FORESAIL-2 AOCS Trade Studies and Design

This thesis aims to design a reliable CubeSat platform, including the avionic subsystems that can sustain a high radiation environment for a mission having a lifetime of at least six months. The science instruments put stringent requirements on the platform to achieve and maintain the desired spin rate. The simulation background is set up in Systems Tool Kit (STK). A trade-off analysis for the Attitude and Orbit Control System (AOCS) of FORESAIL 2 was done, focusing on the actuators and their ability to offer the right amount of torque to fulfill the tether deployment. Mission design analyses were performed to conclude on the form factor of the CubeSat, its ability to generate power, its compliance with the Space Debris Mitigation (SDM) technical requirements, and the total radiation dose accumulated. It was found that a 6U form factor is preferred to allocate more space for each subsystem, alongside with generating enough power for the satellite to work in all modes wanted. The mission is compliant with European Cooperation for Space Standardization (ECSS) and International Organization for Standardization (ISO) standards if the CubeSat is to be launched in September 2022. To allow a threshold limit of 10 krads on the components of the satellite, a shielding wall of 7 mm should be implemented on the CubeSat’s structure. Major requirements for the designed mission were written to initialize the investigation on the sensors and actuators. The results showed that only a propulsion system provided the necessary angular momentum to deploy the tether. The lack of magnetic field makes magnetorquers almost unusable in the desired orbit, leaving reaction wheels as the only option remaining to assist the propulsion units. The different analyses and simulations led to a final AOCS configuration composed of five various sensors (Sun sensors, magnetometers, a GPS, an IMU, and housekeeping sensors) for the attitude determination. A propulsion system and reaction wheels will provide the necessary control over the satellite

Liquid Water : When Hyperpolarizability Fluctuations Boost and Reshape the Second Harmonic Scattering Intensities

Second Harmonic Scattering (SHS) is a method of choice to investigate the molecular structure of liquids. While a clear interpretation of SHS intensity exists for diluted solutions of dyes, the scattering due to solvents remains difficult to interpret quantitatively. Here, we report a quantum mechanics/molecular mechanics (QM/MM) approach to model the polarization-resolved SHS intensity of liquid water, quantifying different contributions to the signal. We point out that the molecular hyperpolarizability fluctuations and correlations cannot be neglected. The intermolecular orientational and hyperpolarizability correlations up to the third solvation layer strongly increase the scattering intensities, and modulate the polarization-resolved oscillation that is predicted here by QM/MM without fitting parameters. Our approach can be generalized to other pure liquids to provide a quantitative interpretation of SHS intensities in terms of short-range molecular ordering

First hyperpolarizability of water in the bulk phase: long-range electrostatic effects included via the second hyperpolarizability

The molecular first hyperpolarizability β contributes to second-order optical non-linear signals collected from molecular liquids. For the Second Harmonic Generation (SHG) response, the first hyperpolarizability β (2ω,ω,ω) often depends on the molecular electrostatic environment. This is especially true for water, due to its large second hyperpolarizability γ(2ω,ω,ω,0). In this study we compute the electronic γ(2ω,ω,ω,0) and β (2ω,ω,ω) for water molecules in their bulk phase using QM/MM calculations. The average value of γ(2ω,ω,ω,0) is smaller than the one for the gaz phase, and its standard deviation among the molecules is relatively small. In addition, we demonstrate that the average second hyperpolarizability ⟨γ(2ω,ω,ω,0)⟩ can be used to describe the electrostatic effects of the neighborhood on the β (2ω,ω,ω) ; but only the more distant neighbors can be accounted this way. This study paves the way towards QM/MM calculations of the first hyperpolarizability of molecules in complex environments, in which long-range electrostatic effects can be crucial, for example nearby charged interfaces

Hyperpolarizability of Water at the Air-Vapor Interface: Numerical Modeling Questions Standard Experimental Approximations

In this article, we investigate the molecular first hyperpolarizability of water molecules nearby the liquid-vapor interface. The hyperpolarizability of each molecule is calculated at the quantum level within an explicit, inhomogeneous electrostatic embedding. We report that the average molecular first hyperpolarizability tensor depends on the distance relative to the interface, but it practically respects the Kleinman symmetry everywhere in the liquid. Within this numerical approach, based on the dipolar approximation, the water layer contributing to the Surface Second Harmonic Generation (S-SHG) intensity is less than a nanometer. We show that within this interfacial layer, the common assumption considering a single, constant hyperpolarizability for all water molecules is not supported by our data: hyperpolarizability fluctuations are expected to impact the S-SHG intensity. These results represent a step forward the molecular interpretation of experimental S-SHG signal of aqueous interfaces. </div

SISPO: Space Imaging Simulator for Proximity Operations

Publisher Copyright: © 2022 Public Library of Science. All rights reserved.This paper describes the architecture and demonstrates the capabilities of a newly developed, physically-based imaging simulator environment called SISPO, developed for small solar system body fly-by and terrestrial planet surface mission simulations. The image simulator utilises the open-source 3-D visualisation system Blender and its Cycles rendering engine, which supports physically based rendering capabilities and procedural micropolygon displacement texture generation. The simulator concentrates on realistic surface rendering and has supplementary models to produce realistic dust- and gas-environment optical models for comets and active asteroids. The framework also includes tools to simulate the most common image aberrations, such as tangential and sagittal astigmatism, internal and external comatic aberration, and simple geometric distortions. The model framework’s primary objective is to support small-body space mission design by allowing better simulations for characterisation of imaging instrument performance, assisting mission planning, and developing computer-vision algorithms. SISPO allows the simulation of trajectories, light parameters and camera’s intrinsic parameters.Peer reviewe

DADA2 diagnosed in adulthood versus childhood: A comparative study on 306 patients including a systematic literature review and 12 French cases

International audienceDeficiency of adenosine deaminase 2 (DADA2) is a rare autoinflammatory disease usually presenting before the age of 10 years. Non-specific clinical features or late-onset presentation may delay its diagnosis until adulthood.Objective: To determine whether DADA2 diagnosed in adulthood is associated with specific characteristics compared to DADA2 diagnosed in childhood.Methods: We pooled a cohort of 12 adult DADA2 patients followed in France with cases identified through a systematic literature review. For each patient, we determined the type of clinical presentation and assessed six key organ involvements.Results: A total of 306 cases were included. Among the 283 patients with available data regarding age at diagnosis, 140 were diagnosed during adulthood and 143 during childhood. The vascular presentation of DADA2 was more frequent in the adult diagnosis group (77.9% vs. 62.9%, p < 0.01), whereas the hematological presentation (bone marrow failure) prevailed in the pediatric diagnosis group (10.0% vs. 20.3% p = 0.02). In patients with vasculopathy, severe skin manifestations developed in 35% and 10% of the adult and pediatric diagnosis groups, respectively. Conversely, fewer strokes occurred in the adult group presenting with systemic vasculopathy (54% vs. 81%). Symptomatic humoral immune deficiency (HID) was rarely a clinical presentation in itself (5% and 2.8%) but accompanied other phenotypes of DADA2, especially the hematological phenotype in the adult group (33% vs. 4%).Conclusion: DADA2 diagnosed in adulthood presents more often with a vascular phenotype and less often with bone marrow failure than DADA2 diagnosed in childhood. Adults diagnosed with DADA2 vasculopathy display more severe skin involvement but fewer strokes

Foresail-2: Space Physics Mission in a Challenging Environment

Earth’s radiation belts are extremely important for space weather because they can store and accelerate particles to relativistic energies, which can have a potential impact on satellite functionality, communications, and navigation systems. The FORESAIL consortium wants to measure these high-energy particle fluxes to understand the dynamics of the radiation belts with its satellite mission Foresail-2. The mission aims to measure magnetic ultra low frequency waves and the plasma environment in the magnetosphere around Earth. The captured data will help to improve our understanding of space weather, and in particular the dynamics of Earth’s radiation belts during periods of large disturbances inside the magnetosphere. A mission design analysis and several trade-off studies are conducted to find the requirements for the science payloads and spacecraft avionics design. Deducted from these requirements, four different payloads are proposed to gather science data in a highly elliptical orbit such as a geostationary transfer orbit. The precision magnetometer uses flux-gate technology to measure magnetic waves from 1 mHz to 10 Hz. The spin scanning particle telescope is built around a detector stack to measure electron spectra in the range of 30 keV to 10 MeV. Additionally, this mission serves as a technology demonstrator for the Coulomb drag experiment which proposes a new kind of electric solar wind sail utilising the Coulomb drag force imposed onto a 300 m long tether. The fourth payload investigates multilayer radiation shielding and single event effects. All payloads will be supported by a newly developed 6U platform using mostly commercial off-the-shelf components. Its proposed avionics face several unique design requirements rising from the payloads and the preferred highly elliptical orbit for this mission.Peer reviewe

Discours présidentiels et de présidentielles

Ce numéro spécial de notre revue est entièrement consacré aux discours présidentiels et de présidentielles. Il s’agit de proposer une recension de recherches prenant pour objets les discours de titulaires de la fonction présidentielle ou ceux de personnes de tout statut intervenant dans la compétition présidentielle, que ce soit pour y participer ou pour en rendre compte. Une série d’articles courts, signés de spécialistes reconnus, traite de la France, mais aussi d’autres pays dont le premier personnage de l’État est élu au suffrage universel, comme l’Argentine, les États-Unis, la Pologne ou le Portugal. Ces synthèses seront utiles aux spécialistes, mais aussi à quiconque voudra prendre quelque distance vis-à-vis de l’actualité immédiate. This Special issue of our journal is entirely devoted to presidential speeches and presidential electoral campaigns. It proposes a research recension taking as objects speeches of holders of the presidential office or those of various categories who intervene in the presidential contest, whether to take part in it or to report about it. A series of short articles, signed by recognised experts, will deal with France, but also other countries whose head of the state is elected by universal suffrage, such as Argentina, the United States, Poland and Portugal. These syntheses will be useful to specialists but also to whoever will take some distance towards the immediate news. 112, número especial de nuestra revista : es totalmente dedicado a los discursos presidenciales y de las elecciones presidenciales. Se trata de proponer una reseña de investigaciones cuyo objetos son los discursos de los titulares de la función presidencial o los de las personas de todo tipo de estatuto que intervienen en la competición presidencial, como participantes o para comunicar información. Una serie de artículos cortos, firmados por especialistas reconocidos, tiene como objeto Francia, pero también otros países cuyo primer representante del Estado es elegido al sufragio universal, como Argentina, Estados Unidos, Polonia o Portugal. Estas síntesis no son solamente útiles para los especialistas, pero para el que quiere también tomar alguna distancia con la actualidad inmediata