Browsing by Author "Convenevole, Carlo"

Now showing 1 - 5 of 5
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    Feasibility of passive bistatic geosynchronous radar using comsat transmissions
    (IEEE, 2018-11-05) Hobbs, Stephen; Convenevole, Carlo; Gashinova, M.; Cherniakov, M.; Cassidy, S.
    Communication satellites in geosynchronous orbit are increasingly broadcasting digital signals with high bandwidth and high power. These signals are in principle well-suited to radar imaging and the study presented here is an initial feasibility study for a passive bistatic synthetic aperture radar using satellites in geosynchronous orbit (GEO). The persistent viewing possible from GEO could enable important new applications. The mission concept is outlined and studies of the available signal formats identify digital TV broadcasts in Ku-band as most suitable for radar imaging. The additional space hardware required is a dedicated receive channel, which could be implemented as a hosted payload at modest cost. Our findings so far suggest that the mission concept is feasible for coarse spatial resolution images and that it could therefore provide a low-cost technology demonstration of geosynchronous radar.
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    Geostare system performance assessment methodology
    (IEEE, 2016-11-03) Hobbs, Stephen E.; Convenevole, Carlo; Monti-Guarnieri, Andrea V. ; Wadge, Geoff
    Geosynchronous synthetic aperture radar (GEO SAR) is attracting growing interest due to its potential for flexible and frequent imaging over continental areas. Studies are underway to evaluate mission design options and to investigate enabling technologies. This article outlines a method for assessing mission performance which accounts for actual land-cover distributions and weather statistics to derive statistical estimates of mission performance relative to user-defined requirements. A technical challenge is to account accurately for the effects of surface “clutter”: several methods for this are available and will be evaluated. The methodology is outlined. The performance estimates will be used to refine and validate mission design options and to build evidence for the expected benefits of GEO SAR
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    Geosynchronous synthetic aperture radar performance estimation and mission design
    (Cranfield University, 2024-01) Convenevole, Carlo; Hobbs, Stephen E.; Sanchez Cuartielles, Joan Pau
    Geosynchronous Synthetic Aperture Radar (GeoSAR) missions have attracted growing interest in the scientific community thanks to their unique capability in terms of persistent coverage and temporal resolution. Despite this, no mission has flown yet and there are some uncertainties concerning the technical feasibility of such missions (in the case of high orbit inclination concept) and the achievable performance (in the case of a low inclination and low eccentricity concept). For the purpose of developing a general Performance Estimation Methodology, the need for a new clutter model arose, because the existing clutter models are not sufficient for the GeoSAR missions studied in Europe. The Billingsley clutter model and the Borealscat clutter model have been developed using an integration time which is much shorter than the typical GeoSTARe or Hydroterra ones. Moreover, these two clutter models have been developed for forests (which accounts for almost 36% of Europe’s landcover according to Eurostat) and the main landcover class, which is agriculture, is around the 39% of the total. Since wind-driven motion of vegetation is the main source of clutter power over land. A direct physics-based simulator has been developed for short vegetation using a database of wheat plant motion in a variety of wind conditions. The output of this simulator was the moving target focused signal, which has been used to create the wheat clutter model. The development of this wheat clutter model (specific for medium-high incidence angles) required a specific GeoSAR clutter simulator (developed in C++). The simulated focused signals have been fitted using clutter power models available in literature (expo- nential clutter model and power law clutter model); a comparison of the exponential model and the power law clutter power model has been performed. The power law clutter model gave a better fit to the wheat data. A Signal to Clutter Ratio (SCR) simulator has been developed using the clutter model to assess the azimuth spread of clutter power and hence to estimate SCR in representative landscapes. With the help of a Bistatic Simulator developed during this thesis, a new Single Input Multiple Output mission concept has been proposed (a single monostatic SAR and two passive bistatic receivers on other two platforms). From the study of the wheat clutter dependence on windspeed a new land scatterometer mission concept (peculiar of low azimuth speed Geosynchronous SAR missions) is suggested (to measure the windspeed at a much higher spatial and temporal resolution than current systems). The road to an End-to-End performance simulator is still long but some interesting steps have been done and the capabilities of the Performance Estimation Methodology have been shown. Further work is needed to develop similar clutter models for tall vegetation and the ocean (existing results are available for both of these), and then to combine these with realistic models of landcover and weather (including seasonal changes) to enable comprehensive end-to-end GeoSAR performance simulation. The source code of the simulators are available in the appendices together with the requirements discussion.
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    ItemOpen Access
    Method for estimating clutter limited geosynchronous synthetic aperture radar performance
    (IEEE, 2019-09-27) Convenevole, Carlo; Hobbs, Stephen
    This paper reviews the geosynchronous synthetic aperture radar (GeoSAR) literature and highlights a gap in land clutter theory.The gap concerns clutter models with weather dependence for incidence angles between 20 and 70 degrees. We update with an improved clutter model the system performance method presented at IGARSS 2016 to estimate the SAR system performance taking into account the weather statistics and the landcover of the target area. The performance statistics obtained with this method allow to estimate the fraction of time (e.g. percentage of a month) in which the SAR system can accomplish the user’s requirement. So far the method has been developed for short vegetation (specifically wheat), as source of clutter, and for bare land and urban area as other target areas. A full clutter model is still under development, but results are presented for the weather dependence of the coherent fraction of the scattered power. Since the azimuth spread of clutter power for GeoSAR can exceed the beam footprint in strong weathe rconditions, we expect improved image quality in these conditions. Two example of the effect of different clutter power probability density function are briefly presented
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    Physics-based clutter model for geosynchronous synthetic aperture radar
    (IEEE, 2020-06-02) Convenevole, Carlo; Hobbs, Stephen
    In this paper the land clutter literature is briefly discussed and a need for a new class of clutter models for the Geosynchronous Synthetic Aperture Radar System Performance Assessment is shown. A new physics-based clutter model that uses data on observed vegetation motion is introduced and a wheat database is presented together with an analysis of the plant motion statistics. After this, the characteristics of the new model are outlined. Then the analysis of the wheat signal is developed for all the available data, and subsequently the properties of the moving target signal are related to a more ideal plant motion.Finally, the obtained model for the target coherent power is illustrated together with the future work needed to complete the clutter model. This approach, developed for the Geosynchronous Synthetic Aperture Radar performance estimation, promises a versatile model suitable for a wide range of SAR systems