Solutions for control point coordinates and librations for the Saturnian satellite Dione: A simulation based on synthetic data

We explore the application of the Inertial Frame Bundle Block Adjustment (IFBBA) to determine the shape and rotation state of small bodies, e.g., asteroids and natural satellites, using images acquired by spacecraft. Within this particular block adjustment implementation control point (CP) coordinates are tied to the body frame, while the camera parameters and the body’s rotation state use a parameterization, referenced to the inertial frame (Burmeister et al., 2018). The flexibility is especially desirable for objects exhibiting notable (but poorly known) rotational variability, which often requires elaborate formulation depending on the regulating mechanisms. Here we present a full simulation case, based on synthetic data for the Saturnian satellite, Dione. First, we studied the orbital characteristics of the satellite and computed the forcing terms for the longitudinal libration using a frequency analysis approach. We focus on the libration terms connected to the orbital period of 2.739 days and a long-period term of 11 years related to the resonance with Enceladus. We select around 1000 images of Dione collected by the Imaging Science Subsystem onboard the Cassini spaceprobe. Using a recent shape model by Gaskell et al. (2018), we establish a network of CPs with a more or less complete surface coverage. Image coordinates of the CPs are simulated for the observing geometries and orientations of Dione at the given epochs of the images and are taken as observables in the adjustment. We test and extend the functionality of the IFBBA, previously applied to the Martian satellite Phobos and the asteroid 4 Vesta (Burmeister et al., 2018), to the present case. We analyze the estimation errors of the camera parameters, CP coordinates, and in particular, the retrieval of the libration amplitude for Dione. The outcome is expected to be instructive to the real data analysis in the future and shed light on the generalizability of the IFBBA software for other Solar System objects

The Ganymede Laser Altimeter (GALA) for the Jupiter Icy Moons Explorer (JUICE): Mission, science, and instrumentation of its receiver modules

The Jupiter Icy Moons Explorer (JUICE) is a science mission led by the European Space Agency, being developed for launch in 2023. The Ganymede Laser Altimeter (GALA) is an instrument onboard JUICE, whose main scientific goals are to understand ice tectonics based on topographic data, the subsurface structure by measuring tidal response, and small-scale roughness and albedo of the surface. In addition, from the perspective of astrobiology, it is imperative to study the subsurface ocean scientifically. The development of GALA has proceeded through an international collaboration between Germany (the lead), Japan, Switzerland, and Spain. Within this framework, the Japanese team (GALA-J) is responsible for developing three receiver modules: the Backend Optics (BEO), the Focal Plane Assembly (FPA), and the Analog Electronics Module (AEM). Like the German team, GALA-J also developed software to simulate the performance of the entire GALA system (performance model). In July 2020, the Proto-Flight Models of BEO, FPA, and AEM were delivered from Japan to Germany. This paper presents an overview of JUICE/GALA and its scientific objectives and describes the instrumentation, mainly focusing on Japan’s contribution

What can inactivity (in its various forms) reveal about affective states in non-human animals? A review

Captive/domestic animals are often described as inactive, with the implicit or explicit implication that this high level of inactivity is a welfare problem. Conversely, not being inactive enough may also indicate or cause poor welfare. In humans, too much inactivity can certainly be associated with either negative or positive affective states. In non-human animals, however, the affective states associated with elevated or suppressed levels of inactivity are still not well understood. Part of the complexity is due to the fact that there are many different forms of inactivity, each likely associated with very different affective states. This paper has two aims. One is to identify specific forms of inactivity that can be used as indicators of specific affective states in animals. The other is to identify issues that need to be resolved before we could validly use the remaining, not yet validated forms of inactivity as indicators of affective state. We briefly discuss how inactivity is defined and assessed in the literature, and then how inactivity in its various forms relates to affective (either negative or positive) states in animals, basing our reasoning on linguistic reports of affective states collected from humans displaying inactivity phenotypically similar to that displayed by animals in similar situations, and, when possible, on pharmacological validation. Specific forms of inactivity expressed in response to perceived threats (freezing, tonic immobility, and hiding) appear to be, to date, the best-validated indicators of specific affective states in animals. We also identify a number of specific forms of inactivity likely to reflect either negative (associated with ill-heath, boredom-like, and depression-like conditions), or positive states (e.g. ‘sun-basking’, post-consummatory inactivity), although further research is warranted before we could use those forms as indicators of the affective states. We further discuss the relationship between increased inactivity and affective states by presenting misleading situations likely to yield wrong conclusions. We conclude that more attention should be paid to inactivity in animal welfare studies: specific forms of inactivity identified in this paper are, or have the potential to be, useful indicators of affective (welfare) states in animals

Observations of Phobos and its shadow: Implications for the Phobos orbit

The orbit of Phobos deep in the gravity field of Mars is strongly affected by various parameters of the Mars interior. The orbit of the small satellite is therefore complex and undergoing a particulate tidal evolution. Our early analysis of im-ages from High Resolution Stereo Camera / Super Resolution Channel (HRSC/SRC) on Mars Express (MEX) [4] have shown stark discrepancies between orbit models and observations of up to 12 km, a fact which renewed the interest in more detailed astro-metric analysis of Phobos data to constrain the orbit models. Since these early studies, we have made a number of new astrometric measurements using new image data and upgraded measurement techniques. The Mars Express spacecraft has continued its Phobos flyby maneuvers and has obtained many more SRC images of the satellite. In addition, the shadow of Phobos was captured on several occasions by the HRSC and the Mars Orbiting Camera (MOC) on the Mars Global Surveyor, which all had not been analyzed yet. These shadow observations provide further constraints on the orbit of Phobos not affected by uncertainties in the spacecraft orbit and camera pointing. In the presentation, we will report on first preliminary results of our ongoing study titled ,Geodesy and Cartography of Phobos", funded by DFG

PhoDEx — a low-cost mission to explore the Martian satellite system

For ESA’s M4 Medium Mission Call, we proposed a low-cost mission to explore the Martian satellite system. PhoDEx (Phobos Deimos Explorer) will carry out investigations on the origin and evolution of the Martian satellites, as well as their interactions with the environments. The mission will shed light on the formation of the satellites by using a variety of complementary techniques to study interior structures, as well as chemical and mineralogical compositions. We foresee that a Soyuz-Fregat launch vehicle will insert PhoDEx into a Mars transfer orbit in 2024. Upon arrival at the Martian system the spacecraft will begin with a Deimos phase consisting of two distinct Quasi-Satellite Orbit (QSO’s) phases about the satellite. Afterwards PhoDEx will rendezvous with Phobos and enter two distinct QSO’s again before deploying a small Lander on the surface. The foreseen landing area is the North Pole region of Phobos during the summer season in 2027, allowing lander operations in daylight for approximately 3 months. For both Martian satellites, comprehensive characterization for morphology and gravity field, and studies of their spectral and thermal soil characteristics will be carried out. Crater statistics will be used to determine the ages of surface units and time scales of geological processes. Sensors onboard the orbiter will monitor the interaction of solar wind with the surfaces to help understand the evolution and weathering of the regolith. A powerful short-wave-radar will explore the deep regolith structures. Finally, using impact detectors, we will identify sources and sinks of the micrometeoroid population and address the question of Phobos/Deimos dust rings. The landing package will be equipped with a powerful LIBS/Raman spectrometer to obtain precise data on the chemistry and mineralogy of Phobos soils at the landing site. A seismometer will capture seismic signals from impacts and thermal quakes. A radio science experiment will provide accurate measurements of Phobos orbital motion and rotational librations to determine the time scales of Phobos’ orbital decay. As M4 missions have a ceiling to mission’s cost to ESA of 450 M€, we have discussed various cost saving options. Among other options, we plan to use a modernized design of Mars Express, built “fasttrack” to catch the narrow launch window and design a custom-made small-sized lander of approximately 45 kg. By this the PhoDEx mission costs (including 30% margin) are estimated to be at ~530 M€, consisting of 425 M€ ESA costs (launch, operations, s/c, lander) and 105 M€ payload costs. PhoDEx will give us a new picture of the Martian satellites and also improve our understanding of other planetary systems