The imaging and slitless spectroscopy instrument for surveys (ISSIS) for the world space observatory-ultraviolet (WSO-UV)     

Ana I. Gómez?de?Castro  Jesús Maíz  Pablo Rodriguez  Maite Gómez  Juan A. Larruquert  José A. Méndez  Tomas Belenguer  Victor Rodrigo-Gudiel  Fátima López-Martínez  Paola Sestito 《Astrophysics and Space Science》2011,335(1):283-289

ISSIS is the Imaging and Slitless Spectroscopy Instrument for the World Space Observatory-Ultraviolet (WSO-UV) mission. ISSIS is a multipurpose instrument designed to carry out high resolution (<0.1 arcsec) imaging in the far UV with fields of view ≥2×2 arcmin². ISSIS has two acquisition channels: the High Sensitivity Channel (HSC) and the Channel for Surveys (CfS). The HSC is equipped with an MCP-type detector to guarantee high sensitivity in the 1150–1750 ? range and high rejection of lower energy radiation. The CfS is equipped with a large CCD detector (4k×4k) to obtain images from the far UV to the red (1150–8500 ?); the CfS is implemented to allow observing UV bright sources such as reflection nebulae or nearby massive star forming regions. The design drivers and the current status of the instrument are described in this contribution.  相似文献   

Depth of faulting and ancient heat flows in the Kuiper region of Mercury from lobate scarp topography     

Isabel Egea-González  Javier Ruiz  Carlos Fernández  Jean-Pierre Williams  Álvaro Márquez  Luisa M. Lara 《Planetary and Space Science》2012,60(1):193-198

Mercurian lobate scarps are interpreted to be the surface expressions of thrust faults formed by planetary cooling and contraction, which deformed the crust down to the brittle–ductile transition (BDT) depth at the time of faulting. In this work we have used a forward modeling procedure in order to analyze the relation between scarp topography and fault geometries and depths associated with a group of prominent lobate scarps (Santa Maria Rupes and two unnamed scarps) located in the Kuiper region of Mercury for which Earth-based radar altimetry is available. Also a backthrust associated with one of the lobate scarps has been included in this study. We have obtained best fits for depths of faulting between 30 and 39 km; the results are consistent with the previous results for other lobate scarps on Mercury.The so-derived fault depths have been used to calculate surface heat flows for the time of faulting, taking into account crustal heat sources and a heterogeneous surface temperature due to the variable insolation pattern. Deduced surface heat flows are between 19 and 39 mW m^?2 for the Kuiper region, and between 22 and 43 mW m^?2 for Discovery Rupes. Both BDT depths and heat flows are consistent with the predictions of thermal history models for the range of time relevant for scarp formation.  相似文献   

Stellar intensity interferometry: Prospects for sub-milliarcsecond optical imaging     

Dainis Dravins  Stephan LeBohec  Hannes Jensen  Paul D. Nuñez 《New Astronomy Reviews》2012,56(5):143-167

Using kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the spatial resolution achieved in optical astronomy by an order of magnitude, enabling images of rapidly rotating hot stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (once pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large airmasses, also at short optical wavelengths. The required large telescopes (～10 m) with very fast detectors (～ns) are becoming available as the arrays primarily erected to measure Cherenkov light emitted in air by particle cascades initiated by energetic gamma rays. Planned facilities (e.g., CTA, Cherenkov Telescope Array) envision many tens of telescopes distributed over a few square km. Digital signal handling enables very many baselines (from tens of meters to over a kilometer) to be simultaneously synthesized between many pairs of telescopes, while stars may be tracked across the sky with electronic time delays, in effect synthesizing an optical interferometer in software. Simulated observations indicate limiting magnitudes around m_V = 8, reaching angular resolutions ～30 μarcsec in the violet. The signal-to-noise ratio favors high-temperature sources and emission-line structures, and is independent of the optical passband, be it a single spectral line or the broad spectral continuum. Intensity interferometry directly provides the modulus (but not phase) of any spatial frequency component of the source image; for this reason a full image reconstruction requires phase retrieval techniques. This is feasible if sufficient coverage of the interferometric (u, v)-plane is available, as was verified through numerical simulations. Laboratory and field experiments are in progress; test telescopes have been erected, intensity interferometry has been achieved in the laboratory, and first full-scale tests of connecting large Cherenkov telescopes have been carried out. This paper reviews this interferometric method in view of the new possibilities offered by arrays of air Cherenkov telescopes, and outlines observational programs that should become realistic already in the rather near future.  相似文献   

On the distribution of GPS signal amplitudes during low-latitude ionospheric scintillation     

Alison de Oliveira Moraes  Eurico Rodrigues de Paula  Waldecir João Perrella  Fabiano da Silveira Rodrigues 《GPS Solutions》2013,17(4):499-510

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PMP and PMF estimations in sparsely-gauged Andean basins and climate change projections     

Miguel A. Lagos-Zúñiga  Ximena Vargas M. 《水文科学杂志》2013,58(11):2027-2042

Abstract

Mixed-regime Andean basins present a complex scenario for flood analysis. In this study, we propose a methodology for incorporating orographic effects influenced by mountainous barriers in the Probable Maximum Precipitation (PMP) estimation method in sparsely-gauged basins. The proposed methodology is applied to the Puclaro Reservoir basin in Chile, which is affected by the Andes. The PMP estimations were calculated by applying statistical and hydrometeorological approaches to the baseline (1960–1999) and climate change scenarios (2045–2065) determined from projections of the ECHAM5 general circulation model. Temperature projections for the 2040–2065 period show that there would be a rise in the catchment contributing area that would lead to an increase in the average liquid precipitation over the basin. Temperature projections would also affect the maximization factors in the calculation of the PMP, as precipitable water content, raising it to 126.6% and 62.5% under scenarios A2 and B1, respectively; the probable maximum flood (PMF) would increase to +175.5% under the A2 scenario. These projections would affect the safety of dam design and would be generalizable to zones with similar mixed hydrology and climate change projections. We propose that the methodology presented could be also applied to basins with similar characteristics.