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Baskaradas, James Arokiasami
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Baskaradas, James Arokiasami
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- PublicationOpen AccessItalian RES Investigation in Antarctica: The New Radar System(2008-07)
; ; ; ; ; ; ; ;Tabacco, I. E.; Dip. Scienze della Terra, Sez. Geofisica, Via Cicognara 2, Milano - Italy ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ; ; A Radio Echo Sounding (RES) system is an active remote-sensing instrument that uses electromagnetic wave penetration into the ice to obtain information on the depth of the bedrock and on the ice thickness and its inhomogeneities, i.e. internal layering of glaciers and subglacial lake exploration. In 1995 the INGV developed its own airborne radio echo sounding system, which is continuously being upgraded. During the 1995, 1997, 1999, 2001 and 2003 Italian Antarctic Expeditions, the RES system was used to investigate different Antarctic regions. During 2007-2008 campaign, new RES systems will be used. In the following the main characteristics of the systems will be briefly described.14875 411 - PublicationRestrictedElectromagnetic ice absorption rate at Dome C, Antarctica(2014-08-20)
; ; ; ; ;Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; Radio-echo sounding (RES) is a radar technique widely employed in Antarctica and Greenland to define bedrock topography but, over the last decade, it has also played an important role in subglacial lake exploration and hydrogeological studies at the bedrock/ice interface. In recent studies, bedrock characterization has been improved through analysis of radar power echoes to evaluate the electromagnetic (EM) properties of the interface and allow the distinction between wet and dry interfaces. The RES received signal power depends on ice absorption and bedrock reflectivity, which is closely linked to the specific physical condition of the bedrock. In this paper, an evaluation of EM ice absorption was conducted starting from RES measurements collected over subglacial lakes in Antarctica. The idea was to calculate ice absorption starting from the radar equation in the case of subglacial lakes, where the EM reflectivity value is considered a known constant. These values were compared with those obtained from analysis of ice-core dielectric profiles from EPICA ice-core drilling data. Our analysis reveals that the ice absorption rate calculated from RES measurements has an average value of 7.2 dBkm–1, and it appears constant, independent of the subglacial lake depth in different zones of the Dome C area.990 136 - PublicationOpen AccessThe New AIS-INGV Ionosonde at Italian Antarctic Observatory(2004)
; ; ; ; ; ; ;Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; TRIL-International Centre for Theoretical Physics, Trieste, Italy ;Doumaz, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ; The Italian Ionospheric Antarctic Observatory of Terra Nova Bay (74.70S, 164.11E) was recently equipped with the AIS-INGV ionosonde developed at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, (Italy). This paper aims to describe briefly which are the main characteristics of the instrument and show the good quality and reliability of the recorded ionograms.54137 458 - PublicationOpen AccessLa ionosonda AIS-2: evoluzione nel progetto del sistema e primi collaudi.(2013)
; ; ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Il presente lavoro descrive lo stato di avanzamento del progetto della ionosonda AIS-2, già descritto nel Rapporto Tecnico [Sciacca, Baskaradas, 2012]. Rispetto alla versione ivi riportata sono stati compiuti vari interventi migliorativi, specialmente nella direzione di una semplificazione ed unione delle funzioni di alcune delle schede previste inizialmente. Parallelamente all’adeguamento del progetto sono state costruite e collaudate alcune delle schede componenti ed il presente rapporto tecnico descrive in dettaglio il loro progetto e collaudo, che ha avuto un sostanziale esito positivo.435 144 - PublicationOpen AccessPower variation analysis of echo signal from ionospheric reflector(2008-08-09)
; ; ; ; ; ; ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; A series of measurements of the radio echo power was performed to study and to monitor some dynamic characteristics of the ionospheric reflector. The sounding system was derived from a phase coded HF radar with the purpose of studying the ionospheric fading channel under certain controlled conditions. The single fixed frequency sounding that lasts a few minutes is carried out between two ionospheric vertical soundings to validate the chosen reflector. This work presents the experimental set-up and some preliminary results of the measurements.174 167 - PublicationOpen AccessAnalysis of Bent Wire Antenna Resonant Frequency for Different Bent Angles(2019-12)
; ; ; ; ; ; ; For the bedrock survey in the temperate glacier regions, low frequency antenna system of the airborne ground penetrating RADAR plays a very important role. A small size antenna, working at 10 MHz, would make its use easier in various radar applications. Reducing the resonant frequency of the wire dipole antenna structure, without increasing the physical size, can be attained by introducing bents in the existing structure. This paper introduces a new bent wire dipole antenna and presents the effects of bent angle of 80°, 70°, 60°, 50°, 45° and 40°of the wire antenna on the antenna parameters such as resonant frequency, S11, VSWR, gain and radiation pattern. A broadband four element equivalent circuit model of a straight dipole is used with some modifications in the R, L, C equations for the new bent wire dipole antenna by utilizing the bent angle. The frequency response of the equivalent circuit model, calculated resonant frequency values using the equations and the simulated results of the bent wire dipole antenna is compared and analyzed. As the antenna placement area inside the anechoic chamber is limited, the size of the 10MHz antenna has been scaled down by a factor of 0.01. This modifies the resonant frequency of the new structure to 1GHz. The scaled down antenna system are simulated, analyzed and tested in a GTEM cell. For bandwidth improvement of the 10 MHz antenna, a lumped element matching circuit has been designed and simulated.480 148 - PublicationOpen AccessInaccuracy assessment for simultaneous measurement of resistivity and permittivity applying sensitivity and transfer function approaches(2010-04)
; ; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; The present study proposes a theoretical modeling of simultaneous and noninvasive measurements of electrical resistivity and dielectric permittivity using a quadrupole probe on a subjacent medium. A mathematical-physical model is applied to the propagation of errors in the measurement of resistivity and permittivity based on a sensitivity functions tool. The findings are also compared with results of the classical method of analysis in the frequency domain, which is useful for determining the behavior of zero and pole frequencies in the linear time invariant circuit of the quadrupole. This study underlines that average values of electrical resistivity and dielectric permittivity can be used to estimate complex impedance over various terrains and concretes, especially when they are characterized by low levels of water saturation (content), and are analyzed within a bandwidth ranging only from low to middle frequencies. To meet the design specifications, that ensure satisfactory performances of the probe (inaccuracies of no more than 10%), the forecasts provided by the sensitivity functions approach are discussed in comparison with those foreseen by the transfer functions method (in terms of both the band of frequency f and the measurable range of resistivity rho, or permittivity epsilon).597 164 - PublicationRestrictedGPR as an effective tool for safety and glacier characterization: experiences and future development(2010-08)
; ; ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; In recent times, the GPR technique has assumed an important role in glacial environment exploration. Ice thickness, bedrock description, internal water floods or underground channel, glacial structures (as snow layering and crevasses detection) form part of our experience in Antarctica and in high alpine glacier ski areas. In this paper, we present some results of these investigations exploring the possibility of combining our technical expertise on Radio Echo Sounding (RES) instrumentation to develop a system for subglacial environment exploration.519 62 - PublicationRestrictedPower variation analysis of echo signals from ionospheric reflectors(2013-02)
; ; ; ; ; ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; A series of Power Virtual Height measurements (PVH) of radio echoes reflected from the ionosphere were acquired at a given frequency during the period 3–22 January 2008 with the purpose of studying the slow fading variations through time of the ionospheric channel. To obtain PVH data, an ionospheric vertical sounding system was suitably adapted to work at a single fixed frequency. PVH measurements were recorded between two routine ionospheric vertical soundings, providing a data type that enables evaluation of fading fluctuation through time. The time stability of the ionospheric layers is determined by analyzing the level of the received signal power within a chosen threshold. In this paper the fading behaviour and its characteristics are described, considering only temporal periodicity above 0.5 s. In a further analysis a relation is demonstrated between the recorded fading and the time stability of the signal within a fixed interval of values.621 86 - PublicationOpen AccessOptimal requirements of a data acquisition system for a quadrupolar probe employed in resistivity and permittivity surveys(2010-12)
; ; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; This paper discusses the development and engineering of a suitable quadrupolar probe for simultaneous and non invasive surveys of electrical resistivity and dielectric permittivity. The quadrupolar probe is able to perform measurements on a subsurface with inaccuracies below a fixed limit (10%) in a bandwidth of low (LF) frequency (100kHz). The quadrupole should be connected to an appropriate analogical digital converter (ADC) which samples in phase and quadrature (IQ) or in uniform mode. If the probe is characterized by a galvanic contact with the surface, the inaccuracies in the measurement of resistivity and permittivity, due to the IQ or uniform sampling ADC, are analytically expressed. A large number of numerical simulations proves that the performances of the probe depend on the selected sampler and that the IQ is better compared to the uniform mode under the same operating conditions, i.e. bit resolution and medium.447 169