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.
125-Fold Time-Lapsed Perijove-04 Fly-Over Animation Derived from Raw JunoCam Images, 2017-02-02
On February 2, 2017, NASA's Juno spacecraft performed her 4th perijove pass (PJ-04), a close flyby over Jupiter. Juno orbits around Jupiter take about 53.5 days. They are elliptical and very eccentrical. The JunoCam instrument, Juno's public outreach and education camera, was operational during PJ04, and took several images.
The images covered all of Jupiter latitudes. This allows rendering seamless animations from above Jupiter's north pole till above its south pole along Juno's trajectory.
The animation shown here is time-lapsed by a factor of 125. Each frame of the animaton is rendered immediately from a respective raw JunoCam image. These raw JunoCam images consist of color strips ("framelets") the camera takes while the Juno spacecraft rotates with a spin rate of about two revolutions per minute. For each frame of the animation, the raw JunoCam framelets are merged to a color image showing Jupiter from a perspective as it has been for the respective simulated trajectory position.
The raw JunoCam colors underwent "decompanding" and weighting in order to reconstruct approximately "natural" colors.
Since the contrast of Jupiter's cloud top is mostly pretty low, for this animation, I've decided to apply two enhancement steps. First dividing by a Lambert shading model, in order to get the colors relative to a white mate solid spheroid illuminated by the Sun.
In contrast to a white mate solid, Jupiter has an atmosphere. This results in a twilight zone beyond the terminator. Therefore, the previously described method of de-Lambertianing results in a brightening effect of the twilight zone. No correction has been applied to this effect.
In order to further enhance constrast, I've squared the resulting radiometric quotients. In other words, I've applied a gamma-stetch of 4.0 (applying 4th power) relative to square-root encoded colors. (Raw JunoCam data are roughly square-root encoded.)
As a side-effect, this additional gamma-stretch further brightens the terminator region. Future versions might adjust for the over-enhancement of the twilight.
The animation is derived from JunoCam's perijove-04 images #099 to #109. The JunoCam images have been taken from different perspective along Juno's trajectory. The same surface point of Jupiter changes appearence with perspective and time. This effect is not adjusted for in the animation. Therefore the changes from one raw JunoCam image to the next is accompanied by a change of Jupiter's appearence.
The simulated real time covers 2017-02-02T12:25:00.000 to 2017-02-02T14:10:00.000.
For most of the sequence, north is to the left.
The projection is spherical with a vertical (latitudinal) field of view (FOV) of 45 degrees, and a horizontal (longitudinal) FOV of 115 degrees.
The simulated pointing is constant except three 45 degree-jumps to the left, in order too keep Jupiter in the field of view.
In parts of the animation, the respective raw JunoCam image doesn't cover the whole simulated field of view. This results e.g. in a curved upper or lower truncation of Jupiter, or in an unsharp or truncated limb zone.
Rendering the stills for the animation took about two days of CPU time.
Besides the raw JunoCam images (credit: NASA / JPL / SwRI / MSSS), the processing uses ffmpeg for graphics and video file conversions, SPICE trajectories dumped with the SPICE/NAIF utility spy.exe, a decompanding table provided by MSSS and accessible via NASA's PDS, preliminary radiometric calibration weights determined by MSSS, and C++ compilers to compile home-made C++ source code into proprietary image processing software.