Analysis of Different Solar Spectral Irradiance Reconstructions and Their Impact on Solar Heating Rates

by on 9 June 2015in Earth Science and Remote Sensing No comment

Proper numerical simulation of the Earth’s climate change requires reliable knowledge of solar irradiance and its variability on different time scales, as well as the wavelength dependence of this variability. As new measurements of the solar spectral irradiance have become available, so too have new reconstructions of historical solar irradiance variations, based on different approaches. However, these various solar spectral irradiance reconstructions have not yet been compared in detail to quantify differences in their absolute values, variability, and implications for climate and atmospheric studies. In this paper we quantitatively compare five different reconstructions of solar spectral irradiance changes during the past four centuries, in order to document and analyze their differences. The impact on atmosphere and climate studies is discussed in terms of the calculation of short wave solar heating rates.

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http://dx.doi.org/10.1007/s11207-013-0381-x

Solid-State Slit Camera (SSC) Aboard MAXI

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The Solid-state Slit Camera (SSC) is an X-ray camera aboard the MAXI mission of the International Space Station. Two sets of SSC sensors view the X-ray sky using charge-coupled devices (CCDs) in the 0.5–12 keV band. The total area for X-ray detection is about 200 cm2, which is the largest among the missions of X-ray astronomy. The energy resolution at the CCD temperature of −70∘C is 145 eV in full width at the half maximum (FWHM) at 5.9 keV, and the field of view is 1∘.5 (FWHM) × 90∘ for each sensor. The SSC could make a whole-sky image with the energy resolution good enough to resolve line emissions, and monitor the whole-sky at the energy band of < 2 keV for the first time in these decades.

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http://pasj.oxfordjournals.org/content/63/2/397.abstract

Revisit of Local X-Ray Luminosity Function of Active Galactic Nuclei with the MAXI Extragalactic Survey

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We constructed a new X-ray (2–10 keV) luminosity function of Compton-thin active galactic nuclei (AGNs) in the local universe, using the first MAXI/GSC source catalog surveyed in the 4–10 keV band. The sample consists of 37 non-blazar AGNs at z = 0.002–0.2, whose identification is highly ( > 97%) complete. We confirmed the trend that the fraction of absorbed AGNs with NH > 10 22 cm −2 rapidly decreases against the luminosity ( LX ), from 0.73 ± 0.10 at LX = 10 42−43.5 erg s −1 to 0.12 ± 0.08 at LX = 10 43.5−45.5 erg s −1 . The obtained luminosity function was well-fitted with a smoothly connected double power-law model whose indices are γ1 = 0.84 (fixed) and γ2 = 2.0 ± 0.2 below and above the break luminosity, L∗ = 10 43.3±0.4 erg s −1 , respectively. While the result of the MAXI/GSC agrees well with that of HEAO-1 at LX ≳ 10 43.5 erg s −1 , it gives a larger number density at the lower luminosity range. A comparison between our luminosity function in the 2–10 keV band and that in the 14–195 keV band obtained from the Swift/BAT survey indicates that the averaged broad-band spectra in the 2–200 keV band should depend on the luminosity, approximated by Γ ∼ 1.7 for LX ≲ 10 44 erg s −1 , while Γ ∼ 2.0 for LX ≳ 10 44 erg s −1 . This trend was confirmed by the correlation between the luminosities in the 2–10 keV and 14–195 keV bands in our sample. We argue that there is no contradiction in the luminosity functions between above and below 10 keV once this effect is taken into account.

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http://pasj.oxfordjournals.org/content/63/sp3/S937.abstract

The Global Lightning and Sprite Measurement (GLIMS) Mission on International Space Station —Concept and Overview&mdash

by on 9 June 2015in Earth Science and Remote Sensing No comment

Global Lightning and sprIte MeasurementS (GLIMS) is a mission on the International Space Station (ISS) to detect and locate optical transient luminous events (TLEs) and associated lightning simultaneously from the non-sun-synchronous orbit. It is scheduled to be launched from Japan in January, 2012 as part of the multi-mission consolidated equipment on the Japanese Exposure Module (JEM). Our mission's goals are (1) to detect and locate lightning and sprites within storm scale resolution over a large region of the Earth's surface along the orbital track of the ISS without any bias, (2) to clarify the mechanism by which sprites are generated, and (3) to identify the conditions under which TLEs occur. To achieve these goals, two CMOS cameras, six Photometers, a VLF receiver and VHF interferometer with two antennas are installed at the bottom of the module to observe the TLEs, as well as causative lightning discharges at nadir direction during day and night time. Though the luminous events' so-called sprites, elves and jets have been investigated by numerous researchers all over the world based mainly on ground observations, some important problems have not been fully understood yet. These include the generation mechanisms of columniform fine structures and horizontal offset of some sprites from the parent lightning discharges. In the JEM-GLIMS mission, observations from our synchronized sensors will shed light on the unsolved problems mentioned above regarding TLEs and causative lightning discharges. In this presentation scientific background, instrumentation, and project summaries are given.

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Outburst of LSV+44 17 Observed by MAXI and RXTE, and Discovery of a Dip Structure in the Pulse Profile

by on 9 June 2015in Earth Science and Remote Sensing No comment

We report on the first observation of an X-ray outburst of a Be/X-ray binary pulsar, LS V +44 17/ RX J0440.9+4431, and the discovery of an absorption dip structure in the pulse profile. An outburst of this source was discovered by MAXI GSC in 2010 April. It was the first detection of transient activity of LS V +44 17 since the source was identified as a Be/X-ray binary in 1997. From the data of a follow-up RXTE observation near the peak of the outburst, we found a narrow dip structure in its pulse profile, which was clearer in the lower-energy bands. The pulse-phase-averaged energy spectra in the 3–100 keV band could be fitted with a continuum model containing a power-law function with an exponential cutoff and a blackbody component, which are modified at low energy by an absorption component. A weak iron Kα emission line was also detected in the spectra. From the pulse-phase-resolved spectroscopy we found that the absorption column density at the dip phase was much higher than those in the other phases. The dip was not seen in subsequent RXTE observations at lower flux levels. These results suggest that the dip in the pulse profile originates from the eclipse of the radiation from the neutron star by the accretion column.

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http://pasj.oxfordjournals.org/content/64/4/79.abstract

A Large X-Ray Flare from a Single Weak-Lined T Tauri Star TWA-7 Detected with MAXI GSC

by on 9 June 2015in Earth Science and Remote Sensing No comment

We present a large X-ray flare from a nearby weak-lined T Tauri star TWA-7 detected with the Gas Slit Camera (GSC) on the Monitor of All-sky X-ray Image (MAXI). The GSC captured X-ray flaring from TWA-7 with a flux of 3 × 10 −9 erg cm −2 s −1 in 2–20 keV band during the scan transit starting at 2010-09-07 18:24:30 (UT). The estimated X-ray luminosity at the scan in the energy band is 3 × 10 32 erg s −1 , indicating that the event is among the largest X-ray flares from T Tauri stars. Since MAXI GSC monitors a target only during a scan transit of about a minute per 92 min orbital cycle, the luminosity at the flare peak might have been higher than that detected. At the scan transit, we observed a high X-ray-to-bolometric luminosity ratio, log LX/Lbol = − 0.1 +0.2−0.3 ; i.e., the X-ray luminosity is comparable to the bolometric luminosity. Since TWA-7 has neither an accreting disk nor a binary companion, the observed event implies that none of those are essential to generate such big flares in T Tauri stars.

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http://pasj.oxfordjournals.org/content/63/sp3/S713.abstract

Surface Velocities From Multiple-Tracer Image Sequences

by on 9 June 2015in Earth Science and Remote Sensing No comment

We discuss a new inverse model to estimate surface velocity using an image sequence with more than one tracer. The method employs the global optimal solution technique, which covers an image scene with subarrays or tiles, within which both velocity components are specified as bilinear forms. Substitution into the tracer conservation equation for each tracer yields a system of equations for the velocity field, which is constrained to fit the image data in a least-squares sense over the entire image domain. Solution is achieved iteratively by a Gauss-Seidel method. A numerical model is used as a benchmark to examine the accuracy of this new technique. Image pairs from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the NASA Terra and Aqua spacecraft and the hyperspectral imager for the coastal ocean instrument currently onboard the International Space Station are also used to demonstrate the new inverse model with actual ocean data. The derived vector field from MODIS is then compared with the velocity field obtained by the single-tracer technique, and the results are found to be qualitatively equivalent.

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Method for identifying sedimentary bodies from images and its application to mineral exploration

by on 9 June 2015in Earth Science and Remote Sensing No comment

A method is disclosed for identifying a sediment accumulation from an image of a part of the earth's surface. The method includes identifying a topographic discontinuity from the image. A river which crosses the discontinuity is identified from the image. From the image, paleocourses of the river are identified which diverge from a point where the river crosses the discontinuity. The paleocourses are disposed on a topographically low side of the discontinuity. A smooth surface which emanates from the point is identified. The smooth surface is also disposed on the topographically low side of the point.

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Early Results From 4K-Cooled Superconducting Submm Wave Limb Emission Sounder SMILES Onboard ISS/JEM

by on 9 June 2015in Earth Science and Remote Sensing No comment

Early comparison of O3, HCl, and HNO3 L2 products (ver. 005-06-0032) of the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) onboard International Space Station has been conducted. Good agreements are observed among SMILES, SVISAT-1/ACE-FTS, AURA/MLS, and ENVISAT.MIPAS, for O3 and HCl below 45 km. SMILES HNO3 profiles are statistically ~20% higher than ACE-FTS and MIPAS. At higher altitude region, 45-60 km, SMILES O3 and HCl are considerably different from ACE-FTS and/or MLS. It is concluded, although future data updates will be necessary, SMILES O3 and HCl below 45 km are both useful for scientific application with special cautions to the SMILES data quality.

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Vegetation Measurements From Digital Astronaut Photography

by on 9 June 2015in Earth Science and Remote Sensing No comment

Astronaut photography of cities collected during Apollo, Skylab, Shuttle, Mir, and International Space Station missions provides a useful dataset for urban analysis that complements the satellite data archive. Recent astronaut photography acquired with digital cameras is now approaching the ground resolutions of commercial satellites such as IKONOS (i.e. less than 6 m/pixel). Astronaut photographs are a relevant source of data for urban analyses, particularly for studies that do not have the resources to purchase commercial-quality data. The CCD image sensors in the cameras currently used for astronaut photography are sensitive to the infrared portion of the electromagnetic spectrum, but infrared signal is filtered out above 700 μm. As such, the digital camera data contain less information on actively synthesizing vegetation than they would with an infrared signal included. We present an analysis of aboveground biomass (i.e. actively photosynthesizing vegetation) derived from astronaut photography of the Paris, France metropolitan area acquired on April 24, 2002 using a Kodak DCS 760C electronic still camera aboard the International Space Station. The accuracy of biomass estimation obtained from the digital camera data is demonstrated by comparison with Advanced Spaceborne Thermal Emission and Reflection Radiometer visible to near infrared data for Paris acquired on April 8, 2002. Correlations of bands between the two instruments allow interpretation of the identified vegetation and soil classes. Collection of astronaut photography over global urban centers is ongoing and planned for future orbital missions, and will be a useful addition to ongoing studies of urban ecosystem change, sustainability, and resilience.

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