Thermophysical Change Detection on the Moon with the Lunar Reconnaissance Orbiter Diviner sensor

The Moon is an archive of the history of the Solar System, as it has recorded and preserved physical events that have occurred over billions of years. NASA’s Lunar Reconnaissance Orbiter (LRO) has been studying the lunar surface for more than 13 years, and its datasets contain valuable information about the evolution of the Moon. However, the vast amount and heterogeneous nature of data collected by LRO make the extraction of scientific insights very challenging - in the past most analyses relied on human review. Here, we present NEPHTHYS, an automated solution for discovering thermophysical changes on the surface using one of LRO’s largest datasets: the thermal data collected by its Diviner instrument. Specifically, NEPHTHYS is able to perform systematic, efficient, and large-scale change detection of present-day impact craters on the surface. Further work could enable more comprehensive studies of lunar surface impact flux rates and surface evolution rates, providing critical new information for future missions

Thermophysical Change Detection on the Moon with the Lunar Reconnaissance Orbiter Diviner sensor

The Moon is an archive of the history of the Solar System, as it has recorded and preserved physical events that have occurred over billions of years. NASA’s Lunar Reconnaissance Orbiter (LRO) has been studying the lunar surface for more than 13 years, and its datasets contain valuable information about the evolution of the Moon. However, the vast amount and heterogeneous nature of data collected by LRO make the extraction of scientific insights very challenging - in the past most analyses relied on human review. Here, we present NEPHTHYS, an automated solution for discovering thermophysical changes on the surface using one of LRO’s largest datasets: the thermal data collected by its Diviner instrument. Specifically, NEPHTHYS is able to perform systematic, efficient, and large-scale change detection of present-day impact craters on the surface. Further work could enable more comprehensive studies of lunar surface impact flux rates and surface evolution rates, providing critical new information for future missions

High Voltage Electrical Power System Architecture optimized for electrical propulsion and high power payload

International audienceThere is a large design variety of power buses, with voltage levels typically ranging from 28 to 100V. This state-of-art is well adapted to past and current needs in term of power conditioning and disctribution for science and telecommunication satellites. NEvertheless, a short-term need is rising for higher operating voltages, especially for the new electric propulsion systems and high-power payloads. The currently available solutions are to add DC/DC converters inisde echa user equipement to generate all its necessary internal supply lines for the satellite primary power bus. For high power/high voltage loads, this DC/DC stage leads to power dissipation and lowers the overall efficiency of the power chain. A major step forward would be to increase the voltage directly at the level of the primary bus in order to remove some voltage conversion stages leading to lower mass, cost, volume and power dissipation. The work performed within the European Union H2020 project "HV-EPSA" was aimed to study benefits and impact of the implementation of a bus voltage from 300V to 600V, including solar array, solar array drive mechnism, power conditioning and distribution, Hall effect thruster with direct drive topology, battery and harnesses. The main problematic to solve were arcing at high voltage/low pressure (Paschen law), interaction between plasma (natural and from plasmic propulsion) and solar arrays, and distribution function using GaN mosfet. Several test campaigns were performed and the results are presented in the paper.Il existe une grande variété de conception de bus d'alimentation, avec des niveaux de tension allant généralement de 28 à 100 V. Cet état de l'art est bien adapté aux besoins passés et actuels en termes de conditionnement et de distribution de puissance pour les satellites scientifiques et de télécommunications. Néanmoins, le besoin à court terme augmente pour des tensions de fonctionnement plus élevées, en particulier pour les nouveaux systèmes de propulsion électrique et les charges utiles à haute puissance. Les solutions actuellement disponibles consistent à ajouter des convertisseurs DC / DC à l'intérieur de chaque équipement utilisateur afin de générer toutes ses lignes d'alimentation interne nécessaires pour le bus d'alimentation primaire du satellite. Pour les charges haute puissance / haute tension, cet étage DC / DC conduit à une dissipation de puissance et diminue l'efficacité globale de la chaîne de puissance. Un grand pas en avant serait d'augmenter la tension directement au niveau du bus primaire afin de supprimer certains étages de conversion de tension conduisant à une diminution de la masse, du coût, du volume et de la dissipation de puissance. Les travaux réalisés dans le cadre du projet H2020 de l'Union européenne "HV-EPSA" visaient à étudier les avantages et l'impact de la mise en œuvre d'une tension de bus de 300V à 600V, y compris les panneaux solaires, les systèmes d'entraînement de panneaux solaires, le conditionnement et la distribution de l'énergie, le propulseur à effet Hall avec topologie à entraînement direct, batterie et cablâge. Les principaux problèmes à résoudre étaient les arcs à haute tension / basse pression (loi de Paschen), l'interaction entre le plasma (naturel et de propulsion plasmique) et les panneaux solaires, et la fonction de distribution à l'aide du mosfet GaN. Plusieurs campagnes de tests ont été réalisées et les résultats sont présentés dans l'article