Meet the winners of The Planetary Society’s 2026 STEP Grants

Sarah Al-Ahmed: Meet the winners of The Planetary Society's 2026 STEP Grants, this week on Planetary Radio. I'm Sarah Al-Ahmed of The Planetary Society with more of the human adventure across our Solar System and beyond. This week, we're featuring the winners of The Planetary Society's 2026 Science and Technology Empowered by the Public Grants, or STEP Grants. All three of this year's winners are building tools to help us better understand the small bodies of our Solar System, from near-Earth asteroids to the icy worlds beyond Neptune.

I'll be speaking with the team at Lowell Observatory in Arizona, building a new kind of polarimeter to measure asteroid sizes, then with a researcher in the Canary Islands creating a shared database for asteroid observations, and an astronomer in Germany scaling up an occultations prediction system for the age of the Vera Rubin Observatory. Plus, Bruce Betts, our chief scientist, joins me for What's Up, including a look at how the STEP Grant program works and what makes this year's class so unusual.

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Every two years, The Planetary Society funds researchers through our STEP Grants, Science and Technology Empowered by the Public. These grants support early-stage projects that advance space science and exploration, and they're funded entirely by our members. This year, all three winning projects are focused on small bodies, asteroids and trans-Neptunian objects. Each one is tackling a version of the same challenge. As we discover more and more small bodies, how do we characterize them and how do we make sure that the whole community can access and build on what we've learned? Humanity has cataloged over a million asteroids, but our knowledge of them is uneven. For some, we have detailed size, shape, and composition data, but for many others, we're still missing something as basic as how big they are.

One of the reasons is a fundamental measurement problem. When you spot an asteroid through a telescope, what you're really measuring is how bright it looks, but brightness alone can't tell you how big something is. A small, shiny asteroid can appear exactly as bright as a large, dark one. The uncertainty can be enormous, up to a factor of 10. For near-Earth asteroids, that's not just a scientific gap. It's a planetary defense problem. A 10-meter object burns up harmlessly in the atmosphere, but a 100-meter object could devastate a city. And right now for a newly discovered asteroid, we might not be able to tell the difference.

Our first interview is with a team at Lowell Observatory in Flagstaff, Arizona, who are building a new instrument to break through that size ambiguity using a technique called polarimetry. To understand how that works, you need to know about how light behaves. Light behaves as both a particle and a wave, but for polarization, it's that wave behavior that matters. Normally, sunlight vibrates in every direction, what physicists call unpolarized. But when that light bounces off of a surface, it can pick up a preferred orientation. It becomes polarized. If you'd like a visual guide to what this means, I'll have resources on the episode webpage.

You might have actually experienced this for yourself. Polarized glasses cut glare by blocking light that's been polarized by bouncing off of roads and water. Asteroid surfaces do the same thing to sunlight, and it turns out the amount of polarization tells you something important about the surface that reflected it. Measuring that polarization precisely is called polarimetry. And if you can do it well, you can break through that brightness ambiguity and figure out how big an asteroid actually is. The catch is that measuring polarization well enough to do this takes a specialized instrument called a polarimeter, and they're surprisingly scarce.

That's part of what this team at Lowell Observatory is trying to fix. The project's principal investigator is Dr. Nick Moskovitz, an astronomer at Lowell Observatory, working with co-investigators, Dr. Ryan Hamilton, Lowell's head of instrumentation, and Katie Breeland-Newcomb, a doctoral student at Northern Arizona University who's designing, building, and testing the instrument through STEP Grant funding. But their goal isn't just to build one polarimeter, it's to create a template that can be replicated easily using off-the-shelf optics and 3D-printed parts. That way, observatories and even advanced amateurs around the world could eventually build their own. Hey, everyone. Thanks for joining.

Nick Moskovitz: Pleasure to be here.

Sarah Al-Ahmed: So over the course of this episode, we're going to be talking about many different ways that we can be characterizing small bodies, but polarimetry I think is one that not a lot of people think about. This is a really interesting one. Nick, we've discovered over a million asteroids at this point, but a lot of them we don't know a lot about. What makes it so hard for us to figure out specifically the size of these asteroids from the ground?

Nick Moskovitz: Yeah, we know of one and a half million asteroids in the Solar System, and we are really good as a community at finding them, but it takes a lot more work to understand what they are, what their basic properties are, and size is maybe the most basic of the properties you could want to measure for an asteroid. We have a variety of techniques that are involved in determining the size of an asteroid, including measuring its thermal emission or during occultations when an asteroid passes in front of a background star, we can measure its size that way. But one of the lesser utilized tools to measure size is using the polarization measurement of an asteroid.

And that is really the focus of our STEP Grant here is to develop an instrument to measure the polarization signature of an asteroid, and that allows us to put constraints on size in a complementary way to some of the other techniques that are out there in the community. And so the hope is that by further developing this technique that's been around for quite a while, as we can increase the rate of characterization of objects that have avoided those measurements in the past.

Sarah Al-Ahmed: And as we'll hear later in this episode, especially in the age of the Vera Rubin Observatory, this is going to be something that we're going to need all hands on deck in order to accomplish. So having an easier way, a more accessible way for more observatories to actually figure out the size could be very, very useful. And also I might add, might potentially save the world someday maybe. So that's really cool. But Ryan, you're the head of instrumentation at Lowell Observatory and you also built that, I don't know if I'm pronouncing this correct, but I'm just going to say it's H-A-W-C+, the polarimeter on NASA Sofia Observatory. What made your team decide to go and build a cheap, replicable version of this kind of thing for asteroid work?

Ryan Hamilton: So the instrument I worked at with SOFIA in my previous job, I was the instrument scientist for during the commissioning process. The instrument itself was a very long, complicated history and collaboration from Yerkes Observatory and also the Jet Propulsion Laboratory. So I came in at the relative tail end of that, and that was really my first experience with polarimetry in the real world. During grad school, I had experienced it in just the abstract, "Here's the math of how it all works," and it was kind of treated as like a black box of just like, "Ooh, this is complicated." So the instrument at SOFIA wasn't quite the same. SOFIA was an infrared telescope, and the instrument there was mainly looking at magnetic fields of star-forming regions in our own galaxy and also bulk magnetic fields across other galaxies outside of the Milky Way. Same process, just totally different science application.

And the science applications of polarization measurements are just innumerable. It's been kind of an untapped field for a little while. It's very niche, very complicated, and the devil is really in all the details to make sure that you're actually measuring what you think you're measuring from great distances from here to another galaxy or a star-forming region inside our own galaxy. So at the observatory, we're lucky to have a wider range of telescopes. We have everything up to a 4.3-meter telescope available to us and also a 1-meter telescope available. That's kind of unique and very lucky for us, and that allows us to kind of come up with an instrument concept that is far more flexible and adaptable to a wider range.

A lot of times instrumentation such as this is very specialized. It's built for one telescope and one telescope only. One of the things we're going to be investigating is to see how much we can kind of genericize and how much we can make kind of more of a platform that's more expandable to 1-meter telescopes, which there are quite a lot of these days, as well as potentially even smaller is the hope, because for some of the brightest objects, you can still do very achievable untapped science from relatively smaller telescopes that would be at the very top of the high-end amateurs and also kind of the midrange for most universities and stuff like that.

Sarah Al-Ahmed: Well, Katie, I understand that you're going to be doing a lot of the building and testing of this instrument. How did you end up on this project?

Katie Breeland-Newcomb: Very good question. I'm sort of the baby astronomer, I think, out of the group here and just really interested in instrumentation. That's a lot of my projects through my PhD work is about instrumentation and, yeah, I just kind of was lucky to fall in with the right group. Nick is my main advisor, and so the fact that this is a possibility and that all of the things that we need for the instrument are off the shelf just made it really easy for me to sort of want to get involved. And so yeah, I just feel lucky to be a part of it.

Sarah Al-Ahmed: Brightness alone isn't enough for us to really understand the reflectivity of the surface of these objects. There could be a lot of factors there, and your team is trying to use polarization in order to get around that problem. So how does the reflectivity of an asteroid surface actually change the polarization of the light that we see coming from it?

Nick Moskovitz: You're absolutely right. The asteroids that we're discovering, the one and a half million objects that we talked about earlier, we are seeing those as points of light. We're not resolving them as objects with boulders and craters or anything like that. These are so far away from us that we see them as points of light through our telescope. And there's a degeneracy there in measuring the sizes of objects when you're just dealing with a point of light. And the example is that if you have a very small object that's highly reflective, what we would call a high albedo, so it's reflecting a lot of sunlight off of it, that object can have the same brightness as a large object with low reflectivity. That range of possibilities for any given object can be an order of magnitude. So we may not know to within a factor of 10 what the size of an object is if we're just measuring that point of light.

So how do we break down that degeneracy? How do we try to probe and reduce that uncertainty and reduce that factor-of-10 uncertainty? One way to do that is understanding what the underlying reflectivity or albedo of the asteroid is. And that's where polarimetry comes in because there are established relationships between the amount of polarization that a surface imparts on over a signal and the albedo of that surface. And this gets into those textbook early grad school seminars that Ryan was talking about where you have to dive into this arcane and somewhat obscure math to understand what's actually going on.

And I think as a whole, the community maybe doesn't even fully understand the detailed quantum mechanics and physics of light interacting with regolith-covered surfaces like asteroids and how that affects the polarization signature. But we do know that the percent of polarization, how much a surface polarizes a signal is related to albedo. So if we can measure polarization, we can get albedo and break that degeneracy and figure out what the size of the object is. So that's the goal for an instrument like this that we're proposing to build.

Sarah Al-Ahmed: If we've only been to a certain number of these asteroids up close, how did we establish a relationship between the polarization and the albedo?

Nick Moskovitz: Yeah, I mean, I would say that's very much ongoing work. This is an active area of research, and I would say one of the bottlenecks in all of this has been the lack of available polarimeters, instruments that can measure polarization signal just out there in the community. I think you would probably count on one hand how many polarimeters are out there in the world for research astronomers to get their hands on. So we want to change that, make this a tool and a technique that's more widely used and more widely accessible.

With the work that a number of groups around the world, including collaborators on our proposal have done over many years and even decades, we're able to target specific objects where we may have that spacecraft measurement or we may have a measure of a diameter through complimentary means and we can start to build out that relationship over time where we say, "Here's an object, we know its diameter already. Now, let's look at its polarization signature and build out that relationship." And as we collect more data and build out a more comprehensive data set, we'll be able to better solidify those relationships to improve the overall knowledge of the objects that we're interested in studying.

Sarah Al-Ahmed: I mean, clearly it's a very complicated relationship, but do we have any hard and fast rules like this amount of polarization compared to this tells us whether it's a darker or a more reflective surface?

Nick Moskovitz: Absolutely. There is a relationship. The general rule of thumb is if you're a low albedo surface, so think like a brick of coal or something even darker than that, reflecting only a few percent of the incident sunlight, those surfaces, those objects can have very high polarization ratios, ratios that can exceed 10, 20, even 30%. And that is a fairly easy signature to measure even with a simple polarimeter like what we're proposing here. The converse of that is if you have a high-albedo surface, they tend to have very low polarization ratios. And so with a single measurement in the right viewing geometry, you can break that degeneracy and figure out whether you're looking at a high- or a low-albedo surface.

Sarah Al-Ahmed: Well, Katie, can you walk me through this instrument that you're actually building? What's physically inside it and how does this thing work?

Katie Breeland-Newcomb: Sure. So this is following sort of one of our figures that we have in the proposal. There are really four main components. We have a field lens, a collimator, which basically just puts all of the light into sort of parallel lines, and then a double Wollaston prism, which splits the flux into those four discrete polarization states. And then, we have our camera on the back of that.

And so it's really just, like I said, very off-the-shelf components, not a crazy complex optical system that we're able to use to get this data. And I think the beauty of it is because of the double-Wollaston prism, we can obtain these four measurements sort of simultaneously and we don't need a super high signal-to-noise, which is why it will potentially work for all of these different aperture telescopes. So yeah, I think the beauty is really in the simplicity of the design.

Sarah Al-Ahmed: Ryan, you've built, obviously, polarimeters at a NASA level. What do you keep and what do you sacrifice when you're building something that you're trying to replicate on this level that you can just give to other observatories?

Ryan Hamilton: The important part is to have that goal in mind at the outset. So our design choices are driven towards the fact that we do want to make this more approachable. We're not going to try to paint ourselves into a corner to make something that only works for one telescope. That does dictate quite a bit of the design. We're pretty good at designing for manufacturability is usually what we say, and it's probably likely that a good portion of this is going to be 3D printed as much as we can, and that really opens up the ability for many, many more people to construct an instrument like this.

The observatory is lucky because we also have a fully stocked machine shop, but not every place has access to a machine shop right next door. You have to send out parts. It's much more expensive. The lead time is enormous, but if we can design with 3D printing in mind, it might be slightly more exotic materials, but still that's achievable at a very low cost compared to even just 10 years ago. So really, it's a new design, but designed for wider manufacturability as much as possible.

Sarah Al-Ahmed: Well, your team's only kind of recently learned that you guys got the STEP Grant funding for this, but where are you in the process of actually developing and building this thing currently?

Ryan Hamilton: One of the things that we're starting to do is to just kind of organize and come up with the high-level concept. You make the outline, all those standard draft-y kind of STEPs. But the other component that we're starting to think about is an aspect of this called instrumental polarization, and that's due to the fact that telescopes and cameras and things are real structures in the real world. They will change the signal in some subtle way, and we have to have a good understanding of what it's doing to that signal before it even enters the instrument. So we're starting to come up with the ideas of what do we need to do to really calibrate and measure instrumental polarization in a reliable, robust way because it really comes down to that, but we'll start in the lab with a known polarization source as well.

Sarah Al-Ahmed: Nick, what would it mean if we could equip not just observatories like Lowell, but amateur astronomers with their own polarimeters? What could that potentially allow us to do when we're looking at this asteroid population?

Nick Moskovitz: Yeah, I think there are a number of different science cases and cool applications of polarimetry to planetary science and asteroid science. One of my favorites is tied to planetary defense and understanding the population of impacting asteroids that are out there. And I'm not necessarily talking about your dinosaur-killer asteroids. I don't spend my time worrying about those or even studying multi-kilometer-scale asteroids all that much. I'm talking about the ones that we're finding now with our ongoing surveys, and will continue with LSST, that are small asteroids, meter-scale objects that impact and don't necessarily pose a significant hazard, but are incredibly valuable for understanding that population of objects in the Solar System and how they interact with the atmosphere when they're coming in and how those are related to what ultimately happens on the ground, if we're talking about landfall of meteorites or air blasts and things like that.

These events happen with some regularity a couple times a year, and we don't get to pick where these events happen. They may happen over Flagstaff, in which case we'd have our telescopes on them, but they could just as easily happen on the other side of the country or even the other side of the world. And so having a community, a planetary defense community that is ready with the right tools and instruments to follow these objects on sometimes very short notice. And in some of these cases we've discovered these objects mere minutes before they actually hit, which means you don't have the luxury of waiting for that object to appear in your night sky.

You need to rely on whomever's in that area to do those observations and collect the data on short notice to get the best science and improve our understanding of this population. So increasing accessibility to these tools, mobilizing and leveraging the wide community of amateur and professional astronomers around the world, I think, is the best way to make headway on this sort of challenging niche of asteroid targets that we are interested in and provide huge scientific value to the planetary defense and planetary science communities.

Sarah Al-Ahmed: It's really cool that you can just take a quick measurement of the polarization coming off of this thing in order to establish the albedo, but I'm honestly more interested in what we could do by looking at these objects from different phase angles as they rotate. There is so much science here that we don't fully understand, but Katie, since you get to play with this thing as you're building it, what are you most looking forward to using this for as you begin your testing?

Katie Breeland-Newcomb: What's most interesting to me, I definitely think that the breaking the degeneracy between age magnitude, visible magnitude of an asteroid and its size is an extremely important thing that we haven't, I think, fully figured out exactly how to do in the best sort of most efficient way. And so I think that's a really powerful tool that we'll be able to have and be able to characterize these populations much better.

Sarah Al-Ahmed: Well, thank you so much for all coming on the show to talk about this and for the work that you're doing to try to make this more accessible for the community. I know all of us here at The Planetary Society are deeply involved in trying to enable people to do this kind of planetary defense work, but even more broadly, there's so much we can learn about our Solar System from understanding these objects more, and I'm looking forward to seeing what people discover by using your new technology. So I really appreciate that you guys reached out to us and that we can all work together to try to make this happen for everyone.

Nick Moskovitz: Absolutely. We're looking forward to it.

Sarah Al-Ahmed: Polarimetry gives us albedo, and albedo gives us size, but size is just one piece of that puzzle. To understand what an asteroid is actually made of, how it's shaped, how fast it's spinning, you need a different technique, photometry. Photometry is, at its core, just carefully measuring how bright something is. That sounds almost too simple to be useful, but as our next guest explains, tracking an asteroid's brightness over time and across different colors can reveal how fast it spins, something about its shape, and even what it's likely to be made of. And because it doesn't take a giant telescope, it's one of the most accessible tools in the field. The problem is that all this photometry data, they're all scattered across individual researchers' hard drives, shared by email, published into papers, but never aggregated into one place.

The Minor Planet Center, which you may have heard of, handles astrometry, the positions and orbits, but there's no equivalent for the physical properties that we're measuring through photometry. That's the gap that Dr. Miguel Alarcón is trying to fill. Alarcón is director of Scientific Operations at Light Bridges, a company that operates telescopes at the Teide Observatory in Tenerife in Spain's Canary Islands. His project, called AsteroidDB, is a database that already holds over 15 million photometric measurements of more than 400,000 asteroids. With STEP Grant funding, Alarcón is taking AsteroidDB public, building tools for researchers and citizen scientists to upload, merge, and analyze photometric data together. Hey, Miguel, thanks for joining us.

Miguel Alarcón: Hi, thank you.

Sarah Al-Ahmed: This is a really exciting time to be into asteroid science, but as it stands right now, the information we get about asteroids is kind of spread out across different papers, different databases. The Minor Planet Center tracks where asteroids are, but what would you say are the biggest gaps there that you're trying to fill with your upcoming asteroid DB?

Miguel Alarcón: Yeah, you're right. We usually report our astrometry to the Minor Planet because it's important to keep track of these asteroids and calculate the orbits and so forth and so on. And when we talk about characterization, it's kind of different. We don't have a common place to have all the measurements, and I work on photometry, but I can talk also about polarimetry or spectra. So the common way to do that is that we the astronomers have the telescope time, we observe, and then we share the information between each other by email or by a collaboration meeting or whatever, but we don't have a place to work together and report. And to be honest, we have many, many measurements of this asteroid because we have more telescope, more capacity to analyze the images. The start of AsteroidDB was creating a platform to put all those measurements here and try to work together.

Sarah Al-Ahmed: What kind of measurements specifically are you hoping to track with this?

Miguel Alarcón: The original of AsteroidDB is photometry, so we keep track of every kind of photometric measurements. When I talk about photometry, it's just knowing the brightness of the asteroid in one band or several bands. So when you are tracking the asteroid with time, you will see how the asteroid is rotating so you can guess information about the physical characteristics of the object. But also if you have several bands, you can know the color and then you can guess the taxonomy, so what kind of asteroid we are talking about. So we work on both of them with photometry.

Sarah Al-Ahmed: It's so interesting that we can tell anything about the composition of something at that distance without even necessarily using a spectrometer, right? You're just looking at the light curve of this object. How is that possible?

Miguel Alarcón: Yeah, I mean, one of the basis of the astronomy is trying to get a lot of information from light, which is the only thing we have access to. If we are not using a spectron, we just have photometry, so an accumulated number of photons within two or within a wave [inaudible 00:26:00] range, just the definition of photometry, we can see several things, especially when we track the asteroid in different points of the orbit and different geometries between the sun, the object, and us. So when we do this, we can see the asteroid, how the light is changing, the light that the asteroid reflects is changing with time, and also with color.

When we compare colors, for instance, we know that, "Hey, this asteroid would be bluer or redder than these other asteroids," so we can guess what kind of composition it has because it tells us about the different materials that they have in the surface. So one of the good things is that you can use a small, medium, or big telescope to get photometry depending on the object.

Sarah Al-Ahmed: We're trying to learn how to deflect some of these near-Earth objects if they come at us. Are you hoping that through AsteroidDB, we might be able to have more information to literally save the world?

Miguel Alarcón: Sure. In the last opportunities we had, for instance, 2024 YR4, that was the subject that the impact probability brought and then it's not going to impact, but we follow it up all around the world. We use AsteroidDB for sharing all our measurements in the Solar System Group of the Instituto de Astrofisica Astrophysical de Canarias. So we have access to different telescopes and we just use AstroidDB to share the data. So yeah, we are using AstroidDB. We are collecting, for instance, measurements from the telescope that is one of the five nodes of the ATLAS Network, which is early warning network for detecting asteroids. And the fifth node is in the data observatory. We already have those measurements on AstroidDB, and we use it for following objects. So yeah, regarding planetary defense, it's important to detect, but it's important to characterize very fast, so as quick as possible. And in that case, we need to collaborate.

Sarah Al-Ahmed: You've mentioned Teide Observatory a few times now. Can you tell us about the observatory and about its connection to your organization Light Bridges?

Miguel Alarcón: Yes, sure. So here in the Canary Islands, we have two observatories, one in La Palma and one in Tenerife. The one in Tenerife is called Teide Observatory because we have a volcano. In La Palma, we have several light telescopes. Indeed, we have GTC, which is actually the biggest optical infrared telescope in the world. It's a 10.4 meter. And in Tenerife, we have several solar telescope, but also a lot of robotic telescopes. So we, Light Bridges, we are a company that at first we built five telescope that we're installing the observatory, five telescope that they are devoted to general use. So they do a lot of science, and one of the main science cases is Solar System [inaudible 00:29:05].

I'm in charge of the operations of the telescope, but as a researcher, I have access to them and I use them regularly to observe asteroids. So one of the things is that we are collecting terabytes of data with this telescope and we analyze them on the fly and we have the photometry of all the point sources, including asteroids. So after two years, we have realized that we have 15 million data points of asteroids and maybe we should release this because we are not going to do science alone. There's a lot of data and it's important to share and release it if we are not going to use it. So these telescopes that are called the 2-meter Twin Telescopes, so they are two 2-meter telescope, 280-centimeter replica and one widefield telescope. They are all accumulating photometry of asteroids every night and sharing on AsteroidDB.

Sarah Al-Ahmed: You've created this pilot for AsteroidDB. It has a bunch of information on it. Is that primarily from the Teide Observatory or are you incorporating data from other places?

Miguel Alarcón: Right now it's from the data observatory, but we are now working on incorporating other published data, ATLAS, Sloan, SkyMapper, and so forth and so on. Everything that is published, we want to include it so we can create or we can analyze objects with a longer baseline of data and also compare with different surveys. There's also an option that we want to include is that users are allowed to upload their own data so they can compare with the existing databases.

So one of the problems we have now is that when we are observing an object and we want to compare with other databases, we have to go there and go to the MPC and download the data and look for ATLAS for photometry and download it and then try to merge. With AstroidDB, we are trying to create the tools to do this merging easy. It's going to be good for users and also good for ATLAS. We are astronomers working in this field and we need it.

Sarah Al-Ahmed: Mm-hmm. What is the STEP Grant funding going to enable you guys to do?

Miguel Alarcón: So the best thing about the STEP, one, is that it's pushing us to make this public. We have this tool, we are using it and we are doing science with it, but we didn't have the opportunity to make it public. So put some effort on doing it like a public tool. So with this, it's like, "Hey, now we have to do it properly. We have to deploy it. We have to allow users to participate on this." And when I say participate, this is not only use it, but this also give us their opinion about the platform and improve it and see what we can do better to make astroid science something collaborative and also being able to do it quickly because we don't have to ask by email people, "Hey, do you have telescope time for doing this?", or look for a private repository of this astronomer that is publishing the data, whatever.

This is the most important thing with the STEP Grants. And also we are giving the opportunity even with telescope time to the The Planetary Society to participate, observing targets and using the platform and giving us their opinion and participating in the papers or whatever, so...

Sarah Al-Ahmed: It's exciting because it is really difficult to get telescope time. This is the reason why so many people who are into asteroid science have their own personal little observatories, but that is not feasible for so many people. So I appreciate that you're giving away some of that observatory time.

Miguel Alarcón: Yeah, we are giving people, I don't remember the numbers now, but some dozens of hours in the 2-meter telescopes, also in the widefield and in the 80-centimeter. But it's not easy especially for amateurs to get access to 2-meter telescope as we have access to them because we manage them. We want to give people the opportunity to use them and see how different it is using a professional observatory telescope where you request time for doing this object and then you wake up and you have the light [inaudible 00:33:24] on AstroidDB and it's like, "Okay, this is pretty easy." And you can share it with your colleagues or see what has been done in the past.

So yeah, from the very beginning of the project, we wanted to do these public calls for participating in observation. So yeah, I guess at the end now. No, but mid-2027 we will release a call for almost everybody. And I guess you in The Planetary Society will know that they will have access to this professional telescope.

Sarah Al-Ahmed: Yeah, we'll notify all of our members. Maybe we'll even announce it here on the show. So if anybody's interested in that, becoming a member of The Planetary Society will grant you some access to this. But you're also planning an expert panel to think more about the standardizing of data formats for AsteroidDB. Why does that matter?

Miguel Alarcón: Yeah, when we participate in campaigns that are organized, for instance, from The International Group for Planetary Defense that we are creating campaigns to characterize some objects and to be ready if we have any important alert, we always have this thing with sharing the data. How we share the data, what's the format, what are the columns, what is your band? So is your R band similar to our R band and whatever? So now, we have a problem when we are studying data, and when we are studying one to one, we have it. So when we send our measurements to someone who's asking a lot of questions, so, "What is this band? Is this timestamp corrected by the distance or not or whatever?" So we wanted to take the chance of doing this platform also to have a panel, a discussion panel with Esper that usually participate in these kind of campaigns to discuss what are the common formats that we should use.

This is discussion that are happening also for astrometry, for instance, when we changed from MPC 80 format to ADES that they are using now in the Minor Planet, they were discussing about what do we do with uncertainties, what do we do with astrometric solution and so forth and so on. So with photometry, I think now we have the moment to do it. LSST is going to come. We will have millions of autometry points. We have a lot of telescopes and a lot of data. So I think it's important to get in touch and find a common format or way to sharing this.

Sarah Al-Ahmed: Yeah, I think the entire community is really just in this interesting moment where we're all trying to figure out what we're going to do with the amount of data coming out of Vera Rubin. So right now is the perfect time to be trying to figure out how to create a central repository for this kind of stuff.

Miguel Alarcón: They're going to observe them, they're going to detect them. I'm not sure if they will be able to characterize them because of the currents, because of the observation and strategies. So we still need smaller telescopes targeting these objects, following up, and being able to go there and characterize them quickly. So yeah, the idea is to being able to share all this information in a public way also, not only by email or by WhatsApp or, "Hey, I have this data. Do you have more data?" It's okay, but maybe it's better to share it as we do with the astrometry and share it and being able to make collaborative studies of more objects as well.

Sarah Al-Ahmed: Thank you so much, Miguel.

Miguel Alarcón: Thank you very much.

Sarah Al-Ahmed: We'll be right back with the rest of our 2026 STEP Grant winners after the short break.

Rae Paoletta: Hi, I'm Rae Paoletta, Program Operations Director at The Planetary Society. I also produce this podcast. You don't have to work in the space industry to help explore the Universe. Let me explain. Back in 1980, the astronomer Carl Sagan saw a problem. All over the world, people were falling in love with space, but here in the United States, NASA's planetary missions were getting cut because politicians didn't believe the public cared. So Carl, along with Bruce Murray and Lou Friedman, started The Planetary Society for one simple reason, to prove that people do care and to give anyone anywhere a real say in how we explore the Cosmos. 46 years later, that mission hasn't changed and no matter where you live in the world, you can be a part of it.

Memberships start at just $4 a month. That helps us champion the search for life beyond earth, the defense of our planet from asteroids, and the exploration of other worlds in our Solar System and beyond. It also powers our fight to protect NASA's science missions from being cut. And you get a lot back, a t-shirt when you join, our quarterly magazine, and a place in our member community app with a book club, conversations with authors and scientists, courses, and so much more. This month, we're hoping to welcome 200 new members. Will you be one of them? Join at planetary.org/join and help us explore the Cosmos together.

Sarah Al-Ahmed: So far, we've talked about two ways to learn what asteroids are really like, polarimetry, which gives you reflectivity in size, and photometry, which gives us rotation, shape, and compositional clues. But there's a third method, one that can measure the size of an object billions of kilometers away, and it doesn't require a giant telescope. It just requires being in the right place at the right time. Stellar occultations happen when a Solar System body passes directly in front of a distant star, blocking its light. The duration of that blink tells you the size of the object. And if you have multiple observers spread across the shadow's path, you can map its shape. But to observe an occultation, you first have to know it's going to happen. Predicting exactly where and when the shadow will fall so you can observe it requires precise orbits and star positions.

And that's exactly what Dr. Mike Kretlow has been doing. Kretlow is an astronomer at The German Center of Astrophysics in Görlitz, Germany, and he built CORA, the Collaborative Occultation Resources and Archive, a system that collects occultation observations from networks around the world and predicts upcoming events. With the Vera Rubin Observatory now discovering new trans-Neptunian objects at an unprecedented rate, potentially 40,000 over the next decade, CORA is going to need to scale up. That's what CORA+ is, a next-generation version funded by the STEP Grant that can handle the flood of new objects automatically. Hi, Mike. Thanks for joining us.

Mike Kretlow: Hi, Sarah. Thanks for having me.

Sarah Al-Ahmed: Well, I know that all of your work is dedicated to this idea of understanding small bodies in our Solar System through stellar occultations. How specifically do you have to be located and timed in order to actually see one of these stellar occultations for a trans-Neptunian object?

Mike Kretlow: This was and is still one of the challenges in predicting such stellar occultations by this very distant objects. For example, the asteroids and the main-belt asteroid, and the sizes are ranging from a couple of kilometers up to 900 or 1,000 kilometers. So essentially the width of the shadow path is in the same size, like the size of the asteroid, the diameter of the asteroid. So if you want to observe in stellar rotation by [inaudible 00:41:11] and trans-Neptunian object in the size of 100 kilometers, the shadow is only a hundred kilometers width, and predicting such an event and the location on the Earth is really hard. And the accuracy, you need to have the prediction accuracy, which should be at least in the range of the width of the shadow to have a good chance to see it. And that was one of the challenges because this distant object, the orbits are not so accurate for closed asteroids like in the main belt or NEOs.

And additionally, because of this huge distance, the projected uncertainty increases with the distance. And that means the same orbit accuracy of a TNO compared to the same orbit accuracy of a main-belt asteroid will reside in different prediction and certainties on the surface of the Earth. So you have to be predictors very accurate to locate the observers in the shadow to have a good coverage of the shadow.

Sarah Al-Ahmed: What are some of the things that we can actually learn about these objects by looking at stellar occultations? Because it turns out there's actually quite a lot we can learn about these bodies.

Mike Kretlow: Yes, it is really a lot and it's just basically with the same method. I mean, you don't need to change very much the kind of how you observe the occultation. It's just measuring the time, the occultation time, more or less recording this we call it occultational light curve. If you measure the star brightness over the time, you see that it's disappearing and reappearing. And if you record this, then you have what we call an occultational light curve. And one of the main outcomes, which is very directly, is the size because the time of disappearance and reappearance of the star corresponds directly to the diameter of this cord of which you're measuring, the specific station.

And that is a direct measurement. It's not indirectly. And you can measure with a kilometer accuracy an object in 40 astronomical units distance, which is huge. You cannot do the same even with the largest telescopes on Earth, you cannot do the same. You would need a spacecraft going there and make images. So deriving the size is a diameter of this objects, asteroids, TNOs, and so on, with such a precision and without a bias is one of the main goals and one of the main outcomes. Together with the size, if you know the absolute magnitude, which is usually derived if you discover an asteroid with a telescope, you measure the brightness of the asteroid. And together with the orbit around the sun, you can conclude what we call the absolute magnitude, which is something like inherent magnitude. And if you have the size and the absolute magnitude, you can derive the albedo, the geometric albedo, which already gives you some clues about the chemical composition of the surface and the evolution. This is one of the main objectives.

Another one is that you also are probing a little bit the environment of the asteroid while it is passing in front of the star. If it has a satellite, a small moon, which was yet not discovered, it might happen by random that it also occults a star. And then, you can discover a satellite which you would never discover from Earth. And the third, for example, the rings of the small bodies like the centaur Chariklo, dwarf plant Haumea, they were all discovered by stellar occultations. And if you go back more than 50 years ago, the rings of the planet Uranus, they were in I think it was in 1972 by the airborne telescope from the NASA during stellar occultation. So there's tiny rings you can discover with the stellar occultation. And last but not least, it is possible to detect a very thin atmosphere.

It is possible that such objects, just distant cold worlds outside in the outer Solar System, which are not always small. I mean, they are several thousand kilometers in diameter. So they can, at least temporary, they can have an atmosphere, and that would be also possible to detect. You get also a very accurate positional information. Let's say the accuracy is even better than you can get with ground-based telescopes because you have this, as I mentioned, this kilometer or even sub-kilometer accuracy. And if you project this into the distance of 40 astronomical units, then you get an accuracy on the sky like one millissecond or so. And that is really a huge accuracy.

Sarah Al-Ahmed: This amount of information needs to be publicly accessible and organized in a way that people can actually use in order to do this kind of science, which is where your database CORA comes in. Can you talk a little bit about what CORA is and how it works? And then, we'll talk afterwards about what you're hoping to do with it in the future.

Mike Kretlow: Well, CORA, I call it CORA, Collaborative Occultational Research and Archive. And the idea was many years ago I had the idea because you already have this big community of occultation observers which observe and some will report their observations. But there was never a really centralized or modern centralized way to collect this data and these reports and observational data and to distribute them, to make them public available to other astronomers, amateurs. It doesn't matter if amateur or professional or just citizen scientist.

So I started with a database to collect those reports and to provide them in a modern way on a web front and over the internet. And later, the next STEP was to also to make my own predictions, the occultation prediction to predict these events. And so to inform people that an occultation is happening and they can look into the database, into this prediction database with different filters and look for events near their location and so on, fitting their instruments.

When I put all these parts together, this was the birth of CORA to provide a centralized tool, a modern tool on the web to collect this observational reports from different sources. And there are different organizations like IOTA, the International Occultation Timing Association, which are collecting these reports, but these reports were always in written form, for example, or just put in a folder, so they were not accessible. And one way was to collect them and to provide them to the community. And that is more or less the central part of CORA to make on one side predictions, predict events, and on the other side to collect or to present and archive the data and to provide them to the community.

Sarah Al-Ahmed: How much of the building of CORA and putting information into it is a manual process?

Mike Kretlow: Well, as many projects like that, it starts with a lot of manual contribution, of course, but I manage... I mean, I have a strong background in software developing and software engineering. So I started to build tools which, more or less, try to automatically collect data from other sources, from websites. For example, in Europe, there was a simple website which collected manually the reports. Some of the things are automated. For example, we have now the so-called SODIS. SODIS is a System for Occultation Data Input from the IOTA European section.

So this data, for example, are pulled every night. I accept their database and get the data to CORA. Other things like the occultation prediction needs some manual process. So if [inaudible 00:49:51] computation is automatically, but then I have to glue everything together, so I have to start manually the occultation prediction process and so on. And so some parts I have modules which do tasks automatically, but the interaction between the modules sometimes need manual trigger, so to say.

Sarah Al-Ahmed: So how are you hoping to use STEP Grant funding to take this thing to the next level?

Mike Kretlow: Yeah, for the next level, CORA+ or CORA next generation, as you know, the Vera Rubin Observatory started right now a couple of months ago with this LSST, this Legacy Survey of Space and Time. It just expected that over the next, let's say, decade, 10 years of operation time, maybe about 40,000 TNOs will be discovered. And CORA currently, because it was and still is a private project, so it is small scale, it's just a small server and it's already at its limits. And one of the reason I proposed or make this proposal to the STEP Grant was my idea is it is great if Vera Rubin will discover a lot of TNOs, but essentially it will be like a numbering, like a census. You will know there's an object and you will know the orbit. Maybe you will know also the absolute magnitude, but for example, you will not know the size or the albedo.

So providing this additional information about physical properties for the next upcoming discoveries, this was the reason why I thought about expanding my system. And expanding means it needs a bigger hardware, it needs a better database. All of this has to be scaled up. It needs more automatization to automate processes like the orbit determination from observational data coming from Vera Rubin, which goes through the pipeline of the Minor Planet Center. But this database luckily is public. You can copy the database. So I would have immediately this observations, this positional observations to make orbit determinations in an automatic way. And this orbit determination calculating the position of the TNO for the future is needed for looking for occultation events.

Sarah Al-Ahmed: I think the entire astronomical community and planetary community is just all up in arms trying to figure out what we're going to do about the amount of data coming out of Vera Rubin. And it's a wonderful problem to have, but every conference I've gone to in the last year is literally just people trying to figure out how they're going to deal with the onslaught of this amount of data. If we could take all the information from the LSST, plug it into CORA+ and give this information to people about occultations, what could that potentially allow us to learn about this population of TNOs out there?

Mike Kretlow: Yeah. I mean, to make conclusions, for example, statistics and looking for families, evolution, dynamical evolution or physical evolution, you need data. First of all, you need data to make data science. So in the future, if we have all those discoveries from LSST, this will enable us to have more occultation data on TNOs. Right now, we know about 7,000 TNOs, and just for a fraction, we have occultation observations and derived sizes and so on. And the discoveries by LSST together with CORA+, which enables us to make more predictions and to get more results, occultational results, will increase this data of physical sizes of albedos. And this will give you the chance to make statistical analysis of the inventory of our outer Solar System. You must imagine right now, as I mentioned, we know about 7,000 TNOs which were discovered from ground-based telescopes in the past, let's say three decades, 30 years more or less.

The first one was discovered in 1991. Currently, we know only 7,000. We even know more extrasolar planets right now in terms of the number than TNOs, than Solar System objects in our own Solar System. So I think it will have a big impact to know about the dynamic, just to have a sensors, just to have an inventory of the outer Solar System, not only to know there are much more objects, to know a little bit more about the sizes. So it will help also to improve the orbits, which is where LSST will not be capable to do that.

And in the end, it might be also give us better, let's say, data and conclusions about the evolution of our Solar System itself, because any theory about the Solar System formation has to explain not only the main belt of asteroids, not only the planets, the formation, the migration of the planets in between different orbits, but, of course, also the outer Solar System. And for that, you need to know more details about the outer Solar System. And LSST will help us, and hopefully CORA+ will help also to achieve this goal.

Sarah Al-Ahmed: Thank you so much for coming on the show to tell us about your work.

Mike Kretlow: Yeah, thank you very much.

Sarah Al-Ahmed: To put this year's STEP Grants in context, let's bring in Dr. Bruce Betts, our chief scientist at The Planetary Society for What's Up. Hey, Bruce, STEP Grant time.

Bruce Betts: Party on. Party on STEP Grants.

Sarah Al-Ahmed: It's always so cool to hear about the new projects that they're doing. Although I do have to ask because one of the people that I interviewed asked me this, we just happened to have all these projects in some way associated with small bodies in our Solar System, but we didn't do that on purpose, right?

Bruce Betts: That is correct. We did not. We chose the highest reviewed grant proposals that we could fit within our budget that we had. And those happen to all be focused on small bodies, which is not entirely a coincidence because all of them made reference to the fact that particularly the Vera Rubin telescope that recently started up and will be doing regular things more and more, we'll discover tens of thousands, hundreds of thousands of objects, both ones in the near area, so to speak, so near the asteroids that some of the grants are focused on and all the way out to things beyond Neptune, which another of the grant is focused on. So once you discover those things, you basically know, "Hey, there's something, it's there. It moved from there to there." If you have enough of those, you can make an orbit, but you still don't know hardly anything about it.

You may have a brightness from the telescope, presumably. So all of these are kind of working different angles, it happens, different angles on now we have all these tens of thousands or more objects to follow up on. How are we going to handle that and how do we learn more about these so they become more than just a number and a catalog, but actually start to have dimensions and physical properties and become in our minds actual worlds that have characteristics? And that happens to be the wonderful theme that I can pretend I planned or say, no, we didn't plan that. But that's also not how we select it because we really try to run a competition where the best reviewed things by our panel, which are scientists and engineers from our board of directors mostly, which ones score the highest, and that's what did it this year.

Sarah Al-Ahmed: Yeah. Well, I mean, all of these projects are very, very useful, and especially in the context of Vera Rubin. I'm throwing back to The American Astronomical Society meeting I went to earlier this year in June. I went to a panel about how to apply AI to research, and the entire thing was basically about the community of people trying to panic vibe code ways of dealing with Vera Rubin's amount of data. It's a huge issue, so I'm glad we're kind of getting out ahead of this.

Bruce Betts: It's the opposite issue that scientists usually have of not enough data.

Sarah Al-Ahmed: Right. Drinking from the fire hose, the small body fire hose. I did want to ask, though, because we've spoken before about some of our other science and technology stuff that we've funded. For example, PlanetVac that's going to be on the Martian Moon Exploration Mission that's going to Phobos, we helped fund that, but it wasn't part of the STEP Grant program because STEP Grants didn't exist at that point. So how do we go from kind of funding things like PlanetVac or, say, LightSail to this more formal STEP Grant program?

Bruce Betts: That'd be me. We did the things in a very ad hoc way before, and we still can do that. I want to emphasize if we have an opportunity like PlanetVac that comes up and is time urgent, we will consider it outside the STEP Grant program. But we want to have most of our program now in a more formal setting just because with putting out calls for proposals, doing things that direction, you cast the net farther. So with PlanetVac, we made the right contacts to the right people at the right time and a match was made, but it was haphazard and by chance.

Whereas, here I was concerned that we were not casting the net. We weren't trying to find things and including from other countries and internationally, people working in different types of organizations that we'd have a chance find them and they'd have a chance to find us hopefully, and that it would result in a higher quality and also a more regular cadence with less chaos. So we still, with people like Sarah and me involved, there's still plenty of chaos in The-

Sarah Al-Ahmed: Always.

Bruce Betts: ... Planetary Society, but we've organized the grant program to be a little more formal, but not at the level of a government bureaucratic, or at least that's my goal is not to raise it to the level of government bureaucracy, but still do a really thorough proposal process. We do pre-proposals and then we invite some of those to do full proposals and we evaluate them and take it very seriously.

So we're good stewards of our donors' money and members because they're the ones who actually are making a difference in space exploration and getting involved and actually doing something meaningful where they can contribute to these projects. Whereas, you can't give money to NASA, or at least it's really hard.

Sarah Al-Ahmed: I know it makes a big difference. And I actually had a personal moment with it just a few months ago because during our last STEP Grant round, one of the projects that we funded was from UCLA and it was a citizen science project for searching for extraterrestrial intelligence, basically techno signatures. And earlier this summer, I was at Griffith Observatory for the L.A. Astronomical Society's Centennial Star Party. And while I was there, one of the talks given was actually by Megan Li, who was one of the grad students working on that project. And she was talking about basically it's the entire foundation of her PhD, and she's one of the only people getting a PhD in the search for extraterrestrial intelligence because of that. It made a huge difference in her life and also in their ability to process through the data. So even just in that one little instance, I can see how much this program is impacting.

Bruce Betts: Yes, that's a great story and a good example of how we make a difference. And they involved even she was running a citizen science project basically where people could get involved and help get the data down to things that might be extraterrestrials and get rid of a lot of the human interference that makes their life hard in trying to look for other signals when either seeing a bunch of us pesky humans making noise.

Sarah Al-Ahmed: Yeah. I mean, especially in those instances when there is so much data, and it's even more helpful these days because not only can humans help sort through data, but that we can use the way that they sort through data to help train algorithms that can do it better in the future themselves. So one more example of science and technology empowered by the public.

Bruce Betts: That would make a great acronym.

Sarah Al-Ahmed: STEP Grants.

Bruce Betts: All right. How about we go on to-

Speaker 9: Random space fact [inaudible 01:02:51].

Sarah Al-Ahmed: Rewind.

Bruce Betts: So I am 1.82 meters tall, at least in the morning, six feet tall. If the sun were the height of me, it's a random space fact focused on me, if the sun were the height of me, then the earth would be about the size of a marble, about two football fields away. And football fields are roughly the same whether you're playing American football or that other thing that is called soccer. However you look at it, things are approximate enough, two football fields away.

Sarah Al-Ahmed: Yeah.

Bruce Betts: Use an oblong ball or a round ball. I don't care.

Sarah Al-Ahmed: Man, Bruce is now the sun. Not the center of the Universe, just the center of our Solar System.

Bruce Betts: It's sufficient as long as people acknowledge that.

Sarah Al-Ahmed: Whatever. You deserve to take a little moment and be excited. You did, you formalized the STEP Grant program. You've been a force behind trying to help people who need it get money to do this kind of science. And you deserve to feel good about that, Bruce.

Bruce Betts: Well, thank you, Sarah. That's nice. I certainly feel good about what these groups have accomplished and that we, through our members, donors, have been able to make a difference and make a real impact in space exploration.

Sarah Al-Ahmed: Great.

Bruce Betts: Yay.

Sarah Al-Ahmed: Yay.

Bruce Betts: All right, everybody. Go out there, look up at the night sky and think about what it would be like if you were the sun. Thank you and good night.

Sarah Al-Ahmed: We've reached the end of this week's episode of Planetary Radio, but we'll be back next week with more space science and exploration. If you love the show, you can get Planetary Radio t-shirts at planetary.org/shop, along with lots of other cool space-y merchandise. Help others discover the passion, beauty, and joy of space science and exploration by leaving a review or a rating on platforms like Apple Podcasts and Spotify. Your feedback not only brightens our day, but helps other curious minds find their place in space through Planetary Radio.

You can also send us your space thoughts, questions, and poetry at our email, [email protected]. Or if you're a Planetary Society member, leave a comment in the Planetary Radio space in our member community app. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible by our STEP Grant funding members. You can join us as we work to support the space community around the world at planetary.org/join.

Rae Paoletta is our producer. Kate Howells and Mark Hilverda are our associate producers. Casey Dreier is the host of our monthly Space Policy Edition, and Mat Kaplan hosts our monthly Book Club Edition. Andrew Lucas is our audio producer. Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. My name is Sarah Al-Ahmed, the host and executive producer of Planetary Radio. And until next week, ad astra.

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