Enceladus Occults Tethys

…but you only got to see it if you were riding the Cassini probe orbiting Saturn.

While browsing the latest raw images from Cassini, I found this image sequence shot on June 6th with the camera was pointed toward Enceladus which was approximately 3,904,788 kilometers away. Based on where Cassini was in it’s orbit I’m fairly certain the larger moon is Tethys, with the mid-point of the occultation occurring on June 6, around about 16:04 UT. I cropped and combined the images in Photoshop to create this short animation.

What confounded me at first was how we could be looking at almost the full night side of Enceladus and NOT Tethys. After looking at the orientation from a polar vantage point atop the Saturnian system I could see Tethys was about a quarter of the way into the sunward side of its orbit around Saturn. Enceladus was barely finishing the night side part it’s orbit. We are indeed seeing the night side of Tethys — lit by sunlight reflected off of Saturn.

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