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.
PJ73 Jet N7
PJ73 JunoCam images are very noisy. The noise with mostly positive values seems to be mostly added on top of the underlying signal similar to thermal noise and elevated dark current.
The underlying idea for denoising in this case is hence to use only the darkest pixels within each raw 4x4 image block. More accurately speaking, the pixels of each 4x4 image block are sorted by brightness, and the 3rd darkest brightess tie is assumed to be the denoised value for the whole 4x4 block. Using a darker tie would result in dark artefacts, conceivably due to occasional companding overflow effects of noise peak values.
In order to account for the assumed dark current, an additional value of 48/256 of the raw grey-scale value range is subtracted.
The resulting modified raw image is then used to derive a reprojected RGB image the same way raws are normally used to derive a reprojected image. Nominally, the square-root of linearized values is used for the final image product, with linear radiometric factors (0.613; 1.0; 3.655) for (R;G;B) derived from PJ72.
Note that the applied method is only supposed to reconstruct information about the structure of the cloud-tops. The applied image processing method isn't suited to provide radiometrically meaningfully calibrated values, since decompanding wasn't adapted to the the noise cleaning approach.