Analytical ray-tracing in planetary atmospheres

Ground-based astro-geodetic observations and atmospheric occultations, are two examples of observational techniques requiring a scrutiny analysis of atmospheric refraction. In both cases, the measured changes in observables are geometrically related to changes in the photon path and the light time of the received electromagnetic signal. In the context of geometrical optics, the change in the physical properties of the signal are related to the refractive profile of the crossed medium. Therefore, having a clear knowledge of how the refractivity governs the photon path and the light time evolution is of prime importance to clearly understand observational features. Analytical studies usually focused on spherically symmetric atmospheres and only few aimed at exploring the effect of the non-spherical symmetry on the observables. In this paper, we analytically perform the integration of the photon path and the light time of rays traveling across a planetary atmosphere. We do not restrict our attention to spherically symmetric atmospheres and introduce a comprehensive mathematical framework which allows to handle any kind of analytical studies in the context of geometrical optics. To highlight the capabilities of this new formalism, we carry out five realistic applications for which we derive analytical solutions. The accuracy of the method of integration is assessed by comparing our results to a numerical integration of the equations of geometrical optics in the presence of a quadrupolar moment $J_2$. This shows that the analytical solution leads to the determination of the light time and the refractive bending with relative errors at the level of one part in $10^8$ and one part in $10^5$, for typical values of the refractivity and the $J_2$ parameter at levels of $10^{-4}$ and $10^{-2}$, respectively

Development Of New Toolkits For Orbit Determination Codes For Precise Radio Tracking Experiments

This thesis describes the developments of new models and toolkits for the orbit determination codes to support and improve the precise radio tracking experiments of the Cassini-Huygens mission, an interplanetary mission to study the Saturn system. The core of the orbit determination process is the comparison between observed observables and computed observables. Disturbances in either the observed or computed observables degrades the orbit determination process. Chapter 2 describes a detailed study of the numerical errors in the Doppler observables computed by NASA's ODP and MONTE, and ESA's AMFIN. A mathematical model of the numerical noise was developed and successfully validated analyzing against the Doppler observables computed by the ODP and MONTE, with typical relative errors smaller than 10%. The numerical noise proved to be, in general, an important source of noise in the orbit determination process and, in some conditions, it may becomes the dominant noise source. Three different approaches to reduce the numerical noise were proposed. Chapter 3 describes the development of the multiarc library, which allows to perform a multi-arc orbit determination with MONTE. The library was developed during the analysis of the Cassini radio science gravity experiments of the Saturn's satellite Rhea. Chapter 4 presents the estimation of the Rhea's gravity field obtained from a joint multi-arc analysis of Cassini R1 and R4 fly-bys, describing in details the spacecraft dynamical model used, the data selection and calibration procedure, and the analysis method followed. In particular, the approach of estimating the full unconstrained quadrupole gravity field was followed, obtaining a solution statistically not compatible with the condition of hydrostatic equilibrium. The solution proved to be stable and reliable. The normalized moment of inertia is in the range 0.37-0.4 indicating that Rhea's may be almost homogeneous, or at least characterized by a small degree of differentiation

Analytical study of the radio signals propagation in planetary atmospheres

The ESA JUICE (JUpiter ICy moons Explorer) mission is planned for launch in 2022 and arrival at Jupiter around 2030. The mission is dedicated to the study of the giant gaseous and its largest moons. While the spacecraft will probe the Jovian system it will be occulted by the atmosphere of Jupiter or its satellites as seen from antennas on Earth. Such a configuration offers a great opportunity to study remotely the physical properties of the occulting atmosphere using radio links as the probe is being occulted. Indeed, non-unity index of refraction causes the electromagnetic waves to depart from the straight line and also impacts the propagation speed of the waves. Both changes modify the wave frequency and conversely, from the time variation of the Doppler measurements the index of refraction profile can be retrieved. In the literature, there are different approaches devoted to the retrieval of the refractive profile from these observables. Let mention, i) the analytic formulation of the Abel inversion which is employed for spherically symmetric atmospheres, and ii) the ray tracing method which is a numerical integration of the fundamental equations of optics and which is well suited for atmospheres with more complicated shapes. Both possess their own advantages and inconveniences. For instance, to invert a complete set of data, the ray tracing method requires more computational time than the Abel transformation. In return, the Abel inversion is based on the spherical symmetry assumption while the ray tracing technique can handle non-radial gradient in the refractive profile. In the context of the future occultations of JUICE by Jupiter, we discuss the benefit of a new formalism based on a full reformulation of the fundamental equations of optics. This new approach let to provide a very comprehensive description of the light trajectory inside a planetary atmosphere with no assumption on the refractive profile. In the special case where the departure from the spherical symmetry is small, we present an analytic solution which is well suited for the data processing of radio occultation experiments. Indeed, this solution can handle the effect of a non-spherically symmetric atmosphere with a low computational cost. We use this solution to process the Cassini Doppler data acquired during an occultation by the oblate atmosphere of Saturn. The validity of the proposed approach is assessed comparing the results with other studies available in the literature

Detection of rapid orbital expansion of Saturn’s moon Titan

The Saturn satellite system is a complex dynamical system with several gravitational interactions happening between the satellites, the rings and the central body, such as resonances, librations and tides. These intricate dynamics carry information on the formation and evolution of the Saturn and Solar systems

The Rivellino degli Invalidi and the fortification system of Turin

This contribution, of a multidisciplinary nature, connects the very recent digital survey of the Rivellino degli Invalidi with the decades-long archaeological studies culminating with the 2015-2016 excavations and with the historical cartography that reveals the substantial consistency with the digital survey in terms of position, geometry and shape of the revelin

Innovation in ventilated tiled roofs : the HEROTILE European project

In ventilated roofs, the so-called Above Sheathing Ventilation (ASV) helps dissipating the excess heat in summer, thus reducing the cooling energy requirement. The ASV can be enhanced by increasing the air permeability of the tiled covering through the development of new tile shapes. This is the purpose of the Life HEROTILE European project, of which this work presents the preliminary analysis. The air permeability of a novel Marsigliese tile is analysed in comparison with the standard tile. The new design is improved with a higher sidelock and a new headlock pattern. A CFD model is then used to simulate the airflow through the tiles, solving the steady-state, incompressible fluid flow, in a 3D domain by means of the RANS-based standard k-ε model. A parametric study is conducted to analyse the variation in the air flow passing through the tile for different speeds and directions of the incident wind. The reference and new tile designs are compared in terms of air pressure drop and volumetric flow rate trough tiles. The novel shape increases the air permeability up to 100%; contrary to the standard shape, the new design allows also an increase of the air flow rate as the wind blows sideways.peer-reviewe

Influence of Lactobacillus kefiri on Intestinal Microbiota and Fecal IgA Content of Healthy Dogs

The increasing incidence of gastrointestinal tract pathologies in dogs and the worrisome topic of antibiotic resistance have raised the need to look for new therapeutic frontiers. Of these, the use of probiotics represents a potential therapeutic alternative. Lactobacillus kefiri (Lk) is a species of Lactobacillus isolated from kefir. Previous studies have demonstrated that its administration in mice downregulates the expression of proinflammatory mediators and increases anti-inflammatory molecules in the gut immune system. It also regulates intestinal homeostasis, incrementing immunoglobulin A (IgA) secretion. Since Lk has never been studied as a single probiotic in dogs, the aim of this study was to evaluate the safety of Lk in dogs, and its effect on IgA secretion and on intestinal microbiota composition. Ten healthy dogs without a history of gastrointestinal diseases were included. The dogs received Lk at a dose of 107 live microorganisms orally, once daily for 30 days. The fecal samples were tested before administration, in the middle, at the end, and 30 days after discontinuation. The IgA secretion concentration and the microbiota composition were evaluated on the fecal samples. The results in this study suggested that Lk did not influence the concentration of IgA, nor significant changes of the intestinal microbiota were observed during and after the treatment. Therefore, additional studies are needed to investigate if a higher daily dosage of Lk can influence the intestinal homeostasis of dogs

Detection of rapid orbital expansion of Saturn’s moon Titan

The Saturn satellite system is a complex dynamical system with several gravitational interactions happening between the satellites, the rings and the central body, such as resonances, librations and tides. These intricate dynamics carry information on the formation and evolution of the Saturn and Solar systems

Non-invasive Assessment of Fecal Stress Biomarkers in Hunting Dogs During Exercise and at Rest

Intense exercise causes to organisms to have oxidative stress and inflammation at the gastrointestinal (GI) level. The reduction in intestinal blood flow and the exercise-linked thermal damage to the intestinal mucosa can cause intestinal barrier disruption, followed by an inflammatory response. Furthermore, the adaptation to exercise may affect the gut microbiota and the metabolome of the biofluids. The aim of the present research was to evaluate the presence of a GI derangement in hunting dogs through a non-invasive sampling as a consequence of a period of intense exercise in comparison with samples collected at rest. The study included nine dogs that underwent the same training regime for hunting wild boar. In order to counterbalance physiological variations, multiple-day replicates were collected and pooled at each experimental point for each dog. The samples were collected immediately at rest before the training (T0), after 60 days of training (T1), after 60 days of hunting wild boar (T2), and finally, at 60 days of rest after hunting (T3). A number of potential stress markers were evaluated: fecal cortisol metabolites (FCMs) as a major indicator of altered physiological states, immunoglobulin A (IgA) as an indicator of intestinal immune protection, and total antioxidant activity [total antioxidant capacity (TAC)]. Since stool samples contain exfoliated cells, we investigated also the presence of some transcripts involved in GI permeability [occludin (OCLN), protease-activated receptor-2 (PAR-2)] and in the inflammatory mechanism [interleukin (IL)-8, IL-6, IL-1b, tumor necrosis factor alpha (TNF\u3b1), calprotectin (CALP), heme oxygenase-1 (HO-1)]. Finally, the metabolome and the microbiota profiles were analyzed. No variation in FCM and IgA content and no differences in OCLN and CALP gene expression between rest and training were observed. On the contrary, an increase in PAR-2 and HO-1 transcripts, a reduction in total antioxidant activity, and a different profile of microbiota and metabolomics data were observed. Collectively, the data in the present study indicated that physical exercise in our model could be considered a mild stressor stimulus