Space gifs

Inspired by videos such as these, showing time-lapse video from raw photographs returned from spacecraft, in May 2012 I started mass downloading these pictures in the hope of making my own such video: I knew that Cassini had sent back the better part of 300,000 photos from Saturn, which is around 3 hours' worth of video at 25 frames per second.

As it turns out, much of the Cassini archive, at least speaking aesthetically, is rather dull. The videos that had been made had skimmed off many of the good sequences, and so instead I decided to make little gifs rather than a long video. My original goal was 50 gifs, with an optimistic hope for 200; I now have just under 400, which I have posted to Tumblr. I believe it is the largest dedicated collection of time-lapse space gifs online, and it covers a wide range of missions, as well as a tour of the outer planets from the (ground-based) Keck Observatory.

Before I began I had no experience in image processing. Most of the sequences require little or no processing: the main problem is fixing the wobble of the camera. (This is only a mild problem for Cassini – frame to frame, the target might move a few pixels. For Voyager images, the frame-to-frame movements might be a few hundred pixels.) While it was a learning experience for me to write code to perform this procedure, it is not particularly interesting: set pixels below a threshold to zero and above the threshold to 1, erode and dilate to get rid of small noisy areas, hopefully you're left with a circle or crescent of pixels and you pick out either the starting row/columns or the tallest/widest, and so on.

Occasionally I veered into slightly more interesting territory (while remaining many levels below, say, Björn Jónsson's work). I've put two such posts here: correcting geometric distortion in Voyager images, and removing noise bands in Rosetta's Phobos photos.

Top-right: One Jovian day, photographed through Voyager 1's orange filter, 2-3 February 1979.