Astronaut Don Pettit tells the stories behind his incredible photos of Earth from space

Astronaut Don Pettit has become one of the most prolific astronaut photographers during his expeditions aboard the International Space Station (ISS). He could (and did) saturate downlink transfers with photos for three full days from just one 30-minute photographic session in space. While photography is part of an astronaut’s job requirement, Pettit’s engineering ingenuity and natural curiosity has led him to create photos that are as stunning for their artistic beauty as they are for their scientific value.

See some of his breathtaking images in this video from SmugMug, then read their fascinating interview with the man himself, where he explains exactly what it’s like to take photos on the ISS.

What led you to become an astronaut?

Becoming an astronaut was something I became aware of as a kid when John Glenn flew. I filed that away in the back of my mind. After I popped out of graduate school with a PhD in chemical engineering, I realized I was qualified to apply to NASA to become an astronaut. And so I put in an application. After being rejected three times, the fourth time was a charm.

What was that experience like?

It was like walking in the clouds when I first found out I’d been selected. Of course, the euphoria vanishes quickly when you find out how much work it’s going to be. But it’s fun work. It’s like going back to school.

You start off with basic astronaut training, which I like to think of as Astronaut 101. We spend two years training full time, which is about equivalent to a four-year college degree.

Physical. Academic. Flying. Tangible skills. We fly T-38s, supersonic twin-engine after-burner training aircraft, for spaceflight readiness training. A lot of the skills involved with flying these are applicable to working in the cockpit of a spacecraft during highly dynamic phases of flying. And we hone these skills in a real environment, not a simulator, where a mistake could cost you more than a reset button.

Do you also train for the photography?

We have training on all kinds of topics. From taking care of the systems on space station to flying a robotic arm to going out and doing spacewalks to doing the scientific experiments.

We also get training on photography and the use of the cameras on space station. And these are professional-level cameras that have a lot of buttons and menus. They’re almost like a little computer in themselves.

We have a cadre of folks here on the ground, professional photographers as well as trainers, who not only teach us how to use the cameras, but also about the specific equipment we have on station. Like how to set it up in that space environment to get the best pictures.

There’s a lot of engineering photography that we do. We have to take macro images of pins in an electrical connector or a bit of grunge in a hydraulic quick-disconnect fitting or little patterns that might develop on the surface of one of the windows. These things need to be documented so the images can be downlinked for engineers on the ground to assess what’s happening to the systems on space station. We get training specifically on doing these engineering images, which, for the most part, are not really interesting to the public.

Photography plays a big role in what you do.

Photography on the space station is more than just taking a bunch of pretty pictures. We take pictures of Earth and the surroundings of earth, and these pictures represent a scientific data set recorded now for over 14 years. About 1.2 million pictures were taken as of July 2012. That number’s obviously ticked up.

These images are also art. They illustrate to people what space is like for those who don’t get a chance to fly in space.

What are some of the differences we might not think about when photographing in gravity versus weightlessness?

As an example, we have one of my favourite telephoto lenses here: the 400mm f/2.8. It weighs quite a few pounds and definitely requires a tripod down here on Earth. In weightlessness, this becomes a beautiful piece of equipment to use. You can completely control it by grabbing on to the camera. And it’s heavy enough that small things like your heartbeat won’t make the lens jiggle. If you pick up a camera body with a small lens on it, the pulse in your fingers will make the camera shake.

To get around that, I taped a stick on the back of the camera in the centre of the optical axis. Then when I was moving the camera, I would just have two fingers on the end of the stick. That way I could fly the camera around without physically having my fingers on the camera. And since the stick was aligned with the optical centre, I could slowly rotate the stick with my fingers and make the camera rotate through 360 degrees.

In some respects, the more massive the camera, and the more massive the lens, the easier it is to manipulate in a weightless environment because small shakes have a smaller diminished effect on the imagery.

What’s the perspective like from space?

Looking at Earth from space is amazingly beautiful. You can see things on the length scale of half a continent. However, I argue it’s no more beautiful than Earth from Earth. It’s just a different perspective of what we’re used to seeing. We find Earth from space exceptionally beautiful because we’re so polarized to the natural beauty around us when we’re walking on Earth.

What have you learned from your adventures photographing from space?

Astronaut imagery of Earth is an example of learning what you need to take pictures of and how to take the pictures. Initially, you would just have a camera with whatever lens, point it out the window, and start shooting. And then you find out there are certain details you may want to focus on in this huge orbital vantage point. In order to take advantage of that, you need to use wider-angle lenses.

If you use telephoto lenses, you could come back with pictures that are just about as good as what you could download from Google Earth. So you need to ask yourself what kind of imagery is going to be the most useful. Telephoto imagery via astronauts can point out things that satellites aren’t programmed to take pictures of.

Once we make some interesting discoveries on imagery from space, then you can program a satellite to do the same thing and do it more frequently and probably collect a better data set. But often times it takes a human being in the loop to take a picture of something that nobody thought would be worth taking a picture of.

What are some of your photographic challenges in space?

The traits that make a good photograph on Earth still apply to taking a picture in space. Focus is really important. And exposure.

In space, you can have huge variations in brightness. The sunny-16 rule sort of applies, but you have to add or subtract about 2 more f-stops because the full exoatmospheric sun on the tops of clouds is really bright. If you just take a standard picture, the cloud tops will all be snow white with no detail at all. So you need to underexpose your picture when you have a lot of clouds within your field of view.

Aurora is also tricky. The green part of the aurora is about two stops brighter than the red part. If you expose for the greens, you won’t see the reds. If you expose for the reds, the greens will be saturated. We see these same things on Earth, compromising between what you can and can’t see.

Composition is important, too. Do you have a bit of the window frame in your field of view? Do you have the whole window frame or exclude it entirely? When you’re looking at Earth, where does the horizon cross your image plane? Is it right in the middle? In thirds?

What about compensating for the speed of the earth and station?

You’re moving at 8 km a second—that’s faster than a speeding bullet. And Earth goes by really quickly. If you’re using a long lens, you need fast shutter speeds. You also need to compensate by panning the camera along the axis of station to cancel out orbital motion. If you just use a fast shutter speed, they’ll be acceptable pictures, but they’ll be a little off in terms of sharpness. So you have to be able to slew the camera at the same rate of orbital motion while you’re taking pictures to actually get the sharpest imagery.

Do you adjust manually?

Yeah, manually! And it’s not easy. Some crewmembers really have the knack and can take really sharp telephoto lens imagery. It’s a skill.

What are some challenges of shooting in the cupola?

Windows. Some of the windows are designed for photography, others are designed for engineering observations and point toward the solar panels and things like that. The cupola windows are designed for getting views of station when flying the robotic arm, and they also happen to look at Earth.

There are the shutters that cover the windows on the cupola to protect them from micrometeorite damage, which is significant. They also act as a thermal barrier due to the heat radiation of space. Things get too cold or too hot, so we’ll close the shutters when we’re not using the windows. When we do use the windows, the shutters open and we have this marvelous view of Earth.

The crew tends to congregate a lot in the cupola. We’ll have maybe six to eight cameras all staged with different lenses so you can just grab a camera and start taking pictures. There might be two or three other people in the same window with you for an interesting pass.

Say a volcano’s going off. Maybe one crewmate has a 400mm, maybe one has a midrange 85-180mm lens. And then someone’s shooting with a wide-angle lens. We’re all shooting at the same subject at the same time in this rather small space. You have to learn not to stick your elbows out and interfere with your partner trying to get the same images.

If you want to take pictures to show the dynamics of what’s going in the cupola itself, I would typically use a 16mm fisheye lens on a full 35mm format digital camera.

When you’re in the cupola, particularly during night time photography, you’re plagued by window reflections. There are four panes of glass you have to look through, separated by about 6 inches from the innermost pane to the outermost pane. So there’s a couple inches between each window pane. They have anti-reflection coatings, but you still get reflections—mostly from internal lights—and they can spoil your imagery.

Is that when you use that black sheet?

It’s like a big turtleneck sweater that’s flattened out, and you stick your head through. It shields all the windows from light coming in from behind the cupola. Or you can make something we call a witch’s hat, where the peak of the witch’s hat fastens onto the camera lens and then flares out to cover the window.

I prefer to have all seven windows shaded, and I’ll have six or seven cameras set up instead of having one window shaded with one camera and one witch’s hat.

How did you create your star-trail images?

Star-trail images have been photographed by amateur astronomers for years. You put your camera on a tripod, point it some place up in the sky, then as Earth turns while the shutter’s open, the stars make trails.

I tried the same thing from station. The dynamics are the same, but the physics behind the motions are different. You still see stars going in circles, but they’re not going in circles around the north star, they’re going in circles around the pitch access of station as it goes around Earth.

You also see cities streak by on the surface of Earth. They move with a combination of our orbital motion and Earth turning at the same time. Then you’ve got the atmosphere on edge, and it glows. Scientists call that air glow. You can’t see it with your bare eye on Earth because it’s too faint. But when you’re on orbit, you can see the air glow with your own eye. It’s like looking at something that’s illuminated with a black light, and it’s fluorescing with a cool green glow.

When you take a timed exposure, the green glow shows up quite vividly. In some pictures it almost looks like a slice of key lime pie that got flopped on the edge of Earth. And the scale height of that in the images is about 100 km.

You get to see these time-integrated exposures of the atmosphere on edge and there are all kinds of other delightful physics and natural phenomenon that you can see in these pictures. I can talk about one picture for a half hour just on the physics of what you can see.

Aside from that, you can sit back and say these pictures look really cool as an art form.

Any other favourite subjects you love to photograph from space?

My favourite subject is the earth at night. Aurora is just amazingly beautiful. It’s this glowing upper part of the atmosphere that crawls around like amoebas in the sky.

Other aspects of night-time photography: atmospheric air glow. Originally people thought the atmosphere glowed more or less uniformly. But the pictures we’re taking on station show that there’s spatial structure in the atmospheric air glow.

Then there’s polar mesospheric clouds, also known as noctilucent clouds. These are clouds in the upper part of the atmosphere, right on the fringes of space, that are sort of a scientific mystery in terms of why they form. In space you can collect a data set that folds in with observations made from Earth and with other platforms.

And cities at night. The way human beings sprinkle their light bulbs around is a fascinating statement on how we as human beings define our urban areas. It’s a juxtaposition between geography, technology that you choose, and culture. There’s a lot of things you can learn about human beings in the way that they sprinkle their lights out at night.

Cities at night were much tougher to photograph during your first expedition.

On my first spaceflight, digital cameras were in their infancy. The highest ISO we could use was 400, which is pretty slow. Taking pictures of cities at night required a half-second to one-and-a-half-second exposure, and the orbital motion would make the images blurry. You could try to compensate by hand, but you really couldn’t do an outstanding job of cancelling out orbital motion.

Now you jump 10 years in the future and cameras have useable ISOs up to maybe 12,000. Coupled with our fast f/1.4 and f/1.2 lenses, we can now hand pan the camera and take beautiful pictures of cities at night.

It sounds like so much to keep track of at once: the star trails being on the axis of station, the lights of the city, plus the air glow—all lining up. And you were doing it manually.

You cannot get a picture where the stars are sharp and the cities on the surface of Earth are sharp because they’re all moving at different rates, and they all require different exposures. However, you can do HDR images, where in rapid succession you take an image that’s exposed properly for the stars and then you take an image that’s exposed properly for cities on Earth, and then maybe an image or two exposed properly for the green part of the aurora and then the red part of the aurora. Then the work comes later on the ground when you take five of these images and put them all together to make a single HDR composite.

We heard a bit before about the labour involved in downloading all the photos you took on station.

Right, once you take the pictures, then you’ve got to get the pictures back to Earth. We can beam them down using the Ku-band satellite asset, but we still have a finite bandwidth. And it can take hours to get your pictures down.

For example, when I was there, in one night pass I could easily shoot 60GB of RAW files, and we could download only about 20GB a day. In one 30-minute period, I could saturate the downlink for three days.

Does that mean you’re eating up the bandwidth for others?

Yep, which is why the bandwidth allocated for imagery was 20GB a day. I had almost every hard drive on station filled with a backlog of images. Imagine 60GB of images in 30 minutes with hard drives that were 120GB, and only being able to download 20GB a day. You could quickly saturate everything with this big bottleneck.

Thankfully, the folks on the ground figured out there were times when bandwidth wasn’t being used, and there were other, more efficient, ways of using the bandwidth. So they figured out a way to get all my images down and speed up the process.

Today they’ve added more channels of Ku band so bringing down these kinds of images is no longer a problem. But when I was last there in 2012, we had these issues and I probably deleted 500GB of images that I just wasn’t able to downlink given the circumstances. I quickly went through the images and the ones that I thought were substandard—maybe there’s a corner of the window frame in the field of view or a big reflection that showed up—those were the ones I flagged for deletion.

Fortunately, I wasn’t required to delete all my pictures. I deleted maybe 10% of them. And I was doing this to show that I was working to do my part to try to help the ground get the images down.

What’s your favourite part of astronaut photography?

I had a friend of mine in New Zealand who took one of my star-trail pictures, made a print of it on fabric, and made a jacket out of it. It’s neat to see people using these images.

That’s exactly what, as a photographer, you want people to do. You want people to use your pictures. And all the pictures that I take with NASA are in the public domain, so people can use them for their own purposes.

It makes my heart sing to see people using my pictures. There’s no point in taking pictures and hiding them in a closet. You want to take pictures and share them freely with anybody who’s willing to look at your photography. And that, to me, is more of a compliment than anything else.