Search

This work is aimed at showing the present capabilities and future potentialities of an imaging radar system that can be mounted onboard flexible aerial platforms, such as helicopters or small airplanes, and may operate in the UHF and VHF frequency bands as Sounder and as Synthetic Aperture Radar (SAR). More specifically, the Sounder operates at 165 MHz, whereas the SAR may operate either at 450 MHz or at 860 MHz. In the work, we present the first results relevant to a set of Sounder and SAR data collected by the radar during a helicopter-borne campaign conducted in 2018 over a desert area in Erfoud, Morocco, just after the conclusion of a system upgrading procedure. In particular, a first analysis of the focusing capabilities of the Sounder mode and of the polarimetric and interferometric capabilities of the SAR mode is conducted. The overall system, originally developed by CO.RI.S.T.A. according to a ASI funding set up in 2010, has been upgraded in the frame of a contract signed in 2015 between ASI and different private and public Italian Research Institutes and Universities, namely CO.RI.S.T.A., IREA-CNR, Politecnico di Milano and University of Trento.

The paper deals with a VH F airborne radar sounder designed for the exploration of ice sheets and arid sub-surfaces. This radar is an improved version of a previously developed prototype and is the product of a project financed by the Italian Space Agency and carried out thanks to the cooperation of Italian research units. The main characteristics of the radar, and a calibration measurement campaign, which has been performed flying over a volcanic area of Lazio region (Central Italy) in September 2017, are herein described. As discussed in the paper, the calibration campaign confirmed a correct system's operation and, in particular, the enhanced along range resolution with respect to the previous prototype. The developed system was, indeed, capable of retrieving the surface topography over a large scale and in a short time. The obtained encouraging results justified the planning of an extensive validation measurement campaign, which will be performed in May 2018 on desert areas.

This paper reports on a model developed for evaluating major system performance of a spaceborne bistatic synthetic aperture radar (SAR) for remote sensing applications. The procedure accounts for formation flying aspects. It is particularly aimed at comparison of monostatic and bistatic cases, and, as a test case, it is applied to study a novel configuration, based on a small satellite equipped with a receiving-only antenna orbiting in tandem with a large, noncooperative transmitting spacecraft, the Italian COSMO-SkyMed mission. Numerical results and plots show the effectiveness of the procedure as a mission design tool and put in evidence key issues and characteristics of the proposed spaceborne bistatic formation.

This work aims to describe the characteristics and the status of development, including the results of a first preliminary testing campaign, of a low frequency airborne imaging radar developed in Italy for the Italian Space Agency.

In the last decade, new device concepts based on novel fabrication methods have emerged as a powerful and general class of supersensitive sensors for the direct detection of biological and chemical targets. Pushed by the opportunity to activate the physical-chemical phenomena at the nanoscale, novel patterning paradigms have gained nanofabrication accuracy accompanied by the fast development of bottom-up strategies. In this frenetic framework, the combination of some heterogeneous techniques-basically nano-imprint lithography, grafting of functional molecules, and synthesis of new ligands and probes to capture specific biological targets-have gained strong attention as enabling emerging technological mixture to fabricate ultra dense array of specialized sensors. Within the scope of this technological convergence, the paper is basically devoted to describe the processes involved in the production of stamps for nanoimprint lithography, the fabrication of printed array of silicon sensors on the micrometer and sub-micrometer resolution, the subsequent covalent biofunctionalization with single strand DNA and some preliminary electrical detection of the hybridization events via water modulating ac resistance. Among the possible choices, focus was given to planar functionalized capacitors for their intrinsic simple configuration and also because they appeared to be the most promising candidates for mass production in printed device architecture. The paper is based on original results but contains also data and achievements taken from the literature to make the discussion self-contained. © 2011 American Scientific Publishers.

The analysis of the electrical properties of polystyrene films containing gold nanoparticles capped with 1-dodecanethiol and 8-hydroxyquinoline molecules is reported. The conductivity of the nanocomposite as a function of the doping level has been investigated both in planar and stacked configurations. While the former configuration evidenced low field tunneling between nanoparticles in the polymer matrix, stacked devices allowed us to investigate the main phenomena ruling the transport properties when switching effects are present close to critical electric fields. In particular, through the analysis of current-voltage characteristics we studied the charge transport at different fillers concentrations and sketched a physical picture of conductivity in such nanocomposite systems.

NASA's Mars Reconnaissance Orbiter mission, MRO, scheduled for launch in 2005, will be equipped with a sounder to find subsurface water and ice: Shallow Radar, SHARAD. This radar has been developed by Alenia Spazio and funded by Italian Space Agency, ASI. An integral part of such kind missions is the development of an EGSE (Electrical Ground Support Equipment) capable to test all the radar functionalities. CORISTA has been responsible to define the EGSE technical requirements and to design, build and test the Mars Echoes Generation System (MEGS). This paper describes the activities developed and the results obtained during the test campaigns of SHARAD. An architectural description of the MEGS will be given with emphasis on the technical aspects related to the signal generation of Mars Echoes and possible operating modes.

MINISAR is a compact airborne interferometric SAR potentially suitable for many applications but mainly finalized for the production of technical topographic maps and monitoring the evolution of landslides events and assessing their extension and risk area. The program is co-funded by the Italian Ministry for Education, Universities and Research (M.I.U.R.). The hardware consists in an airborne X-band radar, able to obtain a resolution less than a meter (because of a 280 MHz stepped chirp signal) and an altimetric accuracy less than 7 meters. Such an accuracy derives from an equivalent 1.5 meters baseline and the high gain antennas that let MINISAR to use a transmitted power of only 80 W. The system will be mounted on board of a small platform and it is thought to have future development for unmanned platform. Data will be processed using a chirp scaling algorithm in order to obtain the two Single Look Complex (SLC) images which can be then processed to obtain high accuracy Digital Elevation Model (DEM).

This letter deals with the design, realization, and validation of a multimode/multifrequency airborne radar designed for both surface and subsurface prospections. The system operates in the frequency band from very high frequency (VHF) to ultrahigh frequency (UHF) and works in two different modes: 1) a nadir-looking sounder in the VHF band (carrier frequency of 163 MHz); and 2) a side-looking imager (i.e., synthetic aperture radar) in the UHF band with two channels at 450 and 860 MHz, respectively. The system validation has been carried out for the “sounder” mode due to helicopter-borne surveys carried out over an area in the Campania region, Southern Italy. The surveys have provided a first proof of system capability in obtaining useful information about the surface and shallower subsurface layers over a large scale and in a relatively short time. In particular, the data collected by the sounder have been processed by means of a microwave tomographic reconstruction approach, and features consistent with tunnels buried at a depth of 15 m have been identified.

This work deals with the design of multimode/multifrequency airborne radar suitable for imaging and subsurface sounding. The system operates at relatively low frequencies in the band ranging from VHF to UHF. It is able to work in two different modalities: (i) nadir-looking sounder in the VHF band (163 MHz) and (ii) side-looking imager (SAR) in the UHF band with two channels at 450 MHz and 860 MHz. The radar has been completely designed by CO.Ri.S.T.A. for what concerns the RF and the electronic aspect, and by the University of Calabria for what concerns the design, realization, and test of SAR antennas. The radar has been installed on a civil helicopter and its operation has been validated in flight in both sounder and imager modality. Preliminary surveys have been carried out over different areas of Campania region, South Italy.

In the recent years a new class of airborne radar system using low frequency have emerged. They are sounder working at VHF/UHF band and SAR (Synthetic Aperture Radar) that are able to provide high resolution images at P and L band. Behind these developments lie technological advances in antenna design, low noise amplifiers, band pass filters, digital receiver technology as well as new processing algorithms. The combination of low frequency and high bandwidth, creates a variety of military an civilian applications, ranging from the detection of targets concealed by foliage and/or camouflage or buried to forestry applications, biomass measuring, Archeological and geological exploration. Following these potentialities, the Italian Space Agency promoted the development of a new multi-mode and multi-band airborne radar system, that can be considered also a “proof-of-concept” for future dedicated spaceborne missions. The research consortium CO.RI.S.T.A. is in charge of the design, development and flight validation of such system, that is the first airborne radar entirely built in Italy.The radar is able to work either as nadir-looking sounder at VHF band (163 Mhz) and as side booking imager (SAR) at P band with two channels at 450 MHz and 900 MHz. The system uses a very flexible architecture due to the implementation of a direct digital synthesis(DDS) of transmitted signal and of stepped-frequency technology that allows the transmission of large bandwidth and facilitates multiple polarizations. Radar is controlled and timed by a powerful control unit based on FPGA technology that is also able to store all data with high data rate directly on SATA disks. Some flight campaigns have been performed on south Italy by using a helicopter of Aeronautica Militare. The present work presents a detailed system description, performance analysis, data processing algorithms and measurement campaign results description.

The current fluctuations in a polystyrene matrix (PS) doped by gold nanoparticles (Au-NPs) and small conjugated molecules of 8-hydroxyquinoline (8HQ) have been characterized. The electrical properties of the PS composite allow using it as a responsive layer in non-volatile memory devices due to its switching capability between two well separated conducting states. The analysis of current fluctuations at fixed bias voltages showed the presence of two states in charge carrier transport regardless of the operating conducting state of the device. Moreover, noise spectra have been investigated in the low frequency region, allowing the estimation of charge relaxation times between current levels in the two memory states. The presence of these slow and large fluctuations can seriously affect the final electrical performances of this class of nanostructured memories.

We explored the modification of polymeric film conductivity by changing the conducting filler percentage in the frame of the percolation theory. The polymeric film is a polystyrene (PS) matrix, while the fillers are gold nanoparticles capped with 1‐dodecanethiol (Au‐DT NPs) and small conjugated molecules 8‐ hydroxyquinoline (8HQ). Experimental results show, that increasing the Au‐ DT and 8HQ wt%, film conductivity increases by up to three orders of magnitude due to charge transfer in the 3D network composed by Au‐ DT NPs and 8HQ.

MINISAR is a compact airborne interferometric SAR potentially suitable for many applications but mainly finalized for the production of technical topographic maps and monitoring the evolution of landslides events and assessing their extension and risk area. The program is co-funded by the Italian Ministry for Education, Universities and Research (M.I.U.R.) The hardware consists in an airborne X-band radar, able to obtain a resolution less than a meter (because of a 280 MHz stepped chirp signal) and an altimetric accuracy less than 7 meters. Such an accuracy derives from an equivalent 1.5 meters baseline and the high gain antennas that let MINISAR to use a transmitted power of only 80 W. The system will be mounted on board of a small platform and it is thought to have future development for unmanned platform. Data will be processed using a chirp scaling algorithm in order to obtain the two Single Look Complex (SLC) images which can be then processed to obtain high accuracy Digital Elevation Model (DEM).

This paper describes scientific rationale and technical approach for a spaceborne bistatic synthetic aperture radar (SAR) mission (BISSAT). The studied configuration is based on a small satellite, equipped with a receiving-only microwave system that catches the echoes of an already existing, main orbiting SAR, without requiring its design modification or additional operating complexities. This experiment has been proposed to the Italian Space Agency as candidate for the third Italian Small Scientific and Technological Mission and preliminary founded for a competitive phase A study. BISSAT experiment offer unique features: (a) to conduct original scientific experiments and to exploit novel applications; (b) to perform a technology demonstration of an original space formation; (c) to keep cost within a small mission budget. Bistatic scattering has proven to be of fundamental importance to many branches of earth sciences and several investigations have been conducted, but considering one or both earth-based antennas and targets of limited dimensions because bistatic observation requires accurate time synchronization and antenna pointing. As an example, bistatic echoes allows innovative characterization of vegetated and urban surfaces for biomass evaluation, or sea surface waves and current to be mapped. Proposed bistatic experiment will allow original scientific activities to be carried out for the first time from space, such as: (i) evaluation of bistatic radar cross section of natural and man-made targets, by means of multi-angle bistatic SAR observations; (ii) acquisition of terrain elevation and slope by means of range and bistatic scattering measurements; (iii) acquisition of velocity measurements thanks to the simultaneous measurement of two Doppler frequencies; (iv) stereogrammetric applications thanks to the large antenna separation involved; (v) improvement of image classification and pattern recognition procedures; (vi) high-resolution measurements of components of sea wave spectra; (vii) signal processing of bistatic data; (viii) across-track and along-track interferometry. Technical feasibility of the mission has been demonstrated, in particular taking advantage from Italian COSMO/SkyMed X-band SAR2000 experience, which has been selected as main mission. Development of bistatic receiver chain can be carried out with wide reuse of components and instruments already qualified within COSMO project. Furthermore, BISSAT will add value and exploit further scientific applications of COSMO mission. Ground segment and bistatic SAR processing require novel, although limited, implementations, again founded on well-assessed expertise. Regarding the platform, BISSAT mission will allow novel experience and potentialities to be fulfilled, such as: propulsion for formation flying and orbit maintenance, and fine attitude and pointing control. It is worth noting that formation flying is an internationally recognized important scenario.

In view of the development of heavy timber seismic-resistant structures, in the context of modern seismic design approach, a possible solution is to allow the timber structure to dissipate a part of the seismic energy. Since timber is a material with an elastic-fragile behaviour, the dissipative function should be delegated to connections, through plastic deformation of steel connectors. However, joints are primary structural elements, with a crucial role in bearing the design loads. Therefore, the role of seismic energy dissipation should be conveniently assumed by ad hoc devices. In this context, the paper deals with the application of fluid viscous dampers (FVD) to timber frames: FVDs dissipate seismic energy, while timber elements and steel connections remain elastic. Specifically, 2D single-storey structures with dissipative bracing systems, equipped with FVDs, in different configurations, are studied, assuming several rates of possible dampings. Non-linear dynamic time history analyses are performed (SAP2000, v18). Results are discussed showing significant reduction of the structural mass compared to the non-dissipative ones, recentering capability of the structures, high dissipative capacity, simpler elastic connections. The reduction of production and maintenance costs follows. All these involve the efficiency of the structural performance and sustainability under earthquakes.