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Season 5, Ep. 30: Gravity Assist: How We Make Webb (and Hubble) Images

Season 5Episode 30Jul 8, 2022

The world will get a first glimpse of the universe as never before when the first images from the James Webb Space Telescope come out on July 12. And this is only the beginning — the telescope will deliver all kinds of insights about galaxies, planets, and more, for years to come.

laguna nebula

laguna nebula

The world will get a first glimpse of the universe as never before when the first images from the James Webb Space Telescope come out on July 12. And this is only the beginning — the telescope will deliver all kinds of insights about galaxies, planets, and more, for years to come. But someone has to translate that data into beautiful imagery, especially since Webb collects light that falls outside of human vision. That’s where Joe DePasquale of the Space Telescope Science Institute comes in. Learn how he makes choices about color and other aspects of space images in this week’s Gravity Assist podcast.

Jim Green:In just a few days, we’re going to see the first images that came from the James Webb Space Telescope. Let’s talk to somebody that’s worked to make these beautiful images come to life.

Joe DePasquale:The images are spectacular. They’re gonna blow people away.

Joe DePasquale:There’s sort of like a universal appeal to these images. They touch on a collective need or want to understand the deeper questions of the universe that we all have, in ways that connect us all together.

Jim Green:Hi, I’m Jim Green, and this Gravity Assist, NASA’s interplanetary talk show. We’re going to explore the inside workings of NASA and meet fascinating people who make space missions happen.

Jim Green:I’m here with Joseph DePasquale and he is the senior data image developer in the Office of Public Outreach at the Space Telescope Science Institute in Baltimore, Maryland. Joe has worked on bringing spectacular space images to life from missions like Hubble and Chandra. But now he’s working with the James Webb Space Telescope group, which will be unveiling its first images on July 12th. So welcome, Joe to Gravity Assist.

Joe DePasquale is a senior data image developer in the Office of Public Outreach at the Space Telescope Science Institute in Baltimore, Maryland.

Joe DePasquale:Hi, Jim, thanks for having me. I’m really happy to be here.

Jim Green:Well, you know, a lot of people probably don’t realize that when we look at a Hubble image, that it’s not exactly what the spacecraft sees. You know, someone such as you has to serve as that intermediate process between the data and the final image and make decisions on how to make that image pop. So how would you describe what you do?

Joe DePasquale: Well, like you said, Jim, it’s, the telescope is not really a point and shoot camera. So it’s not like we can just take a picture and there we have it, right? It’s a scientific instrument. So it was designed first and foremost, to produce scientific results. It just so happens with Hubble, and with Webb, that these instruments are exquisitely sensitive, and they create beautiful images of the universe. But it’s scientific data first, so we have to take that data and convert it into an image. And that’s, that’s where I come in, myself and my colleague, Alyssa Pagan.

Jim Green: All right, well, what kind of training do you have, that really has enabled you to take these images and make them shine?

Joe DePasquale:Yeah, that’s an interesting question. My, my career path has kind of meandered through my life. But, I started out with a degree in astronomy and astrophysics. And I worked for eight years for the Chandra mission as a data analyst, in calibration for the telescope, one of its detectors.

Joe DePasquale:And during that time, I learned a lot about how the images from Chandra were made, and how to create color images from the data. And it was sort of a natural transition from that position into public outreach for Chandra, creating, like press imagery from the data. So my background was really in astronomy, but also, I’ve had a lot of interest in like arts, painting, you know, photography, color theory, and like all of these interests sort of come together to be able to allow me to, you know, have the skill set needed to make these images.

Jim Green:Yeah, I think you point out a really an important aspect about it. And that is, having that science background already gives you the intuition as to what that image is all about. As you say, you paint?

Joe DePasquale:Right.

Jim Green:So in addition to having that science background, you have that artistic flair, now I don’t have much of an artistic flair. (laughs) So it takes a really unique individuals to do that. But that science background is really key, I think. So when you get that image from a spacecraft, what does it look like? Is just a bunch of ones and zeros? And how do you turn them into the beautiful things they are?

Joe DePasquale:(laughs) Yeah, so the data do come down in a digital format of ones and zeros, although the raw data that we get from the archive is, you know, it’s a black and white image, essentially. It’s basically just the brightness levels of the pixels that the detector saw. So it was sitting in one spot looking at some object in space collecting light. And the image that we get is, sort of, that raw image from the detector. And it needs a lot of work to be able to even see what’s in the image. We have to do something called stretch the data, and that is to take the pixel values and sort of reposition them, basically, so that you can see all the detail that’s there.

Joe DePasquale: If you don’t do that, it basically looks like a black image with some white specks in it, because there’s such a huge dynamic range. And what I mean by dynamic range is just the darkest darks and the brightest whites in the image. The whites are super bright and they stand out as these white specks, but all of the other material and interesting stuff is sort of buried in the dark regions of the image. And you have to bring it out without oversaturating it.

Jim Green:Got it.

Joe DePasquale: So if you bring everything up equally, then you’re, you’re bringing up all that dark information, but you’re also over saturating the bright. And so there’s a compression that happens, that allows you to retain the information that’s bright, but also bring up the dark parts of the image.

Jim Green:Well, you know, our eye has is so fantastic, a tool for us to see a very broad range of wavelengths. And, and our eye is sensitive more in certain colors than in others. Does that affect how you actually end up picking the colors and repainting the image?

Joe DePasquale:Yeah, that’s very true. So our eyes, you know, they have cone cells that are sensitive to colors of light, and nominally, red, green, and blue. And so we use that that sort of biology of the eye as a framework within which to apply color to the images.

Joe DePasquale:When we’re working with Hubble, and Webb, or even Chandra, even wavelengths that are beyond what we can see with our eyes, we use a technique called chromatic ordering to the data. And what that means is that, for Hubble, it looks in very specific wavelength ranges. So we have these filters that filter out light, and allow you to see like, if you were taking an image in red light, the filter filters out everything but red, and allows you to see an image in just red light. Of course, it comes down to us black and white, and we have to later apply that color red to it.

Joe DePasquale:But our color images are made up this way by taking red filters and coloring them red, green to green and blue to blue. When you move away from red, green and blue, like visually, we use this same approach. So for example with Webb, if we take short-wavelength infrared light and assign blue to that, and then as you move into the longer wavelengths, you go from blue to green to red, that’s what I mean by chromatic ordering.

Jim Green: Yeah, so you, you actually use as your color palette the spectrum of light, as we break it up in a prism. So it has that specific ordering associated with it.

Joe DePasquale:Yeah, that’s right. The red, green, and blue primary colors, you know, within those, you can have all the colors of the rainbow.

Jim Green:Yeah, to me that’s really important to understand. So it’s not like, “Oh, I’m gonna take this and make it purple. And then right next to that, we’re going to make this yellow.”

Joe DePasquale:That’s right, yeah, you’re absolutely right, that we’re not going in there and applying like painting color on to the image. We are respecting the data from beginning to end. And we’re allowing the data to show through with color. So if you look at a galaxy, for example, in optical light, the regions of the galaxy where there’s active star formation, we expect those to be sort of glowing in hydrogen, which would be red.

Joe DePasquale:And so we know that when we use that red filter, and it’s colored red, you apply red, green, and blue together, you’re going to see like a highlight in red where there are star forming regions. So there’s actually a lot of science that you can learn just by looking at the color image.

Jim Green:So Joe, after you get that initial image that you feel just is right, and it has the, the look and feel about it that really makes the observations in the data pop, is there an interaction period with the scientists about that? And do you then go back and modify that?

Joe DePasquale:Yeah, Jim, it’s very much an iterative process. But I do feel like over the years, I’ve sort of honed my intuition into what looks good. So you know, the initial starting point is always like the springboard for the discussion.

Joe DePasquale:But we do have a lot of back and forth with the scientists that we work with on these images, specifically, to help really bring out the details that they want to specifically bring out for their particular results, their science results. You know, that may require a little extra work here or there, just to get that thing to pop a little more.

The Antennae galaxies, located about 62 million light years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red)

Jim Green:Well, what’s been some of your favorite images to work on from Hubble?

Joe DePasquale:So every year we do an anniversary image, right, where we pick an object that we know is going to be pretty spectacular when viewed with Hubble. And we’ll do an anniversary image release to celebrate the launch of Hubble.

Jim Green:Cool!

Joe DePasquale:And for the 28th anniversary, we looked at the Lagoon Nebula and produce this like beautiful multicolor image in narrowband wavelengths.

Joe DePasquale:So what I was saying before about red, green, and blue, those are sort of wide bands. Hubble has filters that look in like wide swaths of the spectrum. But it also has these filters that are attuned to very specific wavelengths and very narrow regions within those wavelengths. And so that image is actually a combination of three narrowband wavelengths in red, green and blue, that just produce this amazingly detailed tapestry of gas and dust and star formation.

Jim Green:Well, you’ve also worked on Chandra.

Joe DePasquale:That’s right.

You know, and although Hubble does observe in the visible light in the light that we can see, and a little bit into the infrared in the light, we can’t see, Chandra, we can’t see any of that data from the ground and from our eye.

Jim Green:Right.

Joe DePasquale:So what do you do with that data in tell us about your favorite image?

Joe DePasquale:Yeah, so that’s a really interesting challenge when you’re talking about X-ray light, because it is beyond human vision, right? So we like to in the, you know, imaging community in astrophotography like to refer to this process as “representative color,” instead of what it used to be called, are still many people call “false color images.” I dislike the term “false color,” because it has this connotation that we’re faking it, or it’s, you know, this isn’t really what it looks like, the data is the data. That’s, that’s exactly what it looks like.

Jim Green:Yeah. And as you said, you’re keeping true to that data from a scientific perspective by connecting the colors in the right way.

Joe DePasquale:Right.

Jim Green:…with the wavelengths.

Joe DePasquale:Yeah, so and a good example of, you know, working with multi-wavelength imagery, combining Hubble and Chandra, one of my favorite images that we worked on was the Antennae Galaxies, where we have these two interacting galaxies, they’re sort of playing, dancing around each other, and merging together. And that image actually also included infrared data from the Spitzer Space Telescope. And in order to keep everything sort of very cleanly separated, I chose very specific colors for the different wavelengths in that image.

Joe DePasquale:And you know, that there’s a Hubble image there of the Antennae galaxies that on its own is a beautiful, like, very detailed color image, I felt a little bad about the fact that I had to reduce its color from, you know, the beautiful three color image all the way down to just one color, which I colored gold in that version. And then I pulled the Chandra data in, in blue, and the infrared in red. And although each one of those on their own, it’s, it’s kind of like missing something, when you pull them all together, and they each have their own color, there’s actually a wealth of information that you can pull out of that, that you wouldn’t get from any one of them alone.

Jim Green:So what was it like working on this Webb data? Because it’s now taking this data, it’s now coming in, you’re now having your hands on it. You’re the one that knows what’s being done, right?

Joe DePasquale:Yeah, that’s right. (laughs) I can’t speak in detail about it. But I can say that the images are spectacular, they’re gonna blow people away.

Jim Green:Good.

Joe DePasquale:Being among the first people to work on, it has been such a privilege. I feel like I have to pinch myself. Like, I can’t believe that. I’m here at this moment in time, working at Space Telescope, working on the Webb project, pulling together the first data that Webb has taken and turning it into these beautiful color images, is just the highlight of my career right now.

Jim Green:When scientists look at their archive and get the data, you know, how important are these beautiful images that you create to them?

Joe DePasquale:I’d say it has grown in importance over the years. I believe that, know, scientists have their own ways and preferred ways of processing the data to pull out the details that they want to see. But ultimately, when they want to win, if they have newsworthy results, they want to present that in the best way possible. And that’s where, you know, the work that I do comes in, where I can take something that they may have made, and you know, clean it up and turn it into something that’s just a beautiful image, but also tells the story of their science and their results, as well as, you know, presenting a beautiful image.

Jim Green:Well, you know, space images are not only great for scientists. They’re wonderful for the public. And I see Hubble images on all kinds of stuff, T-shirts, lunch box[es], posters, all kinds of other places. I mean, you know, in this area [near Washington, DC], you can go to the Dulles Airport, and if you take the underground walk from the parking lot, one and two, over to the airport, you see the beautiful wall of Hubble images, I don’t know if you have done that. But but you know, millions of people have probably made that walk. So what does that feel like to see those images that you’ve worked on being displayed all over the world?

Joe DePasquale:It feels humbling, I will say, to know, that, like, work that I have done has been seen by millions of people, and is hopefully inspiring people to be like the next generation of scientists and engineers and maybe image processors. (laughs)

Jim Green:Sure.

Joe DePasquale:There’s sort of like a universal appeal to these images. They touch on a collective sort of need or want to understand the deeper questions of the universe that we all have, in ways that connect us all together. You know, Carl Sagan was always a fan of saying that we are star stuff. And I always like to extend that to the fact that like, when we’re observing the universe, when we’re looking at these images, we are the universe thinking about itself. Right? So we’re all connected. And this brings us all together.

Jim Green:So Joe, do you own any clothing with the images that you’ve made on it?

Joe DePasquale:(laughs) I personally don’t own any clothing with my images on it. But my wife has a dress with one of my images on it, or actually the way it was put together. It’s like sort of a mishmash of a couple different images. But something that I worked on is in there. I do have a pair of socks with the Webb telescope on them. So I frequently wear those for good luck.

Joe DePasquale:I remember when I was in college, sitting in class looking at we had a poster of the Pillars of Creation image, the famous Hubble image, right?

Jim Green:Yeah.

Joe DePasquale: And yeah, that was like hugely inspiring for me just sitting there wondering about like, even just how was this image made? Like, how was that actually there? How can we get a picture in such detail and clarity of this object? So that was a huge inspiration for me. And, you know, this is a bit of an aside. But when I started at Space Telescope, I actually worked with Zolt Levay for the first year that I was here, he was the original image processor for Hubble, you know, worked on many of these images that, you know, inspired me to get into astronomy in the first place. And I got to share an office with him for a year. So that was really special time. Yeah.

Jim Green:Well, you’re really touching on the next thing I want to talk about. And that is, I always like to ask my guests to tell me, you know, the person, place or event that propelled them forward to become the scientists they are today. And I call that a gravity assist. So Joe, what was your gravity assist?

Joe DePasquale:Ah, that’s a great question. So I think I have to go all the way back to high school. And, you know, knowing that I always was interested in astronomy and space and just looking up, and look at the stars and wonder what was up there. But I kind of lost a little bit of that through high school. And then I saw the movie “Contact” the summer before I started college. Right?

Jim Green:Ah, interesting! Uh huh!

Joe DePasquale:And I read the book, Carl Sagan’s book, and it just opened my eyes to the possibility of, like, pursuing a career in astronomy, and seeing what that could be like. And I switched my major that summer, right before I started school, I switched into astronomy. I went to Villanova University, which has a wonderful undergraduate astronomy program school.

Jim Green:Yeah. Good school.

Joe DePasquale:Yeah. And, you know, the rest is history. That was sort of the thing that got me going. I would call that my gravity assist.

Jim Green:Yeah, yeah, I would too, I would too. Well, for me in high school, I had the privilege of working on a 12-inch Alvan Clark refractor that was associated with the high school, and it was part of what was called the Witte observatory. So I caught the bug like you did early on in my career, and that really set the tone to move forward.

Joe DePasquale:That’s great.

Jim Green:Well, Joe, thanks so much for telling us about the process of making these fabulous images from the NASA telescopes.

Joe DePasquale:Thank you, Jim. Glad to talk about anytime. (laughs)

Jim Green:Well join me next time as we continue our journey to look under the hood at NASA and see how we do what we do. I’m Jim Green, and this is your Gravity Assist.


Lead producer: Elizabeth Landau

Audio engineer: Manny Cooper