7 research outputs found
The CANVAS Mission: Quantifying the Very-Low-Frequency Radio Energy Input from the Ground into the Earth\u27s Magnetosphere
Very-low-frequency (VLF) electromagnetic waves, emitted by ground-based sources including lightning and VLF transmitters, can impact the lower ionosphere and magnetosphere through their interaction with the local plasma and energetic particle environments. Quantifying the impacts of these waves requires an accurate assessment of the propagation and attenuation of these waves. The Climatology of Anthropogenic and Natural VLF wave Activity in Space (CANVAS) mission is designed to measure VLF waves in low Earth orbit originating from these ground-based sources. The mission aims to characterize the VLF environment in low Earth orbit to address two main goals: i) constrain the VLF wave injection from the ground into the magnetosphere, and ii) improve models of VLF wave attenuation during propagation through the ionosphere.
CANVAS will measure VLF waves using three search coil magnetometers and two electric field dipole antennas that comprise its payload. The search coils are integrated into a 3D-printed Carbon PEEK holder, along with the magnetic field preamplifier board. The search coil system is deployed 1 meter from the spacecraft using a carbon fiber deployable boom, in order to isolate the sensitive search coils from spacecraft noise. The electric field system is composed of four 40 cm monopole antennas, making two orthogonal dipole antennas, integrated into the spacecraft âcrownâ, along with a custom preamplifier circuit for each monopole. The payload is completed by a custom analog receiver board, providing amplification, anti-alias filtering, and centering for the analog-to-digital converters (ADCs); and a custom digital board, which includes an FPGA for onboard signal processing. Spectral data spanning 0.3â40 kHz are saved at 1-second cadence, providing a continuous âfast surveyâ data mode for the duration of the mission.
The CANVAS spacecraft is a 4U CubeSat, 10 Ă 10 Ă 45 cm and under 6 kg. In addition to the 1-meter deployable carbon fiber boom and electric field antennas, the spacecraft incorporates deployable solar panels and a monopole antenna for UHF communications. Data is downlinked in S-band. The spacecraft structure and avionics are custom-designed and built at CU Boulder, while the radios and attitude determination and control system (ADCS) are vendor-supplied components.
The CANVAS mission is designed to operate at âŒ500 km altitude in a moderate-inclination orbit (âŒ50 degrees), to ensure global coverage of lightning-generating regions; most lightning globally is confined to within ±50 degrees latitude. Spectra at 1-second cadence account for âŒ424 MB of data per day, after housekeeping and encoding overhead. A one-year mission will ensure seasonal coverage to observe the Marshall 1 36th Annual Small Satellite Conference variability in global lightning activity.
This paper presents a detailed overview of the CANVAS science goals, payload, spacecraft, and mission. The instrument is now completed and undergoing functional testing and performance characterization, and the spacecraft is beginning integration, expected to be completed in Fall 2022. The CANVAS mission will be ready to launch in early 2023
Le soleil en ligne de mire
International audienceReconnu internationalement pour la trĂšs haute technologie de ses instruments de mesure, le LPC2E est Ă bord de la missionSolar Orbiter pour un long voyage avant lâexploration du proche environnement solaire
AC magnetic field measurements onboard Cross-Scale: scientific objectives and instrument design
International audienceThe ACB search-coil magnetometer for Cross-Scale will measure three components of the AC magnetic field up to 4 kHz, and one component up to 100 kHz. Turbulent and coherent magnetic field fluctuations in that frequency range play an important role in the acceleration, scattering, and thermalisation of particles. ACB will, together with the other instruments of the Cross-Scale wave consortium, allow to address the key science objectives associated with plasma waves. Here, we list some of the important issues, based on the experience drawn from Cluster, and describe the instrument
Large amplification of the sensitivity of symmetric-response magnetic tunnel junctions with a high gain flux concentrator
International audienceMiniaturized, ultra-sensitive and easily integrable magnetometers are needed for many applications like space exploration or medical survey. In this study, we combine innovative magnetic tunnel junctions having a symmetric resistance-field (RâH) response with a high gain flux concentrator. In our junctions, the magnetization of the free layer (FL) is stabilized in an anti-parallel configuration with respect to that of the reference layer. This configuration is achieved by using a soft exchange pinning of the FL. We precisely adjust the exchange field value with a dusting layer of ruthenium used to weakly decouple the magnetization of the FL from the local moments of the antiferromagnet. In order to improve the junction's sensitivity, we study the influence of the exchange field value and of the shape anisotropy on the even-function RâH response. In particular, we compare circular junctions with elliptic or rectangular junctions of various aspect ratios and orientations. We find that the sensitivity of the junctions increases when reducing the soft-pinning exchange field and by using junctions with an elongated shape in the direction of the applied field. Finally, we were able to further increase the sensitivity by a factor 440 due to a flux concentrator placed around the junction by electrochemical deposition of NiFe. Its design is optimized (elongated shape, 5â7âÎŒm thickness and 10âÎŒm air-gap) in order to obtain this very high gain. The complete sensor system composed of these magnetic tunnel junctions and the flux concentrator allows to reach sensitivities larger than 1000%/mT
The Search-coil Magnetometer for the THOR mission
International audienceTurbulence Heating ObserveR (THOR) is the first mission ever flown in space fully dedicated to plasma turbulence. The search-coil magnetometer (SCM) of THOR is a triaxial dual-band antenna dedicated to measuring the magnetic field fluctuations in the frequency range [1Hz,4kHz] and [1,200]kHz. THOR/SCM has a long heritage from earlier space missions such as Cluster, Themis, MMS, BepiColombo, Taranis, Solar orbiter and Solar Probe. In comparison to those missions, the SCM of THOR has a higher sensitivity level, which makes it capable of measuring very low amplitude magnetic fluctuations, in particular in the solar wind. Those measurements are crucial to address the problem of turbulence and energy dissipation at electron scales, a central goal of the THOR mission
First observations of the Search Coil Magnetometer on Solar Orbiter / RPW: results and performances
International audienc
Potent human broadly SARS-CoV-2âneutralizing IgA and IgG antibodies effective against Omicron BA.1 and BA.2
International audienceMemory B-cell and antibody responses to the SARS-CoV-2 spike protein contribute to long-term immune protection against severe COVID-19, which can also be prevented by antibody-based interventions. Here, wide SARS-CoV-2 immunoprofiling in Wuhan COVID-19 convalescents combining serological, cellular, and monoclonal antibody explorations revealed humoral immunity coordination. Detailed characterization of a hundred SARS-CoV-2 spike memory B-cell monoclonal antibodies uncovered diversity in their repertoire and antiviral functions. The latter were influenced by the targeted spike region with strong Fc-dependent effectors to the S2 subunit and potent neutralizers to the receptor-binding domain. Amongst those, Cv2.1169 and Cv2.3194 antibodies cross-neutralized SARS-CoV-2 variants of concern, including Omicron BA.1 and BA.2. Cv2.1169, isolated from a mucosa-derived IgA memory B cell demonstrated potency boost as IgA dimers and therapeutic efficacy as IgG antibodies in animal models. Structural data provided mechanistic clues to Cv2.1169 potency and breadth. Thus, potent broadly neutralizing IgA antibodies elicited in mucosal tissues can stem SARS-CoV-2 infection, and Cv2.1169 and Cv2.3194 are prime candidates for COVID-19 prevention and treatment