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-09 flyby animation, 125-fold time-lapsed
On October 24, 2017, NASA's Juno probe successfully performed her Perijove-09 Jupiter flyby. At that time, Jupiter was close to solar conjunction with respect to Earth. This means, that the sun was between Jupiter and Earth, and blocked reliabale communication.
Jupiter was also hidden for Earth-based observations. So JunoCam, Juno's Education and Outreach camera, took images without detailed knowledge of which features to expect within its field of view during Jupiter flyby.
Fortunately, JunoCam's assigned memory has been incremented, such that JunoCam was able to cover all latitudes with close-up images.
The movie is a reconstruction of the flyby in 125-fold time-lapse, based on the JunoCam images taken, and based on spacecraft trajectory data provided via SPICE kernel files.
In more detail, the 20 Perijove-09 RGB images #75, #76, #78 to #85, #88 to #95, #97, and #98 went into this animation.
In steps of five real-time seconds, one still images of the movie has been rendered from at least one suitable raw image. This resulted in short scenes, usually of a few seconds.
Playing with 25 images per second results in 125-fold time-lapse.
Resulting overlapping scenes have been blended using the ffmpeg tool.
In natural colors, Jupiter looks pretty pale. Therefore, the still images are approximately illumination-adusted, i.e. almost flattened, and consecutively gamma-stretched to the 4th power of radiometric values, in order to enhance contrast and color.
The movie starts with a resonstructed in-bound sequence approaching Jupiter from north. Then the orbit approaches Jupiter down to an altitude of between 3,000 and 4,000 km near the equator.
This is followed by a transition into the outbound orbit, during which Jupiter's south polar region comes into the view.
The movie covers two real-time hours.
Rendering the still images of the movie took about three days on three virtual CPU cores running in parallel.
The rendering software for the stills is proprietary. Trajectory data were retrieved from SPICE kernels with the SPICE/NAIF tool spy.exe. For combining stills to movie files, the tool ffmpeg has been used.
Blending may result in feature-doubling in overlapping scenes due to reprojection inaccuracies.
Most repetitive bright and dark camera artifacts are patched. Due to the intense radiation near Jupiter, several additional bright pixels occured. Those aren't patched in this animation.
In rarer cases, lightnings on Jupiter may also show up as bright pixels.
Some of the close-ups show perceptable macro blocks. Those are effects of lossy data compression, which is necessary in order to store a reasonable number of images in the limited on-bord memory of the spacecraft, especially during solar conjunction when no data can be transmitted to Earth before, and during the perijove pass.
Sometimes, the edges of the raw images show up as black triangular areas in some corners of the movie rendition.
During blending, features may be doubled due to alignment inaccuracies of the blended scenes.
The sometimes very bright limb is an effect of inaccuraties of the applied illumination adjustemt, combined with the high degree of image enhancement.
Some cloud motions are just perceptible, but very small from this distance, and within the short time. So, you may or may not notice them at a small number of locations during scene blendings.
Any residual issues in the movie are due to imperfect image processing.
The movie may nevertheless provide you an idea of Juno's Perijove-09 flyby.
The raw images used for this movie rendition are available via the missionjuno website.
JunoCam was built and is operated by Malin Space Science Systems in San Diego / California / USA.
Many people at NASA, JPL, SwRI, and elsewhere have been, are, and will be required to plan and operate the Juno mission.