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).

[Bjorn Jonsson]

With the first Juno high resolution imaging soon coming up I decided several weeks ago to take a look at Voyager color images at various resolutions - mainly high resolution though (I ended up using 7-24 km/pixel). The idea was to get at least some idea of what might be expected. This resulted in several mosaics and what follows are several posts, one post per mosaic. The posts are ordered by resolution, starting with the lowest resolution mosaic. In all cases the distance from Jupiter's center and resolution is indicated. The approximate distance for JunoCam to achieve comparable resolution is also shown. This applies to JunoCam's resolution at the nadir - due to the very wide angle field of view the resolution will not necessarily be uniform across the hi-res images (this is different from Voyager which has a narrow angle camera).

With the exception of one mosaic (a white oval mosaic), the source images are in all cases green and violet filtered images. Most of the hi-res Voyager color observations were performed using this filter combination. This is not optimal for constructing true color images but I think I managed to get resonably realistic color. Here is a quick and dirty global image I used as a test - the two source images are orange and violet filtered.



Not bad but I suspect the color could be improved a bit. The color processing I used for the hi-res mosaics is comparable to what I did in this global view. The features shown in the mosaics are semi-randomly selected. In particular I'm not attempting to show all possible types of cloud features - I simply selected images where mosaics could be constructed, color was available and the images looked interesting in some way.

In all cases two versions of a mosaic are shown, one approximately true color/contrast version and a version where the color and contrast has been exaggerated and the image sharpened to better show various details. The contrast stretch varies for the different mosaics and depends on things like scene brightness and contrast. North is up in all cases. The mosaics are 10-15% bigger than the original data, i.e. they are slightly oversampled to avoid losing details. In all cases the indicated resolution applies to the original data. As usual I reprojected the images to simple cylindrical projection, did all of the mosaicking and color processing there and then rendered an image using the viewing geometry close to the mid-time of the mosaic's imaging sequence.

The image in the preceding post (posted two days ago) can be considered an 'appetizer'.