Planetary Radio • Jul 21, 2021

Amy Mainzer and a New Asteroid-Hunting Space Telescope

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Amy Mainzer

Professor in the Lunar and Planetary Lab at the University of Arizona, Principal Investigator for the NEOWISE mission, and leads the NEO Surveyor project

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Planetary Radio Host and Producer for The Planetary Society

We may finally get the powerful telescope we’ve needed to find almost all of the near-Earth objects that are big enough to destroy a city. University of Arizona professor Amy Mainzer leads the NEO Surveyor project. She returns to Planetary Radio with the full story. Blue Origin’s Jeff Bezos and three colleagues rode a rocket that briefly put them in space. We’ll hear from Bezos and 82-year-old Wally Funk. The pilot and former astronaut candidate is now the oldest person to have reached space.

NEO Surveyor
NEO Surveyor This artist's concept shows NASA's proposed NEO Surveyor spacecraft, a mission to discover and characterize most of the potentially hazardous asteroids that are near the Earth.Image: NASA/JPL-Caltech
How NEO Surveyor works
How NEO Surveyor works NASA's NEO Surveyor space telescope will scan for asteroids hidden in the Sun's glare. This infographic is free for media and non-commercial use with attribution.Image: The Planetary Society

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Mat Kaplan: Amy Mainzer and her new asteroid hunting space telescope, this week on Planetary Radio.

Mat Kaplan: Welcome, I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. The announcement from NASA came in June. After years of advocacy, planning, proposals and disappointment, the agency gave the green light to what is now known as NEO Surveyor.

Mat Kaplan: This relatively small infrared telescope will help us discover the thousands of big space rocks that threatened our home world. Amy will be here to tell us about the project she leads. Later, we'll hear again from The Planetary Society's chief scientist, Bruce Betts, who will bring us another space trivia contest right after a scan of the current night sky and a random space fact.

Mat Kaplan: Happy 52nd Lunar Landing Anniversary, everyone. I'm recording this week's show on July 20th, and there's now yet another reason to revere that date. Hours ago, Jeff Bezos and three companions climbed aboard a capsule that sat at top one of Blue Origin's New Shepard rockets. Minutes later that rocket carried them above the Karman line, the black of space was above, the blue of earth below.

Mat Kaplan: After four minutes of zero-g fun, the new space travelers experienced as much as five g's of deceleration before setting down in the Texas desert at gentle one mile an hour. 82-year-old Wally Funk nearly stole the show at the post-flight news conference. Wally was one of the Mercury 13, the group of women who trained as hard, or harder, than the famed Mercury 7. They were declared fully qualified for space flight and then saw their dreams crushed.

Mat Kaplan: Here's what Wally had to say after finally making it into space nearly 60 years later. Listen for the kiss on the cheek she shares with Jeff Bezos.

Wally Funk: Whoa, I can't tell you. I had such a good instructor. He talked us through everything that we were going to do. So I went up this morning, the noise wasn't quite as bad, and we went right on up and I saw darkness. I thought I was going to see the world, but we were quite high and up.

Wally Funk: And I felt great. I felt like I was just laying down and I was going into space. And I want to thank you, sweetheart, because you made it possible for me. I've been waiting a long time to finally get it up there and I've done a lot of astronaut training through the world, Russia, America, and I can always beat the guys on what they were doing because I was always stronger and I've always done everything on my own. And I didn't do dolls. I did outside stuff.

Wally Funk: And I flew an airplane and I were 19,000-some hours. I loved it. And I love being here with all of you, your family, the four of us. We had a great time. It was wonderful. I want to go again fast.

Mat Kaplan: On the night before the flight, a CNN host asked Jeff Bezos the question all of us in the space game have gotten used to. Here's how it goes, "With all the problems we need to solve here on earth, many people wonder why money and time should be spent developing opportunities for paying customers to reach space."

Jeff Bezos: They're largely right. We have to do both. We have lots of problems in the here and now on earth and we need to work on those. And we always need to look to the future. We've always done that as a species, as a civilization. We have to do both.

Jeff Bezos: And our job at Blue Origin is to do what this space tourism mission is about. It's having a mission where you can practice so much that we get really good at operational space travel more like a commercial airliner and less like what you think of as traditional space travel.

Jeff Bezos: If we can do that, then we'll be building a road to space for the next generations to do amazing things there, and those amazing things will solve problems here on earth.

Mat Kaplan: Blue Origin plans two more flights this year. As we did last week for Virgin Galactic, we offer our congratulations.

Mat Kaplan: There's more July 20th fun in the July 16 edition of the down link. We heard with great relief since our newsletter was issued that the Hubble Space Telescope has successfully transferred operations to a second computer just as we heard it would from James Webb Space Telescope Project Manager, Bill Ochs, in the July 7 Planetary Radio. It's good to know our best eye on the universe is back in action.

Mat Kaplan: The US House of Representatives has proposed a $25 billion budget for NASA in fiscal year 2022. It's a bit more than the Biden administration requested and it includes money for Amy Mainzer's NEO Surveyor. Amy is a professor in the Lunar and Planetary Lab at the University of Arizona. The U of A tempted her away from NASA's Jet Propulsion Lab about two year ago.

Mat Kaplan: She remains the principal investigator for the NEOWISE mission, an aging space telescope that was repurposed in 2013 for near-Earth object hunting. That was after the end of its first life as the Widefield Infrared Survey Explorer or WISE.

Mat Kaplan: As you'll hear, NASA has given NEOWISE a two-year extension of its important work but Amy has also spent years leading the efforts to put a much more powerful asteroid hunter in space. What started as NEO Cam is now NEO Surveyor and its approval by the Space Agency in June was a triumph for Amy, her mission team and all of us who know how vital it would be for planetary defense.

Mat Kaplan: Amy joined me remotely a few days ago.

Mat Kaplan: Amy Mainzer, thank you so much for returning to Planetary Radio. Double congratulations are in order here. There is that July 1st NEOWISE extension announcement, two-year extension by NASA. Really wasn't it an even bigger announcement three weeks earlier and kind of a wonderful vindication of work that you have been leading for many years?

Amy Mainzer: Yeah, thank you so much, Mat. We are just really delighted to have been able to advance to the next phase of our mission development which we call Phase B or the preliminary design phase. It's a big deal for us because basically, it means we're out of the formulation phase and now, we're into really getting into the serious parts of the design and fabrication even.

Mat Kaplan: I'm going to ask you more about that in a few minutes. But I got to stick with this initial topic, and sort of the entire field of finding NEO's, characterizing them planetary defense, the road to this spacecraft, to this mission, NEO Surveyor was I don't have to tell you long and hard, at least it looked that way from the outside. Were there times when you wondered if the effort was worth it? You were at this for years.

Amy Mainzer: Well, space is definitely a business for the very patient, I will say that. It's just sort of the nature of the business that it takes a long time sometimes for space missions to get going and pick up momentum and eventually get launched.

Amy Mainzer: But I think we've spent our time wisely. We've really worked hard at trying to mature the technology that we required, which is the infrared detectors. So these are the actual camera chips that allow the spacecraft to see the asteroids in the dark. We've not been wasting our time. I'd say we've really gone and spent a lot of effort into refining the technology so that now that we are finally in the development phase, we are ready to go.

Mat Kaplan: This is so much the message that I've heard from so many leaders of missions, principal investigators. In fact, just last week, when I had the leads for the VERITAS and DAVINCI missions on, also the long hard road. It just seems to be the way the game is played. As you've said, patience is awfully important.

Mat Kaplan: I'm also thinking of the work that my colleague, Casey Dreier has done, and Casey says hello by the way. Terrific job of documenting how support for near-Earth object research and planetary defense has skyrocketed in the last few years, which also seems to be a vindication of what so many of us including NASA's own planetary defense coordination office have worked toward. You have to be glad to see all of these.

Amy Mainzer: Yeah. The way I look at it is that we, as a science community, need to do what we can to take care of the problems that fall within our domain, our domain of expertise. This is an area that it's one of the things that we need to kind of cross off our list of worries. And the best way to do that in my opinion is just go look for the asteroids and do a pretty thorough job of it. If we do that, we can pretty much retire the risk that there's something out there that we don't know about.

Amy Mainzer: So I think it's really good that this is getting the necessary attention. The amount of resources required are reasonable. You don't have to move a mountain in order to go find the mountains in space, but you do have to go do your homework, which I'm really glad to see we're going to try to do in a very thorough way.

Mat Kaplan: There are lots of places to go to read about the mission. We have a terrific NEO Surveyor page at and there is a great site hosted by the University of Arizona about the mission. But please, share your elevator speech about NEO Surveyor, what it's designed to do, how it will accomplish this for the few people in this audience who may not know much about it.

Amy Mainzer: Sure. The main thing to know is that the solar system is a really busy place. There are lots of asteroids kind of swarming into the inner solar system ranging in size from teeny little specks of harmless dust all the way up to mountains. The good news is that there are far fewer of the mountain sized objects than there are of the really small ones. That's because over time, the asteroids collided and produced a lot of little pieces.

Amy Mainzer: But even these little pieces, if they're larger than about, say, 50 meters across give or take, they can create some damage on the ground. So our goal is to go out and try to find the majority of objects that are big enough, say, bigger than about a football field sized roughly, to cause really severe regional damage. So in other words, damage to a very large region.

Amy Mainzer: A NEO Surveyor mission really is optimized for finding these objects when they are well away from the earth long before any potential encounters could take place. And that will allow us to find the objects, get orbits for them, make reliable predictions where they're going to go, and make out some basic information about their physical properties, how big are they and maybe how reflective are their surfaces if we can get some additional data on them.

Amy Mainzer: So that in a nutshell is what the mission is designed to do. It's to do a very comprehensive survey of what's in our near solar neighborhood.

Mat Kaplan: I think it's a terrific sign of the progress that has been made, that we have some idea of how many of these larger rocks are out there. I see the figure 25,000, but that's pretty significant, isn't it? We spent most of our time human civilization, not even realizing that they were rocks up there in the sky that could fall on us. And now, we know roughly how many we need to worry about.

Amy Mainzer: Yeah, that's true. And so the 25,000 number comes from estimates based on the objects that we have discovered to date. Like I mentioned, there's a lot more of the smaller objects than there are of the truly, truly large ones which is a good thing. We think that there's roughly about a thousand or so, give or take, of objects that are large enough to cause what we would call global extinction events, things that can take out entire species just in one fell swoop.

Amy Mainzer: When you get down to the size of things that can cause sort of the regional level disaster, say, the size of Southern California for example, that's about the football field sized objects. And we think there's roughly 25,000 of those, for things that are big enough to have problems for an individual city, many more. The numbers just go up in large numbers from there because there are a lot more small pieces.

Amy Mainzer: But that said, we have learned an awful lot about what's out there just from the surveys that we've done to date and that's given us a pretty good idea of where we need to be aiming for in terms of characterizing and finding the rest of the population of interest.

Mat Kaplan: I do not remember how big the rock that exploded over Chelyabinsk was, which fortunately, blew up in the air but still demonstrated the damage that this can do.

Amy Mainzer: Yeah, that was a really pretty small object. It's estimated to have been somewhere between 17 to 20 meters across. That's not very big at all. It's just the defining characteristic of these objects is that they move with just incredible speed with respect to the earth. They're really going very fast, typically maybe a few tens of thousands of miles per hour.

Amy Mainzer: That's where they get such a punch from. They just move really fast. And even a very small one can cause a good bit of damage if it makes it to the ground. Now, the good news is on the small side, like this object that exploded over Chelyabinsk, the atmosphere does a really good job of screening out the majority of the energy from the impact.

Amy Mainzer: And in the case of Chelyabinsk, it really did explode many miles above the surface of the earth and not that much of the energy actually made it to the ground. So there wasn't a big crater. But if the object is even a little bit larger than that, say, 50 meters across, now instead of getting this sort of an airburst effect, now, you can get a big crater in the ground and we have a pretty spectacular example of that in Arizona that's known as meteor crater.

Mat Kaplan: Which I highly recommend visiting. If you're not impressed by the power of these space rocks before your visit, you will be after you look over the edge of that crater. I read that you hope that NEO Surveyor will find about 90% of these 25,000 or so that are 140 meters and larger, which makes me wonder, what about the other 10%? Why will those be more difficult to detect?

Amy Mainzer: Yeah, the good news part of it is we really think we can find the majority of these objects if we are able to operate for long enough. The last 10% though, these are the ones that will be on the trickiest orbits for us, and I guess you can think of it as when you put up a new telescope to look for these things, you can sort of survey a bubble of space around your telescope. And that's how far you can see and how much volume you can see around you.

Amy Mainzer: In our case, we'll have a pretty big bubble with the NEO Surveyor because it's a very sensitive telescope. It will be able to look very far away, so the bubble is large. But it's not infinite. And to some extent, we have to wait for some of the objects to just kind of make it inside the zone that we can see. That last 10% are the objects that are going to be on the most difficult orbits that will just stay just out of reach of our telescope.

Amy Mainzer: That said, this is why planetary defense really is a team sport. You don't just want to rely solely on one telescope. You want to have multiple different telescopes that all have a little bit of different strengths. Each one brings something different to the table, and that's how we're going to mop up those last ones.

Mat Kaplan: I was surprised to see that the NEO Surveyor telescope, the optics, really aren't that much bigger than what we already have in NEOWISE. Is this evidence of the improvements in the detectors as you sort of hinted at?

Amy Mainzer: Yes. That's an important point. So one of the neat things about looking for these objects at infrared wavelength is you don't really need a very large mirror if you go into space and you can get the telescope nice and cold. In this case, the mirror for the Surveyor mission is only a little bit bigger than that of the primary mirror for NEOWISE which is our existing space telescope that we have.

Amy Mainzer: That's doing its best but it's not going to last a whole lot longer, and also really isn't optimized for the task. The reason that Surveyor is so much more sensitive is despite the fact that the mirror is only a little bit bigger, it really does have a much larger focal plane, meaning the camera chips. We just have a lot more of them. They are more sensitive and it lets us cover more of the sky.

Amy Mainzer: Also the other thing we're going to be doing a little differently is we'll be able to look over a much wider zone on the sky and we can integrate for longer times. In other words, we can stare for longer periods of time that NEOWISE can. So these factors all combined make for a telescope that's altogether more sensitive to these asteroids than the existing one that we have is.

Amy Mainzer: And also two, it will hopefully be able to operate for a nice long time so that means we'll have plenty of time to go and look.

Mat Kaplan: I keep hearing and seeing similarities to another space telescope, one that I visited actually just a couple of weeks ago. I'm thinking of the James Webb Space Telescope which is going to operate from Sun-Earth Lagrange endpoint 2 whereas NEO Surveyor will be at L1. They'll both have the advantage of being in these choice neighborhoods which we can also talk about.

Mat Kaplan: But they're both infrared telescopes. And like the James Webb, you're going to be able to do this work, you said, the cold is important but you don't have to bring along a whole bunch of refrigeration equipment or cryogenics that you might run out of. How are you able to maintain the colds you need to detect these infrared sources that are still pretty cool.

Amy Mainzer: Well, that's the trick. So we are going to be out in the Sun-Earth L1 Lagrange point. So, we'll be on the Lagrange point side that's closer to the Sun compared with James Webb which will be on the opposite side. The difference for us is that rather than carrying active refrigeration so either some cryogenics or a really fancy cryocooler ... James Webb has a cryocooler ... we're going to do this purely passively.

Amy Mainzer: The way we will be getting cold is we have a big shiny Sun shade on one side that has our solar panels and then on the opposite side, we paint this spacecraft an incredibly dark black color. And essentially, that allows us to radiate the heat. So we do a combination. We reflect Sun, and try to keep as much of the Sun off the spacecraft as we can. And then on the opposite side, we radiate the heat very efficiently into the deep cold of space. And that's how we're going to keep cool.

Mat Kaplan: Does this mean that you can expect, one reason to expect a pretty long life out of NEO Surveyor?

Amy Mainzer: Well, we sure hope so. With no active cryogens and no cryocoolers onboard, there's really nothing stopping us from lasting pretty long time. This spacecraft does have propulsion. It does have to do a little bit of station keeping to maintain the orbit, but it's pretty minimal. And knock on wood, we're going to get a nice long life out of it, just like we have for NEOWISE.

Mat Kaplan: How will it actually make the detections? Is it something similar to what we got used to the Kepler spacecraft doing simply staring at a patch of sky for a long time and waiting to see if something crosses it?

Amy Mainzer: That's a very interesting question. So we will operate in a mode that is specifically optimized for finding the most hazardous near-Earth asteroids and comets. What we do is take a time series of exposures. So we look at the sky, and then we look back some hours later. And then again, and again, and again. And then we're going to do it again in a couple of weeks roughly. So we had this very kind of, I would say, elaborate scan pattern although it's highly repetitive that is very good for finding fast moving asteroids and comets as they speak across the sky.

Amy Mainzer: Whereas Kepler was really optimized for sitting and staring, holding very still for long periods of time looking for the motion of a planet across the star, for us, our objects are moving pretty fast across the sky. So, we have to do a lot of repetitions and we keep moving to keep up. That said, the survey pattern is entirely repetitive and it is very carefully optimized for finding this specific class of asteroid and comet.

Mat Kaplan: A lot of the focus, of course, is on the spacecraft because that's the more romantic stuff. But from all of what you were talking about, it sounds like the ground operation will be equally important. What will that involve?

Amy Mainzer: Yeah, absolutely. The ground processing system is a huge part of what makes the telescope effective. So basically, we carry out the scan pattern that allows us to get enough detections on a given asteroid or comet that we can get a pretty good fix on its orbit just from the initial discovery.

Amy Mainzer: After that, as soon as we get the images, of course, the first thing we want to be able to do is vet them and make sure that they're really real. We do a very detailed comparison of anything that's in the image with a previously known background of stars and galaxies. We want to make sure we're not looking at something that's actually not moving on the sky. Then we also do a comparison to the other asteroids and comets that are known out there.

Amy Mainzer: And in particular, the main belt asteroids, things that are more distant, totally harmless to us, they outnumber the near-Earth objects by a pretty large number. There's about a thousand times more of these objects than there are the targets that we're seeking, the ones that can get close. So we have to go and basically pick out these needles in the haystack to make sure we're finding the right ones.

Amy Mainzer: That's the big part of the ground processing step, to make sure that the detections are really, really reliable.

Mat Kaplan: Is NEO Surveyor going to also contribute to the search for comets which, of course, pose some danger?

Amy Mainzer: Absolutely. Comets are an important part of the targets for Surveyor because as you mentioned, they really are something we do worry about from an impact perspective. Good news is there's a lot fewer of them compared to the near-Earth asteroids and that's great. Not so good news is they're really a lot larger on average. They tend to be really large and they tend to move much, much faster with respect to the Earth than the asteroids do.

Amy Mainzer: So on balance, we certainly don't want to ignore the comets and we should mop up quite a few of them as part of the survey.

Mat Kaplan: By the way, it was almost exactly one year ago that I had to drive way inland to get away from the coastal cloud cover here in the San Diego area. But I was rewarded by a beautiful view of comet NEOWISE, which I think you also were enjoyed and were pretty proud of.

Amy Mainzer: Yeah, that was a really, really fun find, especially coming at the time that it did with the pandemic. It was really nice to have something to remind us to go outside and look up and know that we are a part of a bigger picture. It was really a beautiful comet and the cool thing about it is we're used to discovering these objects and seeing them on our computer screens as tiny little dots.

Amy Mainzer: And I have to say, it was really something to be able to get out and see it in the sky with my own eyes, and know that other people were enjoying it too. That was really fun. I hope we find another one.

Mat Kaplan: It was thrilling. Yeah, I can't wait. I hope you find one that puts on at least that much of a show with NEO Surveyor. Talk about your team, beginning with your former home, the Jet Propulsion Lab. You have a lot of partners in the NEO Surveyor.

Amy Mainzer: Yeah. As is typical for a lot of these projects, it's really a multiparty effort. We have partners from the Jet Propulsion Lab, of course, the University of Arizona where I'm based at. We're doing work on the detectors. So basically, what we'll be doing is selecting the detectors that we're actually going to fly on the spacecraft. We got to sort through a great number of them to find the very best ones that we will pick and use to fly.

Amy Mainzer: We've also got industrial partners. Ball Aerospace will be contributing the spacecraft, so that's sort of the main gut to the vehicle that has the communications antenna, the main spacecraft computer, all that good stuff, the power subsystem. The telescope is being built by JPL and will be integrated and delivered to the payload integration shop which is at Space Dynamics Lab in Utah.

Amy Mainzer: And they have a lot of expertise in putting together and testing infrared imagers just like this one. So we're really lucky to be partnered up with them. University of Rochester, I've been working with for years and years because they are the absolute pros at infrared detectors of this class going way back, so we've been working together for a long time.

Amy Mainzer: And of course, Teledyne actually manufactures the chips. They are the company that makes the very best chips of this class in the whole world, and I think that's not to brag to say that. They really are the best. So, we've had a great partnership with all these different groups for quite a long time now as we've matured our design and technology.

Amy Mainzer: To be honest, I think a lot of what makes it so fun to work on projects like these is if you have a great team of people who you really like, it just makes it not so much work as fun. It's really a delight to get to work with everybody.

Mat Kaplan: Boy, that is also something that you share with a lot of other mission leaders that I talked to. To clarify, when you talk about the careful work being done to choose the detectors, you know what company they're coming from. You're talking about evaluating each individual chip that will actually go into the telescope?

Amy Mainzer: Yeah, that's right. So, what we do is we make a whole bunch of these chips and we screen them. We basically look through them and we find the ones that have the very best characteristics, the least amount of noise. Everybody has got a camera where you've got one pixel that's just bad or if you look at a laptop or something, [crosstalk 00:25:26] bad pixel or the screen is cracked or something.

Amy Mainzer: So, you want to find the chips that have the least number of bad pixels on them, the very best sensitivity, very best responsivity. And so that's what we'll do. We're gearing up to sort out which ones are going to be the very best. And we have a really beautiful lab. University has given us great facilities, and that's been a lot of fun to get set up and there's nothing like having a brand new lab to play with. So, we're really giddy going there and just having a lot of fun.

Mat Kaplan: You said you're in phase B. Where does that put us? What are you shooting for in terms of a launch and getting out there to a first light at L1?

Amy Mainzer: Right. So, the launch date that we're shooting for right now, we're targeting March of 2026. That's based on what we think is the budget profile that we're likely to receive from NASA and what we think is reasonable given that budget profile. This type of mission fortunately getting to L1, it's kind of in our backyard. It doesn't take us very long to get there. We're talking weeks, not years or anything like that.

Amy Mainzer: So, it doesn't really have a very long cruise phase. We just pop over to L1 and we start doing this sort of big, lazy looping orbit around the L1 Lagrange point, just using little bits of our propulsion system to just keep the orbit just in a way we want, keep us from drifting away from the Earth, and then we start observing.

Amy Mainzer: Basically, as soon as the telescope gets out there and gets on station, we take a few weeks to cool down because we're going to radiatively cool. So, we're going to be dumping all the heat that we've brought with us from the Earth. The telescope will cool down in a matter of weeks. And once that's done, we will begin our science.

Mat Kaplan: A matter of weeks, that's still an impressive time to wait, just to get down to the ambient temperature of space so that you can really do the work that you want to do. It's just amazing to hear a figure like that. Do you have ride yet? Do you know what booster you're going to be on?

Amy Mainzer: That's a really good question. We have not selected a launch vehicle provider yet. So, I'm looking forward to going through the process with NASA to evaluate which one is which, which one we're going to wind up with. I think we do have a couple of very credible choices. And I'm confident we can get a good lift out into space. Fortunately like I said, this orbit, people have done it before. It doesn't take that long to get there.

Mat Kaplan: Turning the page here a little bit, what is it with the University of Arizona and the search for near-Earth objects, Catalina Sky Survey, Spacewatch? You arrived a couple of years ago which I think was kind of a coup for the campus. And now, the university is a full partner in NEO Surveyor, the mission you lead. This seems to be a real priority around there.

Amy Mainzer: Yeah. Well, this is one of the great things about U of A. It's just a long tradition of doing this kind of work with asteroids. Of course, Arizona is known for its very clear dark skies and they are beautiful. If you haven't been to visit and do some stargazing, I highly recommend it. It really is gorgeous out in Arizona.

Amy Mainzer: The thing about the campus is that the science really is well-aligned with work the university is already doing. You mentioned Catalina. About half of all the near-Earth objects that we know of to date are discovered or have been discovered by the Catalina Sky Survey which is operated in the mountains just outside of Tucson. And of course, Spacewatch was one of the pioneering telescopes in surveying four near-Earth objects doing actually a dedicated survey for those things, not just so much discovering them serendipitously while doing other work.

Amy Mainzer: And of course, the OSIRIS-REx mission has been ongoing for a long time at U of A, and they're bringing back a sample of a particular asteroid, the asteroid Bennu. So, we're looking forward to that. For all of these reasons, I think it really made U of A a really great place to go for this project. And also too, I'm just enjoying working with students and just being part of the university life again. It's a lot of fun.

Mat Kaplan: I missed it. I spent 30 years on a university campus and I don't regret leaving for The Planetary Society but I sure missed that atmosphere and being with all of those lively young people and we love to follow OSIRIS-REx, by the way. Speaking of these sky surveys, how will NEO Surveyor complement the work that they are doing? I assumed that the work kind of, maybe the data flow will flow both ways. How is that going to work?

Amy Mainzer: This is a really team intensive activity planetary defense and it really helps that we have multiple telescopes that they occupy multiple parts of phase space, if you will. For the Surveyor mission, we'll be looking in the regions near the sun on the sky, so we'll cover that volume of space. And we're looking using infrared wavelength, so we're sensing the heat emitted by the asteroids and comets as opposed to the sunlight that bounces off the surfaces.

Amy Mainzer: Now, the nice thing is if you have ground-based telescopes like Catalina and you've got the Pan-STARRS Survey, the upcoming Rubin Observatory, these telescopes are operating using visible to, in some cases, near-infrared wavelengths. And when we can combine visible wavelength data for asteroids with infrared data, now, we can actually calculate a whole other range of parameters that we couldn't do before.

Amy Mainzer: From the infrared data, we get the sizes of the objects. But if we can combine it with visible light data, we can now calculate surface reflectivity. And that gives us a little bit of a clue as to what the objects might be made out of. It's sort of a proxy for the composition. If we have a complementary surveys looking at different places on the sky, we can kind of get different classes of orbital elements. In other words, some objects have different orbits from one another and some telescopes are a little better at finding different types, so that's great.

Amy Mainzer: And of course, the more eyes on the sky, the better. We get better orbits and we are more effective at putting together what I have called partial detections. In other words, one survey may see a few detections of an object but not quite enough to really reliably identify it, and another can contribute the rest of the observations. So, lots of reasons to use multiple telescopes.

Mat Kaplan: Composition is kind of a big deal, isn't it? Fluff balls versus giant pieces of nickel and iron?

Amy Mainzer: Absolutely. One of the interesting things we've learned from the OSIRIS-REx mission as well as the Hayabusa2 mission is that some of these objects are ruble piles. They seemed to be loosely held together, almost a ball of gravel, you could sort of think of it. And that's going to be very different in terms of how you might deflect such an object than, say, something that is more of a solid slab of metal.

Amy Mainzer: That's kind of what is interesting to me about these objects is the influence of microgravity of the space environment. There's a whole host of different types of objects out there with different compositions, different porosities, different internal structure and different internal strengths. And we need to be able to look at all of these different things if we ever find something that's headed our way.

Mat Kaplan: You want to say something about the contributions of amateur or maybe I should say those so-called amateur astronomers?

Amy Mainzer: Yeah. I would say these are the unpaid professionals, if you will, of the asteroid world. We really rely heavily on them. These are folks who are incredibly skilled observers and very talented astronomers. They help us in a wide range of ways, not the least of which is making sure that the objects don't get lost.

Amy Mainzer: You would think with the telescopes we have now that we would always be able to find any asteroid any time we want. Unfortunately, that is just not the case. A lot of times, we see the objects and if we can't get additional detections of them from ground-based observers, we cannot reliably locate the objects again. This is where having a lot of friends in many different places really comes in handy, and I can't tell you how many times with NEOWISE, we've really scrambled and called folks in New Zealand, in England, all over the place just looking for additional observations, wherever we can find them.

Amy Mainzer: That's been an important role for the non-paid professional community as well as additional things like looking at the light curves of the objects. In other words, how does the object rotate? That tells us whether or not the object is likely to be elongated or more spherical, also important for figuring out its true nature.

Amy Mainzer: So, there's a whole host of things that it's really great to have a community of folks who look at the objects forward. It tells us a lot about them, make sure we don't lose them and just about their very basic physical properties and nature.

Mat Kaplan: Well, thank you for that. We're always fishing for compliments for those, as you call them unpaid professionals like our Shoemaker NEO Grant winners. You're going to launch, you hope, in 2026 and start looking for these. Where would you hope we will be maybe 10 years later?

Amy Mainzer: Well, my fondest hope for the observatory is that we find a whole bunch of asteroids and comets and we find out that none of them are going to get close to us anytime soon. That would be the very best result. I will be very happy if that's the result actually.

Mat Kaplan: Before we've wrap up here, give us a status report on NEOWISE, which is kind of a senior citizen up there.

Amy Mainzer: It really is. I have to say I am surprised beyond all measure at how long this telescope has lasted. It really was only supposed to last for six months plus one in-orbit checkout phase. Well, that was in 2010 that that all happened. So, it's been a really long time since the spacecraft launched and we've been very, very fortunate that it's lasted as long as it has. It really was not supposed to.

Amy Mainzer: The sun has had a lot to do with that surprisingly. It turns out that solar activity has a significant impact on how much drag forces the atmosphere in the upper layers, right around 500 kilometers, how much force that can exert on a spacecraft like NEOWISE. In this case, the sun has been really quiet for the last few years and that is meant that there's been decreased drag force on the telescope, which is meant that the orbit has not decayed as fast as we thought it would initially.

Amy Mainzer: So that's the good news. It's really taught us a lot about the near-Earth asteroids just in terms of their numbers. The ratio of bright to dark objects, in other words, how many of these dark objects are out there in the population, it's taught us about that. And of course, it's done a pretty good job with helping to fill in the knowledge that we have of the objects that are darker, and therefore, more difficult to detect if you're looking for them with a reflected light telescope.

Amy Mainzer: So, it's really been the little spacecraft that could, and we hope we can get a little more time out of it. We have just been granted a two-year mission extension, which is just really wonderful. And we hope that the sun stays nice and quiet. Hopefully, it will but that's hard to predict.

Mat Kaplan: Great statement of confidence. And we have that same hope, by the way, because our LightSail, which is just about the same kind of orbit or height anyway above the earth that NEOWISE is, has also benefited from that relatively quiet sun.

Mat Kaplan: Amy, I got just one other thing to ask you about, and it's really a story that I told you a few days ago but I will repeat for the audience. Since it's not just doing science that you do but you like to talk about it. My five-year-old grandson, delightful little Rowan, was watching a show on the iPad the other day, and I heard a familiar voice. And I go over and, of course, it was Ready Jet Go. There was you talking about science and my grandson looks up to me because he knows that Baba loves space and says, "Baba, this star is a red dwarf."

Amy Mainzer: Hey, that's great.

Mat Kaplan: You are doing good work. Talk about this. Ready Jet Go, but also just the importance of sharing what the boss likes to call the passion, beauty, and joy.

Amy Mainzer: Oh, absolutely. It's been really an absolute blast to work on Ready Jet Go, and that's just been a ton of fun, not the least of which because the team who wrote the show, the people who produced it really, really care about teaching kids science.

Amy Mainzer: I think the most important thing is you just summed it up. Science is about learning about nature and having fun learning about nature. It's how we understand and interpret the world around us. It really, really is fascinating and you could just never get bored. There's always something to learn.

Amy Mainzer: One of the things I love about working with kids is that they are just naturally in touch with that kind of curiosity and that just happiness that come from figuring out how something works. You want them to never lose it.

Mat Kaplan: And you are so good at this, not just for little kids but big ones like me and I suspect a lot of our audience out there. Amy, it always makes it a great pleasure to talk with you. And I'll just congratulate you again on this two-year extension for NEOWISE and perhaps not very far away, from having this much more powerful instrument up there, trying to do ... It's that other thing that the boss likes to say, all we're trying to do is save the world. Thank you, Amy.

Amy Mainzer: Thank you so much and thanks to The Planetary Society for all of your support over the years. It's just really been wonderful and we are very, very fortunate to get to do this work.

Mat Kaplan: NEO Surveyor mission lead, Amy Mainzer. A quick message and then we'll hear from Bruce.

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Mat Kaplan: It's time for what's up on Planetary Radio. Here again is the chief scientist of The Planetary Society, that is Bruce Betts. Do you remember that that funny Random Space Fact that you provided us? JWST could detect bumblebee's thermal signatures on the moon?

Bruce Betts: Yes. It was a couple of weeks ago. I assume you haven't followed on.

Mat Kaplan: Well, I don't. Daniel Khazard in the UK does. Daniel is the guy who senses these funny little past issues, these cartoons every week. He has done this great drawing. The caption is "Note in space. No one can hear you poot." And one bumblebee is saying to another who looks like he's got a little rocket of gas coming out of his rear end. Where else? He says, "Don't use your thruster. They can detect our heat signals now."

Bruce Betts: Way to keep it classy.

Mat Kaplan: No. Can I still check to box that says this is a clean episode? I think so. I think that's PG. Tell us about the night sky.

Bruce Betts: All righty, low-ish in the western sky in the early evening, you'll find super bright Venus. Jupiter and Saturn coming up in the east in the early mid-evening. August 2nd, Saturn will be at opposition, on the opposite side of the Earth from the sun. By then, it'll be rising around sunset and setting around sunrise. Jupiter is the bright guy and Saturn is the yellowish one to its upper right, if you look at them in the evening.

Bruce Betts: And one more thing, on July 24th, the moon will be joining them and be in between Jupiter and Saturn making bright lovely triumvirate. I don't know if those words have ever been combined before.

Mat Kaplan: I think that works. So, there will be this short period when we won't be able to talk to Cassini, right? Oh, shoot.

Bruce Betts: Okay. There's so much wrong with what you just said. First of all, a sad homage to Cassini whose mission ended and was crashed into Saturn on purpose. But also, no, that's the other thing. That's conjunction when it's on the other side of the sun. Not that it matters because his spacecraft is dead, but this is opposition. You can talk all you want if your spacecraft is alive and communicating.

Mat Kaplan: I forgot. My joke should have been, we'll be able to communicate with Cassini much more quickly ...

Bruce Betts: No. Yeah, now, it's funny. Let's quickly move on to this week in space history. It was 1969, Apollo 11 returned from the moon with those humans aboard. In 1984, Svetlana Savitskaya became the first woman to walk in space. And in 2019, The Planetary Society's LightSail 2 spacecraft successfully deployed its solar sail.

Mat Kaplan: And where were you for that deployment? Actually, where were you and I and several other lucky people?

Bruce Betts: In space. Oh, no, just in my mind I was in space, which is the safest way to fly. We were in San Luis Obispo, California at Cal Poly San Luis Obispo where our communications is coordinated out of with the spacecraft. We were all there being excited and tense. And you can find a nice video on our YouTube channel of that experience.

Mat Kaplan: Yeah, we covered it on Planetary Radio about two years ago as well. It was so exciting to be up there, just as it was for the launch. And LightSail is going to come up again later in the show.

Bruce Betts: Oh, I'm so excited, on to Random Space Fact.

Mat Kaplan: Cue the maniacal laughter.

Bruce Betts: Viking Lander was ... Sorry. Viking Lander 1 was originally scheduled to land on Mars on July 4th, 1976, the bicentennial of the United States. But when they got there, pictures showed the landing area looked too rough, so they delayed the landing to July 20th, at a different location, July 20th, putting it on the seventh anniversary of human's first walking on the moon.

Mat Kaplan: As you were saying last week, July 20th has become a real red letter day in space history.

Bruce Betts: It has indeed.

Mat Kaplan: We have a good contest to go onto here. Get us started.

Bruce Betts: The James Webb Space Telescope that we heard about a couple episodes ago will be stationed at the Earth-Sun Lagrange point 2, or L2. My question to you was, what was the first spacecraft stationed that Earth-Sun L2? How do we do?

Mat Kaplan: We got a very consistent correct answers from almost everybody who answered this weekend and we had a pretty good crowd too. I will allow our Poet Laureate, Dave Fairchild, in Kansas to answer your question. WMAP was a NASA explorer that launched back in 2001. It flew on a Delta then went to Lagrange endpoint number two for its run. It showed Stephen Hawking the proof of inflation. He said, "This expands the frontier. I'd say it's exciting, the best I've seen yet found in physics throughout my career." WMAP, right?

Bruce Betts: WMAP, the Wilkinson Microwave Anisotropy Probe, taught us all sorts of stuff about the origins on the universe and the timing of it and the like. And they were the first to hang out at Earth-Sun L2, which as a reminder, is on the anti-Sun side of the Earth from the sun and is a relatively stable gravitational point, so you don't have to use a lot of fuel to hang out there and you get away from all the interference of the earth and the moon.

Mat Kaplan: Now, this is doubly relevant since we were just talking to Amy Mainzer about hanging out at L1, the Sun-Earth Lagrange endpoint 1.

Bruce Betts: So, that puts you towards the sun and L2 puts you away from the sun.

Mat Kaplan: Here's our winner. It has been since October 19, 2019, that is, when he had his first win, Chip Kaplove in California who said, "Yeah, WMAP, launched June 30th, 2001. Reached L2, what about, three months later." And he says, "Look forward to your show every week. Thanks for all you do to bring us the magic of the solar system and beyond." Congratulations, Chip. You have won yourself a gorgeous Planetary Radio T-shirt which we will be offering once again in just a moment on our new contest. I have some other stuff, of course.

Mat Kaplan: Laura Dott in California says, "There are only two L2 spacecraft currently operating. Four more are planned to arrive in the next 10 or so years, one of those, of course, the JWST." Daniel Sorkin in New York said that, "WMAP was later moved to a heliocentric orbit to avoid posing a hazard to future missions." We don't want it to get too crowded up there, those Lagrange endpoints, right?

Mat Kaplan: Harry Raul asked the question that only you could answer, Bruce. Harry is in Texas.

Bruce Betts: Is it about my childhood?

Mat Kaplan: No, no, but I will save those. "Could we position LightSail at any of the Lagrange endpoints? And if we did that, would it be stable?"

Bruce Betts: You cannot position LightSail 2 itself because we can't get out of low-Earth orbit where a drag pulls us down but you can position a solar sail spacecraft. And in fact, one of the uses that's been proposed for solar sails is to put them at the Earth-Sun L1, so where Amy Mainzer was talking about, so that you and actually instead of going to L1 where you can put normal spacecraft, you can go closer to the sun than L1 and give more warning of solar storms that are coming because you can use the solar sail to balance the forces and being at a place that otherwise would not be stable.

Mat Kaplan: Harry, great answer, huh? Thanks for asking. And Bruce, with that, we're ready to go onto a new contest.

Bruce Betts: Name all the people who have flown longer than one year, so longer than 365 days, who have flown longer than one year in space on single missions so that the people who've spent more than a year in space at one time, go to

Mat Kaplan: Sorry, Captain Scott Kelly. I'm giving you a little give me there for some of you out there. But great book, Endurance, that he has written about his almost long enough time up there. You have until the 28th. That would be July 28 at 8:00 A.M. Pacific Time to get us the answer for this one. And like I said, win yourself a Planetary Radio T-shirt.

Bruce Betts: Okay, everybody, let's go out there, look up at the night sky and think about mingling with fish and space. Thank you and good night.

Mat Kaplan: Okay, bumblebees first, now fish? Why, are there first on the ISS?

Bruce Betts: I can neither confirm nor deny.

Mat Kaplan: Okay. Somebody alert Kilgore Trout, please. That's Bruce Betts. He is the chief scientist of The Planetary Society who joins us every week here for What's Up.

Mat Kaplan: Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by its members who are all defenders of Earth. You won't get a superhero costume if you join them but the work is no less rewarding. Learn more at

Mat Kaplan: Thank you for those ratings and reviews in Apple Podcast. Mark Hilverda and Jason Davis are our associate producers. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad Astra.