Netherlands Institute for Space Research

About: Netherlands Institute for Space Research is a facility organization based out in Utrecht, Netherlands. It is known for research contribution in the topics: Galaxy & Neutron star. The organization has 737 authors who have published 3026 publications receiving 106632 citations. The organization is also known as: SRON & Space Research Organisation Netherlands.

Inverse Modeling of Global and Regional CH4 Emissions Using SCIAMACHY Satellite Retrievals

Abstract: Methane retrievals from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument onboard ENVISAT provide important information on atmospheric CH_4 sources, particularly in tropical regions which are poorly monitored by in situ surface observations Recently, Frankenberg et al (2008a, 2008b) reported a major revision of SCIAMACHY retrievals due to an update of spectroscopic parameters of water vapor and CH_4 Here, we analyze the impact of this revision on global and regional CH_4 emissions estimates in 2004, using the TM5-4DVAR inverse modeling system Inversions based on the revised SCIAMACHY retrievals yield ∼20% lower tropical emissions compared to the previous retrievals The new retrievals improve significantly the consistency between observed and assimilated column average mixing ratios and the agreement with independent validation data Furthermore, the considerable latitudinal and seasonal bias correction of the previous SCIAMACHY retrievals, derived in the TM5-4DVAR system by simultaneously assimilating high-accuracy surface measurements, is reduced by a factor of ∼3 The inversions result in significant changes in the spatial patterns of emissions and their seasonality compared to the bottom-up inventories Sensitivity tests were done to analyze the robustness of retrieved emissions, revealing some dependence on the applied a priori emission inventories and OH fields Furthermore, we performed a detailed validation of simulated CH_4 mixing ratios using NOAA ship and aircraft profile samples, as well as stratospheric balloon samples, showing overall good agreement We use the new SCIAMACHY retrievals for a regional analysis of CH_4 emissions from South America, Africa, and Asia, exploiting the zooming capability of the TM5 model This allows a more detailed analysis of spatial emission patterns and better comparison with aircraft profiles and independent regional emission estimates available for South America Large CH_4 emissions are attributed to various wetland regions in tropical South America and Africa, seasonally varying and opposite in phase with CH_4 emissions from biomass burning India, China and South East Asia are characterized by pronounced emissions from rice paddies peaking in the third quarter of the year, in addition to further anthropogenic emissions throughout the year

Gaia Early Data Release 3. The astrometric solution

Abstract: Context. Gaia Early Data Release 3 (Gaia EDR3) contains results for 1.812 billion sources in the magnitude range G = 3–21 based on observations collected by the European Space Agency Gaia satellite during the first 34 months of its operational phase.Aims. We describe the input data, the models, and the processing used for the astrometric content of Gaia EDR3, as well as the validation of these results performed within the astrometry task.Methods. The processing broadly followed the same procedures as for Gaia DR2, but with significant improvements to the modelling of observations. For the first time in the Gaia data processing, colour-dependent calibrations of the line- and point-spread functions have been used for sources with well-determined colours from DR2. In the astrometric processing these sources obtained five-parameter solutions, whereas other sources were processed using a special calibration that allowed a pseudocolour to be estimated as the sixth astrometric parameter. Compared with DR2, the astrometric calibration models have been extended, and the spin-related distortion model includes a self-consistent determination of basic-angle variations, improving the global parallax zero point.Results. Gaia EDR3 gives full astrometric data (positions at epoch J2016.0, parallaxes, and proper motions) for 1.468 billion sources (585 millionwith five-parameter solutions, 882 million with six parameters), and mean positions at J2016.0 for an additional 344 million.Solutions with five parameters are generally more accurate than six-parameter solutions, and are available for 93% of the sources brighter than the 17th magnitude. The median uncertainty in parallax and annual proper motion is 0.02–0.03 mas at magnitude G = 9–14, and around 0.5 mas at G = 20. Extensive characterisation of the statistical properties of the solutions is provided, including the estimated angular power spectrum of parallax bias from the quasars.

Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station

Abstract: Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

The quiescent intracluster medium in the core of the Perseus cluster

Abstract: The Hitomi collaboration reports X-ray observations of the core of the Perseus cluster of galaxies the brightest X-ray-emitting cluster in the sky. Such clusters typically consist of tens to thousands of galaxies bound together by gravity and are studied as models of both small-scale cosmology and large-scale astrophysical processes. The data reveal a remarkably quiescent atmosphere, where gas velocities are quite low, with a line-of-sight velocity dispersion of about 164 kilometres per second at a distance of 3060 kiloparsecs from the central nucleus.

Gaia Early Data Release 3: The astrometric solution

Abstract: Gaia Early Data Release 3 (Gaia EDR3) contains results for 1.812 billion sources in the magnitude range G = 3 to 21 based on observations collected by the European Space Agency Gaia satellite during the first 34 months of its operational phase. We describe the input data, the models, and the processing used for the astrometric content of Gaia EDR3, as well as the validation of these results performed within the astrometry task. The processing broadly followed the same procedures as for Gaia DR2, but with significant improvements to the modelling of observations. For the first time in the Gaia data processing, colour-dependent calibrations of the line- and point-spread functions have been used for sources with well-determined colours from DR2. In the astrometric processing these sources obtained five-parameter solutions, whereas other sources were processed using a special calibration that allowed a pseudocolour to be estimated as the sixth astrometric parameter. Compared with DR2, the astrometric calibration models have been extended, and the spin-related distortion model includes a self-consistent determination of basic-angle variations, improving the global parallax zero point. Gaia EDR3 gives full astrometric data (positions at epoch J2016.0, parallaxes, and proper motions) for 1.468 billion sources (585 million with five-parameter solutions, 882 million with six parameters), and mean positions at J2016.0 for an additional 344 million. Solutions with five parameters are generally more accurate than six-parameter solutions, and are available for 93% of the sources brighter than G = 17 mag. The median uncertainty in parallax and annual proper motion is 0.02-0.03 mas at magnitude G = 9 to 14, and around 0.5 mas at G = 20. Extensive characterisation of the statistical properties of the solutions is provided, including the estimated angular power spectrum of parallax bias from the quasars.