IMAGE PROCESSING GALLERY
One of the biggest challenges for Juno is Jupiter's intense radiation belts, which are expected to limit the lifetime of both Juno’s engineering and science subsystems. JunoCam is now showing the effects of that radiation on some of its parts. PJ56 images show a reduction in our dynamic range and an increase in background and noise. We invite citizen scientists to explore new ways to process these images to continue to bring out the beauty and mysteries of Jupiter and its moons.
For those of you who have contributed – thank you! Your labors of love have illustrated articles about Juno, Jupiter and JunoCam. Your products show up in all sorts of places. We have used them to report to the scientific community. We are writing papers for scientific journals and using your contributions – always with appropriate attribution of course. Some creations are works of art and we are working out ways to showcase them as art.
We have a methane filter, included for the polar science investigation, that is almost at the limits of our detector’s wavelength range. To get enough photons for an image we need to use a very long exposure. In some images this results in scattered light in the image. For science purposes we will simply crop out the portions of the image that include this artifact. Work is in progress to determine exactly what conditions cause stray light problems so that this can be minimized for future imaging.
The JunoCam images are identified by a small spacecraft icon. You will see both raw and processed versions of the images as they become available. The JunoCam movie posts have too many images to post individually, so we are making them available for download in batches as zip files.
You can filter the gallery by many different characteristics, including by Perijove Pass, Points of Interest and Mission Phase. If you have a favorite “artist” you can create your own gallery. Click on “Submitted by” on the left, select your favorite artist(s), and then click on “Filter”.
A special note about the Earth Flyby mission phase images: these were acquired in 2013 when Juno flew past Earth. Examples of processed images are shown; most contributions are from amateurs.
The spacecraft spin rate would cause more than a pixel's worth of image blurring for exposures longer than about 3.2 milliseconds. For the illumination conditions at Jupiter such short exposures would result in unacceptably low SNR, so the camera provides Time-Delayed-Integration (TDI). TDI vertically shifts the image one row each 3.2 milliseconds over the course of the exposure, cancelling the scene motion induced by rotation. Up to about 100 TDI steps can be used for the orbital timing case while still maintaining the needed frame rate for frame-to-frame overlap. For Earth Flyby the light levels are high enough that TDI is not needed except for the methane band and for nightside imaging.
Junocam pixels are 12 bits deep from the camera but are converted to 8 bits inside the instrument using a lossless "companding" table, a process similar to gamma correction, to reduce their size. All Junocam products on the missionjuno website are in this 8-bit form as received on Earth. Scientific users interested in radiometric analysis should use the "RDR" data products archived with the Planetary Data System, which have been converted back to a linear 12-bit scale.
Complete rotation post-perijove, labelled.
This is the second of two postings of JunoCam's 'marble movie' images, using versions initially processed by Gerald Eichstädt, which are here further enhanced and labelled to identify the features which we were following in amateur images. This set shows the southern hemisphere for a whole rotation in the day after perijove-1 (Aug.27). The most notable change is described at the end of this text: two long-lived white ovals appear likely to merge.
In the SEB following the GRS, there are now large bright ‘rifts’, i.e. the convective activity there has returned to normal, and the SEB will not fade in the next few months.
Oval BA (strongly reddish) is approaching the GRS. The small dark patch following it seems, at last, to have rounded up to form a quiescent small dark brown barge.
There is an unusually dense outbreak of small dark spots on the prograding SSTBn jet, between a large turbulent sector in the SSTB (‘FFR’; this may be inducing them), and the cyclonic ‘STB Ghost’ (this region was imaged by JunoCam at perijove).
The most notable changes are affecting the S.S. Temperate anticyclonic white ovals (S2-AWOs). Two small ones appear to be merging in these images, which is not uncommon. However, the nine numbered AWOs are very stable, and yet two of those – A0 and A8 – have rapidly converged and so are likely to merge in the coming weeks or months. Indeed it is possible that an A0-A8 merged oval could then merge with A1 in turn. In October they will start passing oval BA (which will itself be passing the GRS in November), and this passage may trigger a merger if it has not happened before. Merger(s) will no doubt perturb the relative drifts of the AWOs, which will also be disturbed by expansion of the white oblong that developed in August between A3 and A4. Therefore, predicting the positions of these AWOs will be less reliable than usual – but all of them will be of interest.
More details are given on the BAA Jupiter Section web site.
-- John Rogers.
