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Headshot of Emily Lakdawalla

New work with 35-year-old data: Voyagers at Ganymede and Saturn

Posted By Emily Lakdawalla

25-05-2016 16:44 CDT

Topics: Jupiter's moons, pretty pictures, amateur image processing, Ganymede, Voyager 1 and 2, Saturn's moons, Saturn

The Voyager data set is a gift to Earth that keeps on giving. This week, I've seen three great new images processed from this old data set. The first one was made by Ian Regan at my request. I pointed him to this classic view from Voyager 2, and asked him to make one that was just a bit closer to true color. Here is his result. I love it when moons make cameos in planet portraits.

Saturn and its moons from Voyager 2

NASA / JPL / Ian Regan

Saturn and its moons from Voyager 2
Voyager 2 captured the images for this view of Saturn on July 12, 1981. Three moons are visible: Rhea below the disk, and Tethys and Enceladus on the disk. Tethys' shadow falls on the planet. The image was taken on the same day as this more garish view that was released by NASA.

Another awesome new product this week was made by Bjorn Jonsson. He's been working with the Voyager 1 Ganymede flyby data set, trying to process a global view, for some time. He recently had a breakthrough in repairing several crucial frames that were smeared when the Voyager scan platform moved while the photo was being captured, as he explains here.

Huge color Voyager 1 Ganymede mosaic

NASA / JPL / Bjorn Jonsson

Huge color Voyager 1 Ganymede mosaic
The 17 frames worth of source images were obtained by Voyager 1 on March 5, 1979 over a period of about 2 hours. During these 2 hours Voyager 1's distance from Ganymede dropped from 305,000 to 180,000 km.

Bjorn posting his Ganymede mosaic inspired Justin Cowart to share some work he's been doing on the other Voyager's Ganymede mosaics. Here's a view centered on Osiris crater. The crater is neat, but my favorite part of the image is below and to the left of it, where the slanting sunset light outlines fascinating topography around a different crater. There's another related mosaic at Justin's Flickr page.

Voyager 2 Ganymede mosaic: Osiris crater

NASA / JPL / Justin Cowart

Voyager 2 Ganymede mosaic: Osiris crater
19 frame mosaic of Ganymede taken during Voyager 2's flyby of the moon on July 9, 1979. This image is centered on the bright Osiris Crater and surrounding ejecta deposits.
See other posts from May 2016


Read more blog entries about: Jupiter's moons, pretty pictures, amateur image processing, Ganymede, Voyager 1 and 2, Saturn's moons, Saturn


DrMorbius: 05/25/2016 09:02 CDT

Ganymede is such a fascinating, enigmatic, alien moon. It has some characteristics of Europa mixed in with characteristics of the other moons. Thank you for sharing this with us.

eric: 05/25/2016 11:20 CDT

I have taken the liberty to combine the 3 incredible images Justin recently uploaded/composited of Ganymede and it turned out incredibly well, dare I say seamless! Absolutely all credit to Justin, I am but a humble Photoshop Photomerge user.

rlorenz: 05/26/2016 06:30 CDT

Shows (again) the virtues of archiving data. You never know when analysis techniques will improve

SC: 05/26/2016 12:31 CDT

The quality of the images are really good. But I am wondering How many photo's were actually taken by the Voyagers..and how many need and can use some work? Also, is there any ability or ( intergrity ) in 'artificially' filling in what might be missing or not usable when it comes to the images? ..hmm..

Tim: 05/26/2016 05:55 CDT

What this shows is that it is well worth revisiting older image data and looking at them again with modern image processing techniques and software.

Tom Hopp: 05/26/2016 06:34 CDT

I remember seeing the Voyager data as they came in, on TV and on the pages of Astronomy Magazine. Such were the times, no internet. For decades, I have measured other solar system bodies against Ganymede for the sheer artistry and beauty of its surface. Even now, few can compare. Thanks for the fresh look at Ganymede's gorgeous face!

davispw: 05/26/2016 07:46 CDT

How did they know to get Voyager to point at Osiris crater on Ganymede? Did they discover the crater with long distance photography and then update the flyby sequence so quickly? Incredible that they could sequence a mosaic like that with early-1970's technology.

Justin Cowart: 05/28/2016 08:09 CDT

davispw: I believe capturing Osiris Crater in this image was happenstance. Looking over the full Voyager 2 Ganymede data set, I've found that high-resolution imaging was broken down into multiple mosaics with slightly overlapping footprints. These mosaics simply covered different portions of Ganymede, the one posted here captures the southeastern quadrant, coincidentally where Osiris Crater happened to be at the time. Voyager's pointing was a little inaccurate, even if this crater had been intentionally targeted, it was unlikely to be so perfectly at the mosaic's center. Not trying to knock Voyager or anything, but sometimes luck was a big factor in these missions!

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