Where will you be at 10.27pm (UK time) tonight?

The Cassini spacecraft will be somewhere behind Saturn. But it'll be looking at Earth, at us. So we'd better make sure we're looking back. And don't forget to smile -- you'll be on camera.

Cassini is going to snap a picture of Earth, taking advantage of the sun being eclipsed by Saturn from the spacecraft's vantage point, blocking out the sunlight.

Cassini has done this before. Here's Earth as a dot nestled in the top left hand corner of Saturn's rings.

And so has Voyager -- the famous pale blue dot, taken at Carl Sagan's behest, was first time we'd seen Earth from the outer solar system.

The difference today is that we know the photo will be taken in advance. You can look up what time that will be wherever you are in the world.

Until then, here's an animated adaptation of Carl Sagan on the significance of that first pale blue dot:

Pale Blue Dot - Animation from Ehdubya on Vimeo.

Images: 1. CICLOPS/JPL/ESA/NASA, 2. Voyager 1/NASA