Picture of the Day: How to Make a 'Blue Marble' Image of Earth

Last week NASA released the latest edition in its "Blue Marble" series. The first Blue Marble picture was taken by astronauts on board Apollo 17 as they traveled to the moon. When they took the picture, they were 28,000 miles from the Earth, and they were therefor able to see the entire Earth in their vision. But NASA's Suomi satellite -- the craft responsible for the new Blue Marble picture -- was only 512 miles above the Earth, far too close to get a picture with an entire hemisphere in view. (For comparison, the International Space Station which provides us with all those wonderful "Earth at night" photos is somewhere between 205 and 255 miles over head.) The above image shows how NASA scientists compiled different sets of that up close data to create an image of one of Earth's hemispheres -- on that appears, they say, to have been taken at a distance of 7,918 miles. The data comes from six different passes by Suomi over that hemisphere of Earth during an eight-hour period. Since NASA posted the new image last week, more than 3 million people have viewed it on Flickr, making it one of the most-viewed images for a one-week period in the site's history.

Below, recent Pictures of the Day:

Image: NASA.