Voyager mosaics and images of Jupiter, A fresh look at some ancient stuff Options

[Bjorn Jonsson]

Thanks to modern computers and software the old, 'official' Voyager Jupiter images can be reprocessed into something much better. There is also a lot of Voyager data there that was never processed into color composites and/or mosaics (or at least it has not appeared on the WWW). With proper processing the apparent image quality approaches the quality of the Cassini images but needless to say the wavelength coverage is (vastly) inferior.

I have recently been taking a close look at the high resolution Voyager 1 images, i.e. the images obtained in early March 1979. This is going to result in some new and/or reprocessed mosaics. The first one is now complete and I'm working on another one.

The image below is a 12 image mosaic (12 orange + 12 violet + 12 synthetic green images). The images were obtained on March 2, 1979 at a range of 4.3 million km. The first image (C1629045.IMQ) was obtained at 05:09:23 and the last one (C1629131.IMQ) at 05:46:11. The resolution is roughly 43 km/pixel.



The raw images were calibrated, reprojected to simple cylindrical projection, mosaicked and then rendered using a typical viewing geometry (there is no such thing as a "correct viewing geometry" because the images were obtained over a 37 minute period with Jupiter rotating). I then fixed the color balance. I still haven't 'standardized' how I process the Voyager color. I wasn't completely satisfied with the color I got using an approach similar to what's described in another thread but I think the color could be improved a bit. The final step was to sharpen the resulting image a bit, mainly to compensate for all of the resampling that the previous processing steps required.

This image shows lots of features: The Great Red Spot and one of the three white ovals present during the Voyager flybys, smaller spots, scallopped belt/zone boundaries, gravity waves, a bright equatorial plume and the dusky south polar region.

I don't think I'm bragging by saying that this is probably the best Voyager 1 Jupiter mosaic that I know of, mainly because of its size (12 images).

I will be posting more Jupiter stuff in this thread in the coming days/weeks, both mosaics and interesting images (and needless to say, others are welcome to post images and mosaics as well).

[DrShank]

beauty! would you call this close to natural color now?

the voyager cameras were quite good for the time and Ive gotten lots of mileage out of the images. the big difference was the lack of infrared capability, which allows you to look deeper into the atmosphere and see thermal updrafts and hot lavas (on io that is).

[Bjorn Jonsson]

beauty! would you call this close to natural color now?

The upper one should be fairly close to natural color but this is subjective. It might be a bit too reddish but I'm not sure. After some channel mixing I processed it to make the oval SSE of the GRS roughly white.

A few notes on the mosaics and on images I have noticed in the Voyager dataset:

(1) As should be obvious I have been looking at lots of high-res Voyager images of Jupiter recently. When doing this I have come across several images that show interesting features that I had not noticed before. An example (processed to increase contrast and sharpness):


And a wide angle context image shuttered at the same time:


The features near the top of the image are interesting. These images where obtained on March 4, 1979 at a range of 1.3 million km from Jupiter's center.

Another example (processed to increase contrast and sharpness):


And a context image:


The features (clouds?) at upper right in the narrow angle image look somewhat weird. They are located near (435,375) in the context image. The images were obtained on March 5, 1979 at a range of 630,000 km from Jupiter's center.

(2) I noticed an interesting comment in several images in a brown barge imaging sequence. For example in image C1635958.IMQ:

"ATMOS DYNAMICS 3X2 NA GR MOSAIC OF BARGE, STEREOSCOPIC WITH 16359.50 - 60.07"

This seems to have been an attempt to image Jupiter in stereo - I don't think I'm misunderstanding anything here. However, I don't think imaging Jupiter in stereo using a single spacecraft would work due to cloud motions. Two spacecraft are a different story so here's today's crazy idea: Imaging parts of Jupiter in stereo if both NASA and ESA send spacecraft there simultaneously. I'm not sure it would work though - it requires high resolution and I'm not sure ESA's JGO spacecraft is going to be capable of that due to its distance from Jupiter and maybe due to its camera as well.

(3) I haven't been able to confirm that it is indeed vertical relief and/or shadows that is visble in my mosaic. I've been looking for scientific papers and I haven't found any but I haven't searched very carefully. I also did some simple 3D test renders to see which cloud thickness and altitude might reproduce the appearance of the clouds in the mosaic but the results are inconclusive. Still this looks a lot like vertical relief and it should be noted that cloud shadows are visible in high-phase Voyager images of Jupiter. It would be interesting if someone here knew something about this topic. Also see the cloud shadow thread which has a hi-res image showing what might be shadows or vertical relief.

(4) I'm in the early stages of starting work on yet another mosaic and it's going to be a bit different from the ones I have posted here because OGV is available, not just OV. Actually there is a huge amount of Voyager stuff I'd like to process but this takes a lot of time if high quality results are desired. In particular, the lack of accurate camera pointing angles is a constant source of frustration and requires me to reverse engineer this information for every image. Fortunately, the spacecraft location is available and that data seems accurate - without it this would be even more time consuming.

[tedstryk]

In particular, the lack of accurate camera pointing angles is a constant source of frustration and requires me to reverse engineer this information for every image. Fortunately, the spacecraft location is available and that data seems accurate - without it this would be even more time consuming.

So true. When I was at the New Horizons team meeting in December, I was asked if I used the camera pointing information for my work. I had to be honest - only in situations where I could not ascertain the pointing by studying the image. When it could be done, determining the pointing from the image was significantly more accurate (though much more time consuming).