Updated Ganymede Mosaic from Voyager and Galileo Observations

In preparation of the JUICE mission with the primary target Ganymede [1] we generated a new controlled version of the global Ganymede image mosaic using a combination of Voyager 1 and 2 and Galileo images. Baseline for this work was the new 3D control point network from Zubarev et al., 2016, which uses the best available images from both missions and led to new position and pointing of the images

Controlled Global Ganymede Mosaic from Voyager and Galileo Images

In preparation of the JUICE mission with the primary target Ganymede we generated a new controlled version of the global Ganymede image mosaic using a combination of Voyager 1 and 2 and Galileo images. Baseline for this work was the new 3D control point network from Zubarev et al., 2016, which uses the best available images from both missions and led to new position and pointing of the images. Creating a global mosaic with these corrected images made it reasonable to decide for a higher map scale of the global mosaic as currently existing ones. Therefore, we included very high-resolved Galileo images that cover only a few percent of the surface but can be analyzed directly within their surrounding context. As a consequence, it supports the JUICE operations team during the planning of the Ganymede orbit phase at the end of the mission (Grasset et al., 2013)

Visualizing planetary data by using 3D engines

We examined 3D gaming engines for their usefulness in visualizing large planetary image data sets. These tools allow us to include recent developments in the field of computer graphics in our scientific visualization systems and present data products interactively and in higher quality than before. We started to set up the first applications which will take use of virtual reality (VR) equipment

Updated Ganymede Mosaic from Juno Perijove 34 Images

In preparation of the JUICE mission with the primary target Ganymede we generated a new controlled version of the global Ganymede image mosaic from Voyager 1 and 2, Galileo, and Juno images

Timing of Optical Maturation of Recently Exposed Material on Ceres

On Ceres, multispectral imaging data from the Dawn spacecraft show a distinct bluish characteristic for recently exposed material from the subsurface in, for example, crater ejecta. Ejecta blankets of presumably old craters show a more reddish spectrum. We selected areas in which fresh material from the Cerean subsurface was exposed at a specific time in the past, and no later geologic process is expected to have changed its surface composition or its cratering record. For each area, we determined two color ratios and the crater retention age. The measured color ratios show an exponential diminishment of the bluish characteristic over time. Although the cause of the color change remains uncertain, the time-dependent change in spectral properties is evident, which could help identify the process

Ceres' spectral link to carbonaceous chondrites - Analysis of the dark background materials

Ceres’ surface has commonly been linked with carbonaceous chondrites (CCs) by ground‐based telescopic observations, because of its low albedo, flat to red‐sloped spectra in the visible and near‐infrared (VIS/NIR) wavelength region, and the absence of distinct absorption bands, though no currently known meteorites provide complete spectral matches to Ceres. Spatially resolved data of the Dawn Framing Camera (FC) reveal a generally dark surface covered with bright spots exhibiting reflectance values several times higher than Ceres’ background. In this work, we investigated FC data from High Altitude Mapping Orbit (HAMO) and Ceres eXtended Juling (CXJ) orbit (~140 m/pixel) for global spectral variations. We found that the cerean surface mainly differs by spectral slope over the whole FC wavelength region (0.4–1.0 μm). Areas exhibiting slopes <−10% μm−1 constitute only ~3% of the cerean surface and mainly occur in the bright material in and around young craters, whereas slopes ≥−10% μm−1 occur on more than 90% of the cerean surface; the latter being denoted as Ceres’ background material in this work. FC and Visible and Infrared Spectrometer (VIR) spectra of this background material were compared to the suite of CCs spectrally investigated so far regarding their VIS/NIR region and 2.7 μm absorption, as well as their reflectance at 0.653 μm. This resulted in a good match to heated CI Ivuna (heated to 200–300 °C) and a better match for CM1 meteorites, especially Moapa Valley. This possibly indicates that the alteration of CM2 to CM1 took place on Ceres

Spectrophotometric analysis of the Ryugu rock seen by MASCOT: Searching for a carbonaceous chondrite analog

We analyze images of a rock on Ryugu acquired in situ by MASCam, camera of the MASCOT lander, with the aim of identifying possible carbonaceous chondrite (CC) analogs. The rock's reflectance ($r_{\rm F} = 0.034 \pm 0.003$ at phase angle $4.5^\circ \pm 0.1^\circ$) is consistent with Ryugu's average reflectance, suggesting that the rock is typical for this asteroid. A spectrophotometric analysis of the rock's inclusions provides clues to CC group membership. Inclusions are generally brighter than the matrix. The dominant variation in their color is a change of the visible spectral slope, with many inclusions being either red or blue. Spectral variation in the red channel hints at the presence of the 0.7~$\mu$m absorption band linked to hydrated phyllosilicates. The inclusions are unusually large for a CC; we find that their size distribution may best match that of the Renazzo (CR2) and Leoville (CV3) meteorites. The Ryugu rock does not easily fit into any of the CC groups, consistent with the idea that typical Ryugu-type meteorites are too fragile to survive atmospheric entry

Irregular Moons of the Giant Planets: Potential for Observations by Spacecraft

While the first Irregular moon of a giant planet has been found on photographic plates in 1899 (Phoebe), and another ten (also through photography) until 1975, the vast majority of discoveries (now with CCDs) started no earlier than 1997, with big advances in the early noughties (almost 100 moons) and again since 2017 (well over 100 objects). Ground-based observations are important for discoveries and the determination of orbital elements and physical properties like brightness (size) and colors. However, there are geometric limits – mainly the restriction to low phase angles (25 mag), which requires large telescopes difficult to access over long periods of time. With spacecraft orbiting a giant planet, i.e. at distances at the order of 10e7 km to the Irregulars, long-duration observations to obtain lightcurves can be performed for numerous objects. Even with just one observation session over many hours and a bit of luck, a synodic rotation period at the accuracy of minutes may be deduced. With multiple observations, sidereal periods at millisecond-accuracy level, unambiguous pole solutions, and low-order convex-shape models might be obtained. Furthermore, phase curves up to >50° phase angle (for some objects even >100°, on particularly favorable geometries) can be measured. This is possible because a giant-planet orbiter revolves inside the orbits of the Irregular moons, and the Solar phase angles may in principle reach any value from 0° to 180°. Such an Irregular moons campaign has been performed for the first time with Cassini's Narrow Angle Camera while in orbit around Saturn (Denk & Mottola 2019, Icarus), providing 24 new rotation periods of Saturnian Irregulars and about a dozen sidereal periods, pole solutions, shape models, and phase curves. A similar campaign is under consideration for the Juice mission with the JANUS camera, which has the potential for an even larger sample of Jovian Irregulars. The poster will discuss the options and limits for spacecraft-based observations of Irregular moons while orbiting Jupiter or another giant planet. Beyond unresolved observations, upcoming missions to the gas and ice giant planets should also attempt close flybys of an Irregular moon, as has been done by Cassini at Phoebe in 2004. Best opportunities might occur prior to orbit insertion or during the first (large) orbits