Embedded Imaging Sonar Simulator for AUV Localisation

This paper presents the new RTAC acoustic simulator aimed at embedded use on low power GPUs. The purpose of this simulator is to be used for relocalisation tasks based on front scan sonars for Autonomous Underwater Vehicles in already mapped environments. Relocalisation is to be achieved by registration of the real and estimated sonar images. The RTAC simulator is implemented using the CUDA programming model for a deployment on NVIDIA Jetson. Geometrical accuracy of the simulator was tested by comparing simulated sonar image with their real counterpart acquired in natural environnements. To simulate comparable sonar images, the environment map used in the simulator was generated by a photogrammetry software from optical images acquired at the same location at the sonar images. Results show good geometrical consistency between the real and simulated sonar images and the simulator is able to compute one frame per second on a Jetson TX2 module which is enough for relocalisation purposes

Étude par spectroscopie infrarouge des hydrogéno et deutériocarbonates de rubidium et de césium et des sesquicarbonates de potassium et de rubidium

Les spectres infrarouges des composés RbHCO3, RbDCO3, CsHCO3 et CsDCO3 sont enregistrés entre 4 000 et 625 cm–1 à 20°C et à — 180°C. On propose une attribution des bandes, par analogie avec l’hydrogénocarbonate de potassium. Dans ces sels, les ions HCO3– forment des dimères fermés (HCO3)22–. Les sels K2CO3, KHCO3, 2H2O et Rb2CO3, RbHCO3, 2 H2O ont été préparés : leurs spectres infrarouges, interprétés par analogie avec celui du sesquicarbonate de sodium, suggèrent l’existence d’ions (CO3HCO3)3–

Étude comparée par spectroscopie infrarouge des caractères donneur et accepteur de proton de la diphénylcétimine

Les constantes d'association de la diphénylcétimine évaluées ici avec le diméthylsulfoxyde, l'hexaméthylphosphorotria mide, le trifluoroéthanol et le parachlorophénol dans le tétrachlorure de carbone à 25 °C environ, permettent de comparer le pouvoir donneur ou accepteur de proton de cette imine à celui d'autres composés. En outre, on peut interpréter l'autoassociation de la diphénylcétimine en solution dans le tétrachlorure de carbone au moyen du modèle de COGGESHALL et SAÏER jusqu'à 2,5 M

Quantifying the mixing of trade‐wind cumulus during the NEPHELAE‐EUREC4A field campaign with remotely piloted aircraft

International audienceAbstract During the Network for studying Entrainment and microPHysics of cLouds using Adaptive Exploration (NEPHELAE)–ElUcidating the RolE of Cloud–Circulation Coupling in ClimAte (EUREC4A) field campaign in January and February 2020 in Barbados, remotely piloted aircraft (RPA) were implemented to characterise the structures of trade‐wind cumulus for a total of 40 flights. Two observation methods were tested: one making racetracks to get statistics on the cumulus clouds and a new sampling strategy using sensor‐driven adaptive sampling to track an individual cloud autonomously throughout its lifetime. It appears from the statistics that there are two types of cohabiting cloud population, with small‐diameter clouds (transect lengths less than 500 m) being less buoyant than larger clouds (transect lengths greater than 500 m). Also, this statistical study shows that cumulus clouds do not have an adiabatic core. These results are compared with individual clouds tracked by adaptive sampling, which also show that the core of the cumulus clouds is diluted by the environment. A comparison with high‐resolution large‐eddy simulations shows that these numerical studies tend to underestimate mixing in the whole cloud

Use of Large-Eddy simulations to design an adaptive sampling strategy to assess cumulus cloud heterogeneities by Remotely Piloted Aircraft

Trade wind cumulus clouds have a significant impact on the earth's radiative balance, due to their ubiquitous presence and significant coverage in subtropical regions. Many numerical studies and field campaigns have focused on better understanding the thermodynamic and macroscopic properties of cumulus clouds with ground-based and satellite remote sensing as well as in-situ observations. Aircraft flights have provided a significant contribution, but their resolution remains limited by rectilinear transects and fragmented temporal data of individual clouds. To provide a higher spatial and temporal resolution, Remotely Piloted Aircraft (RPA) can now be employed for direct observations, using numerous technological advances, to map the microphysical cloud structure and to study entrainment mixing. In fact, the numerical representation of mixing processes between a cloud and the surrounding air has been a key issue in model parameterizations for decades. To better study these mixing processes as well as their impacts on cloud microphysical properties, the manuscript aims to improve exploration strategies that can be implemented by a fleet of RPAs. Here, we use a Large-Eddy simulation (LES) of oceanic cumulus clouds to design adaptive sampling strategies. An implementation of the RPA flight simulator within high-frequency LES outputs (every 5 s) allows to track individual clouds. A Rosette sampling strategy is used to explore clouds of different sizes, static in time and space. The adaptive sampling carried out by these explorations is optimized using one ors two RPAs and with or without Gaussian Process Regression (GPR) mapping, 1by comparing the results obtained with those of a reference simulation, in particular the total liquid water content (LWC) and the LWC distributions in a horizontal cross section. Also, a sensitivity test of lengthscale for GPR mapping is performed. The results of exploring a static cloud are then extended to a dynamic case of a cloud evolving with time, to assess the application of this exploration strategy to study the evolution of cloud heterogeneities

Study of thermodynamic properties of trade-wind cumulus clouds with Remotely Piloted Aircrafts during the EUREC4A field campaign

International audienceTrade wind cumulus clouds have a significant impact on the earth's radiative balance, due to their extensive coverage in subtropical regions but due to their characteristic size are still parameterized.<br>The feedback of low clouds on the climate system as well as biases still existing in their representation of Global Climate Models (GCMs) results in a climatic response with relatively large uncertainty and induce a significant divergence in GCMs. Many studies and campaigns have focused on a better understanding of the thermodynamic and macroscopic properties of cumulus clouds with ground-based and satellite-based remote sensing<br>and also in-situ observations from aircraft flights, but few provide information on the three-dimensional properties of individual cumulus clouds. Our understanding of cumulus clouds is also based on high-resolution numerical simulations (LES: 25m, 5m of resolution) that reproduce the<br>average characteristics of cumulus clouds fairly reliably, yet these simulations still depend on parametrizations (turbulence and microphysics).<br>The development of a fleet the sampling of RPAs (Remotely Piloted Aircraft) contributes to the increase in the resolution of the sampling of the evolution of cloud microphysical properties. Recent studies have permitted to have an autonomous adaptive sampling and a mapping using Gaussian<br>Process Regression to interpolate missed values during exploration.<br>An experimental strategy has been developed and tested in a cumulus cloud field simulated in a LES simulation with the Meso-NH model by implementing a simulator of RPA flights. During the EUREC4A field campaign in Barbados in January-February, more than forty RPAs flights have been conducted and thermodynamic properties of cumulus clouds were studied in three dimensions using miniaturized instruments installed on-board (PTU probe, cloud sensor). We validate first the results of cloud sensor with an other microphysics instrument. Several clouds were followed for about ten minutes and their thermodynamic evolution have been compared to cumulus clouds simulated in the LES

Study of thermodynamic properties of cumulus clouds: from strategy design in numerical simulation to application during a measurement campaign

International audienc

Field report: deployment of a fleet of drones for cloud exploration

International audienceDrones are commonly used for many civil applications and the procedures to operate them have evolved during the past years to make them accessible to those with limited piloting skills in several scenarios. However, the deployment of a fleet in the context of scientific research can lead to complex situations that require an important preparation in terms of logistics, permission to fly from authorities, and coordination during the flights. This paper is a field report of the flight campaign held end of January 2020 at the Barbados Island as part of the NEPHELAE project. The main objectives of the project were to fly into trade wind cumulus clouds to understand the microphysical processes involved in their evolution, as well as to provide a proof of concept of sensor-based adaptive navigation patterns to optimize the data collection. After presenting the overall flight strategy and the context of operation, the main challenges and the solutions to address them will be presented, to conclude with the evaluation of some technical evolution developed from these experiments

Experimental flights of adaptive patterns for cloud exploration with UAVs

International audienceThis work presents the deployment of UAVs for the exploration of clouds, from the system architecture and simulation tests to a real-flight campaign and trajectory analyzes. Thanks to their small size and low altitude, light UAVs have proven to be adapted for in-situ cloud data collection. The short life time of the clouds and limited endurance of the planes require to focus on the area of maximum interest to gather relevant data. Based on previous work on cloud adaptive sampling, the article focuses on the overall system architecture, the improvements made to the system based on preliminary tests and simulations, and finally the results of a field campaign. The Barbados experimental flight campaign confirmed the capacity of the system to map clouds and to collect relevant data in dynamic environment, and highlighted areas for improvement

The Erfoud dataset: a comprehensive multi-camera and Lidar data collection for planetary exploration

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