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.
Perijove 1 Context Map (Preliminary)
This image demonstrates, that it's possible to create a context map of Jupiter from JunoCam Marble Movie images. The map covers almost the full surface of Jupiter.
The map consists of 4272x1800 pixels. Each pixel corresponds to a planetocentric square of 0.1 degrees longitude times 0.1 degrees latitude.
The latitude range is from -90 degrees (south pole) at the bottom to +90 degrees (north pole) at the top. The longitude ranges over 427.2 degrees, resulting in an overlap (doubling) at the left and right end.
The map is derived from 40 Marble Movie images, the 20 color images #6121 to #6159 immediately before the perijove 1 (PJ1) images, and the 20 color images #6189 to #6227 immediately after the PJ1 images.
The 20 images before PJ1 cover Jupiter's northern hemisphere, the other 20 images cover the southern hemisphere. The two sequences overlap in the equator region.
Each of the comprised Marble Movie images has been transformed geometrically to a partial map without brightness adjustment, using a rotating rigid Jupiter (MacLaurin) spheroid model. The partial maps have then been composed by selecting the brightest pixel of all maps for each given pixel position.
The resulting map underwent several post-processing steps: multiplying with the negative of the mean grey value over all pixels of the same latitude as a crude de-lamberting avoiding the brightess singularity near the poles, hipass-filtering (radius 100) to prepare for small-scale enhancement, then enhancing brightness and saturation by respective linear stretches.
The map is preliminary in several ways:
Alignment of the partial maps mostly along longitude can be improved considerably. This should be followed by a longitude crop to 360 degrees of one of the standard Jupiter models. Accurate de-lamberting before merging the partial maps should reduce most of the horizontal brightness oscillations induced by the 40 partial maps. This requires a refined merging method, since brightness then can't be used as a criterion for which partial map(s) to use for a final pixel. The maps should be cleaned from noise by energetic particles, hot pixels and small dark spots on JunoCam's camera filters.
