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Return of the Pale Blue Dot

Join the Wave at Saturn (and Mercury)!

Posted by Mat Kaplan

18-07-2013 11:27 CDT

Topics: Cassini, Mercury, fun, astronomy, MESSENGER, spacecraft, Saturn, Saturn's rings, citizen science, pics of Earth by planetary missions, astronomy by planetary missions, events and announcements, Earth

Want to try your hand at interplanetary communication?  I mean that literally.  Cassini is about to take a picture of the dark side of Saturn. It has done this before, of course, but this time is even more special.  It has been timed so that our own planet will be visible below the great ringed beauty.  The Cassini team has invited all of us to become sub-sub-sub pixel resolution contributors by waving at Saturn as the 15-minute exposure is made.

This is a really a doubleheader.  The MESSENGER mission team, inspired by Cassini’s photo op, realized they could catch images of Earth from Mercury during roughly the same period.  So you’ll have your choice of spacecraft to wave to!  Hey, why not both? 

More details are on the Cassini website, but here are the basics.  The shot from Saturn will commence tomorrow, Friday, July 19th, at 21:27 UTC, which is 2:27pm in Pacific Daylight Land, where I’ll be.  MESSENGER will grab its photos at 11:49, 12:38, and 13:41 UTC on both Friday the 19th and Saturday the 20th.  Attention, residents of Europe, the Middle East and Central Asia!  The MESSENGER camera is your best shot.  I’m just sayin’.

I hope to be standing outdoors at JPL with a group of visiting teachers.  One way for you to join in will be watching a 21:00 UTC (2:00pm PDT) Ustream webcast featuring Cassini mission leaders.  Add your own images on Twitter by using the hashtag #waveatsaturn, or uploading to the event’s Flickr page. Facebook is in on this, too.

The spacecraft images will take a few days to process.  A full mosaic from Cassini may take weeks, but it will be worth the wait.  There’s real science going on here.  With the sun hidden by Saturn’s bulk, the planet’s backlit rings can be examined in terrific detail.  MESSENGER will be in the midst of looking for natural satellites of Mercury.

With Saturn currently about 900 million miles or nearly 1.5 billion kilometers away, you might think this is the longest selfie in history.  Not so.  The original Pale Blue Dot image was taken in 1990 by Voyager 1 when it was more than four times as distant. 

I hope you’ll be one of millions showing your support for planetary science and the spirit of exploration!  Don’t forget to smile.

See other posts from July 2013


Or read more blog entries about: Cassini, Mercury, fun, astronomy, MESSENGER, spacecraft, Saturn, Saturn's rings, citizen science, pics of Earth by planetary missions, astronomy by planetary missions, events and announcements, Earth


Patrick Donohue: 07/18/2013 05:32 CDT

If the 21:27 UTC time is the Earth Time start of exposure, what about the one-way light time delay between Earth and Cassini? The Cassini mission page ( notes a delay of ~1.25 hours. Am I missing something here, or are we going to be waving an hour too late?

Mat Kaplan: 07/18/2013 11:49 CDT

Hi, Patrick. Though the news release and website don't address this, I think it's safe to assume that the Cassini folks have adjusted for the light time delay. I'll ask about that while I'm at JPL tomorrow.

Casey Dreier: 07/19/2013 10:49 CDT

@Patrick: I can confirm that the team has taken light time delay into account with those times.

Patrick Donohue: 07/19/2013 11:24 CDT

Thanks, Casey. It seemed like something obvious to take into account, but I had not seen it specifically addressed anywhere.

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