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Tap into the experiences of NASA’s technical workforce as they develop missions to explore distant worlds—from the Moon to Mars, from Titan to Psyche. Learn how they advance technology to make aviation on Earth faster, quieter and more fuel efficient. Each biweekly episode celebrates program and project managers, engineers, scientists and thought leaders working on multiple fronts to advance aeronautics and space exploration in a bold new era of discovery. New episodes are released bi-weekly on Wednesdays. 

NASA Deputy Director of Astrophysics Jeff Volosin discusses the Transiting Exoplanet Survey Satellite (TESS) mission.

TESS is an all-sky survey mission to search for planets outside of our solar system, including those that could support life. Launched aboard a SpaceX Falcon 9 rocket in April 2018, TESS finished its primary mission in July 2020—having already found 66 new exoplanets and over 2,000 candidates astronomers are working to confirm. The mission was designed to find exoplanets that periodically block part of the light from their host stars — events called transits — and survey 200,000 of the brightest stars near the sun to search for transiting exoplanets.

In this episode of Small Steps, Giant Leaps, you’ll learn about:

  • Why TESS is referred to as the “People’s Telescope”
  • Engineering and cultural lessons learned from the TESS mission
  • Exciting TESS scientific discoveries

Related Resources

TESS Exoplanet Mission

Video: TESS Completes Its Primary Mission

APPEL Courses:

Project Planning Analysis and Control (APPEL-PPAC)

Scheduling and Cost Control (APPEL-SCC)

Assessing Project Performance (APPEL-APP)


Jeff Volosin Credit: NASA

Jeff Volosin
Credit: NASA

Jeff Volosin is NASA’s Deputy Director for Astrophysics and served as Transiting Exoplanet Survey Satellite (TESS) Project Manager from project award through launch and commissioning. Volosin has supported a wide array of NASA and NOAA satellite development and operations activities. He spent half of his career in industry, where he served in a variety of roles, including system engineer, program/project manager and senior leadership. As a government employee, Volosin’s career has been split between NASA Headquarters and Goddard Space Flight Center (GSFC). In the early 2000s, he was at NASA Headquarters supporting efforts to send humans to the Moon and Mars as NASA’s lead for the Humans-to-Mars architecture development and for development of a Global Exploration Strategy. More recently, he served as NASA’s Deputy Division Director for Communications at GSFC. Volosin is an adjunct college professor and contributing author to a number of textbooks. He has a bachelor’s in space sciences from the Florida Institute of Technology.


Jeff Volosin: TESS is making significant discoveries. We found I think it’s up to almost 2,500 potential planets outside our solar system.

What’s most important about TESS from a scientific researcher’s standpoint is there are high school students and college students around the world being the first in our history to find a planet around another star.

And hopefully, at some point we’re on the verge of discovering if there’s life outside of our solar system.

Deana Nunley (Host): Welcome back to Small Steps, Giant Leaps, a NASA APPEL Knowledge Services podcast featuring interviews and stories that tap into project experiences to share best practices, lessons learned and novel ideas.

I’m Deana Nunley.

NASA’s Transiting Exoplanet Survey Satellite, or TESS, finished its primary mission July Fourth, imaging about 75 percent of the starry sky as part of a two-year-long survey in the search for planets outside of our solar system.

NASA’s Deputy Director of Astrophysics Jeff Volosin served as TESS Project Manager, and joins us now.

Jeff, thank you for being our guest.

Volosin: Yeah. Thank you, Deana.

Host: How did the TESS mission concept originate?

Volosin: So, TESS came about… Gosh, it was all the way back in like 2005 and originally some folks at MIT in the Kavli Institute, Dr. George Ricker and some cohorts of his, they had this idea, the Kepler mission, if you’ve ever heard of the Kepler mission. The Kepler mission was going to be our first attempt to put a telescope in space that would look for this idea, this transiting exoplanets, that there could be planets around stars outside of our solar system, and that we could catch them as they go in front, as they orbit in their year, as they go between us and the star. So if they just so happen to be orbiting such that they go right in front of the star, from our perspective on Earth, we could see a small lowering in the light level coming from that star, right? So, the planet is blocking a little bit of that light.

And so the idea for the Kepler mission back in the earlier 2000s was to send a mission up and just focus on one area of the sky for a number of years, a very small area of the sky and look to see if we could really see. You’ve got to have a really good camera to detect a teeny, teeny change in the brightness of a star because of a planet going in front of it. And so the Kepler mission was being developed and it was going to launch in 2009. There was a lot of excitement about this idea because the world of exoplanets, when I went to college, there were no such things as exoplanets. We never thought we would see an exoplanet. And so, this idea that you could identify the presence of a planet, maybe even an Earth-like planet around a star outside of our sun, out of our solar system, we didn’t even think it could be done.

So, as technology was getting better, the Kepler mission thought, ‘You know what? We think detectors are good enough now that they can measure individual photons coming from those stars, turning them into electrical current, and we could see that little dip of a planet going in front of a star. So, Kepler was being developed and the MIT Kavli Institute and Dr. Ricker said, ‘You know what? We’ve been working on X-ray telescopes for dozens of years and working on a bunch of international X-ray missions. And one of the things we need for X-ray missions are really good detectors. And so, we’ve done a lot of X-ray science, but you know what? Maybe we could retake those X-ray detectors and use them to do just like what they’re planning to do on Kepler and come up with a mission that could look for planets around other stars by doing this transit science.’

And so, they put together the TESS mission and originally — MIT, they’re creative people — they said, ‘Maybe we’ll do it as a private venture. We’re not even going to go to NASA.’ So, they went to Google, they went to some other organizations. They tried to raise private funding and it was going to be hard. It was going to cost more than they expected. So, they put it in as a proposal for NASA as a small explorer mission, our smaller size missions in astrophysics. They weren’t successful, but somebody said, ‘You know what? That’s a great proposal, but it’s probably too big to put as a small explorer. You’re going to want a bigger spacecraft and more money. Why don’t you re-propose it as a full middle explorer, MIDEX mission, which is another $100 million in cost or so, a more complex, bigger spacecraft?’

And so, they went ahead and re-proposed it with Goddard Space Flight Center as a partner and were successful in getting the TESS mission funded. And this is at a time — so you think of Kepler launched in 2009 for the first proof that this could be done in space. And it was only a few years later that this proposal was accepted and the goal, so just I’ll end this part of the story by saying that the goal of TESS now was not to repeat what Kepler was going to be doing on orbit, which was to prove that this could be done. Nobody ever even tried it, but to take this ability, this technology for doing transit science and take it to the next level. Because it turns out that when Kepler looks deep out into space in this one area, it found a bunch of exoplanets. It found planets around other stars, but they were really far away, hundreds of light years away from Earth. And it would be very difficult to ever study those worlds, right?

So, in the end, you don’t want to just know they exist. You want to know if they have atmospheres. You want to know if they’re like the Earth. You want to know if they have life. And so that would be pretty difficult for humans right now, if the planets and the stars are that far away. And so big telescopes, like the James Webb telescope, when it launches, they’ll be able to look at these planets, but only in stars that are maybe dozens of light years away. So TESS’s job was to go up and survey the entire sky over a two-year period and look for where are the closest planets to Earth, close meaning dozens of light years, and where are there planets that are more Earth-size so that they could harbor life. And then big telescopes like the Webb telescope can say, ‘Ha-ha, I know they’re there now. I’ll study their atmosphere by looking at the light coming through from the star through the atmosphere, looking for absorption by chemicals.’

All of a sudden we can learn is there oxygen in the atmosphere? Is there methane in the atmosphere? Are there signs that those might be Earth-like planets? And so that’s TESS’s role is to take what Kepler did in discovering that transit photometry, transit science can be used in space to identify planets around other stars, take it to the next level, find the nearest ones to Earth and find the ones that are Earth-size that now bigger telescopes could follow up with. And hopefully, at some point we’re on the verge of discovering if there’s life outside of our solar system.

Host: What would you say are the most exciting TESS discoveries?

Volosin: So, I think the biggest shock for me was, we built this telescope. It has a four, 24 by 24 degree field of view cameras. So that means it’s 96 degrees, which means it can cover a big part of the sky almost from like the horizon up to the pole or straight up with one big swath of imagery. And we take pictures every few seconds and collect those images. And so when we first started dumping data to the ground, we took all of that data and we made little movies, right? You can make little movies where you string them all together and show over like a two-week period this view of the sky with this really set of accurate photometry cameras. And it turned out that we saw all kinds of things that are what astronomers call time-domain astronomy events, right? If a supernova goes off, you’re looking at a big part of the sky.

We have discovered lots of supernovas. If a comet flies by, we see it. If an asteroid is moving out in the asteroid belt or near to the Earth, we can see the traces of those asteroids moving around in space. And so what we found was that TESS is making significant discoveries. We found — I think it’s up to almost 2,500 potential planets outside our solar system. Many of them Earth-like many of them closer to Earth. So, we’ve already identified some really great follow-up candidates. So that was almost the expected, what you really hope TESS would do. But I think what’s exciting for me is the unexpected. So, it’s all this other research that we could do. If you study pulsars, stars that brighten and dim over time, TESS is the perfect camera for doing that. So, you’re taking accurate readings of the amount of photons being received from tens of thousands of stars, every few seconds as you snap pictures.

And so when you compile that data set, astronomers now will have a rich data set of the entire sky taken with this really accurate set of cameras. So, lots of different astronomy fields are going to be furthered by the research done on TESS. I think when you look at the number of papers published by scientific researchers over the first two years, which is in the hundreds at this point, almost half of those papers are not about exoplanets. They’re about other things that researchers are finding in the TESS data that they can research.

And so, that’s for me not only the most exciting part of the mission, but I think the longer-term value of TESS will not only be the exoplanet research, but all this other astronomy that it will have furthered. Because if you can see the beginnings of the supernova. So if you just happen to be looking at the right part of the sky, and a supernova goes off, a lot of the things we don’t understand about supernova happen because we don’t usually see them until we notice that something changed. And then we focus all of our attention to that part of the sky. What TESS is doing is having the ability by looking at such a big part of the sky to see it as it happens. So from the very initiation of a supernova, you can see the buildup and the curve of the event, so that now physicists can better understand the mechanisms that might be leading to supernova events and the differences between different kinds of supernova. So, yeah. I think that’ll be the history, the legacy that TESS leaves behind.

Host: Jeff, what are the key lessons learned from TESS?

Volosin: I was project manager for five years. So I started right at the beginning when we started developing. So, in NASA world Phase B. So at the beginning of Phase B, when it was awarded to go into its design and then into construction, I started then and I stayed with it through the commissioning, through the launch and through the commissioning. And I think the biggest thing I learned was that with this mission, and I guess a lot of the smaller to middle sized missions at NASA, you’re working in close partnership with academic institutions. And so MIT Kavli Institute, they provided — Dr. Ricker was the principal investigator. They had the ideas for how to design this great set of detectors and cameras. They were working with MIT’s Lincoln Laboratory outside of Boston, who’s a big Air Force contractor. And so, they were working with them on the design of these cameras.

We’re working with the Orbital Sciences now, Northrop Grumman in Virginia to build the spacecraft itself. And when I came on board, I think I didn’t realize that the cultures of those organizations were so disparate that it was going to cause a lot more problems than I expected. So, NASA we come with a lot of history, a lot of experience and a lot of rules to follow. So, an organization like MIT, they’re much more an academic environment and they’re not very rule-based at all. They liked the creativity that their designers bring to the process. And so, when we would start to try to force them to write down requirements or do things that follow a standard NASA methodology, they balked at that and I think our first reaction was always to say, ‘Hey, we’re the funding organization at NASA. You need to follow the rules that we’ve set in place.’

But I think over those five years, I really got an appreciation for that working with a group that had developed a set of detectors and electronics for those detectors that had evolved over a period of 20 to 30 years for X-ray missions, that really, they didn’t need to approach it in the same way that we might approach something that’s newer or first time. And that their methodology of taking what they’d done in the past and evolving it, and then just quickly putting together prototypes, testing them. And if they didn’t work, making some tweaks, testing them again, that that could be acceptable within the NASA world. But I think at first we all bristled because we brought all of our rules. They brought their imagination and creativity and their history, and they did not want to follow the NASA rules at all. So, they were working with Lincoln Laboratory who works very closely with the Air Force, which caused even more problems because that culture brings a whole different set of rules, not the same as NASA.

And so sometimes we would be investigating an issue with the cameras and I would go up to Lincoln and say, ‘Well, we’re happy with the resolution of this problem. We’d like to move forward.’ And the Lincoln people would say, ‘No, sorry, we follow different rules and we’re going to spend more time investigating, doing more comparison against models.’ And I’d be like, ‘No, no, no, we need to move on.’ So, we had culture challenges there as well. And I think at the beginning as the project manager, I was more than willing to think, ‘Oh, let’s all just try to get along, and this will all work out. Everybody will find a way to fit in.’ And we got through to our critical design review and along the way, our review board had been telling us in earlier reviews in the mission, ‘Your instrument isn’t evolving as quickly as we think it should. We think there’s some disconnects between the team members and we don’t think that everything’s going to fit together very well when you finish, but we’re going to let you go and just kind of keep an eye on you.’

And when we got to our Critical Design Review, the review board understood this was their last opportunity to kind of give us some more harsh direction or advice before we went into actually building the system. And so, we didn’t pass our Critical Design Review. The board said, ‘There are just too many open areas where your team is not working together well, and it’s leaving a lot of questions about how the system’s going to operate.’ And so by not passing that review, I think the biggest lesson learned for me was we hadn’t addressed some of those root issues of cultural differences earlier. And as the project manager, I had to take responsibility that I was just kind of maybe hoping it would work out as individuals work together over time. But I think it scared all of us enough, the thought that our mission might be canceled and that we had really failed. And I think none of us thought of ourselves as those people that would fail in an effort like this.

And so I think that became the rallying call. So I don’t know, in retrospect, the lesson learned of maybe I should have addressed this earlier and maybe we should have learned to work together and set up more rules early on about how we would interact. Okay, maybe, but on the flip side, maybe it took that event of almost being canceled and being threatened a little bit with failure that made all of us who all come from backgrounds where we like to make sure we’re successful, that it made us buckle down and work better together.

So, I think we tried as best we could to understand each other’s cultures, but I had to be a little bit more strict sometimes on, we have to have certain products at certain times. And we all had to learn to march together to get to a launch. But in the end we came in, we finished under budget. We finished ahead of schedule and the mission has completed its two years of on-orbit operation successfully. So, from a culture standpoint, I think I was surprised at how challenging it would be to bring those cultures together and probably underestimated how much that could affect the end mission. Now, the other side of it is there were a number of technical issues that came up along the way that compounded this. Some were things like we have to operate at 26 gigahertz for sending data down to the ground.

So, it turns out that the spectrum of radio frequencies is very valuable. And a lot of the users who want to do say, mobile communications and things like that, commercial companies would like to use a lot of the spectrum that’s available. So the government has to live within very specific areas of the spectrum. So, more recently, say the last 10, 15 years, the government’s been asked to try to utilize some different frequencies that right now, mobile communicators don’t want. So move some of the customers from the government’s side up to these higher frequencies. Well, we were asked to do that on TESS and so we’re using a 26 gigahertz transmitter on board. But problematically, the marketplace has not developed a lot of off-the-shelf products. And so, we went with a company that we felt like had a good design to build one of these transmitters, but it became the most challenging technology development effort.

We tried doing it as a fixed-price contract. I think both we and the contractor kind of underestimated how challenging it would be to design and build this 26 gigahertz transmitter. And so it became the tall pole in our scheduling. One of the things that worked out well for us is that we had the team build an early engineering unit that was built pretty much form, fit and function similar to the flight box, except without flight-qualified parts. And so that early engineering model, although it wasn’t perfect, ended up kind of saving the day. It allowed us to do early testing with the Deep Space Network. That was going to be our communication link. It allowed us to even go into observatory, vibration and acoustic testing without our flight transmitter, which was still being delayed and being finished and in construction and testing as they hit issues.

And so, in the end, having that engineering unit available allowed us to move all the way to observatory thermal vac. And I think the end of that story is, I flew out to San Diego where the company was, and they were trying really hard. We had a lot of NASA engineering staff out there working with them to try to get this thing over the finish line. And so I was going out every month to meet with the team. And I finally went out and stayed for about a week as they finished up the testing with a couple of their engineers working overnight, put in a lot of effort and I took that box, put it on the red-eye flight from San Diego with me as overhead baggage and drove — I landed at Dulles Airport the next morning, drove it out to the Orbital Sciences facility. They inspected it and put it on the spacecraft. And a few days later we rolled into thermal vac.

So, we learned a lot about how to work under pressure while still making sure that we did all the testing and everything to be successful. So, a little bit of cultural challenges, a little bit of technical challenges.

Host: Are there additional takeaways from your experience managing the TESS project that could be helpful to NASA program and project managers?

Volosin: Sure. I think one of the key things we learned is that the technical challenges — some of them are very unpredictable. We had a challenge with our cameras and our cameras use RTV. Think of it as a rubbery eraser material-like, that goes around the outside of every lens inside the camera. There are seven lenses in every camera and those lenses are glass, the shell, the body of the camera’s aluminum. So, thermally, they don’t match up well in how they expand and contract. So we put a little buffer around the outside edge of every one of those lenses, and it turned out that when we operate at a very low temperature and at the temperature we operate at, the rubber material, something was going on and it looked like it was tugging at the lenses in a way.

And so, the one thing I learned — and this happened again, and again, is that when you run into those kinds of problems, you could easily — you put your head down, you’re focused on solving an issue. All your engineers and scientists are perplexed but you’re really into it. You’re like, ‘Wow, this is really interesting problem. What’s exactly going on?’ And then you look back up and you’re like, ‘Oh, my gosh, we just lost another three weeks of schedule, but we’ve got to get this solved.’ So, I think what I learned is in that case, our system engineer, Shane Hynes, he did an incredible job of going out, not just to NASA, but all over industry and he brought in, I think the world’s experts on the use of this material. And within like two or three weeks, they collected all kinds of data. They put together recommendations on some tests we should run at a small level with some instrumentation. And very quickly they got down to a root cause.

And weirdly, even after all that testing, we were still a little perplexed and somebody pulled up a paper, a scientific research paper written in the 1930s, I think it was, from BF Goodrich. And it was about cars sliding off the road in the winter. And it turned out that the rubber tires at cold temperature were starting to crystallize and the rubber became so stiff that it wouldn’t hold onto the road anymore. Well, it turned out that that analysis that they had done back then for a rubber-like material in the tires was very applicable to what we were dealing with. So, I learned that not only can you solve problems, even hard problems when you bring in experts from all over that can work collegially together under a good leader, like our engineer, but also that, you have to go far and wide to find answers. And so, finding a paper from the 1930s on rubber tires was not how we thought we would solve a complex problem on our photometry cameras.

So, I think that for me, was a valuable thing — coming away with how you can get to a root cause with the right people. And I think the leadership of that was critical. So Shane has the personality, he’s an extremely talented engineer, but he’s also somebody who can work with a lot of other talented people and bring them, let their voices be heard, bring them towards recommendations and consensus and ideas. And so I think that was the most valuable thing I saw in how he worked with those teams. And we use that same methodology probably another five or six times as we ran into other challenges along the way.

Host: Now that TESS has completed its primary mission, what’s next?

Volosin: Yeah. So, when we finished up a primary mission, so in this case, it was two years. One year focused on the Northern Hemisphere, one year focused on the Southern Hemisphere. So after collecting the data that represented the baseline, which was to find enough candidates to allow big telescopes like Webb to follow up on them. So that’s completed. So, George Ricker and his team put together a new proposal that said, ‘Okay, over the next three years, if you will approve me to continue operating TESS, I’m going to focus it again, do another check on some areas of the northern and southern hemispheres, where we saw some really interesting planets.’ And we didn’t actually get to go through in the equatorial band kind of between the north and the south. We left a little bit of a gap. So, he proposed that we go back and analyze those areas within that gap.

So, that’s what the next three years will hold. It’s a lot more stare at an area for a month or so, download all of that data, to look for planets and then take the TESS cameras and focus them on another part of the sky. And so, I think, as I mentioned before that the goal over time will be a continued database of information for researchers looking at exoplanets. But I really think that more and more the TESS data set over time will be a valuable research tool for people looking at all kinds of different time-domain astronomy thing. So, the one thing, Dr. Ricker always refers to TESS as the people’s telescope. And this is a big theme within the astrophysics at NASA is in the past and still today, some missions have a proprietary period where only the researchers that are funded to work on the mission can see the data when it first arrives and they get some period of time to do the initial analysis. And that’s how the Kepler mission was.

In the Kepler mission, it was a scientist working on Kepler who made the planet discoveries. And that was the proof of concept that that could be done. But when you think about TESS what’s most important about TESS from a scientific researcher’s standpoint is there are high school students and college students around the world being the first in our history to find a planet around another star. And so, what TESS is, is just this wide field set of cameras, that’s really got these killer detectors that can really do a great job in photometry of all the stars in that field of view. And it’s just putting within a couple of months, we dump all the data that we collect into an archive up in Baltimore, and that’s a publicly accessible archive. And all the tools are out there online for people to take that data and to look for their own planet.

There are games. I think there’s a game you could download on your PC, where you can go through TESS data, you push a button, it’s kind of like a roulette wheel and it throws up some data and it says, ‘Hey, I think this one might be a planet. Here’s a curve from one of the stars.’ And so, people are making discoveries all over the world based on TESS data. And most of those are discoveries being done by young researchers who are really adept at using computer tools, machine learning, all those kinds of things to cull through this ton of data that’s available and make these discoveries. So that’s what’s to me most exciting about the long term of TESS, is that this data set will just keep getting bigger and bigger and bigger, and all of these researchers can come in, grab it and use it. So, the number of papers published so far has been incredible, but I assume that’s only going to go up a ton in the future as more and more people look through the data.

Host: Incredibly intriguing. Jeff, it’s been great talking with and learning more about TESS.

Volosin: Thanks for the opportunity, Deana.

Host: We’d love for you to join us again sometime to talk about other missions you’re involved with in your astrophysics leadership role with the agency.

Volosin: Sure. No, absolutely. Absolutely. That’d be great.

Host: Any closing thoughts?

Volosin: No, no. So, but if anybody has any free time, go off and look at some TESS data and you might discover your own planet.

Host: You can learn more about discovering exoplanets and get additional details about the TESS mission via links on our website at Jeff’s bio and a show transcript are also posted there.

If you have suggestions for future topics, please let us know on Twitter at NASA APPEL – that’s APP-el – and use the hashtag SmallStepsGiantLeaps.

As always, thanks for listening.