The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
Hikaru Nagata - One of the best experts on this subject based on the ideXlab platform.
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Bidirectional Interleaved PWM Converter with High Voltage-Conversion Ratio and Automatic Current Balancing Capability for Single-Cell Battery Power System in Small Scientific Satellites
Energies, 2018Co-Authors: Masatoshi Uno, Masahiko Inoue, Yusuke Sato, Hikaru NagataAbstract:Single-cell battery power systems are a promising bus architecture for small Scientific Satellites. However, to bridge the huge voltage gap between a single-cell battery and power bus, bidirectional converters with a high voltage conversion ratio and a large current capability for the low-voltage side are necessary. This article proposes a bidirectional interleaved pulse width modulation (PWM) converter with a high voltage conversion ratio and an automatic current balancing capability. By adding capacitors to conventional interleaved PWM converters, not only are inductor currents automatically balanced without feedback control or current sensors, but also voltage conversion ratios at a given duty cycle can be enhanced. Furthermore, the added capacitors can reduce voltage stresses of switches and charged-discharged energies of inductors, realizing more efficient power conversion and reduced circuit volume in comparison with conventional converters. A 100-W prototype was built for experimental verification, and results demonstrated the fundamental characteristics and efficacy of the proposed converter.
Evandro Marconi rocco - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of the Terrestrial Albedo Applied to Some Scientific Missions
Space Science Reviews, 2010Co-Authors: Evandro Marconi roccoAbstract:Using the Earth albedo model and the orbital dynamics model developed as part of the First Look Project (Fast Initial In-Orbit Identification of Scientific Satellites) the terrestrial albedo is evaluated considering the orbits of some Scientific missions as Gravity Probe B, MICROSCOPE and STEP. The model of the Earth albedo is based on the reflectivity data measured by NASA’s Earth Probe satellite, which is part of the TOMS project (Total Ozone Mapping Spectrometer). The reflectivity data are available daily, on line at the TOMS website, and they fluctuate because of changes in clouds and ice coverage and seasonal changes. The data resolution partitions the Earth surface into a number of cells. The incident irradiance on each cell is used to calculate total radiant flux from the cell. With the radiant flux from each cell, the irradiance at the satellite is calculated.
R K Barry - One of the best experts on this subject based on the ideXlab platform.
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conversion from full array shunt to partial array shunt topology for two small explorer class near earth orbiting Scientific Satellites
Intersociety Energy Conversion Engineering Conference, 1996Co-Authors: R K BarryAbstract:The Space Power Applications Branch of NASA, Goddard Space Flight Center is designing an improved power subsystem for two Small Explorer-class (SMEX) spacecraft. These spacecraft, the Transition Region And Coronal Explorer (TRACE), and the Widefield infrared Explorer (WIRE) are technological descendants of the SMEX Submillimeter Wave Astronomy Satellite (SWAS) spacecraft and share much of its heritage. Refinements have been made to the SWAS power subsystem architecture to take advantage of partial array shunt technology that will make it more dependable and efficient. Additionally, by identifying and targeting the solar array as the subsystem schedule and budget "tall pole" and designing to reduce that particular component's complexity, the team will provide a spacecraft power subsystem of increased reliability and reduced cost while proving technology for future small Explorer missions.
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conversion from full array shunt to partial array shunt topology for wo Scientific Satellites small explorer class near earth orbiting
1996Co-Authors: R K BarryAbstract:The Space Power Applications Branch of NASA, Goddard Space Flight Center is designing an improved power subsystem for two Small Explorer-class (SMEX) spacecraft. These spacecraft, the Transition Region And Coronal Explorer WCE), and the Widefield intiared Explorer (WIRE) are technological descendants of the SMEX Submillimeter Wave Astronomy Satellite (SWAS) spacecraft and share much of its heritage. Refinements have been made to the SWAS power subsystem architecture to take advantage of partial array shunt technology that will make it more dependable and efficient. Additionally, by identeing and targeting the solar array as the subsystem schedule and budget "tall pole" and designing to reduce that particular component's complexity, the team wiIl provide a spacecraft power subsystem of increased reliability and reduced cost while proving technology for fiture small explorer missions. The change prescribed for the TRACE and WIRE power systems is to move from the original design that shunted the full solar array, to a refinement that shunts only a portion of it. The first benefit derived &om this change is enhanced system reliability. In the original design, large foil resistors on the back of the solar array were required to dissipate the power generated by the fidl array. Through carefil analysis it was demonstrated that in the partial array shunt system no such resistors were needed. The FET switches themselves can dissipate the power with greater than 60% margin over NASA derating guidelines. As a consequence this allowed the choice between removing the shunt resistors, resulting in a modest reduction in mass and a significant reduction in solar array and power bus complexity, or leaving in the shunt resistors and reaping an increase in reliability by having cooler-running FET switches. After showing that the FET junction temperatures
Masatoshi Uno - One of the best experts on this subject based on the ideXlab platform.
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Bidirectional Interleaved PWM Converter with High Voltage-Conversion Ratio and Automatic Current Balancing Capability for Single-Cell Battery Power System in Small Scientific Satellites
Energies, 2018Co-Authors: Masatoshi Uno, Masahiko Inoue, Yusuke Sato, Hikaru NagataAbstract:Single-cell battery power systems are a promising bus architecture for small Scientific Satellites. However, to bridge the huge voltage gap between a single-cell battery and power bus, bidirectional converters with a high voltage conversion ratio and a large current capability for the low-voltage side are necessary. This article proposes a bidirectional interleaved pulse width modulation (PWM) converter with a high voltage conversion ratio and an automatic current balancing capability. By adding capacitors to conventional interleaved PWM converters, not only are inductor currents automatically balanced without feedback control or current sensors, but also voltage conversion ratios at a given duty cycle can be enhanced. Furthermore, the added capacitors can reduce voltage stresses of switches and charged-discharged energies of inductors, realizing more efficient power conversion and reduced circuit volume in comparison with conventional converters. A 100-W prototype was built for experimental verification, and results demonstrated the fundamental characteristics and efficacy of the proposed converter.
Joe Giacalone - One of the best experts on this subject based on the ideXlab platform.
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Large gradual solar energetic particle events
Living Reviews in Solar Physics, 2016Co-Authors: Mihir Desai, Joe GiacaloneAbstract:Solar energetic particles, or SEPs, from suprathermal (few keV) up to relativistic ( $$\sim $$ ∼ few GeV) energies are accelerated near the Sun in at least two ways: (1) by magnetic reconnection-driven processes during solar flares resulting in impulsive SEPs, and (2) at fast coronal-mass-ejection-driven shock waves that produce large gradual SEP events. Large gradual SEP events are of particular interest because the accompanying high-energy ( $${>}10$$ > 10 s MeV) protons pose serious radiation threats to human explorers living and working beyond low-Earth orbit and to technological assets such as communications and Scientific Satellites in space. However, a complete understanding of these large SEP events has eluded us primarily because their properties, as observed in Earth orbit, are smeared due to mixing and contributions from many important physical effects. This paper provides a comprehensive review of the current state of knowledge of these important phenomena, and summarizes some of the key questions that will be addressed by two upcoming missions—NASA’s Solar Probe Plus and ESA’s Solar Orbiter. Both of these missions are designed to directly and repeatedly sample the near-Sun environments where interplanetary scattering and transport effects are significantly reduced, allowing us to discriminate between different acceleration sites and mechanisms and to isolate the contributions of numerous physical processes occurring during large SEP events.