The Planetary Society Weblog
By Emily Lakdawalla
Digging in to the Galileo Earth flyby data sets
May. 10, 2007 | 13:35 PDT | 20:35 UTC
UPDATE: When originally posted, the second animation on this page was running backwards. It's now been corrected so that it runs forward in time. Sorry for the error!
When I was working on the page of images of Earth from planetary spacecraft, I found out that the Galileo mission took some truly amazing movies of Earth and the Moon during its two flybys. After its first flyby of Earth, Galileo spent 25 hours staring almost continuously at the south pole, shooting one image every minute through six camera filters -- for a total of more than 1300 images. The filters included the three necessary to make approximately true color views of Earth, for animation frames of Earth rotating captured once every six minutes. There are low-resolution versions of this animation on the Internet, but I wasn't able to find a high-resolution version. I tried my hand at putting a few of the frames together, but it took a long time and I got sidetracked by being sick; thankfully Doug Ellison took up the challenge for me. The animation below consists of only one frame every hour; download the full-resolution version in Quicktime format for a frame every half-hour. The data set from this movie contains four or five times as many frames! | Earth rotates under GalileoAs Galileo receded from its first flyby of Earth on December 11 and 12, 1990, it took images of Earth in six different filters almost every minute over a 25-hour period. The animation here includes images taken once an hour, representing about a tenth of the full number of frames. Click here for a version of this movie at Galileo's full resolution with images taken every half-hour (Quicktime format, 1.1 MB). Credit: NASA / JPL / Doug Ellison |
Here's another nifty one, from the second flyby, showing Earth rotating as the Moon passes by.Galileo view of an Earth-Moon conjunctionAs Galileo receded from its ssecond flyby of Earth on December 16 and 17, 1992, it captured this sequence of Earth rotating as the Moon zipped by on its orbit. There are 56 frames in total, each separated by 15 minutes, spanning about 14 hours. Click here for a full-resolution version in Quicktime format (151 kb). Credit: NASA / JPL / Doug Ellison |
These two animations really bring home what a tragedy the loss of Galileo's high-gain antenna was. Galileo could take and transmit the high volume of image data for these animations because it was so close to Earth at the time, and it was feasible to transmit relatively large volumes of data through its low-gain antenna. But once it got to Jupiter, its camera -- still capable of taking wonderful image sequences like this -- was hobbled by the tiny amount of data volume that could be returned from such a great distance through the only working antenna. Don't get me wrong, I still think Galileo achieved a lot -- but it could have sent back Cassini-like movies of mutual events, Jupiter's clouds, and Io's volcanoes, not to mention so much more detail on the surfaces of the other moons, and fine structures in Jupiter's rings. Now I want to see a return to the Jupiter system with a camera even better than Cassini's, to do what Galileo missed.
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