Herschel SPIRE fourier transform spectrometer: calibration of its bright-source mode     

Nanyao Lu  Edward T. Polehampton  Bruce M. Swinyard  Dominique Benielli  Trevor Fulton  Rosalind Hopwood  Peter Imhof  Tanya Lim  Nicola Marchili  David A. Naylor  Bernhard Schulz  Sunil Sidher  Ivan Valtchanov 《Experimental Astronomy》2014,37(2):239-252

The Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board the ESA Herschel Space Observatory has two detector setting modes: (a) a nominal mode, which is optimized for observing moderately bright to faint astronomical targets, and (b) a bright-source mode recommended for sources significantly brighter than 500 Jy, within the SPIRE FTS bandwidth of 446.7–1544 GHz (or 194–671 microns in wavelength), which employs a reduced detector responsivity and out-of-phase analog signal amplifier/demodulator. We address in detail the calibration issues unique to the bright-source mode, describe the integration of the bright-mode data processing into the existing pipeline for the nominal mode, and show that the flux calibration accuracy of the bright-source mode is generally within 2 % of that of the nominal mode, and that the bright-source mode is 3 to 4 times less sensitive than the nominal mode.  相似文献   

Herschel SPIRE FTS spectral mapping calibration     

Dominique Benielli  Edward Polehampton  Rosalind Hopwood  Ana Belén Griñón Marín  Trevor Fulton  Peter Imhof  Tanya Lim  Nanyao Lu  Gibion Makiwa  Nicola Marchili  David Naylor  Locke Spencer  Bruce Swinyard  Ivan Valtchanov  Matthijs van der Wiel 《Experimental Astronomy》2014,37(2):357-367

The Herschel SPIRE Fourier transform spectrometer (FTS) performs spectral imaging in the 447–1546 GHz band. It can observe in three spatial sampling modes: sparse mode, with a single pointing on sky, or intermediate or full modes with 1 and 1/2 beam spacing, respectively. In this paper, we investigate the uncertainty and repeatability for fully sampled FTS mapping observations. The repeatability is characterised using nine observations of the Orion Bar. Metrics are derived based on the ratio of the measured intensity in each observation compared to that in the combined spectral cube from all observations. The mean relative deviation is determined to be within 2 %, and the pixel-by-pixel scatter is ～ 7 %. The scatter increases towards the edges of the maps. The uncertainty in the frequency scale is also studied, and the spread in the line centre velocity across the maps is found to be ～ 15 km s ^{? 1}. Other causes of uncertainty are also discussed including the effect of pointing and the additive uncertainty in the continuum.  相似文献   

Nephelines from the Somma-Vesuvius volcanic complex (Southern Italy): crystal-chemical,structural and genetic investigations     

Giuseppina Balassone  Volker Kahlenberg  Angela Altomare  Angela Mormone  Rosanna Rizzi  Michele Saviano  Nicola Mondillo 《Mineralogy and Petrology》2014,108(1):71-90

Sixteen nephelines from different geological occurrences were sampled at the type-locality, the Somma-Vesuvius volcanic complex (southern Italy), and investigated for their chemistry and crystal structure obtained by both single-crystal and powder X-ray diffraction. Nepheline-bearing samples are metamorphic or from magmatic ejecta and pumice deposits. The lower K contents characterize the pumice- and some metamorphic-derived nephelines, whereas the higher ones are found in some samples from magmatic nodules. The amount of the anorthite molecule, quite low on average, can be more variable in the metamorphic nephelines. The crystal-structure investigations on Somma-Vesuvius samples compare well with previous studies of natural nephelines. All 16 nepheline samples adopt space group P6₃. The observed lattice parameters vary between 9.9768–9.9946 Å (for a) and 8.3614–8.3777 Å (for c), respectively. Furthermore, chemical analysis revealed that all specimens exhibit an excess of Si relative the ideal Si:Al ratio of 1:1. The analysis of the T-O distances in our samples clearly indicates a distinct ordering process of aluminium and silicon on the tetrahedral sites which is an agreement with Loewenstein’s rule. A linear correlation between the distance of symmetry equivalent split atoms O(1)-O(1)’ and the T(1)-O(1)-T(2) tilt angle was observed. The average <B-O> (B = Na) distances of all crystals are very similar which is consistent with the outcome of the site population refinement indicating full occupancy with sodium. Oriented precession-type sections of reciprocal space indicated the presence of at least the most intense family of satellite peaks, demonstrating that this group of satellite reflections can occur not only in nephelines from pegmatites and ijolites but also in rocks from completely different petrological settings.  相似文献   

Terrestrial laser scanner and geomechanical surveys for the rapid evaluation of rock fall susceptibility scenarios   总被引：3，自引：1，他引：2  

Giovanni Gigli  Stefano Morelli  Simone Fornera  Nicola Casagli 《Landslides》2014,11(1):1-14

The primary objective of this paper is to present a semiautomatic procedure that, integrated with traditional methods, can be useful for a rapid definition of rock fall susceptibility scenarios with the purpose of civil protection. Due to its morphology (steep slopes and narrow valleys), regional seismicity, and rock mass characteristics, the Nera Valley (Valnerina, Umbria Region, Italy) is characterized by high rock fall risk. With the aim of covering a wide range of features and investigating the main advantages and drawbacks of the proposed approach, data collection (terrestrial laser scanning (TLS) and geomechanical surveys) was carried out at three different slopes. Detailed three-dimensional (3D) models were created to reconstruct the shape and volume of the most unstable blocks, to define the position of the main rock fall source areas, and to precisely distinguish the outcropping materials and the position of the elements at risk for reliable runout analyses. The proposed approach can be useful in supporting proper maintenance and land management programs both in ordinary and in emergency circumstances.  相似文献   

Predictive modeling for preventive Archaeology: overview and case study     

Maria Danese  Nicola Masini  Marilisa Biscione  Rosa Lasaponara 《Central European Journal of Geosciences》2014,6(1):42-55

The use of GIS and Spatial Analysis for predictive models is an important topic in preventive archaeology. Both of these tools play an important role in the Support Decision System (SDS) for archaeological research and for providing information useful to reduce archaeological risk. Over the years, a number of predictive models in the GIS environment have been developed and proposed. The existing models substantially differ from each other in methodological approaches and parameters used for performing the analysis. Until now, only few works consider spatial autocorrelation, which can provide more effective results. This paper provides a brief review of the existing predictive models, and then proposes a new methodological approach, applied to the neolithic sites in the Apulian Tavoliere (Southern Italy), that combines traditional techniques with methods that allow us to include spatial autocorrelation analysis to take into account the spatial relationships among the diverse sites.  相似文献   

Systematic Errors Induced by the Elliptical Power-law model in Galaxy-Galaxy Strong Lens Modeling     

Xiaoyue Cao  Ran Li  J.W.Nightingale  Richard Massey  Andrew Robertson  Carlos S.Frenk  Aristeidis Amvrosiadis  Nicola C.Amorisco  Qiuhan He  Amy Etherington  Shaun Cole  Kai Zhu 《天文和天体物理学研究(英文版)》2022,(2):143-172

The elliptical power-law model of the mass in a galaxy is widely used in strong gravitational lensing analyses.However,the distribution of mass in real galaxies...  相似文献