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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. 

Chandra X-ray Observatory Project Manager Helen Cole and Project Scientist Martin Weisskopf discuss 20 years of exploring the extreme universe.

Chandra is one of NASA’s Great Observatories and has the sharpest vision of any X-ray telescope ever built. July 2019 marks the 20th anniversary of the launch and deployment of the powerful observatory that has contributed to a revolution in the understanding of the cosmos.

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

  • Amazing science discoveries delivered by Chandra
  • Factors that contributed to the flagship mission’s success
  • Challenges of operating an aging spacecraft


Related Resources

Chandra X-ray Observatory

Chandra’s 20th

Chandra 20th Anniversary Events

APPEL Courses:

Risk Management I (APPEL-RM I)

Risk Management II (APPEL-RM II)

Pay It Forward: Capturing, Sharing and Learning NASA Lessons (APPEL-PIF)


Helen Cole
Credit: NASA

Helen Cole is Project Manager of the Chandra X-ray Observatory, a NASA Science Mission Directorate flagship operating mission. Cole has enjoyed the role of managing projects and activities at Marshall Space Flight Center over the past 18 years, and has gained experience with all phases of the flight project life cycle. She worked as an engineer in the area of optics before becoming a project manager. Cole earned a bachelor’s in mechanical engineering from the University of Wisconsin and a doctorate in mechanical and aerospace engineering from the University of Alabama in Huntsville.






Martin Weisskopf
Credit: NASA

Martin Weisskopf is Project Scientist for NASA’s Chandra X-ray Observatory, Principal Investigator of the Imaging X-ray Polarimetry Explorer (IXPE), and Chief Scientist for X-ray Astronomy at Marshall Space Flight Center, where he began his NASA career in 1977. Weisskopf was previously an assistant professor at Columbia University and performed many pioneering experiments in X-ray astronomy—particularly in X-ray polarimetry. He is author or co-author of over 300 publications and has received numerous honors, including the Rossi Prize of the High Energy Astrophysics Division of the American Astronomical Society (shared with Harvey Tananbaum). Weisskopf earned a bachelor’s degree in physics from Oberlin College and a doctorate in physics from Brandeis University.


Martin Weisskopf: Chandra has been as productive in many scientific measures as Hubble or any other scientific observatory that NASA has ever launched.

Helen Cole: It’s performed well beyond anyone’s expectations at the time of launch, and it’s continuing to make incredible discoveries.

Weisskopf: You have to remember this beast was designed for three years, with the goal of five, and we’re in our twentieth year now.

Deana Nunley (Host): You’re listening to Small Steps, Giant Leaps – a NASA APPEL Knowledge Services podcast featuring interviews and stories, tapping into project experiences in order to unravel lessons learned, identify best practices and discover novel ideas. I’m Deana Nunley.

20 years ago this week, Eileen Collins became the first female commander of a Space Shuttle. Collins commanded the STS-93 mission that deployed the Chandra X-ray Observatory.

Two decades later, Chandra is still on orbit and is considered one of NASA’s most successful missions.

We welcome two guests to the podcast today — the Chandra Project Manager and the Project Scientist. Let’s begin with my conversation with Chandra Project Manager Helen Cole.

Host: There’s been so much celebration with the Apollo 50th anniversary, but there is another anniversary happening right now and this year is a big year as far as looking back at the Chandra X-ray Observatory, 20 years on orbit.

Cole: That’s right. On July 23rd, Chandra had its 20th anniversary of launch. Because our anniversary is right on top of the Apollo 50th, what we decided to do was actually celebrate Chandra’s 20th all year long. So, starting in January, at an AAS meeting – this is a science meeting – we began with some celebrations and some media events, and we are continuing to have events throughout the year.

We are going to be planning actually our more formal events for the project in August, and that is on top of the 20th anniversary of first light from Chandra, and we’re going to end the year in December with a science symposium in Boston.

Host: Could you give us an overview of Chandra?

Cole: Chandra is NASA’s flagship X-ray observatory, and it’s a mission that has been operating since 1999, when it launched. It’s performed well beyond anyone’s expectations at the time of launch, and it’s continuing to make incredible discoveries. Marshall has managed Chandra from its inception in the ’80s, at the time of launch and since then in operational phase. The Smithsonian Astrophysical Observatory is our prime contractor, and they’re responsible for actually operating the spacecraft and performing the Science Center efforts for NASA.

Host: For your part of being on the Chandra team, has your role been project manager only or have you had other involvement with the project over the years?

Cole: My experience with Chandra is, of course, now as the PM, but in the early ’90s I was actually hired at Marshall Space Flight Center to be an optical metrologist for the mirror assembly for Chandra. So, I spent a number of years in oversight of the development of the mirror assembly, the HRMA. Then I moved away and did some other spaceflight activities and got to manage some other things. A few years ago, I was asked to come back and manage Chandra, and it’s just been my honor and it’s been very exciting.

Host: What are some of the challenges you face as project manager?

Cole: Some of the challenges in managing this project are what you might expect and some are what you might not expect. Some of the things you might expect is that we have the continuous challenge of planning ahead to make sure we’re ready for any possible anomaly that might come along in operations.

Some of the things that come along, however, with a long-duration mission like this one are a little different. So, we work very hard to keep ahead of any trending behaviors we might see on the spacecraft as it ages, and I think we have a very good track record in doing this effectively.

Another challenge that comes along with a long-duration successful mission is succession. We have some very experienced, even charter members on our team right now. As they ready themselves for retirement, if they choose to retire – some of them are so passionate I don’t think they will – but passing along decades of their experience to the next person, to their successor can take quite a bit of time and effort. So, one of the challenges is always the resources to have that overlap and to have a successful succession of skills from a seasoned person to a newer person. So that’s always a constant challenge.

Host: What do you think are the team attributes that have contributed to Chandra’s success?

Cole: What I’ve encouraged and what also I’ve observed about the Chandra team is an incredible level of passion for the success of Chandra, and for the efficiency by which the science is collected. Another thing I’ve observed is the level of innovation that the team takes in looking forward and trying to plan ahead for things that may occur in the future.

Then there are also innovations that come with things that are unexpected. Another thing that I’ve observed is that this team has rigor. There is an established way of making decisions, and the team is very dedicated in following the decision-making process. So those are the things that I see that contribute most to the success of Chandra.

Host: How long is Chandra expected to last?

Cole: We’d like to think that it will last forever, but we know that that’s not possible. We have recently done a 25-year engineering study on Chandra. All the analysis would say from that study that we expect to be operating fairly nominally for 25 years in total and possibly longer. So, we would be looking at mid-2024 or longer.

Host: And now we’re joined by Project Scientist Martin Weisskopf. Martin, take us back to the early days of Chandra. How did this all get started, and how long have you been working on the project?

Weisskopf: Technically speaking, it started in 1976, when Riccardo Giacconi and Harvey Tananbaum sent an unsolicited proposal to NASA Headquarters for a continuation of the X-ray astronomy mission at that time, known as the HEAO-2. There was a competition that NASA Headquarters held and, long story short, Marshall was chosen to lead that study and to lead that project, and I interviewed for the project science project position. Here I am, 42 years later, and I’m still the project scientist for Chandra. It wasn’t called Chandra then. It was called the Advanced X-ray Astrophysics Facility, or AXAF.

Host: Did you ever imagine the X-ray observatory being on orbit for 20 years or longer?

Weisskopf: That’s a very good question you’ve asked, and the answer is I never thought about it. I certainly thought about how long it would take us to get it up there and be launched, but I never thought one way or the other about the end of Chandra until very recently. We’re considering all the things we’re struggling with after 20 years of operation. You have to remember this beast was designed for three years, with the goal of five, and we’re in our twentieth year now. So, parts are getting old. We’re fighting the environment, but I never thought about the length of life. But it’s truly amazing, isn’t it?

Host: It really is. When you talk about these challenges that you’re facing now, those are unique for a mission like this, for you to be having to think about those things.

Weisskopf: Yes, they are, because, for example, unlike our sister mission, Hubble, we’re not serviceable. We’re deliberately in an orbit that can’t be serviced. That was to convince everybody that we wouldn’t have the huge servicing costs. So, we’ve got to be very clever in the way we operate the observatory to deal with the challenges that we’re facing.

Host: What do you consider to be Chandra’s most remarkable scientific discoveries?

Weisskopf: The true answer is there are so many that there is no one most, but certainly, there are several that come to my mind. First of all, Chandra was built with a superb angular resolution, its ability to position objects in the sky and tell the difference between one and another that’s very close to it, to look very deep and to resolve what we thought of at the time, what we called it the diffuse X-ray background. Was this made up of discreet sources, this X-ray glow, or was there truly a diffuse X-ray glow from hot gas or something like that? That was one of the prime purposes of Chandra, which it did with flying colors.

So, we know a lot more about these distant X-ray sources than we did before, and that was certainly a major input to science and astrophysics. But there have been so many others, everything, Chandra sees X-rays from every type of astronomical object, from comets to stars, to planets to stars, to galaxies to clusters of galaxies, and in all cases we’re learning something fascinating and interesting.

Chandra has been used in its own way to measure dark matter’s cross section, its ability to interact with normal matter. It’s been used to measure the Hubble constant in a different way. It’s been used to try to understand how neutron stars, these objects that are about 20 miles in diameter and weigh as much as the sun, how they radiate X-rays. It’s truly amazing and it’s contributed to everything.

And the surprises keep coming. This past year, there’s been a great change in the way we do astronomy with the building and discovery of gravitational wave detectors. Lo and behold, when two neutron stars collided, Chandra was able to see what happened afterwards and contributed to our understanding there. So, it just keeps coming. It’s wonderful.

Host: As the project scientist, do you still get excited when you see this data coming down on what Chandra is offering and providing to you?

Weisskopf: Yes, I do. I really do. It’s truly amazing and I’m privileged, because as project scientist I get a chance to see things a little bit before the scientists that are doing the experiments publish them. So, I can sort of vicariously share in their excitement, and I’m so proud of being part of having built this scientific cathedral, as one of my colleagues put it, and seeing how wonderful it is and how well it’s paid off. People don’t know outside of the scientific community, but Chandra has been as productive in many scientific measures as Hubble or any other scientific observatory that NASA has ever launched.

Host: What do you find most fascinating about the observatory?

Weisskopf: Well, I think the fascinating thing is the telescope itself. We built this telescope to give sub-arcsecond angular resolution, the ability to see – what is it I used to know, the little, you know, can you see a dime at a distance of 12 kilometers or something like that. And knowing the details of this, it focuses X-rays to a point at the center of the image that’s the width of a human hair. There are four separate optics that co-align and focus and they weigh a ton.

They went through flying from Eastman Kodak to Marshall, back to Eastman Kodak, out to California to be integrated, then to the Cape, then the rocket launch on the shuttle, then Inertial Upper Stage to put it in this orbit that goes a third of the way to the Moon. And it still is aligned. I mean it’s amazing. That’s all held together by 12 beads of epoxy per telescope. It’s just, when I tell it, you don’t believe it, that it would work, but it did. That’s really amazing.

Host: Absolutely. From your perspective, what are some of the lasting benefits of the Chandra mission?

Weisskopf: Well, really, the honest answer is we really don’t know yet. Chandra is building up an archive of all of its observations, and there’s gold in them “thar” hills. We have people that are digging into that data as we speak, every year writing proposals to look at the archived data, and finding new things to look at and new things to suss out of the data.

But its main current output is that there have been so many paradigm shifts and clarifications because of the study of the X-rays that we’ve seen. That runs this gamut from our solar system all the way out of the clusters of galaxies in the deepest Chandra fields, where we find that there are a whole load of X-ray sources that are super-massive black holes that are buried in the center of galaxies, that are so surrounded by dust and stuff that you can’t see them in any other wavelength band.

Host: That’s incredible. Just even in the past year, you were mentioning you’ve really seen some things that are very fascinating coming back from Chandra, right, and there’s been some real interest around some of the findings.

Weisskopf: Yes. That’s one of the great things about the observatory. Because of its capabilities, there are things that we never conceived of during the early years, when we were trying to get the mission going and telling people what we could do.

By the way, we’ve done everything that we said we would do, but there are new things that are discovered. That’s, in general, how science works, right? You build an observatory or an instrument that is 10 times or a hundred times more powerful than whatever came before. Whether you can point to things or not, it’s going to make great discoveries, and Chandra has all of those ingredients.

Host: And Chandra is considered one of the most successful flagship missions NASA has ever flown. What do you think are the major factors in the long-term success of the project?

Weisskopf: Well certainly, obviously, the science. The science output has been tremendous. We have numerous papers, several hundred papers published per year, citations that keep growing, and also, the changes to textbooks’ understanding of astronomical questions and thoughts that we didn’t think of before. Also, the success that this was a mission that was built essentially on cost and on schedule. That’s a major problem for many flagship missions that NASA tries to do, because they’re overly complicated and the scientists and engineers and managers that worked with Chandra worked very hard to keep the mission on track in a number of different ways, by keeping requirements constant. We didn’t change requirements.

We tried to find the knee in the curve for trades of engineering complexity versus scientific return. We worked very hard within the project. As project scientist, I was not just one person that the project trotted out once a year to explain what a quasar was, but I had a group of scientists that I built up with here at Marshall, and I was supported by an even larger group of scientists and engineers at the Smithsonian Astrophysical Observatory, to make sure that we understood and were on top of every aspect of Chandra. I think that was one of the major reasons for its success.

Finally, there was a point in time that, thanks to the management and team, where everybody involved, the principal investigators for the instruments, the prime contractor, Marshall Space Flight Center, the Science Support Center, where we all viewed Chandra and the team as “we” as opposed to “us and them.” That was critical.

Host: What’s it like to be on the same project for over four decades, and specifically in the role of project scientist on one of NASA’s Great Observatories?

Weisskopf: Well, it’s a privilege that I wake up most mornings thinking, “Boy, what a great privilege.” I mean they pay me to do this and it’s such a wonderful privilege to be associated with this. It’s wonderful.

Host: You must have so many stories. What are some of your favorites?

Weisskopf: Most of them I can’t repeat.

Host: [Laughs]. So, can we delve into something that you can repeat, because we’d love to hear some of your stories?

Weisskopf: Yes. There was a time – one of the things that was very important for Chandra was having the ability to calibrate the observatory before it was launched, so to test it out and the X-rays and make sure everything worked right, the telescope, the instruments, et cetera. Not just simply to make sure it worked right, but to understand how it worked, because Chandra was going to be much more powerful than anything that had flown before. So, you couldn’t take old results and use them as calibrations on orbit.

For example, the angular resolution was almost a factor of 10 better than anything that had been flown before. The energy resolution for some of the spectroscopic instruments was hundreds of times more powerful. So, you didn’t have any standards in the sky.

Getting the facility built is a challenge in the government, because construction of facilities is something that is handled by a separate branch of Congress. So, you have to tell that branch of Congress, “Hey, my mission makes no sense unless I have this facility.” But that also means that if they don’t accept your facility, your mission is dead. So, there’s always a lot of pressure from, “Are you sure you really need this? Are you sure you want us to do this, ask for this?” We scientists said, “Absolutely, yes. You had to do it. You had to do it.”

That ran into a lot less difficulty when the Hubble incident took place, where the telescope didn’t perform as they expected. So, we got the facility going.

Then the funny part or this interesting part was the building of the facility, because a NASA Associate Administrator said to Congress, “And I’ll prove to you that we can build the X-ray telescopes through tests in a couple years.” He moved the schedule for the building of the facility up by several years, which made it a real challenge.

The facility was then – construction was managed by our center director. We met in his office every Thursday morning about 7:00 or 7:30 in the morning. In those days, I was not a morning person, so that wasn’t a lot of fun, but it was really nice. It was really nice because that’s the way to really build something. Somebody came in and, “We need this part and it’s not being ordered.” The center director looks at the head of Procurement and says, “You’ll get him this part.”

Host: So that all ended up being a complete success.

Weisskopf: Yes, it was. There were some hiccups along the way. There’s piers. The distance between the X-ray source building and the X-ray sources at the facility and where the telescope and detectors would be is like 1,700 feet – 500 meters. When they first designed the extension, they forgot to take into account the curvature of the Earth on the piers. So, the piers weren’t the right height. It was funny in retrospect, but it was not funny when it was discovered.

Host: I bet nobody was laughing then.

Weisskopf: Nobody was laughing then, but in retrospect, it’s kind of funny.

Host: What do you remember about launch day? Do you have any stories related to the launch of the shuttle or the deployment of the observatory?

Weisskopf: Yes. That was very interesting. Eileen Collins was the commander, the first female commander of a shuttle flight. That turned the launch date into a spectacular, where Hillary Clinton came. The women’s soccer team – this was 1999 now, and the women’s soccer team that had won the World Cup came. Judy Collins, the singer, came and performed a special song that she had written in honor of Eileen and the launch.

It was really nice for us associated with Chandra, because we were concerned that the reporters would concentrate on comparing us to Hubble, in the sense that, “Oh my, this is another telescope. It’s Marshall Space Flight Center. It’s Perkin-Elmer who built the optics. Is something going to go wrong?” Nobody cared about us. They all cared about Eileen and Hillary and the women’s soccer team.

Host: What kind of reaction do you get when you’re with people and you talk about the science and everything that has happened during this Chandra mission?

Weisskopf: I like to think that I get a very positive response. I do a lot of public speaking and conference speaking and certainly in the science community and in the lay community, people seem to respond very positively. There are so many people that are interested in astronomy. As soon as we start talking about black holes and dark energy and dark matter, and the contributions that Chandra has done and what it’s like and how it was built, people like that. They enjoy that very much.

Host: Many thanks to Martin and Helen for joining us on the podcast. Their bios, a show transcript, and links to topics mentioned today are available at

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Thanks for listening.