Enceladus like Europa is a small icy moon that may have an ocean of liquid water under its surface. It’s a fascinating world a object that surprise us again and again whit great pictures; every shot of it is dramatic and intriguing.
Through the raw images from the distant spacecraft, there is a series of pictures depicting the tiny disk of Enceladus with the gigantic visage of Titan sliding past! The images animation showing the scene below:
[It helps to watch full-screen and in hi-res; I recorded it in 1080p. The images from Cassini look pretty good that way.]
Amazing, eh? Between some of the frames of the animation Cassini was programmed to change filters. That’s most obvious by looking at Titan itself; when the blue filter was used the atmospheric layers become more obvious — an upper level haze layer is dark in blue colors. Here’s one of those images using the blue filter:
Image source: Bad Astronomer
The picture isn’t blue even whit a blue filter in use because the detectors used on spacecraft (and most telescope) cameras don’t really detect colors, they only detect light. Astronomers use filters to block out or isolate certain colors of light, say red, green, or blue. Each of those individual images is really just an array of numbers, so an individual filtered image can only be displayed as a grayscale picture like the one above. It’s when you add the three images together that true color emerges. The actual process is pretty detailed, but that’s the boiled-down version.