Earth Photography: It’s Harder Than It Looks

 

From my orbital perspective, I am sitting still and Earth is moving. I sit above the grandest of all globes spinning below my feet, and watch the world speed by at an amazing eight kilometers per second (288 miles per minute, or 17,300 miles per hour).

 

This makes Earth photography complicated.

 

Even with a shutter speed of 1/1000th of a second, eight meters (26 feet) of motion occurs during the exposure. Our 400-millimeter telephoto lens has a resolution of less than three meters on the ground. Simply pointing at a target and squeezing the shutter always yields a less-than-perfect image, and precise manual tracking must be done to capture truly sharp pictures. It usually takes a new space station crewmember a month of on-orbit practice to use the full capability of this telephoto lens.

 

Another surprisingly difficult aspect of Earth photography is capturing a specific target. If I want to take a picture of Silverton, Oregon, my hometown, I have about 10 to 15 seconds of prime nadir (the point directly below us) viewing time to take the picture. If the image is taken off the nadir, a distorted, squashed projection is obtained. If I float up to the window and see my target, it’s too late to take a picture. If the camera has the wrong lens, the memory card is full, the battery depleted, or the camera is on some non-standard setting enabled by its myriad buttons and knobs, the opportunity will be over by the time the situation is corrected. And some targets like my hometown, sitting in the middle of farmland, are low-contrast and difficult to find. If more than a few seconds are needed to spot the target, again the moment is lost. All of us have missed the chance to take that “good one.” Fortunately, when in orbit, what goes around comes around, and in a few days there will be another chance.

 

It takes 90 minutes to circle the Earth, with about 60 minutes in daylight and 30 minutes in darkness. The globe is equally divided into day and night by the shadow line, but being 400 kilometers up, we travel a significant distance over the nighttime earth while the station remains in full sunlight. During those times, as viewed from Earth, we are brightly lit against a dark sky. This is a special period that makes it possible for people on the ground to observe space station pass overhead as a large, bright, moving point of light. This condition lasts for only about seven minutes; after that we are still overhead, but are unlit and so cannot be readily observed.

 

Ironically, when earthlings can see us, we cannot see them. The glare from the full sun effectively turns our windows into mirrors that return our own ghostly reflection. This often plays out when friends want to flash space station from the ground as it travels overhead. They shine green lasers, xenon strobes, and halogen spotlights at us as we sprint across the sky. These well-wishers don’t know that we cannot see a thing during this time. The best time to try this is during a dark pass when orbital calculations show that we are passing overhead. This becomes complicated when highly collimated light from lasers are used, since the beam diameter at our orbital distance is about one kilometer, and this spot has to be tracking us while in the dark. And of course we have to be looking. As often happens, technical details complicate what seems like a simple observation. So far, all attempts at flashing the space station have failed.

Don’s blog also appears at airspacemag.com.

38 thoughts on “Earth Photography: It’s Harder Than It Looks”

  1. Great article and interesting perspective on photography from your orbiting office! I do hope you know that not all of us are simply pointing green lasers at you, but rather have them attached to our telescopes showing the current alignment…

    Now that I know what you are looking for, I just might set the telescope to track you and send you some green laser Morse Code messages!

    .. / .- — / .– .- …- .. -. –. .-.-.- / -.-. .- -. / -.– — ..- / … . . / — . ..–..

  2. Don,
    A Lens combination you might want to try/consider is one of those old Tamron 500mm Mirror lenses with its 2X Convertor. I use mine on my Canon 7D @ 1/1600 you can freeze a baseball at home plate from 450′ and you can see the stitching. It makes for a pretty small light package with an effective 1600mm Lens.

  3. Wow… and I thought I had problems setting up my camera from earth! 17,300 miles per hour?!! Maybe aperture priority and a couple of hundred flyby’s practice is in order – man you are so privileged, what I wouldn’t give to swap places.

  4. In the article, you describe how difficult it is to actually find your target, but you don’t explain how you avoid blur.

    The picture in the article was taken at 1/3s exposure time (according to the exifs) and seems rather sharp, but I think that might be due to the wide lens. But what if you take such a picture with a 400mm lens? A movement of approx. 2.6km would cause significant blur in such a picture, wouldn’t it?
    Or do you use some kind of tracking mechanism that moves the camera along to compensate the earth movement?

  5. I truly can imagine taking a ‘perfect’ photo is very difficult, especially at a speed of 17.300 miles per hour (28.000 km per hour).
    But always remember: a picture is not taken by a camera, but by the photographer. He/she pusses the buttons….

    A few years back I was lucky to take a 30sec picture of a passing ISS and a chasing orbiter (Discovery if my memory serves me right) at an evening in Emmen (N-E of The Netherlands).
    If you like, I am happy to put it online somewhere…

    Please take lots of pictures for us to enjoy!

    Cheers,
    André

  6. With all due respect to Dr. Pettit, I highly doubt he’d make a very good sports photographer. Sounds like he should have had a few lessons on camera technique, albeit space may be just a little different. And why such a fairly long exposure? My grand daughters’ inexpensive digital camera goes down to 1/2000th. I would think NASA would have better equipment. If he’s using a ‘hand-held’ his shaking is far worse than the earths motion.

  7. “So far, all attempts at flashing the space station have failed.”

    All issues like this can be fixed by using MORE POWER.

  8. I see you, however, I will like to see & understand Y O U?

    Sincerely,

    Fabiola Ivii Preciado-Becerra:)

  9. How fast a shutter speed do you have to use ? And does’t it underexpose the image ? And do you use the normal DSLR’s commercially available or NASA makes specific cameras for you all ? Ohh…there are so many questions that I have ! 🙂

  10. Would never really have thought of these problems but they seem obvious when you point them out. Such is life I guess.

    Thanks for sharing and should I ever make it up to a space station or a shuttle I will bear your tips in mind!

    Cheers.

  11. ok really gud information but question iz itz only limited to photography? or really itz appearence also harder than previous or older information about d crust of our earth???

  12. Cool article, thanks.
    But that xtra-small picture in the article with no link to a hires, that’s a shame :/

  13. I’m so glad to have seen this post. I am a photographer myself, and I have over the years often wondered why there aren’t more good photos of Earth taken from orbit. Now I understand some of the difficulties I hadn’t given much thought to.

  14. Thank you for your information in your ongoing blog regarding Space Station activity and your life in space. It is very important that we, the United States of America, continue exploring and looking for answers for the many questions we all have and the questions yet to come.

  15. so when is the next time that the space station will pass over silverton Or. at the right time for me to see it in the night sky? I live in silverton and am a big fan of Don Pettet and it would be so cool to see the space station wise by up in space form down hear on earth.

  16. Hello there; best wishes, from Puerto Rico. Keep up with the good job of you all! Hopefuly you can send me a pic. of my island at either dusk or dawn. No! You should be too busy up there, never mind, best regards!

    Jose Alberto

  17. OK, thank you – that is somehow what I was assuming.
    Why aren’t there more photographs like that very interesting one above?
    I would like to see more like these, even without auroras 😉
    A bit of epxplanation would be fine, too!
    I appreciate your efforts, thanks again and happy shootings.
    Karl.

  18. Interesting post. Is the manual tracking of a target done entirely by hand? That is, without the aid of somekind of stable platform like a panning tripod head? Also, is manual tracking necesssary because the mass of the camera and telephoto lens is too large for an auto tracker of reasonable size and mass, or just too expensive?

  19. Great photo, Don.

    I don’t know what camera or lens you are using, but I’ve read you have a Nikon D3s up there, and you may have a Nikkor 400mm f/2.8 lens? Assuming that is so, try dialing up the ISO to 3200, 6400 and even 12800. Then go into the menu and turn OFF the High ISO NR (you’ll get more noise but greater detail in your photos), and decrease the exposure compensation to -1. Another suggestion – if you are shooting in the P (Program) mode, twirl the back command dial until the aperture is 5.6 (assuming an f/2.8 lens, that’s only two stops above maximum aperture) which should also gain some shutter speed for the same exposure. The D3s has a maximum shutter speed of 1/8000th of a second, so get as close to that as you can which should reduce the motion distance to one meter instead of eight meters. Trial and error might reveal what works.

    Good luck!

  20. i love the pictures. ive always been amazed at the pkanet we live on . im worried easily of our earths safety for our children and generations to come and also hope that our earth will be around for some time to come. Hope that the 2012 prediction is not something for us to worry about . But i do know we need to all come together and start protecting nature and using our resources respectfully!

  21. its amazing,fantastic view from the space,our earth is like a little wonderful in the universe…but so huggiest to the human kind. we must care it…

  22. Amazing! The ring in the middle of the picture is the famous Manicouagan Reservoir, an impact crater with 200 million years old!

  23. Great! Keep taking great pictures of Earth!
    I have a question, though. When I watch the live video feeds from the ISS of the Earth, the Earth is always placed in the upper quadrants of the pictures, as though it is overhead.
    You mentioned that you see it spinning below your feet – and that is how I would like to see it also. But from the video feeds, it is almost always overhead, and that is disconcerting, and disorienting. When I try to figure out where a place is and compare it to a globe, I have to mentally reverse and invert it to get it be comparable. Is there a reason that the video feeds to the Earth are always that way?
    I asked somebody at the imagery place at JSC and they said that is just the way the astronauts park the cameras.
    Regards,

  24. Congratulations for those great pics. Any chance you have a prism up there with you? I’d be curious to see how a sunrise/sunset looks like in the spectral domain, as the Sun rays traverse different layers of the atmosphere.. I don’t know if that setup would work with Auroras, come to think of it..

    Pierre

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