The original pale blue dot - Earth from 3.7 billion miles away (NASA/JPL/Voyager)

One of the most enduring and captivating images from our exploration of space in the late 20th century was Voyager 1's mosaic of our own solar system - a family portrait from 3.7 billion miles away. Captured in these shots was a faint speck of bluish light, in one single pixel of Voyager's digital camera, the result of polarization and scattering of sunlight from a small and otherwise insignificant inner planet. This speck was us, and Carl Sagan's wickedly beautiful prose immortalized this hint of light as 'the pale blue dot' - encapsulating all that we had ever been to that moment.

Human imagination is a powerful thing, and we've drawn enormous inspiration from this rather innocuous looking image, we've been able to see ourselves in its smattering of photons - diminished but unbowed. So it's rather wonderful that we're about to do this again, to make another portrait of our homeworld, another deliberate reach for a sense of cosmic perspective.

On July 19th 2013, between 5.27pm EDT and about 5.42 pm EDT the Cassini mission, currently in orbit around Saturn, will use this giant planet as a sunshade to capture a series of images that will include the glow of reflected light from the Earth peering through some of the rings.

The plan for the portrait - Earth is down on the lower right (NASA/Cassini)

An earlier Earth portrait by Cassini, circa 2006 (NASA/JPL)

Although it's not the first time Earth has been imaged by Cassini, it is the first time using the high resolution camera, and it will be the first time that the color information of visible light will be captured. This will indeed be another version of the pale blue dot - reflected light from the America's and the Pacific ocean.

The view of Earth from Saturn on July 19th, 5.27pm EDT (NASA/Cassini)

At the time of the portrait we'll be some 898 million miles away from Cassini, reduced again to a single pixel, but that doesn't mean you shouldn't mark your calendars. It's not inconceivable that if you are on the right part of the Earth, and you stand outside and wave, that one or two of the photons of sunlight that reflect from you are going to make it out to Saturn and into Cassini's telescope. (Of course they'll take some 80 minutes to get there, but the Cassini team have accounted for that - I presume - the time of the portrait is given appropriately).

NASA is promoting a 'Wave at Saturn' campaign, you can check it out here.

The primary science goal of this Cassini mosaic is to study the detailed structure of Saturn's rings, but I suspect it's the opportunity to pause and consider our rather shockingly diminutive place in the cosmos that most of us will remember.