How'd they do it? NASA explains the Blue Marble photo.

A few days ago, NASA published an incredibly detailed photo, dubbed Blue Marble, of the Earth's western hemisphere. Since then, the photo has generated over 3.1 million views on Flickr, making it one of the all-time most-viewed images on the photo-sharing site. So what did NASA do to celebrate? Not only did they upload a second photo, of the Earth's eastern hemisphere (pictured above), but they also uploaded an explanation of how they created these fabulous images.

NASA scientist Norman Kuring created the images by combining data from six different orbits of the Suomi NPP satellite. Or putting it a different way, the satellite flew above this area of Earth six times over an eight hour time period. This was necessary because the satellite isn't far enough away from the planet to get a complete picture in one view. Kuring describes it by comparing the Earth to a basketball — if your eye is the Suomi NPP satellite, holding the basketball about five-eighths of an inch from your face will approximate the limited view that the satellite has of the planet's surface.


The Earth's diameter is about 7,926 miles, but the Suomi NPP satellite can only capture a view about 1,865 miles wide at one time. So stitching together the data from multiple passes allowed Kuring to "step back" from the actual orbit to give us an apparent view from a distance of about 7,918 miles away, without sacrificing any of the detail of the closer view. The original Blue Marble photograph was taken by NASA astronauts abord the Apollo 17, at a distance of about 28,000 miles. Don't forget to check out the image on Flickr to see all its glorious detail!

[Image credits: NASA/NOAA, NASA/NOAA]

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