between humans and robots. We could talk a little bit more about that, but about the same time, President Richard Nixon approved the space shuttle program, which had similar ambitions. The Voyager program far exceeded expectations and the shuttle program, well, I think we know what happened to that. It did not meet its original expectations.

FLATOW: John Casani, so, in effect, you had to outsmart the original planners of this.

Dr. CASANI: Well, I guess you can put it that way. I don't know, you know, I don't know that we can take that credit in that dimension exactly. I think we were very much aware of the tremendous engineering challenge that the Voyager mission presented to us. Keep in mind the spacecraft, up until that time, were generally, you know, interplanetary spacecraft. There was Pioneer 10 and 11, which were launched in '73, but they're very, very simple spacecrafts, simple spinner spacecraft.

These two spacecrafts were complex and we realized the challenge of having had designed them to guarantee mission lifetime. And we did everything that was within our technology at that time, including hardware liability parts, the use of redundancy, the use of both functional and block redundancy. In other words, putting identical pieces of equipment on to back one another up, but also having thought about other functional paths, the use of different pieces of hardware on the spacecraft that could accomplish the same objective. All with the idea, really, guaranteeing that these two missions would last as long as they did.

FLATOW: Mm-hmm.

Dr. CASANI: Now, the one thing that we did that maybe bordered on outsmarting, we realized early in the design process that there were some limitations to the spacecraft surviving or being able to function satisfactory beyond the orbit of Saturn even though the mission was only required to get to Saturn. For example, the sun sensors, we knew would not go the sensitivity of the sun sensors to the available sunlight at that point.

The mission was such that they would not work beyond - much beyond Saturn and so we put in amplifiers or other devices to guarantee that those sun sensors would continue to work beyond the orbit of Uranus and Neptune. And we did some other things in a way of redundancy, putting in extra memory and being able to configure that memory in different ways. Really the primary justification was that we would have some configurational complex capability if needed due to maybe a failure of some of the equipment.

But we also had in mind that that same configurational complexity could be used to extend the mission beyond Saturn. So maybe there's a little bit of outsmarting. I don't like to think of it that way, but what we did was just the very best we could within available technologies to make these machines last as long as possible.

FLATOW: We'll come back and talk more how those Voyagers compared to the current crop of robotic space exploration when we come back and talk more about the anniversary of the Voyager mission. So stay with us. We'll be right back after the short break.

I'm Ira Flatow. This is TALK OF THE NATION: SCIENCE FRIDAY from NPR News.

(Soundbite of music)

FLATOW: You're listening to TALK OF THE NATION: SCIENCE FRIDAY from NPR News.

I'm Ira Flatow talking about the 30th anniversary of the Voyager missions this hour with John Casani and Ed Massey of NASA's Jet Propulsion Laboratory. Howard McCurdy, author of "Robots in Space: Technology, Evolution, and Interplanetary Travel." Our number 1-800-989-8255.

Howard, what did we learn in the big picture from Voyager that changed the way perhaps our thoughts about human space travel in space?

Dr. McCURDY: I think that in the cultural realm, what Voyager did was to create an image of the solar system that was much more inhospitable to human life than we originally believed in the 1950s and 1960s, or even going back a hundred years where Mars was thought to be the abode of life by Percival Lowell and Venus was thought to be a primordial swamp, and Arthur Clarke was writing about Iapetus, a moon of Saturn that might be a cosmic beacon fashioned by extraterrestrials. And when we got out there, we found that it wasn't a place that humans could easily move about.

Remember the famous movie 2001 "A Space Odyssey," which came out in 1968, postulated that the only way to go to Jupiter and Saturn and really explore them was through this Discover 1 spacecraft with five astronauts, three in suspended animation. And what we found out was through the use of microelectronics, miniaturization, deep space networks and these fantastic technologies of the 21st century, we could actually build spacecraft that could do the work that was really relegated to human beings at the beginning of the space age.

FLATOW: Well, Arthur C. Clark got the moons of the Jupiter right, didn't he? I mean, that's where we're (unintelligible) the possibilities for life?

(Soundbite of laughter)

Dr. McCURDY: The book has it as the moons of Saturn; the movie has it as…

FLATOW: Right.

Dr. McCURDY: …the moons of Jupiter.

FLATOW: 1-800-989-8255 is our number. Let's go to the phones because there are lots of folks who would like to talk about the Voyager. Rachel(ph) from Tallahassee. Hi, welcome to SCIENCE FRIDAY.

RACHEL (Caller): Hi. Thanks for answering my question.

FLATOW: Go ahead.

RACHEL: Okay, we just wanted to know, how long is that delay from the time that Voyager sends data or information until the time that you get it?

Mr. MASSEY: Well, the time of the so-called round-trip light time is the amount of time it takes for us to send a signal to the spacecraft and then receive a response. Right now it's about 28 and a half hours for Voyager 1, and about 22 and a half hours for Voyager 2.

RACHEL: Okay. And what kind of signal is it?

Mr. MASSEY: The radio signal includes science data from the various instruments plus engineering data. And the science data are what we term as plasmas, waves and fields. We're looking at magnetic field intensity, speed of the solar wind, the composition of the solar wind, radio signals that are generated in the solar wind because of the energetic particles, high energy and low energy energetic particles.

FLATOW: Is it…

RACHEL: Okay.

FLATOW: Thanks for calling, Rachel.

RACHEL: All right. Thank you.

FLATOW: You're welcome. Is it a digital signal?

Mr. MASSEY: It is digital when it leaves the spacecraft, it's analog when it reach the ground, and then we convert it back to digital again.

FLATOW: There's something in between.

Mr. MASSEY: Yes. The signal as - when it is transmitted is analog.

FLATOW: It's analog in space?

Mr. MASSEY: Right.

FLATOW: And then it gets transferred to digital.

Mr. MASSEY: Right.

FLATOW: Where is it in relationship to leaving our social system?

Mr. MASSEY: That depends on how you define our solar system. If you define the solar system as the point where the sun no longer has an influence, that's halfway between here and the nearest star, we are quite a ways away. But in terms of being outside the area that's dominated by the sun, Voyager 1 has already crossed that termination shock; Voyager 2 is very close. But we have not reached interstellar space yet.

FLATOW: John Casani, there are no, I mean, no - how should I put it - there are no robotic spacecraft that match the old ones, are they now? I mean, we've got the farther, better cheaper versions and they don't seem to be - work as well as the older versions, do they?

Dr. CASANI: Well, I don't know if I would say that. We've got a lot of spacecraft in orbit at Mars right now, and none of them been there long as Voyager has been up. That's true. We have lost at least one of them. So - but, you know, the environment of an orbiting spacecraft is quite a bit different. It's going in and out of sunlight every day, there's thermal shocks and that sort of thing.

So it's probably a little bit of a harsher environment than very slowly changing steady state thermal environment that the Voyager 1 and 2 spacecraft are in. Also, the spacecraft as complex as Voyager 1 was it had, after all, you might know six computers that were arranged to operate the spacecraft, three pairs of two redundant computers each. Newer spacecrafts have taken a different approach. They generally - it combined all the functions into a single computer and maybe have one redundant version of that.

In some ways that's simpler and maybe cheaper, but there's also some robustness that, you know, that they sacrificed for that. I would say that there are - there's no other spacecraft operating today except for the Pioneer 10. How about those - let me ask, are they, Ed, are they - are either of the Pioneer 10/11 spacecrafts still working, I guess…

Mr. MASSEY: No, they're not.

Dr. CASANI: No, they're not. So we definitely have the two oldest and two longest operating spacecrafts ever launched.

FLATOW: Mm-hmm.

Mr. MASSEY: Yeah, that's true. As of this year, IMP-8 was the longest operating, but it is no longer operational either.

FLATOW: There's no - I guess there's no end date on these Voyagers, is there?

Mr. MASSEY: Well, there is in terms of expendables. The one that's probably will expire first is the amount of electrical power we have and right now we know we can last at least until the year 2020.

FLATOW: With the electrical power.

Mr. MASSEY: Right.

Dr. CASANI: The electricity is generated onboard by the use of thermal electric generators, radio isotopes-heated thermoelectrics, and the radio isotope power source, which is a heat source, has a natural decay of about, I don't know, it's a couple of percent a year. And, you know, so I think we started with about 400 watts of electrical power and now it's down to, what, right around 250 or so, something like that, Ed?

Mr. MASSEY: Two eighty-seven.

Dr. CASANI: Two eighty-seven. So it will continue a very slow gradual degradation and in the up steam had been able to deal with that by modulating the power, turning instruments on and off and being very, very careful about what's on at the same time. But eventually, it'll get to a point where they will be out of options and we'll lose control altogether.

FLATOW: Ed, what useful stuff can they still teach us from where they go? What can we learn from them still? They're 30 yrs old and they've been out there.

Mr. MASSEY: Well, as (unintelligible), the project scientists likes to say, everywhere we go, we are surprised. And we were surprised at each one of the planets. We were surprised when Voyager 1 crossed the termination shock. We've been surprised in the heliosheet because things are not as we expected. And, I think, that will probably the same when we reach interstellar space. So we still have a lot to learn about the sun's environment and the wind that comes from between the stars.

FLATOW: 1-800-989-8255. David(ph) in Greensboro, North Carolina. Hi, welcome.

DAVID (Caller): Hey, how are you doing? Thanks for taking my call.

FLATOW: You're welcome.

DAVID: My question is this - I've been fascinated with space exploration like, you know, my entire life. And, you know, everything we learned I'm just thrilled about and I think it's wonderful. I just - my main question is this. Who decides where our funding goes for NASA as far as, like, I've read that we only spend about a million dollars for searching for nearest objects?

I guess I'm just wondering, you know, what are our priorities? Where do we need to put our money into right now?

FLATOW: Howard McCurdy, can you weigh in on that?

Dr. McCURDY: Sure. A short answer would be - it's about $17 billion a year that is appropriated to NASA, and the nature of science policy is such that people in the agency - the administrators, the scientists and the engineers - have the great deal of discretion over how that money is spent. And I would estimate, there're probably about $34 billion worth of wants every year and so a lot of things don't get done. This was an example of a, back then, a $1 billion project that turned into a $300 million project, but still accomplished more than what was expected of it. That's just very typical of what happens in the agency.

Dr. CASANI: Yeah, if I could add to that.

FLATOW: Sure, John.

Dr. CASANI: President Bush, a couple of years ago, enunciated his new vision for space exploration. It's sort of a presidential policy and it anticipates, you know, retiring the shuttle by 2010. I think that was the original goal, completing the space station, and building a new launch vehicle, a new man-carrying capability crew exploration vehicle with the ultimate goal of going back to the moon first, as a learning or staging area, and then ultimately humans to Mars, while maintaining a vigorous program of robotic exploration.

So that's sort of the high-level guidance from the administration to NASA. And NASA probably doesn't have enough money, through the budgeting process, to really carry out that vision on the timetable that was anticipated at the time. So the director or the administrator of NASA, Dr. Michael Griffin, has a very difficult choice of trying to balance the, challenge, I should say, of trying to balance the resources that are available through the Congress against those elements - the elements of the president's vision for space exploration.

And that has, as it turns out now - there's about two-thirds of the money, or maybe a little bit more, is going into finishing the manned activities that are currently on the plate and starting the new ones. And about one-third, or maybe a little less than one-third, goes into the spy and science and the robotic program.

FLATOW: Now we keep hearing people complaining about, you know, that science is being shortchanged, because we have to finish working on the International Space Station.

John, though, in a few minutes we have left, let's talk about how the Voyager came about to carry this golden record of space sounds.

Dr. CASANI: Okay, well, I think that the - that is probably one of the - at least in my mind, one of the most interesting things about the Voyager mission. I have to take a little bit of credit for it, because I was aware during the - in a year or two before launch that the Pioneer 10/11 spacecraft, which I've mentioned the couple times already on the program here, did carry an emblem or some sort of a plaque that indicated the - its source being the planet Earth and it wasn't very - didn't have very much information of it in that on.

And it had stirred quite a bit of negative controversy among some circles because there was, you know, a figure of a female and male figure that some people thought was a little bit too revealing for public use.

But anyway, with that in mind, I approached Carl Sagan and asked him if he could come up with something that would be appropriate that we could put on our spacecraft in a way of sending a message to whoever might receive it. Then he took up that challenge with great enthusiasm and lined up a couple of other people, Frank Drake, I think he was at Cornell at that time, and Timothy Ferris, and one or two other people. And they went off and came back with a proposal for this record, which would contain images representing life on Earth and sounds representing life on Earth - sounds of human voices and sounds of animals and sounds of waves, and things like that.

And include with it some coded directions for how, not only how to play the record, but where the source of the spacecraft was in terms of location in the, you know, our galaxy. And the design of that was challenging because it had to be done without any pre-knowledge of what the culture or means of communication, anybody who might pick it up would have it there at their disposal to decode it.

So we never really expected that anybody would find it. That wasn't the point, the point merely was if you were going to send a message like that, it was sort of a thought experiment that we are trying to challenge and that Carl was trying to challenge the humanity with, is how would you reach out and communicate to a totally alien civilization and what would you have to say and that was the message of the record.

FLATOW: Talking about Voyager this hour on TALK OF THE NATION: SCIENCE FRIDAY from NPR News. I have to share a story with you. During that time, I interviewed Carl Sagan about one of his books and he came into my office and we were chatting about what he was working on.

And I, he's asked me and I said, I was working on collecting all these natural sounds of Earth and his eyes lit up. He said, can you send some of these things? I said, what are you going to do with them? He says, I can't tell you.

Dr. CASANI: Well, now you know.

FLATOW: I said, I'm not sending them. He said, well, off the record, you know, this is what I'm doing.

(Soundbite of laughter)

FLATOW: So it was quite interesting during those days as I'm trying to collect those sounds and put it on the record.

So in the minute we have gentlemen, you think Voyager is still working, is it still going to serve as the standard by which all other missions occur? Let me ask Howard about that first.

Dr. McCURDY: Well, I think in many ways is a precursor mission for the faster, better, cheaper missions of the 1990s and beyond, because here, you have a spacecraft where the managers are able to accomplish four-fifths of the mission for one-third of the price. If we'd done that in the last 30 years in the human space life program with the shuttle and the space station, we'd be well beyond lower Earth orbit.

But it's happened in the robotics. It hasn't happened in the human space life programs. So it's a remarkable accomplishment; one that still has implications today.

FLATOW: John Casani.

Dr. CASANI: Well, I guess I could echo Howard's remark there. I don't normally think of the Voyager effort as faster, better, cheaper, but I think in the context that he just described it that has probably, appropriately, Voyager did set the standard for how to design and how to think about operating long life spacecraft. I think many, many missions have followed in its footsteps.

But most important is that Voyager showed us what's out there and provided, I think, the motivation and the interest, both on the part of the public and the science community, to continue with the exploration of our solar system.

FLATOW: Ed Massey.

Mr. MASSEY: You know, I also concur with that - what has been said before. I think one of the great things about the Voyagers are the fact that they have been fully adaptable. You know, after finished our planetary missions, we were able to explore the distant heliosphere, and now we're actually anticipating the exploration of interstellar space. A spacecraft that had so many different mission objectives over his lifetime is really fantastic.

FLATOW: Well, thank you gentlemen for - and happy anniversary to all of you.

Dr. CASANI: Thank you very much.

Mr. MASSEY: Thank you.

Dr. McCURDY: Thank you.

FLATOW: Thank you for being with us. Ed Massey, project manager for Voyager mission. John Casani, project manager from '75 to '77 both at the JPL. Howard McCurdy, author of "Robots in Space: Technology, Evolution and Interplanetary Travel."

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