Andres Almeida (Host): Welcome to Small Steps, Giant Leaps. Your NASA APPEL Knowledge Services podcast. In each episode, we dive into the lessons learned and real-life experiences of NASA’s technical workforce. I’m your host, Andres Almeida. 

To map the sky, you need to see it in all of its colors. Our SPHEREx mission, short for the Spectrophotometer for the History of the Universe, Epoch of Reionization and Ices Explorer, launched in March of 2025. It’s a mission with a long name, but with an even bigger objective: to map the sky in greater detail than we’ve never seen before. The spacecraft will also search for water ice and frozen compounds in the Milky Way. On Earth, every living organism needs water to survive. 

SPHEREx’s unique cone shape keeps it at the extremely cold temperatures it needs to operate. We’re here today with Dr. Jim Fanson, SPHEREx Project Manager at NASA’s Jet Propulsion Laboratory in California. Hey, Jim, thanks for joining us today. 

Dr. James Fanson: It’s my pleasure to be here with you, Andres. 

Host: So, I’d love to start with the big picture. What is SPHEREx? What are its primary goals? 

Fanson: SPHEREx, which, by the way, is an acronym for a very long and tortured project name, which in full is the Spectrophotometer for the History of the Universe, the Epoch of Reionization and Ices Explorer. So, hidden in that long name are three science objectives. We’re trying to study or understand the origin of the universe, the origin and evolution of galaxies in the universe, and the location of ices in our galaxy from which the ingredients of life find their way onto planets when planets are forming, such as water, for example, on the Earth, has come from clouds of interstellar ices when the solar system was formed. So those are the three specific objectives of the SPHEREx science team. 

But we’re also producing a rich legacy survey data set, an all-sky spectral survey, so every point in the sky will have a spectrum of 102 different wavelength data points, which is the first such all-sky spectral survey of its kind. And from that data set, many other scientific investigations can and will be done by others outside of our science team over the years and decades to come. 

Just to go into a little more detail on these three science objectives: What we’re interested in, in the theme of understanding the origin of the universe, is to explore the very first instant of the Big Bang, a period that cosmologists call cosmic inflation. And cosmic inflation is a framework for understanding why the universe, on large scales. looks the way it does, which is in fact, the universe is quite simple on large scales. It has a flat geometry. It’s isotropic and homogeneous, meaning it looks the same in every direction, and it looks the same no matter what part of the universe you’re looking at. There are a number of mysteries associated with the universe, for why it looks the way it does, and this framework of cosmic inflation is a way of explaining those characteristics of the universe. 

So, the idea of inflation is that when the universe was a trillionth of a billionth of a billionth of a second old, there was some form of energy which is not predicted by the Standard Model of particle physics, that caused space and time to expand extremely rapidly on an exponential scale, so that what had been a very small piece of the universe got stretched out into a very large size, and this expansion occurred, you know, faster than the speed of light and, and that helps explain why the universe is so uniform looking. There are many models that fit this framework of cosmic inflation. And in order to figure out which models are, are the right way to think about it, we need more data, and that’s what we are doing. 

So, we’re going to be searching for something called non-Gaussianity. When you look at the earliest picture we have of the universe, which is the cosmic microwave background image that was taken when the universe was a few 100,000 years old. When you look at the density fluctuations, which is what we believe, grew or evolved into the galaxies that populate the universe, in the evolved universe we see today, we look at those fluctuations in. They’re very tiny, and they’re thought to have originated in the quantum field fluctuations when the universe was very young. 

So, one way of discerning or distinguishing between various models of cosmic inflation is to look at the distribution of galaxies in the evolved universe. So, we are going to be mapping about 500 million galaxies in three dimensions, and we get the third dimension by means of the spectral survey data that we’re taking and the distribution of galaxies will tell us whether that distribution is Gaussian or not, and that will help us distinguish various models for cosmic inflation, so that that’s the first scientific theme that we’re going after when you 

Host: You mentioned the Big Bang, and you say, for instance, that is not just, you’re not talking about a second. This is a smaller time scale. 

Fanson It’s much less than a second. It’s a very, very tiny fraction of time after the Big Bang. Our principal investigator likes to describe it as the, as a trillionth of a billionth of a billionth of a second. You know, we’re talking about just a very, very early moment in the history of the universe, and it lasted a very, very short amount of time. So, there was this very sudden and short-lived expansion where the universe expanded manyfold, to help explain why the universe has this uniformity to it and other characteristics as well. 

Host: So, you named one of those scientific goals. What are the others? 

Fanson: So, the other two are understanding the formation and evolution of galaxies over cosmic time, and what we’re going to do is measure the extra galactic background light, which is, basically we want to measure all of the light that’s emitted from galaxies that we can image or not image, or, you know, that we can resolve or not resolve. We may not be able to resolve a galaxy that’s, that’s, you know, very faint and far away, but we’re still receiving photons from it and all of the other galaxies that have formed in that particular direction that we’re observing. 

Rather than measure specific individual objects we’re going to take in the totality of the light that is arriving at the Earth from all the way across the universe. And having spectral information about that light will allow us to get some information about the history of cosmic time. So, that’s the second science theme. 

And the third science theme, which is focused more close to home in our own galaxy, the Milky Way, is to look at where the repositories of biogenic ices are located in the galaxy that form or that are part of the formation of planets when planetary systems form in the galaxy. So, we believe that most of the ices, like water or CO2 ice (or, you know, other, other ices that have organic materials, molecules in them), we believe that most of these ices in interstellar space are in the form of mantles that have frozen out on tiny dust particles. 

So, that’s where most of this material is, most of the water, for example. And we can observe the emission, the spectral emission and absorption of those molecules by the spectra that we can take we’re in the process of measuring or mapping where these clouds of biogenic ices are located, and to better understand how they make their way into planet formation when planetary systems are formed. 

Host: So, I imagine SPHEREx also can contribute to the field of astrobiology? 

Fanson: Absolutely. So, we are looking just now at some of the early data coming down from the observatory. And you know, we have very wide field images that we take, because we’re mapping the entire sky over a period of two years. And the way we’re doing this spectral imaging has been borrowed from planetary science. 

So, we have these infrared detectors. These are large arrays that look at a large piece of the sky, you know, several times the size of the Moon in each image. But we have filters over the top of these infrared detectors that basically pass a narrow wave band of light at a particular location on the detector. So, on one side of the detector, we’ve got one narrow wave band, and on the opposite end of the detector, there’s a different wave band. So, depending on how you’re looking in the image, you’re looking at a different wavelength. 

And so, we take an image of the sky, and then we step it slightly over, and we take another image and step it slightly over, so that every point then on the sky ultimately gets imaged in one of 102 different colors. And when you then look at these images, it’s like, it’s like, you have a, you can create a movie looking at a piece of the sky, and you run the movie, and you’re changing the wavelength that you’re looking at, and what we see is that when we come to a particular emission frequency or wavelength that’s characteristic of, let’s say, water molecules or CO2, we can all of a sudden see clouds light up in the galaxy that are otherwise invisible, or you see something that’s very dark and is absorbing, and it’s, it’s a black cloud in one wavelength range, and it vanishes in the other wavelength ranges. 

So, we can quickly see where these clouds of different molecules are located. It’s really like opening a new window on the universe, and you’re seeing the universe in a way that we’ve never seen before. So, we’re actually, as the data comes down, we’re seeing things we’ve never seen before. 

Host: And we’ve seen spectography data from James Webb and other space telescopes. But this sounds particularly unique. 

Fanson: SPHEREx is, is, is taking data a little differently than, say, James Webb or the Hubble would do, and part of that is because we’re trying to map the entire sky. When you talk about a Hubble, a telescope like Hubble or like Webb, those machines are designed to give you maximum magnification on very tiny areas of the sky so you can see them in great detail. 

 Host: Yeah, a target. 

Fanson: So, it’s not, it’s not really practical to map like the whole sky with, with web or with Hubble. You know, would just take far too long to do something like that. So, we take data a little bit differently. There are spectroscopic instruments on both Hubble and Webb, but what we can do is we can see these large clouds in the galaxy that would be more difficult to image with a, with a targeted kind of telescope, like, like Webb or like Hubble. 

Host: How will you handle and manage and analyze all that data? Is machine learning part of this?

Fanson: We have a what is called a scientific pipeline for processing the data as it comes down from the spacecraft. This is being done at IPAC [Infrared Processing and Analysis Center], which is down at the Caltech campus. There, they specialize in infrared data processing. So, there’s an automated pipeline that does various calibrations and corrections and basically creating more refined data products that are ultimately delivered to the science community. And that’s, that’s an automated process at the moment. It does not use any AI or machine learning. Partly, that’s because the scientists want to know exactly what is being done to the data, so they, they want very deterministic algorithms for it. 

However, AI and machine learning techniques are being explored by the science team to then look use the data and search for things in the data. So, I think that’s an area that we will see grow over time, but the actual pipeline is not using any AI at the moment. 

Host: I’d love to switch over to, for now, just from a project management standpoint, what have been some challenges that you’ve encountered throughout this mission? 

Fanson: One of the challenges for this mission is that it is a competed mission. So, NASA does, generally, two kinds of scientific missions. There are the flagship missions, which are strategically arrived at, and which are decided we’re going to do them, you know, maybe out of the decadal survey that the National Academies does every 10 years in various fields. And then there are the competed missions, where you have to submit a proposal against an announcement of opportunity. 

NASA says, “You know, we want a mission in this cost range that does, you know, addresses these scientific themes.” And then proposals will come in and, and one will be competitively selected by NASA. So that’s how SPHEREx came to be. SPHEREx is an Explorer mission. It’s a relatively small mission in the, in the range of missions that NASA does. 

And one of the challenges that we have with SPHEREx is we’re trying to do an all-sky survey in the infrared, a spectral survey in the infrared. And the natural place to put an observatory like that is out at the L2, the Lagrange point where Webb is located. But we could not propose a mission that would go out to the Lagrange point and stay within the cost range for this particular competition. So, one of the challenges we have is how to do this mission while in Earth orbit. 

So, other missions have been in Earth orbit that do all-sky survey, the Wide-field Spectroscopic Explorer, WISE mission, that did an imaging survey of the whole sky in the infrared. But typically, then you would carry like a thermos bottle of super cold fluid that would cool the telescope and detectors down. You have to remember that in the infrared, you’re looking at basically heat emission. It’s like night vision goggles. You’re looking at heat emission, and in order to see faint objects, and have the sensitivity that we need, the telescope and the detectors have to be very cold. We’re talking about like 360 degrees below zero Fahrenheit, right? Just a few degrees above absolute zero. And that’s hard to do when you’re in Earth orbit, because the Earth is a warm planet. 

And so, you typically would carry a thermos bottle of very cold fluid that would eventually boil away, or you would have cryocoolers running these mechanical cooling devices. But what we tried to do for SPHEREx was passively cool the telescope and the detectors down to these extremely cold temperatures, and we did this with a collection of mirrored surfaces that we call photon shields and V-groove radiators. These are fancy terms for just basically mirrored surfaces in a certain geometry that will bounce any infrared photons off into space. 

So, when you look at a picture of SPHEREx, it has a very unusual shape. It looks like you’ve got a big martini glass attached to the top of the spacecraft. Those are these conical photon shields, which are there only to cool. Well, they, you know, they, they block the telescope from the light of the Sun and so on. So, we don’t get straight light, but they’re really there to cool the telescope and the detectors to these very, very low temperatures. So, this was a new innovation. 

We’ve done similar kinds of things on other missions, but this was the first time that we built such a such a passive cooling system in low Earth orbit, and it worked exactly as predicted, and in our telescope and detectors are sitting at the desired temperatures. So, it worked extremely well, but it was challenging to design and build this thermal cooling system. So, that was one of the challenges we had. 

Host: Does this mission build upon – even in the engineering, the shape and the instruments of the spacecraft itself – does it build upon previous missions, like non-NASA missions, NASA missions at all? 

Fanson: There have been some missions that have needed to be at cryogenic temperatures that have used some of these techniques before. Some European missions, you know, the Planck mission, for example. We did some of this for the Spitzer Space Telescope, the infrared companion to Hubble. And some of these techniques have been used as well on James Webb, but to do this on a low Earth orbiting mission, to get to these temperatures is a bit of a novel development for SPHEREx. What 

Host: What are some of the milestones that’s already hit, and what are we looking forward to? 

Fanson: We launched on the 11th of march out of the Western Range at Vandenberg Space Force Base, and some of the key accomplishments so far is that we have turned on all of the observatory subsystems, those on the spacecraft and the science instrument, and we have checked out that they’re all functioning basically as designed and as expected. And that includes ejecting the cover over the telescope. 

We have a cover to protect the telescope from contamination when we’re processing on the ground and when we’re launching in the fairing of the launch vehicle, but the cover has to be ejected or deployed out into space to allow light to get into the telescope. So that was a key deployment for us, if you will, to make sure we got rid of the cover successfully, and that went as according as planned. 

And then we’re learning to fly the vehicle in this period of time after launch that we call in-orbit checkout. So, we’re learning how agile is the attitude control, how well can we point the telescope and move from one line of sight to another? How quickly does the pointing settle out and become stable? What is the actual performance of the detectors? Do we have any noise sources that we hadn’t measured on the ground? In space, you know, we see satellite tracks because there are other objects that are orbiting the Earth, so we try to characterize those kinds of sources and make sure our pipeline, data processing pipeline flags them appropriately. 

And then there’s a number of phenomenon associated with the environment around the Earth. So, we’re at 650 kilometers altitude, but there’s still a thin atmosphere at that height, and it consists mostly of oxygen and helium. And we can see the glow from molecular, atomic helium. The helium one line is very prominent. 

We also experience a glow from just the vehicle moving so quickly through the atmosphere. It’s called shuttle glow. So, we have to make some fine tuning of the parameters for how we’re going to do the survey, so we minimize the effects of these air glows. There’s also a radiation environment around the Earth. The Earth’s magnetic field tends to focus those radiation effects in certain areas, and we calibrate them and understand how much of the data is going to be affected by it. So, we’re learning how to fly the vehicle in orbit, and fine tuning the parameters to squeeze out the maximum scientific performance before we undertake the science survey, which will take about two years. 

Host: That’s a plan of two years, because these missions can get extended, correct, not a guarantee? 

Fanson: True. So, one of the advantages of having this purely passive cooling system is that there’s no cryogen to boil off to end the mission. There’s no mechanical cooler that could break down. So, we don’t carry any propellant or anything that is consumable in that sense. 

So, we could have a, potentially, a very successful extended mission. And NASA has a system for process for projects to propose for extended mission funding if they’re performing well and doing competitive science that can, they can run beyond their baseline mission. And for us, the baseline mission is, is two years. 

Host: Did you come on to this project early on? 

Fanson: I came on to this project about two years ago. The project had already been in development for, for several years, so this was a case where the project manager had to step down for personal reasons, and they were looking for someone to be his successor, and, and they chose me. And I came onto the project just after the critical design review, but when hardware was actually being built. 

Host: From a project management standpoint, what have been some lessons learned for you and your team? 

Fanson: The lessons learned from SPHEREx are similar to the lessons that we tend to learn and that I’ve learned on other projects, and one of them is that you have to be very careful in how you do risk management and assess the risks, because the problems tend to develop where you’re not really spending a lot of attention or resources to understand and mitigate risks. 

So, in some cases, very simple things can go wrong and, and there, because they’re simple, you didn’t spend a lot of time worrying about them. So, it’s, it’s important to, to pay attention, not just to the advanced technology areas, but some of the simpler areas as well that can, you know, go wrong and cost you time or money. 

Another lesson that, that I’ve learned on this mission, as well as others, is that it really is important that you have the right team of talent to do something like this, even though SPHEREx is a small-ish mission in the NASA system, every space mission is very complex, and there are a lot of interfaces. There are a lot of requirements. There’s a lot of verification and validation, we call it, that has to be done to make sure that it, will the system will work once it’s in space, and it’s important to have people that have a diverse set of skills and relevant experience, so that they know what to pay attention to. It seems to always be the case that you’re not able to test the spacecraft precisely the way it’s going to be in space. Either you can’t reach the temperatures you’re going to reach in space, or because of gravity on the ground, you can’t really test the attitude control system that will be pointing the spacecraft, and so you have to back up the testing that you can do with analysis that can predict from the testing that you can do, can predict, predict how it will actually perform in space. 

So these are things that you have to pay also very close attention to how you do the verification and validation. 

Host: What do you consider to be your giant leap? 

Fanson: I would say my giant leap occurred early in my career when I changed lanes from being a technologist to managing the delivery of spaceflight systems. And that occurred for me when we discovered that the Hubble Space Telescope had a problem with not being able to come to a sharp focus after it was launched, and we at the Jet Propulsion Laboratory were part of the team that basically fixed the telescope back in the day. And it just so happened that I was working on a technology as a technologist that was needed in the camera that we built that had [been] built in correction of the so-called spherical aberration in the Hubble telescope. 

 And so, I was found myself on a very rapid schedule, bringing a new technology to bear on a flight instrument that you know was a high priority to get flown by a particular date. So, after I made that, you know that that adventure with the Hubble telescope, my course in my career was, was permanently changed, basically, to, to working on one telescope project after another for flight, and some on the ground as well. So that was, that was the biggest pivot for me in my in my career. 

Host: Well, thanks, Jim. We look forward to following more on SPHEREx. We’ll add more info on the podcast page at appel.nasa.gov 

Fanson: Thank you, very happy to be with you. 

Host: That’s it for this episode of Small Steps, Giant Leaps. For more on Dr. Fanson and the topics we discussed today, visit our resource page at appel.nasa.gov. That’s A-P-P-E-L dot nasa dot gov. And don’t forget to check out our other podcasts like Houston, We have a Podcast, Curious Universe and Universo curioso de la NASA. Thanks for listening,  

Outro: 3-2-1. This is an official NASA podcast.