Étalonnage au sol de l’instrument SIMBIO-SYS à bord de la mission ESA/BEPICOLOMBO

BepiColombo is one of the cornerstones of the scientific program of ESA. It will study the planet Mercury with two spacecrafts in orbit around the planet. One of the two spacecrafts, the Mercury Planetary Orbiter (MPO), will be dedicated to the study of the surface and interior of the planet. The mission is scheduled for launch in 2016 and arrival at Mercury in January 2024. IAS is responsible for the calibration of the imaging system SIMBIO-SYS (Spectrometers and Imagers for MPO BepiColombo Integrated Observatory-SYStem) which consists of a high-resolution camera (HRIC), a stereoscopic camera (STC) and a visible and near-infrared hyperspectral imager (VIHI). These instruments should deeply change our understanding of the composition and geomorphology of Mercury surface. My research subject allowed me to participate in all the activities concerning the definition, implementation and validation of the calibration facilities at the IAS. These facilities are divided into different sub-systems: a thermal vacuum chamber containing the instrument during all the calibration campaign that shall simulate the environmental conditions (temperature and pressure), an optical bench with optical components and radiometrically calibrated sources reproducing the observational conditions as it will be seen by the instrument once placed in Mercury’s orbit, mechanical interfaces allowing the positioning and guidance of the instrument when placed inside the vacuum chamber with the required precision and accuracy, thermal interfaces facilitating the thermal excursion of the detectors, software interfaces so as to automatize and control the entire system. I developed a radiometric model of the calibration system and instrument to refine the calibration sources. In parallel, I performed several measurements of some subsystems so as to validate the optical assembly and to improve its control. Finally as a result of a close collaboration with the three Italian scientific teams of the instrument, I elaborate the fully package of the calibration sequences and the detailed instrument configuration that will be used during the calibration campaign.La mission BepiColombo est une des pierres angulaires du programme scientifique de l'ESA. Elle permettra l'étude de la planète Mercure grâce à deux sondes mises en orbite autour de la planète. Une des deux sondes, Mercury Planetary Orbiter (MPO) développée par l'ESA, sera dédiée à l'étude de la surface et de l'intérieur de la planète. La mission est prévue pour un lancement en 2016 et une arrivée sur Mercure en janvier 2024. L’IAS est responsable de l’étalonnage de l'ensemble d'imageurs SIMBIO-SYS (Spectrometer and Imagers for MPO BepiColombo-Integrated Observatory SYStem) composé d’une caméra haute résolution (HRIC), d’une caméra stéréoscopique (STC) et d’un imageur hyperspectral visible et proche-infrarouge (VIHI). Ces instruments devraient profondément modifier nos connaissances de la composition et de la géomorphologie de la surface de Mercure. Ma thèse a consisté à participer à la définition et à la mise en place des caractéristiques et des fonctionnalités du dispositif expérimental d'étalonnage qui se compose principalement d’une cuve à vide contenant les instruments, d’un banc optique rassemblant les sources d'étalonnage et les éléments optiques qui reconstituent les conditions d'observation de Mercure, des interfaces mécaniques permettant le positionnement de l'expérience à l'intérieur de la cuve, des interfaces thermiques visant à explorer les températures de fonctionnement des différentes parties des expériences, des interfaces informatiques assurant la communication avec l'expérience et le pilotage du dispositif d'étalonnage en fonction des tests à réaliser. J’ai modélisés et validé expérimentalement certaines performances du dispositif. Enfin, j’ai défini en étroite collaboration avec les équipes italiennes co-responsables des trois instruments les différentes séquences d’étalonnage qui seront utilisées lors de l’étalonnage

The impact of SARS-CoV-2 in dementia across Latin America : A call for an urgent regional plan and coordinated response

The SARS-CoV-2 global pandemic will disproportionately impact countries with weak economies and vulnerable populations including people with dementia. Latin American and Caribbean countries (LACs) are burdened with unstable economic development, fragile health systems, massive economic disparities, and a high prevalence of dementia. Here, we underscore the selective impact of SARS-CoV-2 on dementia among LACs, the specific strain on health systems devoted to dementia, and the subsequent effect of increasing inequalities among those with dementia in the region. Implementation of best practices for mitigation and containment faces particularly steep challenges in LACs. Based upon our consideration of these issues, we urgently call for a coordinated action plan, including the development of inexpensive mass testing and multilevel regional coordination for dementia care and related actions. Brain health diplomacy should lead to a shared and escalated response across the region, coordinating leadership, and triangulation between governments and international multilateral networks

Prospective individual patient data meta-analysis of two randomized trials on convalescent plasma for COVID-19 outpatients

Data on convalescent plasma (CP) treatment in COVID-19 outpatients are scarce. We aimed to assess whether CP administered during the first week of symptoms reduced the disease progression or risk of hospitalization of outpatients. Two multicenter, double-blind randomized trials (NCT04621123, NCT04589949) were merged with data pooling starting when = 50 years and symptomatic for <= 7days were included. The intervention consisted of 200-300mL of CP with a predefined minimum level of antibodies. Primary endpoints were a 5-point disease severity scale and a composite of hospitalization or death by 28 days. Amongst the 797 patients included, 390 received CP and 392 placebo; they had a median age of 58 years, 1 comorbidity, 5 days symptoms and 93% had negative IgG antibody-test. Seventy-four patients were hospitalized, 6 required mechanical ventilation and 3 died. The odds ratio (OR) of CP for improved disease severity scale was 0.936 (credible interval (CI) 0.667-1.311); OR for hospitalization or death was 0.919 (CI 0.592-1.416). CP effect on hospital admission or death was largest in patients with <= 5 days of symptoms (OR 0.658, 95%CI 0.394-1.085). CP did not decrease the time to full symptom resolution

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity