UPDATE: The photos of Earth from Saturn by Cassini and from Mercury by Messenger were released Monday (July 22). See the amazing photos here.
A distant spacecraft charged with studying the Saturn system will turn its cameras to Earth today (July 19), and you can get in on Earth's photo session in person or online.
NASA's Cassini spacecraft will take a series of photos of Earth from Saturn's perspective beginning at 5:27 p.m. EDT (2127 GMT) and lasting until 5:42 p.m. EDT (2142 GMT). The planet will appear as a small dot — only one or two pixels wide — near Saturn's ring plane.
Although Earth will look something like a nondescript, distant star in the photo, NASA officials want Earthlings to "wave at Saturn" from their place on our planet during that time. If you don't have the chance get outside, however, two skywatching webcasts can help you take part in NASA's "first interplanetary photobomb." [See stunning photos taken by Cassini]
You can watch both Saturn-spotting webcasts live on SPACE.com today.
The first webcast, set to begin at 3:30 p.m. EDT (1930 GMT), will feature live views of Saturn hosted by the Virtual Telescope Project.
"Tonight, the Cassini spacecraft is taking an historic image of Saturn with our planet, Earth, in the same field of view," Gianluca Masi with the Virtual Telescope Project said in a video announcement. "For the first time, such a picture from so far away is taken while humans are aware of the picture."
The webcast will also be available here: http://www.virtualtelescope.eu/2013/07/18/the-day-the-earth-smiled-cassini-images-our-planet-from-saturn/
Officials from the online Slooh Space Camera, which organizes live views of celestial sights in telescopes around the world, will start their broadcast at 5:30 p.m. EDT (2130 GMT) with live shots of Saturn as seen from the Canary Islands.
"At the exact time the Cassini spacecraft is snapping pics of Earth, Slooh will be snapping images of Saturn — live and in true color — with live broadcast team," said Slooh President Patrick Paolucci in a statement.
You can also watch the webcast directly through the Slooh website: www.slooh.com
Interested skywatchers that happen to be in New York City can also wave at Saturn during a "flash mob" that will gather at 5:30 p.m. EDT (2130 GMT) in Columbus Circle at 59th Street. Organizers are asking participants to "bring something 'Saturnian'" to the event. Telescopes that can be used to look at the moon and Saturn will be set up after sunset, and a professional photographer will be on hand to take photos of the crowd.
Another NASA spacecraft took photos of Earth from its vantage point in the solar system earlier today. The Messenger probe in orbit around Mercury took photos of Earth from Mercury's point of view at 7:49 a.m., 8:38 a.m. and 9:41 a.m. EDT (1149, 1238 and 1341 GMT). The spacecraft will also take photos of Earth again tomorrow at the same time.
Editor's note: If you have an amazing night sky photo of Saturn or any other celestial sight that you'd like to share for a possible story or image gallery, please contact SPACE.com Managing Editor Tariq Malik at email@example.com.