The Day the Earth Smiled
The Day the Earth Smiled refers to the date July 19, 2013, on which the Cassini spacecraft turned to image Saturn, its entire ring system, and the Earth during an eclipse of the Sun, as it had done twice before (in 2006 and 2012) during its previous nine years in orbit. The name also refers to all the activities associated with that event as well as The Day the Earth Smiled, the mosaic photograph itself. 
Conceived by the Cassini imaging team leader and planetary scientist Carolyn Porco, the concept called for all the world's people to reflect on their place in the cosmos, to marvel at life on Earth, and, at the time the pictures were taken, to look up and smile in celebration.
The final mosaic from July 19, processed at the Cassini Imaging Central Laboratory for Operations (CICLOPS), was released to the public on November 12, 2013. The Day the Earth Smiled photograph includes Earth, Mars, Venus, and many Saturnian moons. A higher-resolution view taken with the Cassini narrow-angle camera of the Earth and its moon as distinct points of light was released shortly afterwards.
The Cassini probe took images of Earth from close to a billion miles away at 21:27 UTC, July 19, 2013. A number of activities were planned in conjunction with this occasion:
- The Day the Earth Smiled website was set up as a portal to activities associated with July 19. On it, Porco encourages the world to celebrate life on planet Earth and humanity's accomplishments in the exploration of the solar system.
- Astronomers Without Borders coordinated events internationally.
- NASA spearheaded a related event called Wave at Saturn "to help acknowledge the historic interplanetary portrait as it is being taken".
- A "Message to the Milky Way" contest is being held by Porco's company, Diamond Sky Productions. It is a two-part contest: People can submit a digital photo taken on July 19 and/or a music composition. The winning entries will be beamed as a message to extraterrestrials, "into the Milky Way from the Arecibo Radio Telescope in Puerto Rico". This follows the example set in 1974, when the first serious communication to alien civilizations, the Arecibo message, was broadcast from Arecibo.
Raw images from Cassini were received back on Earth shortly after the event, and a couple of processed images—a high resolution image of the Earth and the Moon, and a small portion of the final wide-angle mosaic showing the Earth—were released to the public a few days following the July 19 imaging sequence.
Processing of the full mosaic took place at the Cassini Imaging Central Laboratory for Operations (CICLOPS) under Porco's direction over the course of approximately two months. During the four hours it took Cassini to image the entire 404,880-mile-wide scene, the spacecraft captured a total of 323 images, 141 of which were used in the final mosaic. NASA revealed that image marked the first time four planets – Saturn, Earth, Mars, and Venus – had been captured at once in visible light by the Cassini craft. It was also the first time the public had advance warning their picture was being taken from the outer solar system.
NASA's official release of the final The Day the Earth Smiled mosaic on November 12, 2013, was met with much fanfare in news media outlets around the world. The image graced the front page of The New York Times the following day. Public figures including media producer Seth MacFarlane lauded the image. The mosaic was also presented by Carolyn Porco, and dedicated to the late astronomer Carl Sagan, at a ceremony at the Library of Congress in honor of its acquisition of Sagan's papers. In addition, a collage of images submitted by 1,600 members of the public to NASA's Wave at Saturn campaign was released on November 12.
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