Showing papers by "Japan Aerospace Exploration Agency published in 2021"
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Nagoya University1, University of Tokyo2, Kyoto University3, Hosei University4, University of Electro-Communications5, Japan Aerospace Exploration Agency6, Yukawa Institute for Theoretical Physics7, University of Birmingham8, Hirosaki University9, Nihon University10, Fukuoka University11, Tokyo Keizai University12, Otemon Gakuin University13, Kyoto Sangyo University14, Rikkyo University15, College of Industrial Technology16, Yokohama National University17, National Institute of Information and Communications Technology18, Osaka City University19, Osaka University20, Leibniz University of Hanover21, Liverpool John Moores University22, KEK23, Hiroshima University24, Waseda University25, Ryukoku University26, Niigata University27, Niigata College of Technology28, Max Planck Society29, Osaka Institute of Technology30, Tokyo Institute of Technology31, Nagaoka University of Technology32, University of the Ryukyus33, University of Virginia34, Beijing Normal University35
TL;DR: The Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz as discussed by the authors.
Abstract: The Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO aims at the detection of primordial gravitational waves, which could have been produced during the inflationary period right after the birth of the Universe. There are many other scientific objectives of DECIGO, including the direct measurement of the acceleration of the expansion of the Universe, and reliable and accurate predictions of the timing and locations of neutron star/black hole binary coalescences. DECIGO consists of four clusters of observatories placed in heliocentric orbit. Each cluster consists of three spacecraft, which form three Fabry-Perot Michelson interferometers with an arm length of 1000 km. Three DECIGO clusters will be placed far from each other, and the fourth will be placed in the same position as one of the other three to obtain correlation signals for the detection of primordial gravitational waves. We plan to launch B-DECIGO, which is a scientific pathfinder for DECIGO, before DECIGO in the 2030s to demonstrate the technologies required for DECIGO, as well as to obtain fruitful scientific results to further expand multi-messenger astronomy.
101 citations
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Netherlands Institute for Space Research1, Heidelberg University2, Karlsruhe Institute of Technology3, Finnish Meteorological Institute4, University of Toronto5, National Institute of Water and Atmospheric Research6, Japan Aerospace Exploration Agency7, University of Wollongong8, California Institute of Technology9, University of Bremen10
TL;DR: In this paper, the authors describe the improvements that have been implemented to retrieve CH 4 from TROPOMI using the RemoTeC full-physics algorithm, which features a constant regularization scheme of the inversion that stabilizes the retrieval and yields less scatter in the data and includes a higher resolution surface altitude database.
Abstract: . The TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor (S5-P) satellite provides methane (CH 4 ) measurements with high accuracy and exceptional temporal and spatial resolution and sampling. TROPOMI CH 4 measurements are highly valuable to constrain emissions inventories and for trend analysis, with strict requirements on the data quality. This study describes the improvements that we have implemented to retrieve CH 4 from TROPOMI using the RemoTeC full-physics algorithm. The updated retrieval algorithm features a constant regularization scheme of the inversion that stabilizes the retrieval and yields less scatter in the data and includes a higher resolution surface altitude database. We have tested the impact of three state-of-the-art molecular spectroscopic databases (HITRAN 2008, HITRAN 2016 and Scientific Exploitation of Operational Missions – Improved Atmospheric Spectroscopy Databases SEOM-IAS) and found that SEOM-IAS provides the best fitting results. The most relevant update in the TROPOMI XCH 4 data product is the implementation of an a posteriori correction fully independent of any reference data that is more accurate and corrects for the underestimation at low surface albedo scenes and the overestimation at high surface albedo scenes. After applying the correction, the albedo dependence is removed to a large extent in the TROPOMI versus satellite (Greenhouse gases Observing SATellite – GOSAT) and TROPOMI versus ground-based observations (Total Carbon Column Observing Network – TCCON) comparison, which is an independent verification of the correction scheme. We validate 2 years of TROPOMI CH 4 data that show the good agreement of the updated TROPOMI CH 4 with TCCON ( − 3.4 ± 5.6 ppb) and GOSAT ( − 10.3 ± 16.8 ppb) (mean bias and standard deviation). Low- and high-albedo scenes as well as snow-covered scenes are the most challenging for the CH 4 retrieval algorithm, and although the a posteriori correction accounts for most of the bias, there is a need to further investigate the underlying cause.
96 citations
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Hirosaki University1, Nanjing University2, Chinese Academy of Sciences3, Tibet University4, Hebei Normal University5, Shandong University6, Southwest Jiaotong University7, Kanagawa University8, Utsunomiya University9, Shibaura Institute of Technology10, Yokohama National University11, Shinshu University12, University of Tokyo13, Japan Aerospace Exploration Agency14, China Meteorological Administration15, University of Science and Technology of China16, Tsinghua University17, National Institute of Informatics18, National Institute of Information and Communications Technology19, China University of Petroleum20, College of Industrial Technology21, Konan University22, Shonan Institute of Technology23, Waseda University24, Japan Atomic Energy Agency25
TL;DR: For the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk was reported in this paper, which is consistent with expectations from the hadronic emission scenario in which gamma rays originate from the decay of π 0's produced through the interaction of protons with the interstellar medium.
Abstract: We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of π^{0}'s produced through the interaction of protons with the interstellar medium in the Galaxy This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk
95 citations
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Belgian Institute for Space Aeronomy1, California Institute of Technology2, Karlsruhe Institute of Technology3, Netherlands Institute for Space Research4, University of Bremen5, European Space Agency6, University of Wollongong7, Ludwig Maximilian University of Munich8, Max Planck Society9, German Aerospace Center10, International Agency for Research on Cancer11, National Autonomous University of Mexico12, National Center for Atmospheric Research13, Finnish Meteorological Institute14, Ames Research Center15, University of Paris16, University of Liège17, Saint Petersburg State University18, Chalmers University of Technology19, University of La Réunion20, National Institute for Environmental Studies21, Nagoya University22, National Institute of Water and Atmospheric Research23, University of Toronto24, The Cyprus Institute25, Japan Aerospace Exploration Agency26, Chinese Academy of Sciences27, Remote Sensing Center28
TL;DR: In this article, the Sentinel-5 Precursor (S5P) data were validated using global Total Carbon Column Observing Network (TCCON) and Infrared Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC-IRWG) network data, accounting for a prior alignment and smoothing uncertainties in the validation.
Abstract: . The Sentinel-5 Precursor (S5P) mission with the TROPOspheric Monitoring Instrument (TROPOMI) on board has been measuring solar radiation backscattered by the Earth's atmosphere and surface since its launch on 13 October 2017. In this paper, we present for the first time the S5P operational methane ( CH4 ) and carbon monoxide (CO) products' validation results covering a period of about 3 years using global Total Carbon Column Observing Network (TCCON) and Infrared Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC-IRWG) network data, accounting for a priori alignment and smoothing uncertainties in the validation, and testing the sensitivity of validation results towards the application of advanced co-location criteria. We found that the S5P standard and bias-corrected CH4 data over land surface for the recommended quality filtering fulfil the mission requirements. The systematic difference of the bias-corrected total column-averaged dry air mole fraction of methane ( XCH4 ) data with respect to TCCON data is - 0.26 ± 0.56 % in comparison to - 0.68 ± 0.74 % for the standard XCH4 data, with a correlation of 0.6 for most stations. The bias shows a seasonal dependence. We found that the S5P CO data over all surfaces for the recommended quality filtering generally fulfil the missions requirements, with a few exceptions, which are mostly due to co-location mismatches and limited availability of data. The systematic difference between the S5P total column-averaged dry air mole fraction of carbon monoxide (XCO) and the TCCON data is on average 9.22±3.45 % (standard TCCON XCO) and 2.45±3.38 % (unscaled TCCON XCO). We found that the systematic difference between the S5P CO column and NDACC CO column (excluding two outlier stations) is on average 6.5±3.54 %. We found a correlation of above 0.9 for most TCCON and NDACC stations. The study shows the high quality of S5P CH4 and CO data by validating the products against reference global TCCON and NDACC stations covering a wide range of latitudinal bands, atmospheric conditions and surface conditions.
50 citations
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University of Tokyo1, Spanish National Research Council2, University of La Laguna3, Japan Aerospace Exploration Agency4, Chiba Institute of Technology5, Tohoku University6, Brown University7, Romanian Academy8, Kindai University9, University of Aizu10, Rikkyo University11, Kōchi University12, National Institute of Advanced Industrial Science and Technology13, Meiji University14, Planetary Science Institute15, Kobe University16, Osaka University17, University of Paris18, Centre national de la recherche scientifique19, Nagoya University20, Graduate University for Advanced Studies21, Mitsubishi Electric22, University of Liverpool23, Seoul National University24, Hiroshima University25
TL;DR: In this article, the authors used Hayabusa2 observations to show that some of the bright boulders on the dark, carbonaceous (C-type) asteroid Ryugu4 are remnants of an impactor with a different composition as well as an anomalous portion of its parent body.
Abstract: The asteroid (162173) Ryugu and other rubble-pile asteroids are likely re-accumulated fragments of much larger parent bodies that were disrupted by impacts. However, the collisional and orbital pathways from the original parent bodies to subkilometre rubble-pile asteroids are not yet well understood1–3. Here we use Hayabusa2 observations to show that some of the bright boulders on the dark, carbonaceous (C-type) asteroid Ryugu4 are remnants of an impactor with a different composition as well as an anomalous portion of its parent body. The bright boulders on Ryugu can be classified into two spectral groups: most are featureless and similar to Ryugu’s average spectrum4,5, while others show distinct compositional signatures consistent with ordinary chondrites—a class of meteorites that originate from anhydrous silicate-rich asteroids6. The observed anhydrous silicate-like material is likely the result of collisional mixing between Ryugu’s parent body and one or multiple anhydrous silicate-rich asteroid(s) before and during Ryugu’s formation. In addition, the bright boulders with featureless spectra and less ultraviolet upturn are consistent with thermal metamorphism of carbonaceous meteorites7,8. They might sample different thermal-metamorphosed regions, which the returned sample will allow us to verify. Hence, the bright boulders on Ryugu provide new insights into the collisional evolution and accumulation of subkilometre rubble-pile asteroids. The Hayabusa2 team has discovered two types of bright boulder on the dark, carbonaceous asteroid Ryugu. One type has a spectrum consistent with material from an anhydrous silicate-rich asteroid, likely introduced by one or more collisions in Ryugu’s past.
50 citations
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TL;DR: The Japanese Greenhouse gases Observing SATellite-2 (GOSAT-2) as mentioned in this paper has been in orbit since 29 October 2018 and is equipped with a thermal and near-infrared spectrometer.
Abstract: . The Japanese Greenhouse gases Observing SATellite-2
(GOSAT-2), in orbit since 29 October 2018, follows up the GOSAT mission,
itself in orbit since 23 January 2009. GOSAT-2 monitors carbon dioxide and
methane in order to increase our understanding of the global carbon cycle.
It simultaneously measures carbon monoxide emitted from fossil fuel
combustion and biomass burning and permits identification of the amount of
combustion-related carbon. To do this, the satellite utilizes the Thermal
and Near Infrared Sensor for Carbon Observation Fourier-Transform
Spectrometer-2 (TANSO-FTS-2). This spectrometer detects gas absorption spectra
of solar radiation reflected from the Earth's surface in the
shortwave-infrared (SWIR) region as well as the emitted thermal infrared
radiation (TIR) from the ground and the atmosphere. TANSO-FTS-2 can measure
the oxygen A band (0.76 µ m), weak and strong CO 2 bands (1.6 and 2.0 µ m), weak and strong CH 4 bands (1.6 and 2.3 µ m), a weak CO band (2.3 µ m), a mid-wave TIR band (5.5–8.4 µ m), and a long-wave TIR band (8.4–14.3 µ m) with 0.2 cm −1 spectral
sampling intervals. TANSO-FTS-2 is equipped with a solar diffuser target, a
monochromatic light source, and a blackbody for spectral radiance
calibration. These calibration sources permit characterization of
time-dependent instrument changes in orbit. The onboard-recalibrated
instrumental parameters are considered in operational level-1 processing and
released as TANSO-FTS-2 level-1 version 102102 products, which were
officially released on 25 May 2020. This paper provides an overview of the
TANSO-FTS-2 instrument, the level-1 processing, and the first-year in-orbit
performance. To validate the spectral radiance calibration during the first
year of operation, the spectral radiance of the version 102102 product is
compared at temporally coincident and spatially collocated points from
February 2019 to March 2020 with TANSO-FTS on GOSAT for SWIR and with AIRS
on Aqua and IASI on METOP-B for TIR. The spectral radiances measured by
TANSO-FTS and TANSO-FTS-2 agree within 2 % of the averaged bias and 0.5 % standard deviation for SWIR bands. The agreement of brightness
temperature between TANSO-FTS-2 and AIRS–IASI is better than 1 K in the
range from 220 to 320 K. GOSAT-2 not only provides seamless global
CO 2 and CH 4 observation but also observes local emissions and
uptake with an additional CO channel, fully customized sampling patterns,
higher signal-to-noise ratios, and wider pointing angles than GOSAT.
47 citations
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Chinese Academy of Sciences1, Center for Excellence in Education2, Shanghai Normal University3, Nanchang Institute of Technology4, University of Helsinki5, Finnish Meteorological Institute6, University of Oulu7, Northeast Forestry University8, University of Oslo9, Japan Aerospace Exploration Agency10, Hunan University of Science and Technology11
TL;DR: In this article, the authors presented a new permafrost dataset for the Northern Hemisphere (NH), including predictions of the mean annual ground temperature (MAGT) at the zero annual amplitude depth and active layer thickness (ALT) with a 1-km resolution for the period of 2000-2016.
Abstract: . Monitoring of the thermal state of permafrost is important in environmental science and engineering applications. However, such data are generally unavailable mainly due to the lack of ground observations and the uncertainty of traditional physical models. This study produces novel permafrost datasets for the Northern Hemisphere (NH), including predictions of the mean annual ground temperature (MAGT) at the zero annual amplitude depth and active layer thickness (ALT) with a 1-km resolution for the period of 2000–2016, as well as estimates of the probability of permafrost occurrence and permafrost zonation based on hydrothermal conditions. These datasets integrate unprecedentedly large amounts of field data (1,002 boreholes for MAGT and 452 sites for ALT) and multisource geospatial data, especially remote sensing data, using statistical learning modelling with an ensemble strategy. Thus, these data are more accurate than those of previous circumpolar maps (bias = 0.02 ± 0.16 °C, RMSE = 1.32 ± 0.13 °C for MAGT; bias = 2.71 ± 16.46 cm, RMSE = 86.93 ± 19.61 cm for ALT). The datasets suggest that the areal extent of permafrost (MAGT ≤ 0 °C) in the NH, excluding glaciers and lakes, is approximately 15.03 (13.84–19.29) × 106 km2, and the areal extent of permafrost regions (permafrost probability > 0) is approximately 20.14 × 106 km2. The areal fractions of humid, semiarid/subhumid, and arid permafrost regions are 51.84 %, 44.83 %, and 3.33 %, respectively. The areal fractions of cold (≤ −3.0 °C), cool (−3.0 °C to −1.5 °C), and warm (> −1.5 °C) permafrost regions are 37.93 %, 14.35 %, and 47.72 %, respectively. These new datasets based on the most comprehensive field data to date contribute to an updated understanding of the thermal state and zonation of permafrost in the NH. They are potentially useful for various fields, such as in climatology, hydrology, ecology, agriculture, public health, and engineering planning. As a baseline, these datasets are also of great importance for evaluating future changes in MAGT, ALT, permafrost extent, and other spatial features of permafrost in the NH. All of the datasets are published through the National Tibetan Plateau Data Center (TPDC), and the link is https://data.tpdc.ac.cn/en/data/5093d9ff-a5fc-4f10-a53f-c01e7b781368 or https://doi.org/10.11888/Geocry.tpdc.271190 (Ran et al., 2021b).
46 citations
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39 citations
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TL;DR: In this paper, very long baseline interferometry (VLBI) is used to compare two optical clocks located in Japan and Italy through the observation of extragalactic radio sources.
Abstract: The comparison of distant atomic clocks is foundational to international timekeeping, global positioning and tests of fundamental physics. Optical-fibre links allow the most precise optical clocks to be compared, without degradation, over intracontinental distances up to thousands of kilometres, but intercontinental comparisons remain limited by the performance of satellite transfer techniques. Here we show that very long baseline interferometry (VLBI), although originally developed for radio astronomy and geodesy, can overcome this limit and compare remote clocks through the observation of extragalactic radio sources. We developed dedicated transportable VLBI stations that use broadband detection and demonstrate the comparison of two optical clocks located in Italy and Japan separated by 9,000 km. This system demonstrates performance beyond satellite techniques and can pave the way for future long-term stable international clock comparisons. Very long baseline interferometry is used to compare two optical clocks located in Japan and Italy through the observation of extragalactic radio sources. This approach overcomes limitations of the performance of satellite transfer techniques.
35 citations
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University of Aizu1, Brown University2, Graduate University for Advanced Studies3, Kwansei Gakuin University4, Toho University5, Tohoku University6, Tokyo City University7, Ashikaga Institute of Technology8, Chiba Institute of Technology9, University of Paris10, University of Paris-Sud11, Planetary Science Institute12, INAF13, Japan Atomic Energy Agency14, National Institutes of Natural Sciences, Japan15, National Institute for Environmental Studies16, Kobe University17, University of Occupational and Environmental Health Japan18, Japan Aerospace Exploration Agency19, University of Tokyo20, Kōchi University21, Rikkyo University22, University of La Laguna23, National Institute of Advanced Industrial Science and Technology24, Meiji University25, Nihon University26, Hiroshima University27, Seoul National University28, University of Liverpool29, NEC30, Mitsubishi Electric31, Nagoya University32
TL;DR: In this paper, the authors used the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft to investigate exposed subsurface material and test potential effects of radiative heating.
Abstract: Analyses of meteorites and theoretical models indicate that some carbonaceous near-Earth asteroids may have been thermally altered due to radiative heating during close approaches to the Sun1–3. However, the lack of direct measurements on the subsurface doesn’t allow us to distinguish thermal alteration due to radiative heating from parent-body processes. In April 2019, the Hayabusa2 mission successfully completed an artificial impact experiment on the carbonaceous near-Earth asteroid (162173) Ryugu4,5, which provided an opportunity to investigate exposed subsurface material and test potential effects of radiative heating. Here we report observations of Ryugu’s subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. The strength and shape of the OH feature suggests that the subsurface material experienced heating above 300 °C, similar to the surface. In contrast, thermophysical modelling indicates that radiative heating cannot increase the temperature above 200 °C at the estimated excavation depth of 1 m, even at the smallest heliocentric distance possible for Ryugu. This supports the hypothesis that primary thermal alteration occurred on Ryugu’s parent body. Hayabusa2 created an artificial crater on Ryugu to analyse the subsurficial material of the asteroid. Results show that the subsurface is more hydrated than the surface. It experienced alteration processes that can be traced back to Ryugu’s parent body.
35 citations
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European Space Agency1, Istituto di Scienza e Tecnologie dell'Informazione2, International Federation of Accountants3, AXA4, Japan Aerospace Exploration Agency5, University of Southampton6, Chinese Academy of Sciences7, Keldysh Institute of Applied Mathematics8, Bauman Moscow State Technical University9
TL;DR: This cooperative international assessment provides a useful ranking of the most hazardous massive derelicts in low Earth orbit as a prioritized list for remediation to enhance space safety and assure long-term space sustainability.
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31 May 2021••
TL;DR: In this article, the authors present the key issues of current and future requirements for the mapping of global precipitation from satellite sensors can be summarised as providing: 1) sufficiently fine spatial resolutions to capture precipitation-scale systems and reduce the beam-filling effects of the observations; 2) a wide channel diversity for each sensor to cover the range of precipitation types, characteristics and intensities observed across the globe; 3) an observation interval that provides temporal sampling commensurate with the variability of precipitation; and 4) precipitation radars and radiometers in low inclination orbit to provide a
Abstract: To address the need to map precipitation on a global scale a collection of satellites carrying passive microwave (PMW) radiometers has grown over the last 20 years to form a constellation of about 10-12 sensors at any one time. Over the same period, a broad range of science and user communities has become increasingly dependent on the precipitation products provided by these sensors. The constellation presently consists of both conical and cross-track scanning precipitation-capable multi-channel instruments, many of which are beyond their operational and design lifetime but continue to operate through the cooperation of the responsible agencies. The Group on Earth Observations and the Coordinating Group for Meteorological Satellites (CGMS), among other groups, have raised the issue of how a robust, future precipitation constellation should be constructed. The key issues of current and future requirements for the mapping of global precipitation from satellite sensors can be summarised as providing: 1) sufficiently fine spatial resolutions to capture precipitation-scale systems and reduce the beam-filling effects of the observations; 2) a wide channel diversity for each sensor to cover the range of precipitation types, characteristics and intensities observed across the globe; 3) an observation interval that provides temporal sampling commensurate with the variability of precipitation; and 4) precipitation radars and radiometers in low inclination orbit to provide a consistent calibration source, as demonstrated by the first two spaceborne radar/radiometer combinations on the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) mission Core Observatory (CO). These issues are critical in determining the direction of future constellation requirements, while preserving the continuity of the existing constellation necessary for long-term climate-scale studies.
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Nagoya University1, University of Electro-Communications2, Kyoto University3, National Institute of Polar Research4, University of Oulu5, National Institute of Information and Communications Technology6, Japan Aerospace Exploration Agency7, Finnish Meteorological Institute8, University of Tokyo9, Osaka University10, Kanazawa University11, Tohoku University12, Kyushu Institute of Technology13
TL;DR: In this paper, the authors reported unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a pulsating aurorae associated with a weak geomagnetic storm.
Abstract: Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.
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Rikkyo University1, Japan Aerospace Exploration Agency2, University of Tokyo3, Graduate University for Advanced Studies4, Kōchi University5, Spanish National Research Council6, University of Aizu7, National Institute of Advanced Industrial Science and Technology8, Chiba Institute of Technology9, Maebashi Institute of Technology10, Hokkaido Kitami Hokuto High School11, Hokkaido University of Education12, Max Planck Society13, Luleå University of Technology14, German Aerospace Center15, University of Potsdam16, Centre national de la recherche scientifique17, Heidelberg University18, National Institute for Environmental Studies19, Meiji University20, Kwansei Gakuin University21, Toho University22, Kobe University23, Mitsubishi Electric24, NEC25, University of Liverpool26, Seoul National University27, Hiroshima University28, Nagoya University29
TL;DR: In this article, the authors used high-resolution thermal and optical imaging of Ryugu's surface to find high porosity boulders on the floor of fresh small craters ( 70%, which is as high as in cometary bodies) and suggested that these boulders are probably the most pristine parts of the planetesimals that formed Ryugu.
Abstract: Planetesimals—the initial stage of the planetary formation process—are considered to be initially very porous aggregates of dusts1,2, and subsequent thermal and compaction processes reduce their porosity3. The Hayabusa2 spacecraft found that boulders on the surface of asteroid (162173) Ryugu have an average porosity of 30–50% (refs. 4–6), higher than meteorites but lower than cometary nuclei7, which are considered to be remnants of the original planetesimals8. Here, using high-resolution thermal and optical imaging of Ryugu’s surface, we discovered, on the floor of fresh small craters ( 70%, which is as high as in cometary bodies. The artificial crater formed by Hayabusa2’s impact experiment9 is similar to these craters in size but does not have such high-porosity boulders. Thus, we argue that the observed high porosity is intrinsic and not created by subsequent impact comminution and/or cracking. We propose that these boulders are the least processed material on Ryugu and represent remnants of porous planetesimals that did not undergo a high degree of heating and compaction3. Our multi-instrumental analysis suggests that fragments of the highly porous boulders are mixed within the surface regolith globally, implying that they might be captured within collected samples by touch-down operations10,11. The Hayabusa2 spacecraft found dark boulders with very high porosity (>70%, as high as cometary nuclei) at the bottom of small craters on Ryugu. Such boulders are probably the most pristine parts of the planetesimals that formed Ryugu’s parent body and might have been captured by Hayabusa2 sampling.
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TL;DR: In this paper, the authors explore how SEEs have evolved along with the progress in complementary metal-oxide-semiconductor (CMOS) digital IC technology, or device scaling, from the early micrometer-scale generations to the current nanometerscale generations.
Abstract: The history of integrated circuit (IC) development is another record of human challenges involving space. Efforts have been made to protect ICs from sudden malfunctions due to single-event effects (SEEs). These effects are triggered by only a single strike of particle radiation, such as an $\alpha $ -ray or cosmic ray, originating from our solar activity and galactic events including supernovas. This article explores how SEEs have evolved along with the progress in complementary metal-oxide-semiconductor (CMOS) digital IC technology, or device scaling, from the early micrometer-scale generations to the current nanometer-scale generations. For this purpose, focusing on basic digital elements, that is, inverters and static random access memories (SRAMs), this study collected more than 100 sets of data on four characteristic parameters of single-event upsets (SEUs) and single-event transients (SETs), both of which are undesired flips in digital logic states. The results show that all the examined parameters, such as the SEU critical charge, decrease with the device feature size. Analysis involving structure classification, such as bulk versus silicon-on-insulator (SOI) substrates and planar versus fin channels, reveals relationships between the examined SEE parameters and other device features such as the power supply voltage. All the data collected in this survey are explicitly given in tables for future exploration of IC reliability.
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Kōchi University1, Kobe University2, Japan Aerospace Exploration Agency3, Chiba Institute of Technology4, Rikkyo University5, University of Tokyo6, Spanish National Research Council7, National Institute of Advanced Industrial Science and Technology8, Meiji University9, University of Aizu10, Toho University11
TL;DR: In this paper, the resurfacing process on Ryugu accompanying the artificial impact crater formation by Hayabusa2's Small Carry-on Impactor (SCI) was studied by comparing pre-and post-impact images of this region captured by an optical navigation camera.
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TL;DR: In this article, the authors show that during the regolith migration driven by Yarkovsky-O'Keefe-Radzievskii-Paddack spin-up, surface boulders coevolve with the underlying regolith and exhibit diverse dynamical behaviours: they can remain undisturbed, sink into the regool layer and become tilted, or be totally buried by the downslope deposition, depending on their latitudes.
Abstract: Finding the basic mechanism governing the surface history of asteroids of various shapes is essential for understanding their origin and evolution. In particular, the asteroids (162173) Ryugu1 and (101955) Bennu2 currently being visited by Hayabusa2 and OSIRIS-REx appear to be top shaped. This distinctive shape, characterized by a raised equatorial bulge, is shared by other similarly sized asteroids, including Didymos A3, 2008 EV54 and 1999 KW4 Alpha5. However, the possibly common formation mechanism that causes the top-like shape is still under debate. One clue may lie in the boulders on their surfaces. The distribution of these boulders, which was precisely measured in unprecedented detail by the two spacecraft1,2, constitutes a record of the geological evolution of the surface regolith since the origin of these asteroids. Here, we show that during the regolith migration driven by Yarkovsky–O’Keefe–Radzievskii–Paddack spin-up6–9 the surface boulders coevolve with the underlying regolith and exhibit diverse dynamical behaviours: they can remain undisturbed, sink into the regolith layer and become tilted, or be totally buried by the downslope deposition, depending on their latitudes. The predominant geological features commonly observed on top-shaped asteroids, including the boulder-rich region near the pole1,10, the deficiency of large boulders in the equatorial area10,11 and partially buried, oblique boulders exposed on the regolith surface12,13, are commensurate with this coevolution scenario. The surface regolith migration thus is the prevalent mechanism for the formation history of the top-shaped asteroids with stiffer cores. The distribution of boulders on the surface of top-shaped asteroids such as Bennu or Ryugu tells us about the processes driving their evolution. A model shows that the spin-up induced by the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect can explain simultaneously both the latitudinal behaviour of the boulders and the regolith migration.
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Japan Aerospace Exploration Agency1, École Polytechnique2, Nagoya University3, Swedish Institute of Space Physics4, University of Toulouse5, Osaka University6, University of California, Berkeley7, Kyoto University8, Charles University in Prague9, INAF10, Tokai University11, University of Tokyo12, University College London13, Centre national de la recherche scientifique14, Rikkyo University15, Peking University16, University of Bern17, Academia Sinica Institute of Astronomy and Astrophysics18, National Central University19, Tohoku University20
TL;DR: The Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package onboard the BepiColombo/Mio spacecraft used for plasma, high-energy particle and energetic neutral atom measurements as discussed by the authors.
Abstract: BepiColombo Mio (previously called MMO: Mercury Magnetospheric Orbiter) was successfully launched by Ariane 5 from Kourou, French Guiana on October 20, 2018. The Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package onboard Mio spacecraft used for plasma, high-energy particle and energetic neutral atom measurements. It consists of seven sensors including two Mercury Electron Analyzers (MEA1 and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High Energy Particle instrument for electron (HEP-ele), High Energy Particle instrument for ion (HEP-ion), and Energetic Neutrals Analyzer (ENA). Significant efforts were made pre-flight to calibrate all of the MPPE sensors at the appropriate facilities on the ground. High voltage commissioning of MPPE analyzers was successfully performed between June and August 2019 and in February 2020 following the completion of the low voltage commissioning in November 2018. Although all of the MPPE analyzers are now ready to begin observation, the full service performance has been delayed until Mio’s arrival at Mercury. Most of the fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surrounding the Mio spacecraft during the cruising phase. Together with other instruments on Mio including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that measure plasma field parameters, MPPE will contribute to the comprehensive understanding of the plasma environment around Mercury when BepiColombo/Mio begins observation after arriving at the planet Mercury in December 2025.
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TL;DR: In this paper, a systematic review suggests that microgravity and its analogues may induce an enhanced coagulation state due to venous changes most prominent in the cephalad venous system, as a consequence of changes in venous flow, distension, pressures, endothelial damage and possibly hypercoagulability.
Abstract: New findings What is the central question of this study? Recently, an internal jugular venous thrombus was identified during spaceflight: does microgravity induce venous and/or coagulation pathophysiology, and thus an increased risk of venous thromboembolism (VTE)? What is the main finding and its importance? Whilst data are limited, this systematic review suggests that microgravity and its analogues may induce an enhanced coagulation state due to venous changes most prominent in the cephalad venous system, as a consequence of changes in venous flow, distension, pressures, endothelial damage and possibly hypercoagulability in microgravity and its analogues. However, whether such changes precipitate an increased VTE risk in spaceflight remains to be determined. Abstract Recently, an internal jugular venous thrombus was identified during spaceflight, but whether microgravity induces venous and/or coagulation pathophysiology, and thus, an increased risk of venous thromboembolism (VTE) is unclear. Therefore, a systematic (Cochrane compliant) review was performed of venous system or coagulation parameters in actual spaceflight (microgravity) or ground-based analogues in PubMed, MEDLINE, Ovid EMBASE, Cochrane Library, European Space Agency, National Aeronautics and Space Administration, and Deutsches Zentrum fur Luft-und Raumfahrt databases. Seven-hundred and eight articles were retrieved, of which 26 were included for evaluation with 21 evaluating venous, and five coagulation parameters. Nine articles contained spaceflight data, whereas the rest reported ground-based analogue data. There is substantial variability in study design, objectives and outcomes. Yet, data suggested cephalad venous system dilatation, increased venous pressures and decreased/reversed flow in microgravity. Increased fibrinogen levels, presence of thrombin generation markers and endothelial damage were also reported. Limited human venous and coagulation system data exist in spaceflight, or its analogues. Nevertheless, data suggest spaceflight may induce an enhanced coagulation state in the cephalad venous system, as a consequence of changes in venous flow, distension, pressures, endothelial damage and possibly hypercoagulability. Whether such changes precipitate an increased VTE risk in spaceflight remains to be determined.
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TL;DR: In this article, the authors proposed a comprehensive framework for the automatic production of the first Vietnam-wide annual land use/land cover (LULC) data sets (VLUCDs) from 1990 to 2020, using available remotely sensed and inventory data.
Abstract: Extensive studies have highlighted a need for frequently consistent land cover information for interdisciplinary studies. This paper proposes a comprehensive framework for the automatic production of the first Vietnam-wide annual land use/land cover (LULC) data sets (VLUCDs) from 1990 to 2020, using available remotely sensed and inventory data. Classification accuracies ranged from 85.7 ± 1.3 to 92.0 ± 1.2% with the primary dominant LULC and 77.6 ± 1.2% to 84.7 ± 1.1% with the secondary dominant LULC. This confirmed the potential of the proposed framework for systematically long-term monitoring LULC in Vietnam. Results reveal that despite slight recoveries in 2000 and 2010, the net loss of forests (19,940 km2) mainly transformed to croplands over 30 years. Meanwhile, productive croplands were converted to urban areas, which increased approximately ten times. A threefold increase in aquaculture was a major driver of the wetland loss (1914 km2). The spatial–temporal changes varied, but the most dynamic regions were the western north, the southern centre, and the south. These findings can provide evidence-based information on formulating and implementing coherent land management policies. The explicitly spatio-temporal VLUCDs can be benchmarks for global LULC validation, and utilized for a variety of applications in the research of environmental changes towards the Sustainable Development Goals.
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Radboud University Nijmegen1, Charles University in Prague2, Space Telescope Science Institute3, Pennsylvania State University4, California Institute of Technology5, University of Minnesota6, University of Arizona7, Texas Tech University8, Japan Aerospace Exploration Agency9, University of California10
TL;DR: In this paper, the results of a follow-up campaign of luminous red novae (LRN) discovered in NGC 45, and investigate its progenitor system using binary stellar-evolution models are presented.
Abstract: Luminous red novae (LRNe) are astrophysical transients associated with the partial ejection of a binary system’s common envelope shortly before its merger. Here we present the results of our photometric and spectroscopic follow-up campaign of AT 2018bwo (DLT 18x), a LRN discovered in NGC 45, and investigate its progenitor system using binary stellar-evolution models. The transient reached a peak magnitude of M r = −10.97 ± 0.11 and maintained this brightness during its optical plateau of t p = 41 ± 5 days. During this phase, it showed a rather stable photospheric temperature of ∼3300 K and a luminosity of ∼1040 erg s−1 . Although the luminosity and duration of AT 2018bwo is comparable to the LRNe V838 Mon and M31-2015LRN, its photosphere at early times appears larger and cooler, likely due to an extended mass-loss episode before the merger. Toward the end of the plateau, optical spectra showed a reddened continuum with strong molecular absorption bands. The IR spectrum at +103 days after discovery was comparable to that of a M8.5 II type star, analogous to an extended AGB star. The reprocessed emission by the cooling dust was also detected in the mid-infrared bands ∼1.5 years after the outburst. Archival Spitzer and Hubble Space Telescope data taken 10−14 yrs before the transient event suggest a progenitor star with T prog ∼ 6500 K, R prog ∼ 100 R ⊙ , and L prog = 2 × 104 L ⊙ , and an upper limit for optically thin warm (1000 K) dust mass of M d M ⊙ . Using stellar binary-evolution models, we determined the properties of binary systems consistent with the progenitor parameter space. For AT 2018bwo, we infer a primary mass of 12–16 M ⊙ , which is 9–45% larger than the ∼11 M ⊙ obtained using single-star evolution models. The system, consistent with a yellow-supergiant primary, was likely in a stable mass-transfer regime with −2.4 ≤ log(Ṁ /M ⊙ yr−1 ) ≤ −1.2 a decade before the main instability occurred. During the dynamical merger, the system would have ejected 0.15–0.5 M ⊙ with a velocity of ∼500 km s−1 .
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Johns Hopkins University Applied Physics Laboratory1, University of Arizona2, Southwest Research Institute3, University of Colorado Boulder4, Centre national de la recherche scientifique5, University of Maryland, College Park6, Lockheed Martin Corporation7, Rowan University8, University of Glasgow9, Japan Aerospace Exploration Agency10
TL;DR: In this article, the impact of the OSIRIS-REx Touch-and-Go Sampling Acquisition Mechanism (TAGSAM) interacting with the surface of an asteroid in the framework of granular physics was studied.
Abstract: The OSIRIS-REx mission collected a sample from the surface of the asteroid (101955) Bennu in 2020 October. Here, we study the impact of the OSIRIS-REx Touch-and-Go Sampling Acquisition Mechanism (TAGSAM) interacting with the surface of an asteroid in the framework of granular physics. Traditional approaches to estimating the penetration depth of a projectile into a granular medium include force laws and scaling relationships formulated from laboratory experiments in terrestrial-gravity conditions. However, it is unclear that these formulations extend to the OSIRIS-REx scenario of a 1300-kg spacecraft interacting with regolith in a microgravity environment. We studied the TAGSAM interaction with Bennu through numerical simulations using two collisional codes, pkdgrav and gdc-i. We validated their accuracy by reproducing the results of laboratory impact experiments in terrestrial gravity. We then performed TAGSAM penetration simulations varying the following geotechnical properties of the regolith: packing fraction (P), bulk density, inter-particle cohesion (σc), and angle of friction (ϕ). We find that the outcome of a spacecraft-regolith impact has a non-linear dependence on packing fraction. Closely packed regolith (P ≳ 0.6) can effectively resist the penetration of TAGSAM if ϕ ≳ 28° and/or σc ≳ 50 Pa. For loosely packed regolith (P ≲ 0.5), the penetration depth is governed by a drag force that scales with impact velocity to the 4/3 power, consistent with energy conservation. We discuss the importance of low-speed impact studies for predicting and interpreting spacecraft–surface interactions. We show that these low-energy events also provide a framework for interpreting the burial depths of large boulders in asteroidal regolith.
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TL;DR: The results of the two astronauts with optic disc oedema suggest that both increases and decreases in nICP are observed post‐flight in astronauts with ocular alterations, arguing against a primary causal relationship between elevated ICP and spaceflight associated optical changes.
Abstract: Key points During long-duration spaceflights, some astronauts develop structural ocular changes including optic disc oedema that resemble signs of intracranial hypertension. In the present study, intracranial pressure was estimated non-invasively (nICP) using a model-based analysis of cerebral blood velocity and arterial blood pressure waveforms in 11 astronauts before and after long-duration spaceflights. Our results show that group-averaged estimates of nICP decreased significantly in nine astronauts without optic disc oedema, suggesting that the cephalad fluid shift during long-duration spaceflight rarely increased postflight intracranial pressure. The results of the two astronauts with optic disc oedema suggest that both increases and decreases in nICP are observed post-flight in astronauts with ocular alterations, arguing against a primary causal relationship between elevated ICP and spaceflight associated optical changes. Cerebral blood velocity increased independently of nICP and spaceflight-associated ocular alterations. This increase may be caused by the reduced haemoglobin concentration after long-duration spaceflight. Abstract Persistently elevated intracranial pressure (ICP) above upright values is a suspected cause of optic disc oedema in astronauts. However, no systematic studies have evaluated changes in ICP from preflight. Therefore, ICP was estimated non-invasively before and after spaceflight to test whether ICP would increase after long-duration spaceflight. Cerebral blood velocity in the middle cerebral artery (MCAv) was obtained by transcranial Doppler sonography and arterial pressure in the radial artery was obtained by tonometry, in the supine and sitting positions before and after 4-12 months of spaceflight in 11 astronauts (10 males and 1 female, 46 ± 7 years old at launch). Non-invasive ICP (nICP) was computed using a validated model-based estimation method. Mean MCAv increased significantly after spaceflight (ANOVA, P = 0.007). Haemoglobin decreased significantly after spaceflight (14.6 ± 0.8 to 13.3 ± 0.7 g/dL, P 90%) of astronauts, suggesting that the cephalad fluid shift during spaceflight does not systematically or consistently elevate postflight ICP in astronauts. Independently of nICP and ocular alterations, the present results of mean MCAv suggest that long-duration spaceflight may increase cerebral blood flow, possibly due to reduced haemoglobin concentration.
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TL;DR: In this paper, a new aerosol satellite retrieval algorithm was developed by combining a numerical aerosol forecast with a short-term forecast from an aerosol data assimilation system, which was used as an a priori estimate instead of spatially and temporally constant values.
Abstract: . We developed a new aerosol satellite retrieval algorithm
combining a numerical aerosol forecast. In the retrieval algorithm, the
short-term forecast from an aerosol data assimilation system was used as an a priori estimate instead of spatially and temporally constant values. This
method was demonstrated using observation of the Advanced Himawari Imager
onboard the Japan Meteorological Agency's geostationary satellite
Himawari-8. Overall, the retrieval results incorporated strengths of the
observation and the model and complemented their respective weaknesses,
showing spatially finer distributions than the model forecast and less noisy
distributions than the original algorithm. We validated the new algorithm
using ground observation data and found that the aerosol parameters
detectable by satellite sensors were retrieved more accurately than an a priori
model forecast by adding satellite information. Further, the satellite
retrieval accuracy was improved by introducing the model forecast instead of
the constant a priori estimates. By using the assimilated forecast for an a priori estimate, information from previous observations can be propagated to
future retrievals, leading to better retrieval accuracy. Observational
information from the satellite and aerosol transport by the model are
incorporated cyclically to effectively estimate the optimum field of
aerosol.
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TL;DR: In this paper, the authors present results from observations of the 12CO (J=1-0), 13CO (j=1 -0), and 12CO(J=2-1) emission lines toward the Carina nebula complex (CNC) obtained with the Mopra and NANTEN2 telescopes.
Abstract: Herein, we present results from observations of the 12CO (J=1-0), 13CO (J=1-0), and 12CO (J=2-1) emission lines toward the Carina nebula complex (CNC) obtained with the Mopra and NANTEN2 telescopes. We focused on massive-star-forming regions associated with the CNC including the three star clusters Tr14, Tr15, and Tr16, and the isolated WR-star HD92740. We found that the molecular clouds in the CNC are separated into mainly four clouds at velocities -27, -20, -14, and -8 km/s. Their masses are 0.7x10^4Msun, 5.0x10^4 Msun, 1.6x10^4 Msun, and 0.7x10^4 Msun, respectively. Most are likely associated with the star clusters, because of their high 12CO (J=2-1)/12CO (J=1-0) intensity ratios and their correspondence to the Spitzer 8 micron distributions. In addition, these clouds show the observational signatures of cloud--cloud collisions. In particular, there is a V-shaped structure in the position--velocity diagram and a complementary spatial distribution between the -20 km/s cloud and the -14 km/s cloud. Based on these observational signatures, we propose a scenario wherein the formation of massive stars in the clusters was triggered by a collision between the two clouds. By using the path length of the collision and the assumed velocity separation, we estimate the timescale of the collision to be ~1 Myr. This is comparable to the ages of the clusters estimated in previous studies.
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Tsinghua University1, Korea Astronomy and Space Science Institute2, University of Warsaw3, Princeton University4, Osaka University5, Smithsonian Institution6, Ohio State University7, Max Planck Society8, Chinese Academy of Sciences9, University of Canterbury10, Korea University of Science and Technology11, Chungbuk National University12, Weizmann Institute of Science13, Kyung Hee University14, California Institute of Technology15, University of Warwick16, Massey University17, Nagoya University18, Goddard Space Flight Center19, University of Maryland, College Park20, University of Auckland21, Spanish National Research Council22, University of Tokyo23, The Catholic University of America24, Japan Aerospace Exploration Agency25, Kyoto Sangyo University26
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TL;DR: In this article, the structure of the human Xkr8-Basigin complex was investigated using both cryo-EM and X-ray crystallography to investigate its structure at an overall resolution of 3.8
Abstract: Xkr8–Basigin is a plasma membrane phospholipid scramblase activated by kinases or caspases. We combined cryo-EM and X-ray crystallography to investigate its structure at an overall resolution of 3.8 A. Its membrane-spanning region carrying 22 charged amino acids adopts a cuboid-like structure stabilized by salt bridges between hydrophilic residues in transmembrane helices. Phosphatidylcholine binding was observed in a hydrophobic cleft on the surface exposed to the outer leaflet of the plasma membrane. Six charged residues placed from top to bottom inside the molecule were essential for scrambling phospholipids in inward and outward directions, apparently providing a pathway for their translocation. A tryptophan residue was present between the head group of phosphatidylcholine and the extracellular end of the path. Its mutation to alanine made the Xkr8–Basigin complex constitutively active, indicating that it plays a vital role in regulating its scramblase activity. The structure of Xkr8–Basigin provides insights into the molecular mechanisms underlying phospholipid scrambling. Cryo-EM and X-ray crystal structures reveal the architecture of the human Xkr8–Basigin complex, providing insights into the molecular mechanism of phospholipid scrambling.