Planetary Radio • May 04, 2022

Heavy Metal: An encounter with the Psyche spacecraft

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On This Episode

Lindy elkins tanton portrait

Lindy Elkins-Tanton

Foundation and Regents Professor in the School of Earth and Space Exploration at ASU

Bruce betts portrait hq library

Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

Additional guests include:

  • Henry Stone, Psyche Project Manager at JPL
  • Abhijit “Abi” Biswas, Deep Space Optical Communications Project Technologist at JPL

Psyche is a 279 kilometer-wide (173 mile-wide) hunk of metal in space. Psyche is also a magnificent spacecraft that will soon head toward its namesake in the asteroid belt. Host Mat Kaplan recently visited the JPL clean room where the probe was in final preparation for launch. You’ll hear conversations with mission leaders including principal investigator Lindy Elkins-Tanton and project manager Henry Stone. We’re fresh out of metal asteroids at The Planetary Society, but you might win the rubber variety in this week’s What’s Up space trivia contest.

Mat Kaplan and Lindy Elkins-Tanton with Psyche
Mat Kaplan and Lindy Elkins-Tanton with Psyche Mat Kaplan and Lindy Elkins-Tanton in the JPL cleanroom with the Psyche spacecraft.
Psyche the spacecraft at Psyche the asteroid
Psyche the spacecraft at Psyche the asteroid This artist's illustration depicts NASA’s Psyche spacecraft exploring the asteroid Psyche.Image: Credits: NASA / JPL-Caltech / ASU / SSL / Peter Rubin

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Trivia Contest

This Week’s Question:

Name all asteroids that are bigger than Psyche and that have already been visited by a spacecraft. Exclude Ceres as it is now classified as a dwarf planet.

This Week’s Prize:

A very non-metallic Planetary Society KickAsteroid rubber asteroid.

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, May 11 at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

What was the last spacecraft to do a Venus flyby? Venus orbiters do not qualify.


The winner will be revealed next week.

Question from the April 20, 2022 space trivia contest:

Who was the youngest person to walk on the Moon at the time he walked on the Moon?


The youngest of the 12 people who walked on the Moon was Apollo 16’s Charlie Duke. He was 36 at the time.


Mat Kaplan: Heavy metal this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. No spacecraft has ever visited a metal asteroid. That's about to change. Psyche is both a 279 kilometer wide rock and a new magnificent spacecraft that will set out toward its namesake in August of this year. Come with me to the jet propulsion lab, clean room, where we will meet leaders of this exciting mission, including principal investigator, Lindy Elkins-Tanton. We'll also hear about the deep space laser communications experiment that will travel across the solar system with Psyche. And while we're fresh out of metal asteroids at The Planetary Society, there's a rubber one waiting for the winner of Bruce's new space trivia contest. Hey, there are UK listeners and especially those of you within easy reach of London. I won't have details till next week, but here's a heads up, I'll be in town on Monday evening, May 23rd for a very special Planetary radio Live at Imperial College London. We'll be celebrating the MOONS SYMPHONY with composer, Amanda Lee Falkenberg, astronaut and artist Nicole Scott, Cassini Saturn mission, project scientist Linda Spilker, and other distinguished guests. More soon, I promise. Busy, busy. I'm also looking forward to the Humans to Mars Summit that kicks off in Washington, DC on Tuesday, May 17. You can learn more about it at exploremars.O-R-G. I'll be there with lots of your favorite Martians and here's a special offer. Explore Mars needs volunteers for the summit, if you help out for a couple of hours, you can attend the rest of that day's program for free, write to [email protected], if you're interested. As always our great weekly newsletter is waiting for you at You won't believe the top image in the April 29 edition. That's the International Space Station crossing the huge and violent disc of the sun, flares, sunspots, and all, simply amazing. And it's free. It's rare that I can welcome an external guest to Planetary Radio, knowing that she'll return a few weeks later, actually it's unheard of. But when I entered a JPL clean room on April 11th, I just finished Lindy Elkins-Tanton's excellent new memoir, A Portrait of the Scientist as a Young Woman. The book is only partially about the Psyche mission that Lindy leads. It tells the sometimes brutally honest and intensely personal tale of how Lindy's entire life led her to this job. I knew I'd want to bring her back soon, but my immediate joy was joining her and others in that clean room where the Psyche spacecraft was being prepared for its trip to Florida. That's where it will be lifted to the top of a SpaceX Falcon Heavy to begin its journey to the asteroid belt, and an object unlike anything previously visited by we earthlings. Lindy is a planetary scientist at Arizona State University, where she also serves as Vice President for the Interplanetary Initiative. Lindy, with any luck, this is the first of two conversations that we will have on Planetary Radio, because I'm looking forward, not too long from now talking with you about your absolutely wonderful book. I've already shared with you how much I enjoyed it, and how I've been recommending it to others. But here we are in front of this spacecraft that is about to go out to visit a body in our solar system that is unlike anything else that has ever been visited. This is really the realization of a dream, isn't it?

Lindy Elkins-Tanton: It is the realization of a dream. The privilege of working on a space mission is something I actually never envision for myself. And to be standing here in this clean room and looking at this gorgeous spacecraft, feeling confident that we're going to launch in just a few months, it's unbelievable.

Mat Kaplan: And there is no better place to get a feeling for what goes into a mission like this than standing in this high bay or clean room. It's always a thrill to be in one of these rooms. There is so much technology spread all around us just to support this mission that you lead.

Lindy Elkins-Tanton: The complexity of space missions is beyond any person to really communicate. We're in this room with a couple of dozen people. Everyone is gowned up as clean as we can be. God forbid a piece of dust would get on the camera. There's no one in space to wipe it off. By this spacecraft that has taken us more than five years to build, even with a team of over 800 people, it's very complicated.

Mat Kaplan: Something that's going to come out of the discussion when we talk about your book is how much of your life, even if you weren't expecting it, led you to this moment. To being put in charge of a mission like this. Which is still, there are not that many principal investigators who have had this kind of opportunity or responsibility, and there are even fewer who are women.

Lindy Elkins-Tanton: That is true. There aren't that many of us who've been so fortunate as to lead a space mission. And of course, how do you prepare for this? There's no high school class in building spacecraft or understanding how to lead a giant complicated team of people from all different disciplines. How to have responsibility without literally having authority over all of the many, many groups that have contributed to this around the world. So in the end, it's all about teamwork and what humans can do when they decide to have a shared vision. To me, that is the purpose of space exploration. It shows us here on Earth, what we can do when we all pull in the same direction.

Mat Kaplan: I'm thinking back to, and it's toward the end of the book, because there are so many other things that, when people read it, and they should, they will see how your life has prepared you for this, but it was that time when all of you got together, was it at Ames? I know it was in Silicon Valley, now I'm forgetting.

Lindy Elkins-Tanton: I'm not sure what story, do tell.

Mat Kaplan: This was for the final evaluation.

Lindy Elkins-Tanton: Oh, yeah.

Mat Kaplan: When the whole team got together and you had to face the people who would say, "Yay," of, "Nay," to whether this spacecraft would ever actually exist.

Lindy Elkins-Tanton: That's right.

Mat Kaplan: And it's a terrific story. The preparation that went into that alone.

Lindy Elkins-Tanton: I love talking about this so much. It's called the site visit, and we were holding it at Maxar, our industry partners-

Mat Kaplan: Of course.

Lindy Elkins-Tanton: ... in Palo Alto, trying to show the NASA review panel what Maxar had to offer, because they've never partnered on a deep space mission before. So the scenario is, we had been competing already for a couple of years. We'd finished our step one proposal that was 240 pages, competed with 28 other missions. We became one of five finalists. We'd written a thousand page concept study report, everything that needed to go into this mission, 150 people worked on it. Finally, we have one week. We're at Maxar. The whole professional review panel is going to fly out and spend the final day of the week with us, asking us the hard questions, the ones we didn't answer in the 1200 pages of writing that we'd already done. We had to stand up and answer these questions in front of the team. Oh, my goodness. They redecorated their executive lunchroom. We-

Mat Kaplan: Yes.

Lindy Elkins-Tanton: ... oiled every single chair, so there would not be a squeak in the room. We checked the light angles. We had professional speaker training, so we knew how to hit our mark. But the thing that really carried the day was that we worked together as a team. And the review panel noticed that. I didn't stand up at the front going, "I'm the big person in charge. And I'm going to answer all your questions, how I please," nor did Henry Stone, our project manager, or David Oh, our leads systems engineer. We all passed the question to the person who knew the answer best, which seems so obvious, but it turns out it's unusual. That was a real moment.

Mat Kaplan: I want you to add to that story, the one facet of it, that involved someone, I know well, your colleague at ASU, Jim Bell-

Lindy Elkins-Tanton: Oh, yeah.

Mat Kaplan: ... who until recently was president of The Planetary society. I call him the Ansel Adams of Mars, but he has lots of experience beyond the red planet.

Lindy Elkins-Tanton: So exactly right.

Mat Kaplan: He was kind of brought in at the last minute, right? He wasn't going to be at this meeting.

Lindy Elkins-Tanton: Well, he was going to be there in a supporting role, because we thought we knew what the review panel was going to be asking us questions about. And we expected them to focus on the very complicated gamma ray neutron spectrometer, which they did not. It turned out all their questions were about magnetometers and magnetic field, the science questions, not the engineering questions, and the imagers. We thought the imagers were just a slam dunk, who needs to even ask questions about imagers. Jim Bell, the Ansel Adams of Mars is running our imagers. This is the guy who knows more about planetary photos than anybody else on Earth, I think, therefore in the solar system. And there were many questions for him. And there were some questions that we thought were a little naive or maybe even not quite right. And we were a little worried Jim was going to lose his temper. So he's striding back and forth in front of the panel. And finally, he just turns and says, "I might not really understand what you're asking. Could you rephrase that question?"

Mat Kaplan: Well, played.

Lindy Elkins-Tanton: Well played Jim Bell. Yes, well played. It worked out fine.

Mat Kaplan: Well, obviously, because here we are in front of the spacecraft. I want to talk about it more generally, but the fact that you mentioned it has a magnetometer.

Lindy Elkins-Tanton: Yes.

Mat Kaplan: My guest a few weeks ago on the show was the great Margaret Kivelson. And I actually mentioned to her, spacecraft now like this, like Psyche that have these devices for detecting-

Lindy Elkins-Tanton: That's right.

Mat Kaplan: ... and measuring magnetic fields, and she was very pleased.

Lindy Elkins-Tanton: I'm so glad that Margie was pleased. She's an amazing human being, and such an expert in that in other aspects of planetary science. We're very proud to be flying these beautiful magnetometers. You can see up on the boom, sticking out the top of the spacecraft, to keep it away from the spacecraft magnetic field, although our spacecraft is very magnetically clean. These were built by Danish Technical University. They're gorgeous. And the science investigation is led by Ben Weiss, on my team, my friend, who, with Maria Zuber, was the co-author of the paper that got us going 11 years ago, starting on this mission.

Mat Kaplan: The first thing that got to me. And so I was kind of prepared for coming in, because I'd seen pictures of it, it's huge. It's so much bigger than I expected it to be when I first heard about the mission.

Lindy Elkins-Tanton: I love the fact that this spacecraft is huge. Somehow it's physical manifestation fits how it feels to me, so big and important. The solar panels aren't even on it right now. But when they're unfolded, they make the whole spacecraft the size of a singles tennis court. It's huge. And here's the other's irony, this is about the smallest spacecraft chassis that Maxar builds. And so it's largely space inside. It's not crammed with instruments. Our instruments hang off the outside. We saved a lot of money by buying something that's very similar to what they normally build. So that's why it's so big.

Mat Kaplan: Those solar panels that add so much to the width of this spacecraft, when they'll be extended-

Lindy Elkins-Tanton: That's right.

Mat Kaplan: ... I mean, you couldn't even extend both of them at the same time here, could you?

Lindy Elkins-Tanton: We could not. We could only extend one of the panels here to test it. And it filled up the whole room. That's how big they are.

Mat Kaplan: There is this strange space frame sort of structure over here. Did that have something to do with it?

Lindy Elkins-Tanton: Yeah. That amazing structure was is just a million triangles and tubes of metal, sort of a scaffolding, has been taken down, but it was the scaffolding that allowed us to extend the solar array and test it, when it was set up. Because the solar rays are not built to work under Earth gravity, they don't have the strength to hold themselves out that great long distance under Earth gravity. So you have to hold up the weight of gravity and allow them then to practice extending.

Mat Kaplan: What about the other instruments on this spacecraft?

Lindy Elkins-Tanton: Right, the one that we have not talked about yet really is the gamma ray and neutron spectrometer, which is on that other boom near the magnetometers. It is an amazing instrument which contains a crystal of the element germanium, which is the purest substance made by humans. It's a crystal the size of a baseball, and that crystal detects radiation coming off the surface of Psyche and can tell what atom produced the radiation. So that crystal will tell us what the surface of Psyche is made of. So we have that, the magnetometers, we have a gravity experiment that we use our radio communications to figure out the gravity field of Psyche.

Mat Kaplan: Using the Doppler effect, right?

Lindy Elkins-Tanton: Using the Doppler effect, exactly. Much like the GRAIL spacecraft did. Then, of course, the imagers. And the thing to add to the imagers story, Jim Bell's imagers, is that we built a pipeline that will alow us to put the images on the internet within 30 minutes of our receiving them from the spacecraft through the Deep Space Network. So we're not going to edit them or censor them. We want everyone in the world to be looking at the same time and saying, "What is this thing?"

Mat Kaplan: I think that also says something about your philosophy, your approach to this mission, you talked about the team that has come together behind it. But, also, being that open with your data, which not all missions are.

Lindy Elkins-Tanton: Yeah. There's a huge human urge to hold our information to ourselves. Knowledge is power.

Mat Kaplan: I work hard to get this. Why should I give it away right up front?

Lindy Elkins-Tanton: That's right. I'm going to milk it of all the information. I'm going to publish my ideas first. I don't think that's what space missions are really about. I think they're really to inspire and engage all of humanity. We're going to have plenty of time to publish our ideas. Other people can publish them too. It's not just me saying this, the whole team feels this way, and it's Jim himself who said, "We can do this pipeline. Let's do it."

Mat Kaplan: One of the other fascinating design characteristics to the spacecraft is, well, you have ion engines, electric engines, but I don't know, correct me if I'm wrong, I have not seen a spacecraft before that puts its rocket engines, they are, even though they may not have tremendous thrust-

Lindy Elkins-Tanton: That's right.

Mat Kaplan: ... out on robotic arms.

Lindy Elkins-Tanton: Yeah. These beautiful two-degrees-of-freedom arms that hold these quite small ion thrusters. So that just like your shoulder and your elbow, we can decide what direction we want these to point in. There are two thrusters on each arm at, at a given time only one of them will be firing, and they'll be pointing kind of back and toward each other, so that we can have it driving the center of mass of our spacecraft forward. We're excited about it. They're very futuristic. They make a sort of a blue glowing plasma. Pretty cool.

Mat Kaplan: Does this explain why you needed those gigantic solar panels?

Lindy Elkins-Tanton: Exactly right. Our spacecraft runs on solar energy. It's a solar electric spacecraft. So our solar panels power, not just the thrusters, but also everything that happens on the spacecraft. It powers the heaters and the coolers and the science instruments and the communications. Everything that happens comes from the sun.

Mat Kaplan: Let's talk about your objective. As we said, it's not like any object that has actually been visited by humans before. How do we know that? How do we know from this distance that it's not just another ball of fluff or dirt and rocks?

Lindy Elkins-Tanton: Yeah. Is it just a giant space dust bunny? No, it is not. What can we discover from Earth? Well, one thing we do is we look at the light that reflects off asteroids and comes to the Earth. The asteroids absorb certain kinds of light and reflect others, and that shows us what they're made of, to some degree. So we know that Psyche is different from most asteroids, it has different light reflectance. We also, amazingly, have the ability to bounce radar off of asteroids and receive the radar returns, and learn how radar interacts with the surface. Then we can watch it spinning in optical light telescopes and begin to get a sense of its shape. Not a very good sense. We have no pictures of it, but all these things together, along with the density of Psyche, which is very important data, we figured out its mass, not me personally, but other brilliant people who know to do this, figure out what its mass, its weight is, by how it interacts with very distant other objects in the solar system. Then if we combine with what its volume is, we get a sense of how dense it is that density and that reflected light tells us it has to be largely made of metal. There are almost no other asteroids that seem to be largely made of metal, maybe nine of them or fewer, and Psyche is by far the biggest. So that's the information we have from Earth, and now we got to go there to find out more.

Mat Kaplan: And the significance of this, that it is made of metal. I mean, when we look at the big world's around our solar system, we suspect, that there's some metal down there-

Lindy Elkins-Tanton: That's right.

Mat Kaplan: ... at the core.

Lindy Elkins-Tanton: That's right. We can tell from Mercury, Venus Earth, Mars, and also the moon from the way they spin and the way they orbit that they have a very dense middle that has to be iron metal. So the cores, the iron metal cores of all of our planets, we're very curious about them. They make our magnetic fields, they protect the atmosphere. They may be very important to making the Earth habitable, but we are never, ever going to see them, way too much pressure, way too much temperature, never possible to see them. Psyche may be the only way humans will ever see a part of a core. So ironically, as my husband says, "We have to go to outer space to visit inner space."

Mat Kaplan: How do we know... I mean, a lot of the artist concepts, the renderings that I have seen of this asteroid and others that are like it, iron, nickel, asteroid types, the metal is exposed. But I mean, we know from recent experience that asteroids are notorious collectors of space flotsam.

Lindy Elkins-Tanton: So right.

Mat Kaplan: Do expect we'll be able to actually see the metal surface.

Lindy Elkins-Tanton: I really hope we'll see some metal surface. And so the radar and the reflected light, and also the thermal properties, other people who've been researching this, report in their papers that they believe that the surface has to be made partly of metal. It could be just metal granules like metal sand, but that would be pretty cool to see. In my fantasies, there are kind of planes of metal, like big regions of metal. That may not be it all the case. It might be covered with little rocks and grains and things of metal and rock. I think it's going to surprise us. I think it's going to show us things we haven't seen before.

Mat Kaplan: I've been having much too good of time talking with you, but you're in demand. There are people waiting to catch you with their microphones.

Lindy Elkins-Tanton: Media guys.

Mat Kaplan: But I look forward to that conversation, maybe a month or two from now-

Lindy Elkins-Tanton: Very much.

Mat Kaplan: ... when your book comes out.

Lindy Elkins-Tanton: I'm so appreciative of you for reading my book and for saying kind words about it. It's very personal, obviously.

Mat Kaplan: Thank you. And best of success with this, of course.

Lindy Elkins-Tanton: Thanks a lot. Thanks for coming and looking at our beautiful spacecraft.

Mat Kaplan: Wouldn't have missed it.

Lindy Elkins-Tanton: Love it.

Mat Kaplan: Stick around. When we come back, I'll still be in that JPL clean room where we'll meet Henry Stone, the Psyche mission project manager.

George Takei: Hello, I'm George Takei. And as you know, I'm very proud of my association with Star Trek. Star Trek was a show that looked to the future with optimism, boldly going where no one had gone before. I want you to know about a very special organization called The Planetary Society. They are working to make the future that Star Trek represents a reality. When you become a member of The Planetary Society, you join their mission to increase discoveries in our solar system, to elevate the search for life outside our planet, and decrease the risk of Earth being hit by asteroid. Co-founded by Carl Sagan and led today by CEO, Bill Nye, The Planetary Society exists for those who believe in space exploration to take action together. So join The Planetary Society and boldly go together to build our future.

Mat Kaplan: We're back not far from Lindy in that clean room was another leader of the Psyche mission.

Henry Stone: Henry Stone, and I'm the project manager for Psyche here at JPL.

Mat Kaplan: And part of this terrific team that we were just talking with Lindy about.

Henry Stone: Yeah, it is an absolutely fabulous team. And I've been honored and blessed to be able to be chosen to kind of lead that team to the extent that it needs leading, because they do a great job on their own, but it's fabulous. We're building, as you can see here, a really incredible, sophisticated spacecraft, that's going to do some really one of a kind science and exploration of a body as Lindy was surely telling you, we've never been to, and know very little about. So no matter what we find, it's going to be scientifically exciting and interesting.

Mat Kaplan: It is an absolutely gorgeous spacecraft. And as I said to Lindy, much bigger than I thought it was going to be for what it's doing.

Henry Stone: It is much bigger than a lot of people think it is. In part because we decided to leverage the bus from a commercial satellite made by Maxar Spacecraft that they use for comsat and their whole electric propulsion system. And then merge that with the deep space capabilities that we have here at JPL, a really unique and new arrangement that we put together here for NASA to fly this mission. So we didn't try to over-optimize the size, because then we'd have to start from scratch. And we had a great starting point with the Maxar Bus.

Mat Kaplan: It sounds like the kind of approach that other people might want to try and emulate, take a bus for commercial purposes and put some great instruments on it.

Henry Stone: Absolutely, but you have to do that carefully, because depending on where you going in deep space, you got to make sure that bus in fact is compatible with where you're going. And it turns out it worked out really well for this particular mission. Hopefully, it will for other missions as well.

Mat Kaplan: So what is the current status of the spacecraft? Are we looking good for launch in August?

Henry Stone: We are looking good. We are in the tail end of system integration and test, what at JPL we refer to as ATLO, which is assembly test and launch operations. So we are just wrapping up, in the next two weeks, the activities here at JPL, in this wonderful clean room here, getting the spacecraft all buttoned up after all the testing that we've been performing now for a year and a half and integration activities, and we're going to ship it at the end of this month, we're going to get it out to March Air Force Base in a shipping container, get it on a C-17, fly it out to Cape Canaveral. Once we get to Cape Canaveral, we are going to do some final testing and close out activities there. Get the solar rays put on, and then we do the integration of the spacecraft onto the launch vehicle. We're going to be launching on a Falcon Heavy from SpaceX, that's excitement as well. We should be ready to go in August for our planetary launch.

Mat Kaplan: Ever seen a Falcon Heavy launch? I did because we were there for the launch of our LightSail, which did not, a three minute cubesat, it didn't need a Falcon Heavy, but we got a good free ride.

Henry Stone: No, I personally have not seen a Falcon Heavy.

Mat Kaplan: Spectacular.

Henry Stone: So this will be my first one. So the fact that I get to see that for the first time around, and watch our baby take off here is going to be throwing.

Mat Kaplan: Okay. And then a trip out across the solar system, a swing by Mars. And you finally get out to your objective that fascinating asteroid, when?

Henry Stone: We're going to get out there in January of 2026. It's about a three and a half year cruise as we spiral out. And as you said, pass by Mars, we'll get a good kick from a gravity assist off of Mars. When we combine that with the ion engines on this thrusting all the way, yeah, it'll be January 2026. And that's when we start the science portion of the mission, which will last about two years. As we consecutively orbit around the body, getting lower and lower and lower, so that our instruments can take finer and finer measurements of the characteristics and the materials that make up this body, very unique body, Psyche.

Mat Kaplan: What is your tightest orbit? I mean, I saw a picture of it upstairs and I wondered why you weren't even going to approach closer.

Henry Stone: We may, the problem is, or not the problem, but the issue right now is we know so little about it. We only have some rough shape models of how it's shaped. We don't understand the distribution of the density, and hence we don't know the gravitational field. So one of the first things we do is, as we approach, we go into a very high orbit where we have high confidence it's a safe orbit. And then using our tracking system to watch the undulations of the spacecraft in that orbit, we can map out the actual gravitational field of that body that then allows us to say, "Here are the next successively lower orbits that we can go." Now we intend right now to do four basic orbits down to, on the order of about a 100 kilometers off the surface at the moment. The exact amount will have to be determined, like I said, once we get there. And that's our prime mission, there is nothing on this spacecraft that will prevent us from continuing to go on after that. And if we were to secure the funding and everything is working fine, then maybe we will get an extended mission. The initial idea, at the moment, would be to go even lower and lower and lower, and refine all the measurements from this incredible set of scientific instruments we're carrying.

Mat Kaplan: Absolutely thrilling, a lot to look forward to. I think they're ready to move us out of here so that they can get back to work on your spacecraft.

Henry Stone: Probably, we got to get it buttoned up and packaged up. And my ATLO manager here is saying, "Get out of here."

Mat Kaplan: Thank you so much.

Henry Stone: You're welcome.

Mat Kaplan: Best of success.

Henry Stone: Yes.

Mat Kaplan: We're all looking forward to it.

Henry Stone: Thank you. Thank you very much.

Mat Kaplan: Henry Stone of JPL is the Psyche mission project manager. There's one more person I want you to meet. We talked outside the clean room on that sunny day at JPL.

Abi Biswas: My name is Abi Biswas. I'm the project technologist for the deep space optical communication project.

Mat Kaplan: Where lasers have never gone before, at least communication lasers, deep space. Tell me about this project, that's fascinating.

Abi Biswas: Yeah, it's a very exciting time for us. We've been working on this technology for a number of years. We are fielding a number of new technologies, both in terms of the lasers, the detectors that are flying on the spacecraft, and then the detectors on the ground. And of course we have lasers also in flight and on the ground, we have some very powerful layers on the ground. So every aspect of this technology demonstration has novelty. It's either being something that's been never done before, or it's a new kind of engineering. It's a privilege, and it's also a lot of trepidation, because it hasn't been done before. Is it going to work? I mean, we hope it will, but we've tried our best to do everything.

Mat Kaplan: It's worked, I mean, other technology, similar technology has worked to geostationary orbit. It's worked as far as the moon-

Abi Biswas: It worked [inaudible 00:27:13]-

Mat Kaplan: ... but you're hoping to be able to communicate via photons, well, light photons, much farther than anyone ever has.

Abi Biswas: That's correct. So if you think about it, it's almost a 1,000 times farther. That's why the technologies have to be different. The same technologies that have been proven at lunar distances wouldn't work when we go this far, both in terms of the ground lasers, the flight laser, the flight optics, the flight sensors, the pointing system, everything is novel.

Mat Kaplan: Tell me about the transceiver that is actually mounted on the spacecraft. It's a telescope as well, right?

Abi Biswas: Yeah. The difference between telescope and transceiver, of course, it's a 22 centimeter aperture. A telescope usually just receives, but this thing can receive and transmit. It can send a 22 centimeter laser beam out and it can receive a laser using a 22 centimeter aperture. It has a photon counting camera in the focal plane, which senses the laser that goes from Earth, centers it on the focal plane of that photon counting camera and tracks it. And so it gives it a pointing reference. And then relative to that received spot, it knows where to point the transmit spot. And, of course, the transmitter here on Earth is at Table Mountain near Wrightwood, California. And the receiver is at Palomar Mountain.

Mat Kaplan: Palomar, that Hale Telescope, one of my favorite places on Earth or off Earth for that matter. How powerful is the laser that is on the spacecraft?

Abi Biswas: So the laser has four watts of average power, but it's turned on and off, so it's pulsed at a very low duty cycle. So the pulses themselves have higher peak power, the highest peak power pulses, which we use at the farthest distance about 600 watts.

Mat Kaplan: Well, and even four watts is a sizeable laser for anybody who doesn't realize, that's actually a pretty good size laser, but 600 watts.

Abi Biswas: 600 watts peak power. The whole train of pulses, if you average them over time, you get four watts, but the individual pulse itself for that short instance of time peaks at about 600 watts.

Mat Kaplan: So the beam passes through that telescope, it collimates the beam, straighten, makes it spread out or propagate less than it would otherwise. How wide is that beam when it starts at Mars, by the time it gets to Earth?

Abi Biswas: It's a 22 centimeter beam when it starts at Mars, and if you look at it in terms of its angular width, it's about 15 microradians. And by the time it gets to Earth, it's spreading out due to defraction, it's a few thousand kilometers by the time it gets to California.

Mat Kaplan: So you still need a pretty sensitive receiver-

Abi Biswas: Yes.

Mat Kaplan: ... and you have one, and it's attached to that 200 inch-

Abi Biswas: Yes.

Mat Kaplan: ... Hale Telescope, which for so many years was the biggest on the planet.

Abi Biswas: Yeah. So we have a 300 micron array detector, which is made up of array of superconducting nanowires. These are made of tungsten silicide, and they are cooled down to sub-kelvin. Basically, whenever a photon hits that wire, it transitions it from a superconducting state to a non-superconducting state for about 40 nanoseconds. And it puts out an electrical pulse.

Mat Kaplan: A single photon?

Abi Biswas: A single photon will do that. Yes. So of course the mix of photons that hit it are both signal photons and background photons. But the signal photons come at a certain time, there's a timing relationship. So the signal processing electronics in the backend stamps every photon that arrives, it gets a timestamped out of that. And then it processes those timestamps to find the pattern, and it finds the symbol boundaries and things like that. And then it goes through decoding, because these are encoded and then it can extract the information that was put on it.

Mat Kaplan: So there is obviously a very accurate clock that's helping with this synchronization on the spacecraft, as well as at the receivers.

Abi Biswas: Yes. Yes. The clocks on the two ends are not synchronized, of course, it's asynchronous on the ground. But, yeah, the clock is, we tolerate about 150 picoseconds or so of jitter. So in terms of a clock, it's not the greatest clock, but it's good enough for our communication.

Mat Kaplan: Better than what I've got on my arm right now, anyway.

Abi Biswas: Yes. Yes. Yes. Yes.

Mat Kaplan: What kind of throughput, what kind of data rates are you hoping to achieve when you're out, maybe as far as Mars?

Abi Biswas: So from the Mars distance. So let's say from two AU, we can do about two point seven megabits per second.

Mat Kaplan: And how does that compare with what we're currently able to do? For example, from an orbiter at Mars right now with a high gain antenna.

Abi Biswas: It's typically we are doing 200 to 300 kilobits per second, so it's almost a factor of 10 from those distances. That's what our technology goal is to achieve 10 times the data rate for more or less the same power and mass that our telecom system has.

Mat Kaplan: And this something we've talked about before on Planetary Radio, but if you could remind us, why this is becoming so important? Why we need to push so many more bits across the solar system?

Abi Biswas: You have higher resolution instruments, there's a desire for human exploration. So there's a need for exchanging much more information from missions back to Earth and radio frequencies are reaching their bandwidth limit. Because there's also such a demand for radio frequencies on near Earth satellites to terrestrial things, social media, what have you, so there's a bandwidth crunch. And by going to the optical bandwidth, you're just letting that whole thing explode. I mean, you're going from tens to hundreds of gigahertz. You're going up to hundreds of terahertz. So that whole bandwidth thing is opening an up, it's unrestricted bandwidth, at least for now. It allows you to do higher data rates, initially, but in time, it'll also allow you to do higher precision navigation, to do better ranging capability. And just like you have radio science in the matured radio technology, you'll get light science in the laser technology. So you'll be able to do gravity mapping and other kinds of neat scientific things, which will sort of be an auxiliary capability of the laser comm system.

Mat Kaplan: And for a member of the public like myself, if we look down the line 10, 15, 20 years, am I going to be able to put her on a virtual reality headset, like a Rover Driver does and see the astronauts on Mars?

Abi Biswas: Not in the next 10 years, but in the 20 years, maybe, because one of the things that's lacking to go operational with this technology, assuming our tech demo works out well, is we don't have ground infrastructure. We're using Hale Telescope, we're using astronomical assets, but NASA and JPL are working on that issue. They're trying to put mirrors on the Goldstone antennas.

Mat Kaplan: Oh, really? Part of the DSN, the Deep Space Network.

Abi Biswas: Yeah. They're trying to see if they can repurpose the antennas, so the inner ring of the antennas they're putting mirrors on. And they're going to start doing some tests very shortly to see if that'll work, because then they can get about eight meters of aperture that'll work in the night and day. Because that's another thing a Mars orbiter, two thirds of the time, it's in the daytime sky. So you need assets on the ground that can operate in the daytime now. Astronomical assets don't do that, they get very upset if you open the dome during the daytime.

Mat Kaplan: That's true. It's great to hear that the DSN is just going to evolve along with-

Abi Biswas: Yes.

Mat Kaplan: ... the rest of our technologies. It is a technology demonstration, but that makes me also think of a certain little whirlybird named ingenuity that started as a technology demonstration and is now an operational part of that mission of perseverance. Could you see this, if it's as successful as you probably hope, or it might be used to help get data back from Psyche.

Abi Biswas: One of the limitations in our case is, again, like I said, ground infrastructure. We don't have anything that can receive during the day. So as long as you're doing stuff at night, yes. But that's a pretty big constraint, because as you're going around the sun, you're mostly in the daytime sky.

Mat Kaplan: Do you have any doubt that the future of communication across the solar system is going to be optical?

Abi Biswas: It's compelling, it has to be. I mean, there's no other way, because, especially people are already starting to think about Interstellar missions and all that, and there lasers are the only way to do it.

Mat Kaplan: Fascinating. Thank you very much, Abi.

Abi Biswas: You're welcome. You're very welcome. Thank you.

Mat Kaplan: Psyche is set to launch no earlier than August 1st. Time for what's up on Planetary Radio. Here is the chief scientist of The Planetary Society, Dr. Bruce Betts is back with all the usual fun. We couldn't find a metal asteroid to give away, but we do have a rubber one.

Bruce Betts: At least safer, I guess.

Mat Kaplan: Yeah. I have a metal one in a little box up above my head that was given to me years ago, little meteorite that a friend gave me. But I'm not parting with that. Sorry, folks.

Bruce Betts: So you keep metal meteorites above your head on a regular... I wondered what those were.

Mat Kaplan: Hadn't thought about that. I'll just get out of the way when the big one comes.

Bruce Betts: Yeah, I was going to say, it's not, like there are earthquakes here, so I wouldn't worry about it.

Mat Kaplan: How about you, are you safe?

Bruce Betts: No, definitely not, but we're not going into that right now. So we got those planets in the sky, still looking cool in the predawn, and a little something special. Let's start with the planets. We got in the predawn East, super bright Venus is still close to bright Jupiter. That's a little above it to the right. Farther up is Mars, reddish and yellowish Saturn, both dimmer, so you got four planets, nicely lined up there. On May 15th and 16th that night, Mat, total lunar eclipse. And even in the realm of total lunar eclipses, it's a pretty cool one. Visible, so here are the happy people, from North America, portions of Western Europe and Western Africa. The moon is passing along a nearly central line, meaning the total eclipse is longer. So it's almost an hour and a half of total eclipse with about an hour of good partial eclipse before that. And an hour after that. When might it be? Well, the partial eclipse, partial umbral eclipse begins at 2:27 UTC on May 16th. That's, for us in Western North America, Pacific Time, 7:27 PM on May 15th. So you can look up details. I'll come back to it next week, one more time, but it's going to be cool.

Mat Kaplan: My good friends at Southern Illinois University Carbondale, they're going to put on a big party for this lunar eclipse on the night of the 15th, of course. Man, they get all the luck. I mean, five years ago, the total solar, this time, the total lunar, and then in two years, it's just two years away, the return of the total solar eclipse to Carbondale, Illinois. It's exciting. I hope to be there again.

Bruce Betts: It is cool, but do they really get all the luck? I heard there was rumors of a cloud at really bad time, in the last total solar eclipse.

Mat Kaplan: You had to remind me. Okay, please go on, before I start to cry.

Bruce Betts: This week in space history, reasons not to cry 1961, Alan Shepard becomes the first American in space. 1968, I know this fascinates you, Mat, me too, the video is amazing. 1968, this week, Neil Armstrong ejected from the Lunar Lander trainer. Which is just an amazing video, if you haven't seen it, of this thing getting completely out of control and him ejecting just before it crashes.

Mat Kaplan: Even if he hadn't had that adventure on the Gemini capsule, that proved he had the right stuff. This would be enough. People need to see this video, it's just beyond belief.

Bruce Betts: Yeah. You can look it up. Speaking of looking things up, this has nothing to do with it. Random space fact.

Mat Kaplan: Love it.

Bruce Betts: Psyche, you've heard of Psyche, right?

Mat Kaplan: Oh, yeah. Right.

Bruce Betts: Well, I don't know whether you covered this, but is the largest single asteroid currently scheduled to be visited in the future by a spacecraft.

Mat Kaplan: That particular random space fact did not come up in conversation, so thank you.

Bruce Betts: You are welcome. We may even come back to things in the trivia contest, but first we've got a fun and interesting trivia contest for you from last time. Who is the youngest person to walk on the moon at the time of walking on the moon? How do we do Mat?

Mat Kaplan: Another huge response. We are getting lots of entries nowadays. I got to read this one. It is unrelated to the contest, but it's just lovely, from Kim Roberts in California. He says he recently rejoined The Planetary Society after nearly two decades away. Welcome back Kim. He says, "I've always been interested in space exploration, but I am truly thrilled to be back investing in our future, and gaining knowledge of the heavens and our place in them." Wow, Kim.

Bruce Betts: Well, that's very nice. Welcome back.

Mat Kaplan: Here is, I believe, the answer, not from our poet laureate, who took the week off, but from Gene Lewin in Washington, atop of Saturn five, they launched in April '72, Apollo's 10th crude mission from our planet blue, within the LEM Orion, they landed on the moon, examining the Descartes lands to provide us with more clues. Young would be the oldest and commander of this trip. Mattingly, the youngest, piloting the Casper ship. Duke was in the middle of these encapsulated mates, but of those who walked upon the moon, he's still youngest to date. Charlie Duke.

Bruce Betts: Nice, well played. Indeed, Charlie Duke at 36 years, six months, and 18 days when he stepped onto the surface of the moon.

Mat Kaplan: And here is a little bit of Charlie Duke before he got his ticket to ride. We've used this before, but I still had it handy, so I'm going to play it.

Charlie Duke: We copy you down Eagle. Everybody-

Neil Armstrong: Houston-

Charlie Duke: ... T-1, stand by for T-1.

Neil Armstrong: Tranquility base here, the Eagle has landed.

Charlie Duke: Roger, Tranquility. We caught you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot.

Mat Kaplan: That was Charlie Duke, who was the Capcom, apparently requested by Neil Armstrong for the Apollo 11 mission to be the capsule communicator, who was one of those turning blue at mission control, Johnson Space Center. It wasn't... Well, I guess it was Johnson Space Center by '72. Yeah. Anyway, wasn't that cool?

Bruce Betts: That was super cool.

Mat Kaplan: Hey, Paul Mundy, congratulations you first time winner. Long time entrant. Paul Mundy in the United Kingdom. Charlie Duke aged 36 for Apollo 16. Paul, congratulations. We're going to send you a Planetary Society Kick Asteroid rubber asteroid for your trouble.

Bruce Betts: Metal asteroid. Oh, no, rubber. Rubber asteroid.

Mat Kaplan: Sorry. Metal, that's your line.

Bruce Betts: Metal.

Mat Kaplan: Norman [Kasoon 00:42:35], also in the UK. Duke was the subject of the documentary Lunar Tribute, which premiered at the American Museum of Natural History's, Hayden Planetarium, October 20th, 2017. At a panel, after the screening, Neil deGrasse Tyson noted that Duke was the youngest person to walk on the moon. Duke responded that at age 82, he still was. Good one, Charlie. Kent Murley in Washington on the last days salute to the '72 Olympics, Duke and John Young took pictures of each other trying jumps. Duke got 12 centimeters higher, but fell over backwards.

Bruce Betts: Wow, now, that is some cool trivia random space fact.

Mat Kaplan: [Danu Batrami 00:43:22] in Australia says that the Apollo 16 splashdown was 50 years to the day before the cutoff for entries for this space trivia contest. How did NASA know that Bruce?

Bruce Betts: They carefully time their mission based upon that, the secret future seeing division of NASA.

Mat Kaplan: Couple of other interesting random space facts here. One from <ark Moffitt in Georgia, at 47, Alan Shepherd was the oldest of the moonwalking 12. And Shea Davidson in Illinois lets us know that Charlie Duke was also the first person to bring country music to the moon.

Bruce Betts: Wow. There's something I did not know. I'm curious what songs they were. I don't know that I want to listen to them, but I'm curious what songs they were.

Mat Kaplan: Yeah. Somebody must have that playlist somewhere, probably on their phone.

Bruce Betts: Did he bring like a record player, and a... No probably not.

Mat Kaplan: We're ready to move on.

Bruce Betts: Speaking of Psyche, the asteroid, name all asteroids that are bigger than the asteroid Psyche that have been visited by spacecraft. And to be clear, since Ceres is confusing, let's not include Ceres as it is now a dwarf planet. Give me everything, not including Ceres that's bigger than Psyche that has already been visited by spacecraft. Go to

Mat Kaplan: You have until Wednesday, May 11, Wednesday, May 11 at 8:00 AM Pacific Time, because that's where we live, to get us this answer. And maybe, maybe, maybe win yourself a Planetary Society Kick Asteroid rubber asteroid.

Bruce Betts: Metal asteroid.

Mat Kaplan: We're done.

Bruce Betts: All right, everybody go out there, look up the night sky and think about what you would've said to Neil Armstrong, when they got safely on the surface of the moon. Would you have been turning blue or some other shade of, I don't know? Thank you, and goodnight.

Mat Kaplan: Was that song Love is Blue still a hit? It was the number one hit I know. It had to be around '72.

Bruce Betts: Country music?

Mat Kaplan: No, hardly. He's Bruce Betts, country music fan and Chief Scientist of The Planetary Society, who joins us every week here for, What's Up? Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by its totally psyched members. You won't need a lot of coin to become one of them at Mark Hilverda and Rae Paoletta are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.