170,606 research outputs found
A stable auroral red arc over Europe
No full textUsing a new all-sky-imaging system, M Mendillo, C Barbieri, J Baumgardner, J Wroten, G Cremonese and G Umbriaco observed two distinctive types of aurora over London and western Europe on the night of 26-27 September 2011, including the first ground-based image of a stable auroral red arc over Europe. 2012 Royal Astronomical Society
A stable auroral red arc over Europe
No full textUsing a new all-sky-imaging system, M Mendillo, C Barbieri, J Baumgardner, J Wroten, G Cremonese and G Umbriaco observed two distinctive types of aurora over London and western Europe on the night of 26-27 September 2011, including the first ground-based image of a stable auroral red arc over Europe
The 1999 Quadrantids and the lunar Na atmosphere
No full textEnhancements of the Na emission and temperature from the lunar atmosphere were reported during the Leonid meteor showers of 1995, 1997 and 1998. Here we report a search for similar enhancement during the 1999 Quadrantids, which have the highest mass flux of any of the major streams. No enhancements were detected. We suggest that different chemical-physical properties of the Leonid and Quadrantid streams may be responsible for the difference
Detection of a southern peak in Mercury's sodium exosphere with the TNG in 2005
No full textA long term plan of observations of the sodium exosphere of Mercury began in 2002 by using the high resolution echelle spectrograph SARG and a devoted sodium filter at the 3.5 m Galileo National Telescope (TNG) located in La Palma, Canary Islands. This program is meant to investigate the variations of the sodium exosphere appearance under different conditions of observations, namely Mercury's position along its orbit, phase angle and different solar conditions, as reported by previous observations in August 2002 and August 2003 [Barbieri, C., Verani, S., Cremonese, G., Sprague, A., Mendillo, M., Cosentino, R., Hunten, D., 2004. Planet. Space Sci. 52, 1169-1175; Leblanc, F., Barbieri, C., Cremonese, G., Verani, S., Cosentino, R., Mendillo, M., Sprague, A., Hunten, D., 2006. Icarus 185 (2), 395-402]. Here we present the analysis of data taken in June 29th and 30th and in July 1st 2005, when Mercury's true anomaly angle (TAA) was in the range 124-130°. The spectra show particularly intense sodium lines with a distinctive peak in emission localized in the southern hemisphere at mid-latitudes. This seems to be a persistent feature related to consecutive favorable IMF conditions inducing localized enhancements of surface sodium density. The comparison with previous data taken by Potter et al. [Potter, A.E., Killen, R.M., Morgan, T.H., 2002. Meteorit. Planet. Sci. 37 (9), 1165-1172] evidences a surprising consistency of the anti-sunward component, which appears to remain constant regardless of the changing illumination and space weather conditions at Mercury
Manuale Cremonese. Informatica e telecomunicazioni per i nuovi tecnici a indirizzo informatica e telecomunicazioni. Discipline propedeutiche, informatica, telecomunicazioni
No full textLa seconda edizione del Manuale Cremonese di Informatica e Telecomunicazioni è stata rivista e notevolmente ampliata per rispondere alle esigenze didattiche dei Nuovi Istituti Tecnici a indirizzo Informatica e Telecomunicazioni: un unico volume raccoglie ora le discipline propedeutiche e le trattazioni specialistiche.
Si è ritenuto utile riproporre nelle linee essenziali le discipline propedeutiche per agevolare lo studente in un rapido ripasso di molti argomenti di base, anche di elettronica.
La sezione di Informatica è stata profondamente arricchita e aggiornata al fine di rendere questo strumento davvero utile per l’Esame di Stato, grazie alla rapida consultabilità e al corredo di tabelle e di esempi di codice. Sono stati infatti ripensati anche in termini didattici temi fondamentali come la Programmazione di rete, la Gestione dei database e il linguaggio PHP nel capitolo dedicato alle Tecnologie web lato server. Il volume spazia da capitoli specifici relativi alla Programmazione concorrente e al Linguaggio XML ad argomenti più trasversali come la Tecnologia .NET e linguaggio C# o la Sicurezza informatica delle tecnologie di rete. Si affrontano poi il Web service, la Programmazione di App per dispositivi con sistema operativo Android, e le Tecnologie web lato client (HTML5, CSS3 e JavaScript), visto l’interesse sempre maggiore che tali argomenti riscuotono.
Per le Telecomunicazioni si è reso indispensabile un significativo aggiornamento, in particolare per le Reti di nuova generazione, i Data center, i sistemi di accesso alla rete e quelli di tipo cellulare per la comunicazione in mobilità.
Un manuale completo, quindi, che accompagna lo studente durante lo studio e all’Esame di Stato, ma che potrà essere di aiuto anche nell’esercizio della professione: si spazia da discipline fondamentali quali la Fisica e la Matematica a specifici approfondimenti (Statistica, Matematica finanziaria, Elettrotecnica) per arrivare ad argomenti di stringente attualità relativi al mondo dell’Informatica e delle Telecomunicazioni, facilmente reperibili grazie al ricco Indice analitico
Topographic correction of HiRISE and CaSSIS images: Validation and application to color observations of Martian albedo features
No full textThe topographic correction of satellite images has to be applied to both disentangle albedo features from illumination effects induced by local topography and performspectrophotometric analyses of planetary surfaces. This work focuses on the modeling and removal of surface brightness variations induced by topography, referred astopographic shading, from high resolution images of Mars. Topographic shading can be modeled through functions of the surface illumination and observation anglescalled disk functions. We consider four disk functions that are widely used in planetary photometry: the Lambert, Lommel-Seeliger, Akimov and Minnaert diskfunctions. We test and evaluate their performances in removing topographic shading from High Resolution Imaging Science Experiment (HiRISE) and Colour andSurface Science Imaging System (CaSSIS) images. We here validate our method, moreover, we report scientific applications to single or multi-band datasets byanalyzing topographically corrected HiRISE colour observations of Martian recurring slope lineae and dust devil tracks, as well as CaSSIS panchromatic observations
Warming permafrost and active layer variability at Cime Bianche, Western European Alps
No full textThe objective of this paper is to provide a first synthesis on the state and recent evolution of permafrost at the monitoring site of Cime Bianche (3100 m a.s.l.) on the Italian side of the Western Alps. The analysis is based on 7 years of ground temperature observations in two boreholes and seven surface points. The analysis aims to quantify the spatial and temporal variability of ground surface temperature in relation to snow cover, the small-scale spatial variability of the active layer thickness and current temperature trends in deep permafrost.Results show that the heterogeneity of snow cover thickness, both in space and time, is the main factor controlling ground surface temperatures and leads to a mean range of spatial variability (2.5 ± 0.1 °C) which far exceeds the mean range of observed inter-annual variability (1.6 ± 0.1 °C). The active layer thickness measured in two boreholes at a distance of 30 m shows a mean difference of 2.0 ± 0.1 m with the active layer of one borehole consistently deeper. As revealed by temperature analysis and geophysical soundings, such a difference is mainly driven by the ice/water content in the sub-surface and not by the snow cover regimes. The analysis of deep temperature time series reveals that permafrost is warming. The detected trends are statistically significant starting from a depth below 8 m with warming rates between 0.1 and 0.01 °C yr⁻¹
Using Advanced Geometric Models in Image Matching with High Resolution Space Images
No full textHigh resolution Digital Terrain Models (DTMs), suita-ble for geomorphological studies of planets and aster-oids, are today among the main scientific goals of space missions. In the last decades, the great progress in high-resolution imaging of planetary surfaces (with ground-sample-distance that can reach 25 cm/pixel) finds two significant examples in the High Resolution Imaging Science Experiment (HiRISE) on Mars Re-connaissance Orbiter, and in the NAC of the Lunar Reconnaissance Orbiter Camera (LROC) on LRO. These images have provided the widest data-volume ever obtained before from any space mission and are characterized by strong potentialities associated with their astonishing capability of acquire details and fea-tures on the planetary surfaces.
The process for deriving DTMs starting from these raw data is very complex because it has to answer to two main requirements: operate very accurately and work with extremely large data volumes.
Nowadays the most important institutes involved in the planetary mapping are working on developing strategies to fulfil these requests. Despite the introduc-tion of a series of new algorithms for image matching (e.g. the Semi Global Matching: [1]) that yield superior results especially in qualitative terms (smooth and con-tinuous surfaces) and in terms of processing time, the common trend in the planetary-photogrammetry field stays in opting for the established area-based tech-niques and the efforts are more to improving each sin-gle phase of the photogrammetric process (from the image pre-processing stage to the final interpolation of the DTMs).
In this context, the Dense Matcher software (DM) developed at University of Parma has been recently optimized to cope with very high resolution images provided by the most recent missions (LROC NAC and HiRISE) putting the efforts mainly at the correlation phase and at the improvement of the process automa-tion.
In order to improve the performance of the software, a new image correlation code based on advanced Least Squares Matching (LSM) algorithms has been devel-oped.
Perspective changes due to terrain morphology are difficult to accommodate by an area-based stereo cor-relator. The solution has been the use of an iterative algorithm to adapt the correlation window with differ-ent shape functions. Many authors [2] found that the use of a simplified shape function leads to lower com-putational efforts but provides lower accuracy when significant changing in the terrain curvature occurs. Also Bethmann [3] showed that using different shape functions to model the geometric transformation in LSM can bring higher accuracy and solve, in some cases, numerical problems like pixel-locking. In this context, the new DM software uses, rather than the common affine transformation, alternative functional models in the geometrical transformation involved dur-ing LSM to handle perspective differences.
At the same time, working with orbital-space images, usually means to be able to manage large amount of data. Due to that, in order to guarantee good computa-tional performances, efforts have been put in the opti-mization of the processes developing new strategies (grid-matching and tile approach).
Since the stereo-recontruction is strongly correlated to the quality of the image-correlation process (that in many cases can produce outliers and mis-matches) leading to uncorrected interpretations of the topogra-phy, a comparison between uncorrelated data (that don’t participate in the generation of the DTM ) as the laser height points can be used to assess the effective height resolution and the exterior quality (accuracy) of the photogrammetric product.
The paper first describes the main features of the optimized version of Dense Matcher, with particular regard to the mathematical model implemented in the Least Squares Matching. Then, the performance of the image correlation kernel of the program is evaluated through comparisons with DTMs generated by other well established software like Socet Set by Bae System and Ames Stereo Pipeline (NASA) on HiRISE stereo pairs. Finally a comparison is also made with the DTMs produced on NAC stereo-pairs by the Vicar software by DLR (German Aerospace Center), as well as against the LOLA altimeter tracks.
The results look very promising and represent a concrete proof of the capability of Dense Matcher in dealing with two of the most significant examples of high resolution orbital imaging: HiRISE images and the ones acquired by NAC
Asteroid detection at millimetric wavelengths with the PLANCK survey
No full textThe PLANCK mission, originally devised for cosmological studies, offers the opportunity to observe Solar System objects at millimetric and submillimetric wavelengths. In this paper we concentrate on the asteroids of the Main Belt, a large class of minor bodies in the Solar System. At present, more that 40000 of these asteroids have been discovered and their detection rate is rapidly increasing. We intend to estimate the number of asteroids that can be detected during the mission and to evaluate the strength of their signal. We have rescaled the instrument sensitivities, calculated by the LFI and HFI teams for sources fixed in the sky, introducing some degradation factors to properly account for moving objects. In this way a detection threshold is derived for asteroidal detection that is related to the diameter of the asteroid and its geocentric distance. We have developed a numerical code that models the detection of asteroids in the LFI and HFI channels during the mission. This code performs a detailed integration of the orbits of the asteroids in the timespan of the mission and identifies those bodies that fall in the beams of PLANCK and their signal strength. According to our simulations, a total of 397 objects will be observed by PLANCK and an asteroidal body will be detected in some beam in 30% of the total sky scan-circles. A significant fraction (in the range from ~50 to 100 objects) of the 397 asteroids will be observed with a high /S/N ratio. Flux measurements of a large sample of asteroids in the submillimeter and millimeter range are relevant since they allow to analyze the thermal emission and its relation to the surface and regolith properties. Furthermore, it will be possible to check on a wider base, the two standard thermal models, based on a nonrotating or rapidly rotating sphere. Our method can also be used to separate Solar System sources from cosmological sources in the survey. This work is based on PLANCK LFI activities
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