Cassini · 19 July 2013, 22:54 UTC
The Day the Earth Smiled
Cassini slipped into Saturn's shadow and looked back toward the Sun: the rings lit from behind, and the Earth a pale dot at the lower right between the G and E rings, 1.45 billion kilometres away. People on Earth knew the picture was being taken.
Slide between them
The original laid over the live view at the same scale, as the viewer does when you press Both or Original. Drag across the picture, or use the arrow keys.
Where it was taken from
Cassini was 1.2 million km from Saturn, 1.45 billion km from the Earth at 22:54 UTC on 19 July 2013.
The live view puts the viewer's camera right there. The clock goes to that moment, everything switches to true scale, and the camera sits where the spacecraft was, its position from JPL Horizons, NASA's ephemeris service, for that moment [5]. The lens matches the published picture, 11.9° from top to bottom, and the camera is turned to the picture's own orientation, so the original lies over the view at the same scale.
Where the two differ
The original is a mosaic of 141 frames over four hours, with the Earth brightened eight and a half times; here the Earth carries the same stretch.
Everything in the live view comes from the viewer's own maps and its own light, drawn at one instant. The geometry comes from the spacecraft's position, the lens and the picture's orientation, so where everything was, how big it looked and which way it was lit should all line up with the original.
The facts
- On 19 July 2013 Cassini slipped into Saturn's shadow and imaged the planet, seven moons, the inner rings and the Earth. [1]
- It was the first time people on Earth knew in advance that their picture would be taken from such a distance. [1]
- Cassini took 323 images in just over four hours; the mosaic uses 141 wide-angle frames. [1]
- The Earth was 1.45 billion km (898 million miles) away, and in the narrow-angle frame the Moon shows as a separate dot. [2]
- The Earth, Venus and Mars were brightened 8.5 times in the mosaic so they would show. [1]
- NASA set the Earth's part of the mosaic for 21:27 UTC, for about 15 minutes, and invited people to wave at Saturn. [3]
- Light from the waving Earth took just over 80 minutes to reach Cassini. [4]
Open it live
In the viewer the clock runs on from the moment at real pace, so you can watch the scene move the way it did after the shutter closed. Press Both or Original to lay the original over it, or drag to look around from where Cassini was.
Open it live in 3D → All eight as a Mac screensaver
The other seven
The Blue Marble
Earthrise
The Moon crossing the Earth
The Earth and Moon, together
Pale Blue Dot
In Saturn's Shadow
Pluto in true colour
All the famous photos, and how the views are made
Sources
- NASA Photojournal: The Day the Earth Smiled
- NASA Photojournal: One Special Day in the Life of Planet Earth
- NASA JPL: Cassini Probe to Take Photo of Earth from Deep Space
- NASA (apod.nasa.gov): Ap130824
- NASA JPL: Horizons ephemeris system
Original picture: NASA/JPL-Caltech/SSI, from NASA Photojournal: The Day the Earth Smiled. JPL pictures may be used for any purpose without prior permission, with the credit line. JPL image use policy. The live view is ours, rendered by the Our Solar System viewer.