Planetary Radio • Jun 17, 2020

LightSail 2: A Year of Solar Sailing

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David Spencer

LightSail project manager and Mission System Manager for Mars Sample Return Campaign, NASA/JPL.

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Jennifer Vaughn

Chief Operating Officer for The Planetary Society

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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

The LightSail 2 team and 50,000 supporters around the world will celebrate the little spacecraft’s first anniversary on orbit in a few days. Planetary Society Chief Operating Officer Jennifer Vaughn remembers the long road to this accomplishment. LightSail Program Manager Bruce Betts and LightSail Project Manager Dave Spencer tell us what we’ve learned over the last year and look to the future of solar sailing. Dave also reveals his exciting new job at the Jet Propulsion Lab.

The Red Sea and Nile River from LightSail 2
The Red Sea and Nile River from LightSail 2 This image taken by LightSail 2's camera 2 on 9 February 2020 shows the Red Sea and the Nile River. North is approximately at right. The sail appears slightly curved due to the spacecraft's 185-degree fisheye camera lens. The image has been color corrected and some of the distortion has been removed.Image: The Planetary Society
LightSail 2 Mission Readiness Review team
LightSail 2 Mission Readiness Review team The LightSail 2 Mission Readiness Review team at Cal Poly San Luis Obispo on July 17, 2018. Back row: John Bellardo, Cal Poly; Dave Spencer, Purdue. Middle row: Barbara Plante, Boreal Space; Bruce Betts, The Planetary Society. Front row: Alicia Johnstone, Cal Poly; Alex Diaz, Ecliptic Enterprises Corporation. Not pictured: Darren Garber, NXTRAC.Image: Jason Davis / The Planetary Society
Mat Kaplan, John Bellardo, Jordan Ticktin and Aaron Fielden
Mat Kaplan, John Bellardo, Jordan Ticktin and Aaron Fielden Mat Kaplan, John Bellardo, Jordan Ticktin and Aaron Fielden with LightSail 2 in the Cal Poly clean roomImage: Mat Kaplan

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An ancient Greek analog computer used to predict planetary motions was retrieved from the sea in 1901. It dates from somewhere between 87 BCE and 205 BCE. What was this relic called?

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What was the last two-person, orbital spaceflight launched from the United States?


The last two-person orbital spaceflight launched from the United States was NOT Gemini XII. It was the STS-4 mission of space shuttle Columbia in June of 1982.


Mat Kaplan: LightSail 2 reaches one year in space 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. That's right. The earth has made one full revolution around the sun since the society's little CubeSat with 32 square meters of Mylar sails rocketed into orbit, aboard a roaring Falcon Heavy. We'll look back with Planetary Society, chief operating officer, Jennifer Vaughn, and then get the mission status and outlook from LightSail program manager, Bruce Betts, and LightSail 2 project manager, Dave Spencer. Dave also has some very special news about his own work that he'll share.

Mat Kaplan: Bruce will stay with us for this week's What's Up Trek across the night sky and a new space trivia contest. My favorite image in the latest edition of the down lake might be hard to decipher without a caption, Bennu suited technicians are reaching up to a matrix of brass colored cylinders over their heads as a complex piece of technology that would be unrecognizable to many, at least from this angle. What we're watching is members of the perseverance Mars Rover team installing sample tubes in the belly of the Rover. Someday, those very tubes filled with martian soil will be returned to the great labs back here on earth. And the dream of Mars sample return will have been realized. NASA says Crew Dragon, astronauts, Bob Behnken, and Doug Hurley are likely to make the international space station their home till at least August and possibly longer.

Mat Kaplan: The extra hands are much appreciated by the other occupants, Bob and Doug might even get to help with some work outside the station suitable for framing. That's a huge mosaic image of asteroid Bennu surface taken by NASA's OSIRIS Rex spacecraft last month. You can see this small crater called Osprey. It's a backup location for collection of a sample later this year. I swear the picture is so sharp, you feel like you could reach in and pick up a sample or two yourself. And that's no more than a sample of what you'll find at, where you can also subscribe to our great weekly newsletter for free. By the way, the June edition of my own monthly newsletter is now available at We weren't the first to set sail on the light of the sun. That honor goes to Japan and it's Ikaros solar sail, but we tried to be first with our cosmos one craft. That episode was just one chapter in the Planetary Society's long-held dream.

Mat Kaplan: A dream that was finally realized last year with LightSail 2. We'll get into the details with Bruce Betts and Dave Spencer. First though, I wanted to get the bigger picture from chief operating officer, Jennifer Vaughn. She joined me just a couple of days ago. Jennifer, welcome back to the show. Nobody is going to be surprised to hear that you and I and our colleagues and all of our members are pretty proud right now to be reaching this milestone. I know you feel that way.

Jennifer Vaughn: I do. And so proud and I know above all, it's our members that they should be so proud that they came together and not only made this mission happen, but we have achieved our goals and we're still fine. And we're still fine a year out, hard to believe.

Mat Kaplan: Seriously, did you suspect I did not, that we would be at this point B, going into an extended mission.

Jennifer Vaughn: No, I certainly when we put out the estimates in the very beginning, we thought that it could easily stay up for a year, but that wasn't part of our primary goals. We were out there to, one, get the first crowdfunded spacecraft up there and orbiting and actually achieved those goals of controlling our orbit. How long it stayed up in orbit was really just a bonus. And those early estimates have said it could be up for a year sounded like a very long time at that point. But now it feels like yesterday that we were in Florida watching the launch.

Mat Kaplan: And how gosh, I was just talking with somebody about that, how it does not feel like it's been a year since we heard and felt that that Falcon Heavy take LightSail 2 up into orbit. I mean, has anything surprised you about this mission and especially the reaction to it? How well it's been received?

Jennifer Vaughn: That's an interesting question. I don't know about surprise. It took us so long to get to this point that just the idea that we not only got off the ground, but that it was operational, I don't want to call that a surprise, but it was such a wonderful, welcome relief when that happened. Seeing those sails deploy, getting those images back, confirming, just it was so exciting to see it actually coming to fruition after 10 years of preparation. Over time though the fact that I continue to meet people and they say, "Oh yeah, I contributed to solar sailing," when they find out what I do. I just love that connection point that all these people around the world are feeling such ownership over this spacecraft and they're very clear that they made this happen.

Mat Kaplan: I hear the same from people all the time. You know, you talk about 10 years of developing LightSail, but I say, in fact, this is in my newsletter for this month that also comes out like this episode on the 17th of June. This is really has been a long, hard road. And it stretches back to the beginning of the society, I guess, right? Because I mean, at least the two of our founders, maybe all three, this sailing on the light of the sun was a dream that they share.

Jennifer Vaughn: Yes. And that was one of the things that they shared before the organization even existed. There was this connection with the concept of flying a solar sail out to Halley's comet. And Lou Freeman had an essential role in that mission design and concept. Bruce Murray was the head of the Jet Propulsion Laboratory at the time. And Carl Sagan was a Namor with this idea of sailing on sunlight. So all three of them had this connection. And when the organization was formed in 1980, it was written into a lot of our very early documents that we as an organization were going to pursue the opportunity of solar sailing.

Mat Kaplan: Right from the start and even before. What's next? Do you get the question that I still get from people which is specifically, "Hey, when is LightSail three?"

Jennifer Vaughn: Oh, of course I get that question. It's an obvious question. That is the next line of thought, but I always say the same thing. We're not in a solar sail business, so while we would never preclude the opportunity of doing something in solar sailing again, it's not our mission. Our mission is to involve the public in pushing space exploration forward. To that end, we're always looking for the next best opportunity for the public to make a real difference. So as we've mentioned a little bit before, we are developing a proposal opportunity and open call for proposals that we will announce early in 21. And the idea behind that is that we can reach out to a very large community of people around the world. So it's not specific to any particular space agency or university system.

Jennifer Vaughn: It's going to be an open call letting the organization know, how could the members of the Planetary Society help advance a new concept, a new way of exploring space and new way of understanding the planets. We're excited to get that going and it's really an extension of the way we've always done our work. We've always found great individuals who have compelling ideas and need the public support to get those things done. So all we're doing with this proposal process is adding a schedule, adding an expected opportunity, adding some dollar figures of what we're hoping to support. So that there's just clarity that this is what the organization is seeking. We want to hear from the community about where we can do the most good.

Mat Kaplan: And there does seem to be precedent for this. It's not a duplication in any way in the Shoemaker NEO Grants that the Planetary Society has been distributing and getting such good results with for a long time. We're enablers.

Jennifer Vaughn: We are. And we use that model because that model has been so successful. One of the things that makes it successful is that it's predictable. You know, every two years we're going to offer this. And it's very clear what we're looking for. And that community of people who propose to the community grants has continued to grow over time. So we use that model and say we want to apply it to a much larger portfolio of project ideas.

Mat Kaplan: We are happy to share what we've learned.

Jennifer Vaughn: Very, very happy to share. It was really built into our initial goals that any work that we were doing on testing solar sailing in earth orbit, we wanted to be able to share with the community. And we've already been quite successful while it's been a whole year in orbit. It's only a year in orbit and we've had a number of professional papers already in place, presentations. We do have these professional working relationships with NASA. We are a big part of the international solar sailing community. So for all these reasons, it takes the organization's effort and it just multiplies it, amplifies it by bringing in all these other opportunities to share the wealth.

Mat Kaplan: Just one other point of pride that I know I share is in having met these young people, interns and students undergraduates, as well as graduate students who have been a part of this project, some of whom have gone on to professions in aerospace. And they unanimously talk about the value of this project. Is that something you also think about?

Jennifer Vaughn: We do, yes. I think about it and a number of us the organization are really looking at that as a success story for this particular project. But I think even more so looking at where can we build in student opportunities, intern opportunities and fellowship opportunities into the work of the Planetary Society. So we're looking at it beyond just our projects, but where else can we reach out as far as our communications efforts, our political advocacy efforts and start developing real programming to bring young people very closely to these efforts.

Mat Kaplan: Jennifer, I look forward to raising a glass with you on June 25th when LightSail 2 graduates into the next phase of its existence. So thank you for this and I'm delighted to be able to share your thoughts and share this experience with you.

Jennifer Vaughn: Well, thank you. We are so excited. Once again, this is just testament to the power of people coming together, rallying around a very big audacious idea and making it happen. Everyone should be very proud.

Mat Kaplan: Empowering the world citizens.

Jennifer Vaughn: You got it.

Mat Kaplan: That's Jennifer Vaughn. She is the chief operating officer of the Planetary Society. We'll hopefully Jen be talking to you again on this program before too long. Thanks again.

Jennifer Vaughn: Thank you, Mat.

Mat Kaplan: You know Bruce Betts as chief scientist for the Planetary Society and as my partner for the What's Up segment, you may also have heard his occasional updates on the LightSail mission. He delivers those as the longtime LightSail program manager. You may not know Dave Spencer as well. Up until just days ago, Dave was an associate professor of aeronautics and astronautics in the Purdue University, College of Engineering. He's also the founder and director of the Space Flight Projects Lab at Purdue. Then there were the 17 years he spent at JPL, including his service as mission manager for Mars Odyssey and deep impact, and as deputy project manager for the Phoenix Mars Lander. He even helped Pathfinder make it to the surface of the Red Planet back in 1997.

Mat Kaplan: Now, he is about to return to the Jet Propulsion Lab in a new and exciting position. One that we'll ask him about in a few minutes, but Dave primarily joined Bruce and me to help us mark the first anniversary of LightSail 2, on orbit. Gentlemen, congratulations. I did not think as I said to Jennifer Vaughn, that we would a year later be talking about this transition into an extended mission for LightSail 2. And we have you and the rest of the team to thank, and obviously a great spacecraft and a lot of members of the Planetary Society. So again, congratulations and welcome to the show.

Bruce Betts: Thank you. Good to be here, Matt.

Dave Spencer: Thank you, Matt.

Mat Kaplan: As we speak, where's that LightSail, Bruce?

Bruce Betts: It's flying somewhere between 24 degrees North and 24 degrees South. I'll check Matt. I'll get you an answer in just a moment.

Mat Kaplan: Why you must be going to that handy dashboard at

Bruce Betts: Oh yeah. I could have done that. I went to my more detailed program. I used to plan the imaging and things like that.

Mat Kaplan: Yeah. I'm not surprised that you guys have something, a great deal more detailed to tell you about where LightSail is, but also what it's up to. Dave, what is it up to? What is the current status of the spacecraft?

Dave Spencer: We're solar sailing just about every day. We turn the spacecraft twice in orbit so that we get a little boost from solar photons and we're actively controlling the spacecraft on a daily basis. Every day it takes a few hours to basically damp attitude rates and manage the momentum on the momentum wheel, which is used to reorient the spacecraft. We take a couple hours to dispend the spacecraft, get the wheel speeds down and then go back into solar sailing. So that's been pretty much the routine for quite a while. And we've been addressing a number of different challenges and trying also to improve the solar sail performance. Things are going well and we're pretty much in the routine of solar sailing at this point.

Mat Kaplan: Is this reorientation of the spacecraft of LightSail 2, is it automatic? Or is somebody saying, "No, okay, we're coming back into the sun. It's time to turn X degrees."

Dave Spencer: No, it's automatic. We have onboard software that was developed before launch and we have made some updates to it, but basically it's autonomously controlled onboard the spacecraft, and we have several different attitude control modes of which solar sailing is just one. I've also mentioned the detumble mode where we damp rates. We've also got a no torque mode where we don't have any actuation that would change the orientation of the spacecraft. We've also uploaded recently a mode where we point the sale directly at the sun, which is useful for recharging the batteries.

Mat Kaplan: Other than these sort of gross adjustments to catch those rays, whether it's to propel you or to charge the batteries. Are there other kind of minor attitude adjustments being made perhaps more often?

Dave Spencer: Other than the ones I've already mentioned? No. And with the control that we have with the spacecraft, we're not able to do really fine pointing. We've come to the realization of recognition, which is not too far from what we predicted that we can orient the sale within about 15 degrees of the desired orientation. So that's about as good as we can do. And we don't do a lot of fine tuning. We do have one more attitude mode where we can basically align the orientation of the CubeSat with the earth's magnetic field. But we haven't used that too much since we actually started solar sailing.

Mat Kaplan: Bruce, I mean, maybe not optimal attitude adjustment, but obviously adequate. Does this meet the expectations that you had before the launch and the deployment of the sails?

Bruce Betts: Yes. First, let me give you that important answer, Matt, we're over the South Pacific in the middle of the ocean right at the moment, we're recording. It will of course be different when people are listening now. I'll keep you updated. We should hit South America in a few minutes.

Mat Kaplan: Well, Aloha.

Bruce Betts: We're kind of far South, but we do pass near and over Hawaii at times. Yeah, this definitely has met the expectations. I mean, we set the fundamental goal for the mission was to demonstrate controlled solar sailing in a small spacecraft, a CubeSat in this case size of a loaf of bread, demonstrate it for the first time as a way to spur interest in solar sailing, but also demonstrate that you can use these CubeSats that have been used in earth orbit. You could use solar sails as a propulsion technique in interplanetary space. Our opportunity for launch was to earth orbit, so that's what we're doing. But yes, even with the errors and pointing, et cetera, we definitely see that we're able to control the spacecraft. And it does usually does what we want it to be doing, and we can adjust the orbit they're in. So we achieved the desired big goal early on and the rest is a whole lot of icing that we're putting on the cake to learn more about solar sailing and share that with the world.

Mat Kaplan: Bruce Betts and Dave Spencer have much more to share about LightSail after a break, stay with us.

Bill Nye: Greetings, Bill Nye here, CEO of the Planetary Society. Even with everything going on in our world right now, I know that a positive future is ahead of us. Space exploration is an inherently optimistic enterprise. An active space program, raises expectations and fosters collective hope. As part of the Planetary Society team, you can help kickstart the most exciting time for US space exploration since the moon landings. With the upcoming election, only months away, our time to act is now. You can make a gift to support our work. Visit Your financial contribution will help us tell the next administration and every member of Congress how the US space program benefits their constituents and the world. Then you can sign the petitions to president Trump and presumptive nominee Biden and let them know that you vote for space exploration. Go to today. Thank you. Let's change the world.

Mat Kaplan: So it's worked, Bruce you've told us many times it did exactly what it was supposed to raising its orbit, but it is also losing altitude, right? I mean, how much longer before LightSail just starts picking up too many molecules of air and not enough photons?

Bruce Betts: Well, it'll be at least many months. I don't know if Dave has more to say about it, but the fundamental thing is you know, Matt is that even though we're in space and we're some 700 kilometers up in altitude, there's still molecules there. And when you've got a little tiny, slow mass spacecraft and a big sail area, you're getting atmospheric drag. So we are gradually going down and although we'd make adjustments through orbit and when we're solar sailing efficiently, we decrease how quickly we're going down and even a few days of increased altitude. Generally, we're fighting a losing battle with the atmosphere and atmospheric drags. So it's a matter of time, but we've got time and so we're trying to keep things going, learn more, take pretty pictures and understand things.

Dave Spencer: And just about a year into operations, we've lost only 10 or 15 kilometers worth of altitude. So the orbit's decaying very slowly. We do expect that decay rate to accelerate, but it's really difficult to tell because the atmosphere responds to solar events when the sun gets more active and throws off energetic particles. The atmosphere expands and atmospheric density is up where we're solar sailing get higher and that increases the atmospheric drag. So we can't really give a precise prediction about when we're going to deal with, but we do expect the decay rate to pick up here in the next year.

Mat Kaplan: What about the technology? You've got batteries, they don't last forever. You've got that spinning wheel that has to spin up and spin down a couple of times each day at least. Is there any sign of those starting to show the wear and tear that is almost inevitable in space?

Dave Spencer: We don't really see any obvious signs of degradation on the spacecraft. You mentioned a couple of the life-limiting technologies. The batteries are lithium polymer batteries. They have a limit to the number of cycles they can go through before they start losing charge. And I would expect that we're getting fairly close to that limit. So it wouldn't be surprising to see some degradation in the batteries here in the next several months. Also, as a CubeSat, there's no radiation hardening on the electronics. We do get periodic spontaneous reboots of the flight computer that are likely caused by energetic particle interactions, radiation. But at some point we could have a catastrophic failure of the spacecraft due to radiation. We hope that doesn't happen.

Mat Kaplan: It's kind of uplifting to think of our little CubeSat suffering from the same cosmic ray hits that have at least temporarily taken out so many other spacecraft that have gone far deeper into the solar system. Speaking of other spacecraft, Dave, you've been a part of, in fact, you've led several other missions with slightly larger budgets than LightSail 2.

Dave Spencer: [inaudible 00:22:28].

Mat Kaplan: How does it compare? I mean, doing a project like this on almost a literal shoestring and pulling it off.

Dave Spencer: Well, I'll tell you there are a lot of similarities and there are some key differences. On the similarity side, I get the same amount of excitement and enthusiasm and just get as charged up about LightSail as I have any of the other missions that I've worked on, including the Phoenix Mars Lander, and Mars Pathfinder, Odyssey, Deep Impact, the excitement and enjoyment I get from operating LightSail is just in family with those other missions. One of the key differences is that the team's a lot smaller. We've got six people that basically operate the LightSail 2 spacecraft on a day to day basis. Everybody's got a lot of responsibility and it's just a very close knit team, but that's a much smaller flight team than what I'm used to. So that's a big difference.

Mat Kaplan: Bruce, I'm going to give you a chance to talk a little bit about Dave. You've been part of this program from the start, Dave is not. You've worked with a lot of people. How has Dave been as somebody to work with on this team and what has he brought to the project?

Bruce Betts: He's terrible. He's obnoxious. Wait, are we recording [inaudible 00:23:46]?

Mat Kaplan: Yeah, I'm afraid we did start.

Bruce Betts: Okay. I mean, Dave's great. Sorry, I couldn't resist. Now, Dave's brought a great sense of experience organization. He's easy to work with and has everything you want in a project and mission manager, which is the roles he's filled very well and has dealt with the fact that we do have a shoestring budget. We do have a small team. We have the breadth of the team, but we necessarily don't have the depth. So he's been great at adapting to the situations as they occur.

Mat Kaplan: Because you've been with it for so long, Bruce, you've weathered all of the many challenges of getting the spacecraft built, launched, deployed. What would you point to? What were the biggest challenges outside of the things that I know you had to deal with as well, but at least you had help with finding the money to make all this happen and pulling the team together. What were some of the expected and unexpected challenges?

Bruce Betts: Well, I think the expected broad challenge is you're flying in a hostile environment with little forgiveness on a comparatively small budget, trying to do something that no one's done with such a small spacecraft. The Japanese with a much larger spacecraft and larger budget flew Ikaros and there was a solar sail. But trying to shove a boxing ring size, Mylar sail into a loaf of bread sized spacecraft and operated has been challenging to say the least. Now, the good news and bad news, we had the challenge of the launch of the Falcon Heavy kept slipping and slipping and slipping, but it was never clear when it was slipping to. So we had a lot of early just schedule trying to figure out what to do, but it did give us a chance to do a lot more testing on the ground. So that has helped us considerably.

Bruce Betts: In orbit than we've had different challenges that come up as we go along, things that are unexpected. One of the solar panels didn't deploy fully and then took us while on an image of shadows to figure that out. But once we did it made a lot more things make sense, and we adapted to it. It isn't a major effect on the mission. Various glitches here and there, but all of them thanks to Dave and the team at Cal Poly San Luis Obispo and Boreal Space and Ecliptic Enterprises. Thanks to the team, we've come through all of those. So that's a long, unwieldy explanation, but you like to get me into those, don't you?

Mat Kaplan: I liked it. I liked it, Dave, anything to add and it's your chance to get back at Bruce?

Dave Spencer: Well, yeah, likewise, Bruce is really tough to work with. He's just not a very likable guy, if you get right down to it. No, I'm [crosstalk 00:26:39]. Bruce is great. And the team that we've got, we talk on a daily basis. We've I think developed a very close working relationship. So it's really a great team, but we're all distributed. We've got a lot of university involvement as well as industry partners involvement. So it's a really neat makeup for team, I think in terms of challenges that we've overcome, that maybe were unexpected. The one that we've really been wrestling with since we initially deployed the sail back in July of last year is momentum management, managing the angular momentum of the solar sail craft. We've got one small momentum wheel on board that's used for doing these turns along with some torque rods, basically running a charge through a coil of copper wire and having that electric field generate a magnetic field that interacts with the earth's magnetic field.

Dave Spencer: With those actuators, we try to turn the sail craft twice every orbit and the momentum wheel tends to rapidly reach its maximum wheel speed. So just being able to come up with an approach to manage that and get the wheel speeds down to where we're not saturating the wheel. That's been one of the key challenges that we've dealt with really since the beginning of the mission. We've continued to try to automate that process, and I think we've gotten better and better at it as the missions proceeded.

Mat Kaplan: I failed to mention Dave's host institution that he's been at, which is Purdue, and one of Dave's grad students has been critical to the team and figuring things out like that, Justin, man.

Dave Spencer: Yeah, that's one thing that's been really neat is Justin has had a key role throughout operations. There have also been a couple of Cal Poly students and I'll mention Michael Fernandez specifically that have really been key in operations, as well as just communicating with the spacecraft. The students have carried a lot of weight in terms of making sure that they're on console for those shifts where we need to do manual commanding of the spacecraft.

Bruce Betts: No, it's been great. The student involvement and John Balardo who manages everything in the software and the ground stations at Cal Poly has been working with undergrads there. So it's been a great experience for us and for the students.

Mat Kaplan: I brought this up with Jennifer when we talked as well about how rewarding it has been to watch these students, some of whom are now off in aerospace careers and point to this experience with great fondness, but also talk about the tremendous experience that it gave them. I don't know, Dave, Bruce, did you have an opportunity? Anything like this when you were at that age?

Dave Spencer: This is Dave and I certainly didn't. I basically came out of college and having done a master's degree that was purely based on analysis, no real hands on experience, no real flight project experience. I think that that is a key selling point for students. I tell students when they go into an interview position, they need to be able to explain to the interviewer how they can fit into the organization, how they can contribute and hopefully point back to relevant experience where they've actually done that sort of thing. Hands on experience on LightSail is really key for these young students career. So I'm happy that we could provide some of that opportunity.

Bruce Betts: I did not have flight operations experience per se, but I did do image planning. And how is it accepted by the Soviet Phobos 88 Mission and then had a mission failure before anything our plan got done. So I learned learning the early lessons of the challenges, space flight. But no this has been a great opportunity with these students and one to work on everything from the hardware to flight operations, to modeling the spacecraft and what's going on.

Mat Kaplan: Bruce, I had forgotten about that early imaging or image planning experience that you had. That must make it even sweeter to now see these gorgeous images coming back from LightSail 2 into a program that you manage.

Bruce Betts: Oh, it is. I got into planetary science originally because I love the pictures going back to childhood. So to have a spacecraft and where we're taking pictures or we're taking... the primary reason is for engineering to see, look for variations in the spacecraft originally to confirm the deployment of the sail. But we're also, we're the Planetary Society. We're about public interests and exciting the public about space and seeing that big, shiny sail with pictures of the Nile river in the background or Central Australia or the Himalayas, it just makes for exciting stuff. So, yeah, I'm having fun.

Dave Spencer: From LightSail 1, we got one image down and we were ecstatic to get that one image down. And we got lucky in having the sun centered in the field of view, but for LightSail 2, we've gotten dozens of really beautiful images down that have the earth in the background. Bruce mentioned my favorite, which is one that shows, the Nile River and the Red Sea, but it's really tough to pick a favorite because there are so many stunning images. So I encourage your members to go to LightSail website and take a look at those images.

Mat Kaplan: And how, yeah. If you haven't folks do it today, don't do it right now, unless you want to, I think it'll enhance this conversation. My favorite, I think, has to be the one of looking up from Baja California toward my home actually in the San Diego area. And I'm sure I was out there waving at the time. As we celebrate this year and as you share what we've learned, this is something I also talk with Jennifer about and the collaboration that is underway with the NASA folks behind the Near-Earth Asteroids Scout mission, NEA scout, what kinds of things are you telling folks like that? What are you putting in the papers that you're presenting? The kind of thing that would be like, if you're going to build LightSail three, because we're not whatever you do, don't do this, Bruce.

Bruce Betts: Don't let Matt near the hardware.

Mat Kaplan: I don't know if you heard Dave, but John Balardo at Cal Poly insisted that I pull the spacecraft out of the Peapod, it's little ejector. And I said, "I really should not be touching this [inaudible 00:33:06] I'm never going to hear the end of it from Bruce."

Bruce Betts: It's true. I would have been harassing you week after week on Planetary Radio. No, I think the lessons are similar to, first of all what's always there, which is test as much as he can, but that it's challenging as Dave mentioned, the momentum management, I think is something that we have helped contribute to, which is just an understanding of how hard it is to spin down your momentum wheel and get the momentum out of it or whatever you're using. They are using multiple momentum wheels I believe on NEA Scout. But it's similar just thinking through those things as much as you can beforehand. Dave may have some other insight here.

Dave Spencer: Well, I think one thing and Bruce alluded to this, we found an imaging months into the mission that apparently one of the four booms that pulled the sail material out from their storage compartment and that keep the sail and is fully deployed configuration. One of those booms apparently has partially buckled. It's not real obvious from the imaging, but we see a boom in a location where it just shouldn't be. That's the key finding because solar sails and drag sails are going to be dependent on structures like booms. In fact, NEA Scout has a similar grooms although made out of a different material that they're going to be flying. So anytime you get experience with these sort of mechanisms in flight, it's very useful to characterize the performance. So that's a key takeaway as well. But I think from my perspective, one of the things that the LightSail did which sets it apart from other missions is the fact that it was member funded by donors, not funded by a national space agency. And it's such an ambitious mission, that really sets it apart from previous missions.

Bruce Betts: We're just crossing the Coast of South America now.

Mat Kaplan: Dave, I'm glad you mentioned drag sails because that takes me into the future. What is the contribution of LightSail 2, for the future? Is this a technology that beyond NEA Scout seems to have promise, perhaps even as I know, you've talked about at times, Bruce getting us to the stars someday.

Bruce Betts: Yeah. I mean, I think we've helped demonstrate that you can do solar sailing. You can it in a smaller configuration and there are a lot of potential applications of solar sailing. And the far reaching one is getting us to the stars because you can conceptually accelerate this with a high powered lasers, but there are a lot of near term ones like NEA Scout using it to go to an asteroid. You can also, because you're not dependent on fuel, you can visit multiple asteroids. We can have missions that are in what would otherwise be unstable orbits. For example, solar monitoring missions that are closer to the sun than the stable L1 point of gravity balance. So you get more warning for solar storms coming. I think that we're really at the infancy of this technology and we played a role in it but it'll be great to see what happens going forward.

Dave Spencer: You mentioned drag sail technology. So drag sails are used to de-orbit spacecraft or space objects at the end of their useful lifetime. Think about the satellite mega constellations that SpaceX and others are planning for global internet service. At the end of mission, they're going to have to de-orbit in order to keep that orbital region usable. Otherwise, if you have defunct satellites flying around, they pose a major hazard for collision. Drag sails are technology that can be used to basically deploy at the end of mission and get those space objects out of orbit, much more quickly than they would otherwise be able to de-orbit. They can be used for a launch vehicle, upper stage to orbit as well as spacecraft.

Dave Spencer: So at Purdue, we've got a couple of drag sail technologies that we're planning on flying demonstration missions. And conceptually they're very similar to LightSail. They use the same sort of a sails deployment technique can use similar sale material. The difference is generally they're passive. Once you deploy the sail, you don't control them, unlike what we're doing on LightSail 2 where we are actively controlling the attitude.

Mat Kaplan: What about just that the basic science? I mean the amount of acceleration that we've been able to get from those photons flying out of the sun, has LightSail 2 also help to refine any of that science, Bruce?

Bruce Betts: It's once again verified that it works as physics tells us [inaudible 00:37:58] because of the uncertainties we've got with things like pointing at least I would say, "No, we haven't made any revisions to the basic understanding of the amount of momentum delivered. It's certainly consistent with what we'd expect."

Mat Kaplan: So Newton and Einstein are safe.

Bruce Betts: Well, I don't know about that.

Mat Kaplan: Guys, this is just the beginning of a celebration. I look forward to joining the two of you and others including our CEO, Bill Nye, the science guy and even more folks, including Jennifer Vaughn on the 25th of when we're going to have a little online video celebration on the actual anniversary of that launch of LightSail 2 on the space X Falcon heavy. So I look forward to joining you there, it's a celebration. I think we've already opened it up, I think to our members and supporters of the LightSail Project. So hopefully we'll have lots of space leftover for other members of the public who are excited about this project, where they can join in too. All the details should be at by the time anybody can hear this show. Thank you for this. Just one more thing, Dave, congratulations. You've got a new job. Tell us about what it means to be headed back to JPL.

Dave Spencer: Well, thank you, Matt. Yeah, I'm extremely excited about this. I've just recently accepted a position as the mission system manager for the Mars Sample Return Campaign. The Sample Return Campaign is actually just about to get going with the launch of the Mars 2020 Rover next month. It's going to go out to Mars and land and cache samples, store samples and sample tubes for future return to earth. And then in 2026, there'll be a Lander and an orbiter, a European orbiter that go out and retrieve those samples, bring them back into Mars orbit. And then that European orbiter is going to return it to earth for a landing in Utah in 2031. So it's probably, in my opinion, it's the most ambitious planetary science undertaking that NASA or anyone has ever attempted.

Dave Spencer: I'm really excited to be a part of it. So as the mission system manager, I'm going to be working on mission design and navigation, mission operations, those sorts of things, similar in many ways to what I've been doing on LightSail, but on a much larger scale with many more people involved. So can't wait to get into it. And I've just recently started that position.

Mat Kaplan: I have often called this on Planetary Radio, the Holy grail of robotic space exploration. There are, I don't know how many thousands of planetary scientists and others and just members of the public like me who are going to be hoping and praying that you're able to successfully pull this off. But I know it's a big challenge, exciting though.

Dave Spencer: Yeah. Thank you. And from a planetary science standpoint, this has been the number one priority for the last couple of decades. So from a science standpoint, the community is really looking forward to actually achieving this mission.

Mat Kaplan: Bruce, before we go. Anything else that you would want to add? Although you will be back with us in seconds for this week's What's Up.

Bruce Betts: Hey, it's appropriate to return back, as Dave mentioned, this is completely funded by individuals. So thank you. Thank you to the 50,000 people from pretty much all over the world who contributed to make this mission a success. We appreciate it.

Mat Kaplan: All right, guys. Thanks again, very much. We'll continue to follow the mission and I will see both of you on the 25th for that celebration on the one year anniversary of LightSail 2's launch.

Dave Spencer: Thanks Matt.

Mat Kaplan: That was Dave Spencer, associate professor of aeronautics and astronautics in the Purdue University, College of Engineering. But moving from that position to the one you just heard about mission system manager for the Mars Sample Return Campaign after Jet Propulsion Lab, not far from the headquarters of the Planetary Society. And of course he has been the project manager for LightSail working with the program manager for LightSail. That's Bruce Betts who's also the chief scientist for the Planetary Society who joins us for What's Up. Indeed, it is time for What's Up with Bruce Betts, who I bet you know, is the chief scientist for the Planetary Society in addition to being the program manager for LightSail. Welcome back.

Bruce Betts: I missed you so much Matt. It's been so long.

Mat Kaplan: I know. I know. And I bet the stars have shifted in the sky since we last spoke.

Bruce Betts: Well, certainly LightSail moved to over Africa now.

Mat Kaplan: Is it really? Wow, boy, time flies and so does LightSail.

Bruce Betts: Nah.

Mat Kaplan: So what is up? What's up there above LightSail.

Bruce Betts: All sorts of things, but we're going to talk about the ones that are easy to see in the night sky. So that would be in the late evening. So now 10:00, 11:00 PM, or after coming up in the East, we've got two planets, very bright Jupiter, and then to it's left dimmer, but still bright Saturn. And if you follow a line from Saturn to Jupiter, it'll lead you to the teapot asterism of Sagittarius. So it looks kind of like a teapot and forms part of the constellation Sagittarius. A couple hours later, if you're up later, we got Mars coming up. Mars is brightening. It is getting quite bright and it will get brighter and brighter until October when it's at opposition. Pre dawn, you can still see Mars nicely over then in the South or the Southwest.

Bruce Betts: And then low in the East, we got Venus coming up, coming up, coming up, getting higher and higher, super bright. Depending on when you're getting this, you might be able to see the moon next to Venus on the 19th. Crescent moon, Venus, still very low, you're going to need a really a good view to the horizon in the East there. And last time to let you know, June 21st annular eclipse whose path crosses Central Africa, Saudi Arabia, Northern India and Southern China. A partial eclipse will be visible throughout most of Eastern Africa, the middle East and Southern Asia. So for those of you out there in those parts of the world, enjoy.

Mat Kaplan: I'm a parsec's wide teapot short [inaudible 00:44:23].

Bruce Betts: Oh, God, I just had this terrible image of you doing the dance like in the sky. Oh, that's going to haunt me.

Mat Kaplan: Had to do that once in high school, I will save that story for another time.

Bruce Betts: I looked forward to it.

Mat Kaplan: I hope some of you who will be under that annular eclipse will write to tell us about it.

Bruce Betts: That'd be great. Onto this week in space history. It was 1983 that Sally ride became the first American woman in space. In 2009 lunar reconnaissance orbiter, as well as the impact or LCROSS both launched and LCROSS did its things slamming into the moon and LRO, still doing good stuff at the moon. On we go to [inaudible 00:45:14].

Mat Kaplan: I don't know, maybe think of David Burn for some reason.

Bruce Betts: Same as it ever was. All right. So astronauts, this is an interesting little tidbit, astronauts often experience a lessened sense of taste in space. So they often request spicy food or spicy condiments for example, on the space station for long stays in space.

Mat Kaplan: I remember reading that the sriracha sauce is pretty popular if I remember correctly.

Bruce Betts: That's actually what one of the Ss stands for, ISS.

Mat Kaplan: I think sriracha... very hard to say. I think sriracha sauce actually probably originates from somewhere in space.

Bruce Betts: If they're aliens, they're definitely involved in the creation of that. All right.

Mat Kaplan: Take us to your sauce.

Bruce Betts: We try to move on to the trivia contest. Before Crew Dragon Demo-2, what was the last two person, orbital space flight launched from the United States? That was your question. How'd we do Matt.

Mat Kaplan: You really have frustrated a lot of people who entered the contest with this one.

Bruce Betts: It's my goal in life.

Mat Kaplan: So here's what we heard along this line of frustration from Mel Powell in California. Bruce was trying to trick us into guessing Gemini 12 with Jim Lovell and buzz Aldrin. Wasn't he? Wasn't he? Don't even bother making him admit it. It's also clear to us now can take that guy anywhere. Can you, Matt?

Bruce Betts: I didn't do it. I wasn't trying to fool you.

Mat Kaplan: Here's our poem from Dave Fairchild, the poet Laureate. Prior to SpaceX in May, 2020, you have to go back to the 80's or more. That's when Columbia lifted for NASA flight that was called STS number four. It left the launching pad in June of 82 Mattingly Hartsfield safely on board. Prior to that, it was Gemini 12 that had two crew aboard her as records record. I'm not sure that last line may not scan perfectly, but is that right?

Bruce Betts: STS-4 Columbia is correct in '82. I also will note that STS-1, two, and three also had two person cruises. They were a test runs for the space shuttle before they loaded them up with more people.

Mat Kaplan: Here's our winner Perry Metzker. Perry Metzker long time listener in New York, New York. The town is so great they named it twice. Who is it that says that? Anyway, Perry, he's a previous winner, but it has been over three years since he hit the jackpot. Perry, congratulations. You are the winner of that celestial buddy, little earth, our earthy plush toy just like the one that is now up on the international space station. It's going to be brought home by Bob Behnken and Doug Hurley. When they climb back on the Crew Dragon there, they're going to bring little earth along with them. I imagine it's going to end up in the Smithsonian. Well, yours won't go on the Smithsonian it'll go to your house [inaudible 00:48:33] Perry, so again, congratulations.

Bruce Betts: All right, we move on. Now this question, you got to stick with me. It's definitely different, little weird, but it takes you down an interesting rabbit hole if you followed through with finding the answer. So here we go. An ancient Greek analog computer used predict planetary motions was retrieved from the sea in 1901. It dates from somewhere between 87 BCE and 205 BCE. Here's your question? What is this Relic called? Go to

Mat Kaplan: If I have a favorite computer in the entire history of earth, this is it. I've loved this story so much. I want to go to... I forget what museum it is, where they've actually rebuilt it based on all the X rays, they've done an analysis and it's this anachronistic piece of technology that has no business existing 200 years BCE, but there it is anyway.

Bruce Betts: And they found evidence of sriracha on it.

Mat Kaplan: Yeah. And our friend Kim Stanley Robinson, the great writer, he wrote it into his story. I think it's in Galileo's dream that book of Kim Stanley Robinson. Enough of that you've got until the 24th, that'd be June 24th at 8:00 AM Pacific time to get us this answer and win yourself an ancient Greek computing device. No, I'm sorry. You'll have to settle for a rubber asteroid. We're done.

Bruce Betts: An ancient Greek rubber asteroid. All right, everybody, go out there look up on night sky. And think if you were to put one thing in your house, in the Smithsonian, what would it be? Thank you and good night.

Mat Kaplan: I would want to put two things in this Smithsonian, your microphone and my microphone, because there are such great historic value. And also there are people who'd be very happy to hear that we no longer have microphones.

Bruce Betts: We'd get more.

Mat Kaplan: Okay. He's Bruce. He's the chief scientist of the Planetary Society, you knew that, and he joins us every week for What's Up and you knew that too. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its LightSailing members. Big, thanks to those of you who have given us a rating or review in Apple podcasts. I hope more of you will join them. Mark Hilverda is our associate producer. Josh Doyle composed our theme, which is ranged and performed by Peter Schlosser. Stay safe and well. Ad Astra.