263 research outputs found
Radar Signal Propagation and Detection Through Ice
No full textIn this paper we describe the existing and planned radar measurements of the
planetary bodies. The dielectric properties of water ice and other potential surface and subsurface
materials are discussed, as well as their dependency on temperature and structure.
We then evaluate the performance of subsurface sounding radars using these parameters.
Finally we describe some laboratory technique to help interpret the radar data, presenting
some results obtained using dielectric spectroscopy methods
INNOVATIVE FRACTAL-BASED MODELS FOR RADAR ALTIMETER DATA
No full textAn innovative electromagnetic model for the radar echoes received by a
microwave altimeter is proposed: it is based on fractal models employed both to describe the natural surface and to evaluate the surface scattering behaviour. The scattering surface is modelled by means of the fractional Brownian model (fBm) process, whose realizations are obtained by using the band-limited Weierstrass-Mandelbrot (WM) function. The scattering
process is evaluated by means of the Physical Optics solution specifically derived for fractal surfaces. Rationale to apply this solution to the evaluation (in time domain) of the received echoes is provided. Dependence of the return pulse shapes on surface topography at different roughness scales is highlighted: some relevant meaningful examples are presented. Simulation
results are provided to show the potential of the proposed technique that could be the fundamental element to generate an atlas of expected returns from a given radar altimeter
A simple inversion model for the estimation of subsurface features of Mars poles
No full textRadar observations from Marsis have demonstrated that Martian Polar Layered Deposits (PLD's) are very transparent to radar waves. Thus, the sounder is able to detect the presence of subsurface reflections in the polar regions below the ice-rich layered deposits. The analysis of radar data makes it possible to gain information about some physical features of Mars surface. In this work an electromagnetic inversion model is used to characterize the shallower structures. This approach assumes that structure consists of layers with parallel plane interfaces and that the electromagnetic properties of the first layer are known a priori. Under these assumptions it is possible to estimate the dielectric permittivity of the subsurface structure. The inversion method has been tested in an area of South Pole and reconstruction results are shown
Surface and subsurface radar backscattering coefficient over the Martian South Polar Layered Deposits from MARSIS data
No full textNote Illustrative della Carta geologica d'Italia alla scala 1:50.000, F. 501 Orosei, Servizio Geologico d'Italia - ISPRA
No full text<p>Note illustrative redatte per il Foglio geologico n. 501 Orosei della Carta Geologica d'Italia alla scala 1:50.000. 230 pp.</p>
Osservazioni preliminari sui vertebrati fossili plio-pleistocenici del Monte Tuttavista (Orosei, Sardegna)
No full textIn this paper the preliminary results of the study of fossil vertebrates collected in numerous fissure fillings of Monte Tuttavista (Orosei, Eastern Sardinia) are published. Five species of fishes, four species of amphibians, eight species of reptiles, twenty-two species of birds and twenty-seven species of mammals have been identified. All these taxa belong to at least four successive assemblages, spanning from the Late Pliocene to the Holocene
A working environment for digital planetary data processing and mapping using ISIS and GRASS GIS
No full textSince the beginning of planetary exploration, mapping has been fundamental to summarize observations returned by scientific missions. Sensor-based mapping has been used to highlight specific features from the planetary surfaces by means of processing. Interpretative mapping makes use of instrumental observations to produce thematic maps that summarize observations of actual data into a specific theme. Geologic maps, for example, are thematic interpretative maps that focus on the representation of materials and processes and their relative timing. The advancements in technology of the last 30 years have allowed us to develop specialized systems where the mapping process can be made entirely in the digital domain. The spread of networked computers on a global scale allowed the rapid propagation of software and digital data such that every researcher can now access digital mapping facilities on his desktop.
The efforts to maintain planetary missions data accessible to the scientific community have led to the creation of standardized digital archives that facilitate the access to different datasets by software capable of processing these data from the raw level to the map projected one.
Geographic Information Systems (GIS) have been developed to optimize the storage, the analysis, and the retrieval of spatially referenced Earth based environmental geodata; since the last decade these computer programs have become popular among the planetary science community, and recent mission data start to be distributed in formats compatible with these systems.
Among all the systems developed for the analysis of planetary and spatially referenced data, we have created a working environment combining two software suites that have similar characteristics in their modular design, their development history, their policy of distribution and their support system. The first, the Integrated Software for Imagers and Spectrometers (ISIS) developed by the United States Geological Survey, represents the state of the art for processing planetary remote sensing data, from the raw unprocessed state to the map projected product. The second, the Geographic Resources Analysis Support System (GRASS) is a Geographic Information System developed by an international team of developers, and one of the core projects promoted by the Open Source Geospatial Foundation (OSGeo). We have worked on enabling the combined use of these software systems throughout the set-up of a common user interface, the unification of the cartographic reference system nomenclature and the minimization of data conversion. Both software packages are distributed with free open source licenses, as well as the source code, scripts and configuration files hereafter presented. In this paper we describe our work done to merge these working environments into a common one, where the user benefits from functionalities of both systems without the need to switch or transfer data from one software suite to the other one. Thereafter we provide an example of its usage in the handling of planetary data and the crafting of a digital geologic map.
Research highlights:
ISIS allows to process planetary imagers and spectrometers data. GRASS GIS allows to process geodata and to produce thematic digital maps. We developed computer code and scripts to allow the combined use of ISIS and GRASS. We crafted a digital geologic map starting from mosaics, topography and raw data. Digital geologic maps produced can be published in interoperable data formats
A strategy for an accurate estimation of the basal permittivity in the Martian North Polar Layered Deposits
No full textThis paper deals with the investigation of the Mars subsurface by means of data collected by the Mars Advanced Radar for Subsurface and Ionosphere Sounding working at few megahertz frequencies. A data processing strategy, which combines a simple inversion model and an accurate procedure for data selection is presented. This strategy permits to mitigate the theoretical and practical difficulties of the inverse problem arising because of the inaccurate knowledge of the parameters regarding both the scenario under investigation and the radiated electromagnetic field impinging on the Mars surface. The results presented in this paper show that it is possible to reliably retrieve the electromagnetic properties of deeper structures if such strategy is accurately applied. An example is given here, where the analysis of the data collected on Gemina Lingula, a region of the North Polar layer deposits, allowed us to retrieve permittivity values for the basal unit in agreement with those usually associated to the Earth basaltic rocks
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