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Headshot of Emily Lakdawalla

DSCOVR mission releases first EPIC global view of Earth, more to come in September

Posted By Emily Lakdawalla

20-07-2015 14:33 CDT

Topics: Earth observing missions, pretty pictures, Earth

Five months after its launch, the Deep Space Climate Observatory (DSCOVR) mission has successfully journeyed to the region of space where Sun and Earth gravitational attraction offset each other. From the vantage point of L1, DSCOVR's EPIC camera has captured its first full-globe view of Earth, and it's well, epic.

EPIC's first view of a full Earth from the Sun-Earth L1 point


EPIC's first view of a full Earth from the Sun-Earth L1 point
This is the Deep Space Climate Observatory (DSCOVR) mission's first view of the entire sunlit side of Earth from 1.6 million kilometers away. It was taken by the Earth Polychromatic Imaging Camera (EPIC), a four-megapixel CCD camera and telescope. The image was taken July 6, 2015, and shows North and Central America. The central turquoise areas are shallow seas around the Caribbean islands. This Earth image shows the effects of sunlight scattered by air molecules, giving the image a characteristic bluish tint. For more about how this image was taken, read this blog post.

There's something very moving about this photo -- its color is more muted than a lot of previous NASA "blue marble" pictures. From its point of view at L1, DSCOVR will always see a fully-lit Earth, rotating in place as the days pass, and pitching up and down with the shifting of seasons. I can't wait for more like this, of course, so I fired off a couple of emails asking for more details about how it was taken and what the plan for future data release is.

According to the release accompanying the photo, "Once the instrument begins regular data acquisition, EPIC will provide a daily series of Earth images allowing for the first time study of daily variations over the entire globe. These images, available 12 to 36 hours after they are acquired, will be posted to a dedicated web page by September 2015." NASA spokesman Stephen Cole further explained to me that the goal is to have this website up by September 1, but the actual date depends on when they get the processing pipeline ready. Images will be released once per day, and the daily release will include images between 12 and 36 hours old. The posted images will be derived color products.

The images are being taken with the Earth Polychromatic Imaging Camera (EPIC), which has a detector 2048 by 2048 pixels square. Here is a fact sheet about EPIC(PDF). EPIC has a monochromatic detector and a filter wheel with 10 very narrowband filters from ultraviolet to near-infrared wavelengths, 317 to 779 nanometers. For more information about the image released today, Cole put me in touch with DSCOVR project scientist Adam Szabo.

Szabo told me that EPIC takes images once every 1.8 hours, continuously. For this first image, red (680±0.2 nm), green (551±1 nm), and blue (443±1 nm) were returned at their full 2048-pixel-square resolution. But once EPIC starts regular imaging, data volume constraints will prevent all of these from being returned at full resolution. They will send back the blue-channel image at 2048 square, and downsample the red and green images to 1024 by 1024 before downlinking them.

Because the filters are so narrowband, a straight combination of red, green, and blue filter images wouldn't make a photo with as much verisimilitude as the one released today. I asked Szabo about that, and he told me:

Standard RGB jpeg images are encoded as three numbers, one for red, one for green and one for blue. We have three numbers on DSCOVR. The question is how to scale the three relative to each other. We have adjusted the exposure times to make sure that we are neither saturated nor lost in low signal to noise values. Then we followed the human eye color response spectrum. The human eye is much more sensitive to red and green than blue colors. But the EPIC instrument is equally sensitive to all of the filter settings. So, before combining the three filtered images, we have reduced the contribution of blue and slightly changed red. This is our best guess as how a human observer would see the Earth from L1.

The popular MODIS Earth images are enhanced in color to bring out surface features. Also, they have removed the effect of light scattered by atmospheric molecules. We will do the same for the regular processing and distribute both the human eye response coloring and the enhanced images.

The first light images are all human eye response colors.

I can't wait for this new data set to begin to build before our eyes. It is going to be a spectacular perspective on our beautiful home planet. Congratulations to the DSCOVR team on a wonderful first-light photo.

One last thing I thought I'd mention about it is that you might have noticed that North America looks smaller than it does in the most familiar "blue marble" picture previously released by NASA. Here's that one:

Earth! A Spectacular

NASA Goddard Space Flight Center

Earth! A Spectacular "Blue Marble"
Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights). This spectacular "blue marble" image is the most detailed true-color view of Earth ever published.

The difference between the two is one of distance. DSCOVR, located 1.6 million kilometers from Earth, has a similar perspective as though it were sitting at infinity; the effective map projection is an orthographic one. MODIS, orbiting only 700 kilometers above Earth, sees much less of the globe at a time. The Blue Marble image is a vertical perspective projection at some higher altitude than 700 kilometers, though I don't know what the altitude of projection is. As a result of its closer viewpoint, points near the center of the globe are much closer to the viewer than points at the globe's edge, so features near the center bulge -- it's the same effect that tends to make your nose look big when you take a selfie. I like the new perspective better!

See other posts from July 2015


Read more blog entries about: Earth observing missions, pretty pictures, Earth


Gozlemci: 07/21/2015 05:35 CDT

Hi Emily, There must be other-side views of Earth, such as Africa/Middle East,... We would like to see them, also...!

Merc: 07/21/2015 12:07 CDT

I see two dots, one near the upper left and one near the lower left. I wonder if they are just photo artifacts or if they are other satellites reflecting brightly?

ea2000: 07/21/2015 12:46 CDT

You can achieve the same perspective as the EPIC photo in Google Earth by zooming the globe all the way out.

Rick Boatright: 07/21/2015 12:57 CDT

Emily, any idea what the bright blue areas north of Cuba and east of Florida are in the "real world"?

Emily Lakdawalla: 07/21/2015 07:09 CDT

Gozlemci: I agree! They only took this one image as a test. In September, when they begin regular image release, we will see all of the rest of the world that sees sunlight. Merc: They're artifacts. Satellites would be invisible at this scale. Rick: shallow Caribbean waters; you're seeing bright white sand through the water.

David Juaquin: 07/22/2015 02:43 CDT

Emily or anyone, please help me understand, Why does this image which was taken in 2015 look so similar to the 1972 image? / Wouldn't the quality be drastically different by now? Why don't we have thousands of these "blue marble" pics? The moon is approximately 240,000 miles away from Earth but this shot was taken at a distance of 1.6 million miles, so where's the moon? The shot was allegedly taken with a "four-megapixel CCD camera and telescope" but there's a 10-megapixel CCD camera available on Amazon, what am I missing here? We recently got shots of Pluto which is "4.6 Billion miles away" but we're just now coming around to getting these shots of our own Earth, help me believe, please.

Seraph: 07/22/2015 09:13 CDT

Is the Earth not, as previously stated by Neil deGrasse Tyson, an oblate spheroid? Rather than this perfect sphere that we have been presented with here? Look forward to your clarification.

Emily Lakdawalla: 07/23/2015 04:20 CDT

David: - The resolution of this photo is quite a bit higher than that of the Apollo one. - The Moon is not in the same field of view. The field of view is very small. The Moon would only be visible in it if there happened to be a solar or lunar eclipse at the moment that this photo was taken, and there was not. - Try launching a 10-megapixel CCD into space and see how well it survives (a) shaking and G-forces of launch (b) hot and cold temperature extremes (c) radiation environment. Flight-qualified technology is older and less capable than the cutting-edge stuff you can use in the benign environment of the surface. - I'm not sure what there is not to believe. This is a photo taken by a spacecraft located 1.6 million kilometers away. One of this spacecraft's reasons for existence is to take photos like these, which aren't possible from Earth orbiters located much closer, as I explained above. Seraph: Earth has an equatorial radius of 6378.1 km and a polar radius of 6356.8 km (source: ). The difference, or flattening, is less than half of one percent. It's too subtle to see it by eye, but it exists.

Seraph : 07/23/2015 07:40 CDT

Ms Lakdawalla, Thank you for your clarification. So Earth is a subtle oblate spheroid or, more spherical than oblate. That indeed answers my question. One might want to have a scientific discussion on that very subject, "Is the Earth more Spherical than Oblate? " In order for Mr. deGrasse Tyson to avoid further confusion for us layman. From his statements on February 1, 2007 at 92nd Street Y, he indeed lead me to believe the Earth was less spherical than oblate. Tony Johnson Member-The Planetary Society

Sherbet: 08/01/2015 03:25 CDT

Earth without "make-up" is just as beautiful and more representative of Earth as a planet. I think I probably prefer it that way too.

Topher: 08/07/2015 05:51 CDT

I would really like to see the raw constiuent images captured with the red, blue and green filters. Is there any plan to make these available in addition to the composites?

Chris Sourgeon: 09/17/2015 04:30 CDT

Hi Emily! These EPIC images are going to be released regularly, correct? If so, do you have a link where they are available? If they haven't started regular image updates, do you know about when that will begin?

UrsaMajor: 02/18/2016 03:32 CST

Is DSCOVER orbiting the Earth or the Sun? Thanks.

Donald Kronos: 03/07/2016 12:35 CST

I see plenty of questions, and of course I can't answer them all, but if this will allow me to include it, here is a link to a video of the moon passing in front of the Earth... Now, keep in mind that the camera (EPIC) used to capture the 20 images in that movie, does not have a very wide field of view, so you would not normally see the moon and Earth in the same image taken by that camera. The Earth Polychromatic Imaging Camera (EPIC) is part of the Deep Space Climate Observatory (DSCOVR) at Lagrange point 1, about a million miles closer to the sun than Earth is. From such a distance you can get a good idea of the actual size relation between the planet Earth and it's moon, but to clearly see their distance from each other, I'm afraid you would need a much wider field of view than the EPIC camera can give you... unless perhaps they have a way of adjusting that, which I'm not aware of. However, there is an image on this site which shows the distance relation of out home planet and it's moon, but they are in fact so far apart that both are barely visible in the image. Here's a link to that one.

Donald Kronos: 03/07/2016 12:41 CST

UrsaMajor, that's a good question. DSCOVER is orbiting the sun, about a million miles closer to it than Earth is, which normally would mean it would have a shorter orbital time, but because it is positioned directly between the two, the Earth's gravity compensates for some of the Sun's gravity, effectively reducing the Sun's pull and allowing DSCOVER to orbit at almost the exact same angular speed as Earth. Of course, the match isn't going to be perfect, so occasional small adjustments must be made, but effectively it's just hanging in the balance between the gravitational sources.

Donald Kronos: 03/07/2016 12:59 CST

Seraph -- I think perhaps what's happening is that you are taking "perfect sphere" less less literally than Neil deGrasse Tyson is. He's probably also taking it less literally than a mathematician or geometer would. There really isn't such a thing as being "more Spherical than Oblate" since technically something is either one or the other. All spheres are of course the tiniest deformation away from being oblate spheroids, but depending on the extent of the deformation an oblate spheroid may be closer to or farther from being a sphere, so I think the real question should be "does the Earth look more like sphere than oblate spheroid?" and I think the answer is an arguably clear "yes, it does, at least to the human eye", since the deformation is not visibly obvious. However, it is technically not actually precisely a sphere, but rather, precisely an oblate spheroid which is approximately spherical.

Donald Kronos: 03/07/2016 01:08 CST

Just a clarification on something I commented earlier in response to a question. Actually, as I understand it, DSCOVER is basically orbiting a point in space between the Earth and the Sun, where the gravitational effects between them ate balanced. That point, in turn, moves through space as the Earth and Sun move through space, maintaining a position between them. I may have over-simplified this earlier, because I wanted to avoid confusing anyone, so if this description is too complicated or seems too mysterious, stick with the simpler one for now... and come back to this one if you get curious about the details. :)

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