Browsing by Author "Urbina, J."
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Item Restricted Development of a passive VHF radar system using software‐defined radio for equatorial plasma instability studies(American Geophysical Union, 2013-06-25) Tuysuz, B.; Urbina, J.; Lind, F. D.In this paper, a bistatic passive radar receiver system named “Coherent‐scatter Atmospheric Passive Radar Imager (CAPRI)” is described. It is primarily designed to study the dynamics of the upper atmosphere by utilizing “transmitters of opportunity” as the RF target illuminators. CAPRI is constructed using the open source software‐defined radio toolkit, GNU Radio, to meet the signal processing requirements in combination with the open source hardware, Universal Software Radio Peripheral 2, for data acquisition. The resultant system is highly flexible, and we present the details of the design as well as a performance analysis. CAPRI will be deployed in Peru, near the magnetic equator, for long‐term operations in the area. FM stations near Lima, Peru, will be utilized with the targets of interest being the equatorial electrojet and the spread F. The results will then be compared to the Jicamarca Unattended Long‐term investigations of the Ionosphere and Atmosphere (JULIA) radar data, and CAPRI will be used to improve the simultaneous time and spatial coverage in the region in a more cost‐effective manner.Item Open Access Diurnal variation of non-specular meteor trails(European Geosciences Union, 2009-05-04) Hinrichs, J.; Dyrud, L. P.; Urbina, J.We present results of simulated radar observations of meteor trails in an effort to show how non-specular meteor trails are expected to vary as a function of a number of key atmospheric, ionospheric and meteoroid parameters. This paper identifies which geophysical sources effect the variability in non-specular trail radar observations, and provides an approach that uses some of these parameter dependencies to determine meteoroid and atmospheric properties based upon the radar meteor observations. The numerical model used follows meteor evolution from ablation and ionization to head echo plasma generation and through formation of field aligned irregularities (FAI). Our main finding is that non-specular meteor trail duration is highly sensitive to the presence of lower thermospheric winds or electric fields and the background ionospheric electron density. In an effort to make key predictions we present the first results of how the same meteoroid is expected to produce dramatically different meteor trails as a function of location and local time. For example, we show that mid-latitude trail durations are often shorter lasting than equatorial trail observations because of the difference in mid-latitude wind speed and equatorial drift speed. The simulated trails also account for observations showing that equatorial nighttime non-specular meteor trails last significantly longer and are observed more often than daytime trails.Item Open Access On the characterization of radar receivers for meteor-head echoes studies(American Geophysical Union, 2013-01) Galindo, F. R.; Urbina, J.; Chau Chong Shing, Jorge Luis; Dyrud, L.; Milla, MarcoWe report the role that the ambiguity function (AF) plays on the determination of signal to noise ratio (SNR) collected from meteor head echoes. Theoretical analysis shows that any measured meteor SNR exhibits temporal ripples whose shape is related to both the transmitted pulse envelope and the filter impulse response of the receiver. These theoretical findings are corroborated with (1) experimental meteor data recorded with Jicamarca 50 MHz radar (11.95 S, 76.87 W) and (2) simulated meteor data obtained by replicating the acquisition system of Jicamarca. A statistical analysis of the experimental meteor data reveals that at least 14% of the population collected each day at Jicamarca exhibits these ripples. On the remaining 86% of meteor events, the ripples cannot be distinguished due to noise, contamination from other sources of scattering (i.e., nonspecular echoes), and ensemble average applied to the data. In general, these ripples demonstrate the importance of obtaining an accurate model of a radar system to avoid misinterpretation of SNR.Item Restricted On the lack of southern hemisphere polar mesosphere summer echoes(American Geophysical Union, 1995-06-20) Balsley, B.B.; Woodman Pollitt, Ronald Francisco; Sarango, M.; Rodriguez, R.; Urbina, J.; E. Ragaini; Carey, J.; Huaman, M.; Giraldez, A.We report VHF radar observations of the southern high-latitude mesopause region using wind profilers that were installed recently on King George Island, Antarctica, and Ushuaia, Argentina. Briefly, our observations, which were made during January and February 1993, show almost no evidence of so-called polar mesosphere summer echoes, or PMSE. Since these echoes are a predominant feature of the northern high-latitude mesosphere in summer, their absence in the southern hemisphere is both surprising and intriguing. In this paper we present evidence demonstrating the virtual absence of the echoes and demonstrate that our systems were capable of detecting them had they been present. We also outline some of the consequences of this intriguing result, which are supported by observed hemispheric differences in polar mesospheric clouds, mesospheric temperatures, upper atmospheric gravity wave activity, and mean circulation patterns.Item Open Access On the possible effect of the signal processing in the meteor-head data at Jicamarca: preliminary results(Instituto Geofísico del Perú, 2010) Galindo, F.; Urbina, J.; Chau Chong Shing, Jorge Luis; Dyrud, I.Diapositivas presentadas en el 2010 CEDAR Workshop, University of Colorado, Boulder, CO, 20-25 June 2010.Item Restricted Southern-hemisphere PMSE: Where are they?(American Geophysical Union, 1993-09) Balsley, B. B.; Woodman Pollitt, Ronald Francisco; Sarango, M.; Urbina, J.; Rodríguez, R.; Ragaini, E.; Carey, J.We report a surprising absence of PMSE (Polar Mesospheric Summer Echoes) in VHF radar observations of the southern summer high-latitude mesosphere. Our observations cover about twenty days during January-February, 1993, from King George Island, Antarctica.Item Restricted Wind profiler installed in Antarctica(American Geophysical Union, 1993-08) Balsley, B. B; Carey, J.; Woodman Pollitt, Ronald Francisco; Sarango, M.; Urbina, J.; Rodríguez, R.; Ragaini, E.A VHF (50 MHz) wind profiler was installed in Antarctica at the Peruvian Base Machu Picchu on King George Island from January 21 to 26. The wind profiler will provide a first look at atmospheric dynamics over the region. The profiler-the first of its kind in Antarctica-is a National Science Foundation sponsored cooperative project of the University of Colorado, the Geophysical Institute of Peru, the University of Piura (Peru), and the Peruvian Navy. This venture was also greatly facilitated by Peru's Comision Nacional de Asuntos Antartidos and Consejo Nacional de Ciencias y Tecnologia, with additional logis tics support provided by the Argentinean Navy and the Uruguayan Air Force.