Earth’s Group Photo

Staff at JPL celebrate Earth’s snapshot.

Last week, people all across the world waved at the skies in a group celebration of Earth’s portrait shot from 898,000,000 miles away. The Cassini spacecraft has been orbiting Saturn for nearly a decade, and in fact most of the dazzling images you’ve seen of Saturn, its rings, and its moons were captured by Cassini. On Friday, July 19, 2013 Cassini’s cameras captured images of Earth, the Moon, and Saturn in the same image frame. This wasn’t the first time Earth’s picture was taken from the outer Solar System, but this time the event was made known to the public in advance of its happening. “Wave at Saturn” images flooded social media sites as waving people took pictures with hula hoops to show their excitement and support.

Artist’s conception of Cassini orbiting Saturn.

Today we saw the first images released of Saturn and Earth. It has taken several days for the images to be ready. Why is this?

Have you ever tried to take a picture in the dark? It’s difficult… You need to keep your camera still, and leave your shutter open for a long time to capture more light. The same idea applies here. Earth was 898 million miles away from Cassini when these pictures were taken, showing up as only a faint blue dot. To add to the challenge, bright and shiny Saturn sits in the foreground of the image. On top of this, Cassini is in motion as it orbits Saturn.  Imagine trying to take a picture of a car with its headlights on and a tiny firefly sitting in a tree behind it, while riding a bicycle past the scene….

Cassini accomplishes this by taking hundreds of images. These images were sent back to humans on Earth for processing. For the past several days, scientists at NASA have been combining these images together with special computer software. To put it simply, the images are layered on top of each other and combined to form a single image.

The finished product of Cassini’s Earth, Moon, and Saturn portrait is not yet complete. The image released today is one of 33 “tiles” of the final mosaic that will show the entire planet Saturn, its rings, and Earth. Creating this picture takes a lot of work. Stay tuned as more of the puzzle is pieced together…

The first image released by NASA of Earth, Moon, and Saturn’s group photo. Earth is marked by an arrow. The moon is barely visible as a faint smudge to the lower right. This image alone was created by combining over 200 individual images captured by Cassini.

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