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NAKAMURA, Kenji, Shinsuke SATOH, Fumie A. FURUZAWA, and Haruya MINDA. "Bird Migration Echoes Observed by Polarimetric Radar." Institute of Electronics, Information and Communication Engineers, 2008. http://hdl.handle.net/2237/15008.
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Dorfman, Seth E. "Intense spreading of radar echoes from ionospheric plasmas." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32897.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (leaf 41).
On December 25, 2004, a large-scale ionospheric plasma bubble was observed over Arecibo Observatory in Puerto Rico, inducing significant range spreading on ionograms. This phenomena may be explained by means of the E x B instability and gravitational Rayleigh-Taylor instability. A derivation of the dispersion relations for X and O mode waves transmitted from an ionosonde and an analysis of the collisional Rayleigh-Taylor instability leading to an expression for the growth rate are presented as background information. Ray tracing code developed by Nathan Dalrymple, a previous graduate student of Professor Min-Chang Lee, is extended, first to draw refractive index surfaces to illustrate a key principle in ray tracing and later to simulate range spreading due to depleted ionospheric ducts [1]. Data from Arecibo incoherent scatter radar and Arecibo's CADI digisonde is examined showing strong evidence for the development of a plasma bubble following a rise in the plasma layer and the appearance of a horizontal density gradient. In one portion of the ionosphere, this gradient is found to be at an angle of approximately 70 degrees to the Earth's magnetic field, a favorable condition for the excitation of the Rayleigh-Taylor instability over Arecibo.
by Seth E. Dorfman.
S.B.
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Georgiev, Krasin. "Biologically inspired processing of radar and sonar target echoes." Thesis, Cranfield University, 2017. http://dspace.lib.cranfield.ac.uk/handle/1826/12692.
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Modern radar and sonar systems rely on active sensing to accomplish a variety of tasks, including detection and classification of targets, accurate localization and tracking, autonomous navigation and collision avoidance. Bats have relied on active sensing for over 50 million years and their echolocation system provides remarkable perceptual and navigational performance that are of envy to synthetic systems.
The aim of this study is to investigate the mechanisms bats use to process echo acoustic signals and investigate if there are lessons that can be learned and ultimately applied to radar systems. The basic principles of the bat auditory system processing are studied and applied to radio frequencies.
A baseband derivative of the Spectrogram Correlation and Transformation (SCAT) model of the bat auditory system, called Baseband SCAT (BSCT), has been developed. The BSCT receiver is designed for processing radio-frequency signals and to allow an analytical treatment of the expected performance. Simulations and experiments have been carried out to confirm that the outputs of interest of both models are “equivalent”.
The response of the BSCT to two closely spaced targets is studied and it is shown that the problem of measuring the relative distance between two targets is converted to a problem of measuring the range to a single target. Nearly double improvement in the resolution between two close scatterers is achieved with respect to the matched filter.
The robustness of the algorithm has been demonstrated through laboratory measurements using ultrasound and radio frequencies (RF). Pairs of spheres, flat plates and vertical rods were used as targets to represent two main reflectors.
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Nordström, Per. "Anomalous Meteor Head Echoes Detected by the MU Radar." Thesis, Luleå tekniska universitet, Rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79101.
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This study have identified and analysed anomalous meteor head echos detected by the MU Radar, as well as reproduced an interference anomaly through simulation with the use of an existing analysis pipeline. The parameters used to detect anomalies were High Start Altitude [HSAA], High Radar Cross Section [HRCSA] and High Eccentricity [HEA]. A cut-off of the head echo signal were the cause of the HSAA’s. Trail echos misclassified as head echoes and low agreement with the multiple emitter location and signal parameter estimation (MUSIC) method gave rise to the HRCSA’s. The majority of the HEA’s were given a falsely high eccentric- ity due to high beam angle and trail echos detection. Three found HEA’s showed a small possibility of having an hyperbolic orbit. Additionally, a simulation was made which concluded that signal interference will occur between two echos if the range is the same to the radar.
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Jackson, Dawood. "The retrieval of ice sheet topography from satellite radar altimeter echoes." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338956.
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Mead, Reginald Marshall. "A system for automating identification of biological echoes in NEXRAD level II radar data." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/mead/MeadR1209.pdf.
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Since its inception in the mid twentieth century, radar ornithology has provided scientists with new tools for studying the behavior of birds, especially with regards to migration. A number of studies have shown that birds can be detected using a wide variety of radar devices. Generally, these studies have focused on small portable radars that typically have a finer resolution than large weather surveillance radars. Recently, however, a number of researchers have presented qualitative evidence suggesting that birds, or at least migration events, can be identified using large broad scale radars such as the WSR-88D used in the NEXRAD weather surveillance system. This is potentially a boon for ornithologists because NEXRAD data covers a large portion of the country, is constantly being produced, is freely available, and is archived back into the early 1990s. A major obstacle is that identifying birds in NEXRAD data currently requires having a trained technician manually inspect a graphically rendered radar sweep. The immense amount of available data makes manual classification of radar echoes infeasible over any practical span of space or time. In this thesis, a system is presented for automating this process using machine learning techniques. This approach begins with classified training data that has been interpreted by experts or collected from direct observations. The data is preprocessed to ensure quality and to emphasize relevant features. A classifier is then trained using this data and cross validation is used to measure performance. The experiments in this thesis compare neural network, naïve Bayes, and k-nearest neighbor classifiers. Empirical evidence is provided showing that this system can achieve classification accuracies in the 80th to 90th percentile.
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Hardaker, Paul J. "A study of the melting layer in single polarisation radar echoes with application to operational weather radar." Thesis, University of Essex, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316205.
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Dean, Timothy J. Physical Environmental & Mathematical Sciences Australian Defence Force Academy UNSW. "Development and evaluation of automated radar systems for monitoring and characterising echoes from insect targets." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Physical, Environmental and Mathematical Sciences, 2007. http://handle.unsw.edu.au/1959.4/38667.
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This thesis describes the construction of a mobile Insect Monitoring Radars (IMR) and investigations of: the reliability of IMRs for observing insect migration in inland Australia; possible biases in IMR migration estimates; the relation between an insect???s size and its radar properties; radar discrimination between insect species; the effect of weather on the migrations of Australian plague locusts and of moths; the scale of these migrations; and here IMRs are best located. The principles of entomological radar design, and the main features of insect migration in inland Australia, are reviewed. The main procedures used in the study are: calculation of radar performance and of insect radar cross sections (RCSs); reanalysis of a laboratory RCS dataset; statistical analysis of a fouryear dataset of IMR and weather observations; and a field campaign using both two existing fixed IMRs and the new mobile unit. Statistical techniques used include correlation, multiple regression, discriminant analysis, and principal components analysis. The original results of this work include design details of the mobile IMR, extension of radar performance calculations to IMRs and evaluation of flight speed biases, a holistic approach to IMR design, the relation of insect RCS magnitudes and polarization patterns to morphological variables, an estimate of the accuracy of the retrieved parameters, evaluations of three approaches (oneparameter, theory-based, and a novel two-stage method) to target identification, and verification of inferred target identities using results from nearby light traps. Possible sites for future IMRs are identified. The major conclusions are that: a mobile IMR can be built with a performance equal to that of a fixed IMR but at half the cost; significant biases in the signal processing results arise from insect speed; locusts and moths can be distinguished if all RCS parameters are used; IMRs can be designed to match particular requirements; weather has a significant effect on insect migration, the best single predictor of insect numbers being temperature; moonlight has no effect; the spatial correlation of migration properties falls to 50% at a separation of 300 km; and migrating insects can be carried by the wind for 500 km in a single night
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Smirnova, Maria. "Long-term observations of polar mesosphere summer echoes using the ESRAD MST radar." Doctoral thesis, Luleå tekniska universitet, Rymdteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18134.
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Polar Mesosphere Summer Echoes (PMSE) are strong radar echoes observed from altitudes of 80-90 km in polar regions, during summer time. PMSE are closely related to the fascinating atmospheric phenomenon known as noctilucent clouds (NLC). Since it has been suspected that NLC could respond to climate change in the mesosphere, they have attracted considerable interest in the scientific community during recent years. However, continuous visual or photographic NLC observations suffer from weather restrictions and the human factor. In contrast, PMSE radar measurements can easily be made over a long interval and are very attractive for long-term studies of the atmospheric parameters at the polar mesopause. This thesis uses the world’s longest data set of PMSE observations made by the same radar at the same place. Since 1997 these measurements have been carried out with the 52 MHz ESRAD MST radar located near Kiruna in Northern Sweden. The data set for 1997-2008 has been used for studies of diurnal, day-to-day and year-to-year variations of PMSE. We showed that PMSE occurrence rate and volume reflectivity on a daily scale show predominantly semidiurnal variations with the shape of the diurnal curves remaining consistent from year to year. We found that day-to-day and inter-annual variations of PMSE correlate with geomagnetic activity while they do not correlate with mesopause temperature or solar activity. We did not find any statistically significant trends in PMSE occurrence rate and length of PMSE season over 1997-2008. The thesis also presents also a new, independent calibration method, which can be used to estimate changes in transmitter output and antenna feed losses from year to year (for example due to changes of antenna configuration) and allows making accurate calculations of PMSE strength. This method is based on radar-radiosonde comparisons in the upper troposphere/lower stratosphere region simultaneously with PMSE observations. Using this calibration we calculated the distribution of PMSE strength over magnitudes; it varies from year to year with the peak of the distribution varying from 2×10−15 to 3×10−14 m−1. We found that inter-annual variations of PMSE volume reflectivity strongly correlate with the local geomagnetic k-index and anticorrelate with solar 10.7 cm flux. We did not identify any significant trend in PMSE volume reflectivity over 1997–2009. Finally, using 11 years of measurements, we calculated in-beam the PMSE aspect sensitivities using the FCA technique. We showed that half of PMSE detected each year cannot be explained by isotropic turbulence since they are highly aspect sensitive echoes. The distribution of these echoes remains consistent from year to year with median values of aspect sensitivity from 2.9 to 3.7°. The remaining half of the PMSE have aspect sensitivity parameters larger than 9-11°. We found that PMSE aspect sensitivity has altitude dependence: the scatter becomes more isotropic with increasing height. We did not identify any dependence of PMSE aspect sensitivity on backscattered power for any year. We analysed limitations of the in-beam and off-zenith beam methods and concluded that the former is suitable for highly aspect sensitive echoes while the latter is needed for more isotropic scatterers.Godkänd; 2011; 20110926 (marsmi); DISPUTATION Ämnesområde: Rymdteknik/Space Technology Opponent: Professor Patrick Joseph Espy, Dep of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway, Ordförande: Docent Evgenia Belova, Swedish Institute of Spaces Physics, Kiruna Tid: Måndag den 31 oktober 2011, kl 10.00 Plats: Aulan, Swedish Institute of Spaces Physics, Kiruna
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Hermawan, Eddy. "Characteristics of Clear Air Echoes in the Troposphere and Lower Stratosphere Observed with the MU radar." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/181445.
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Trivej, Panu. "Spatio-temporal properties of shallow clouds with an emphasis on the area distribution of radar echoes." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1872176351&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Barabash, Victoria. "Investigation of Polar Mesosphere Summer Echoes in Northern Scandinavia." Doctoral thesis, Umeå University, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-176.
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This PhD thesis deals with phenomena which are closely related to the unique thermal structure of the polar summer mesosphere, namely Polar Mesosphere Summer Echoes (PMSE). PMSE are strong radar echoes commonly observed by VHF MST radars from thin layers in the 80-90 km altitude interval at high latitudes during summer. They follow a seasonal pattern of abrupt appearance in late May and a gradual disappearance in mid-August. This period corresponds roughly to the time between the completion of the summer time cooling of the polar mesopause to the time of reversal of the mesospheric circulation to autumn condition. In this connection, PMSE are associated with the extremely low temperatures, i.e. below 140 K, which are unique to the polar summer mesopause. Traditional theories of radar (partial) reflection and scattering have been unable to explain the PMSE and the exact mechanism for their occurrence remains unclear despite the steadily increasing interest in them over the past 20 years. Currently accepted theories regarding the mechanism giving rise to PMSE agree that one of the conditions needed for enhanced radar echoes is the presence of low-mobility charge carries such as large cluster ions and ice aerosols which capture the ambient electrons. It has been established that the PMSE are in some way associated with noctilucent clouds (NLC), layers of ice crystals, which constitute the highest observed clouds in the earth’s atmosphere. PMSE occurrence and dynamics are also found to be closely connected with the planetary and gravity waves.
Observations of PMSE presented in this thesis have been carried out by the Esrange MST radar (ESRAD) located at Esrange (67°56’N, 21°04’E) just outside Kiruna in northernmost Sweden. The radar operates at 52 MHz with 72 kW peak power and a maximum duty cycle of 5%. The antenna consists of 12x12 array of 5-element Yagis with a 0.7l spacing. During the PMSE measurements the radar used a 16-bit complementary code having a baud length of 1mS. This corresponds to height resolution of 150 m. The sampling frequency was set at 1450 Hz. The covered height range was 80-90 km. The presence of PMSE was determined on the basis of the radar SNR (signal-to-noise ratio). The PMSE measurements have been made during May-August each year since 1997.
PMSE seasonal and diurnal occurrence rates as well as dynamics have been studied in connection with tidal winds, planetary waves, temperature and water vapor content in the mesosphere (Papers I, IV and VI). Simultaneous and common-volume observations of PMSE and noctilucent clouds have been performed by radar, lidar and CCD camera (Paper V). Correlation between variations in PMSE and variations in extra ionization added by precipitating energetic electrons or high-energy particles from the Sun has been examined (Papers II and III). Possible influence of transport effects due to the electric field on PMSE appearance has been studied during a solar proton event (Paper III).
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Li, Yanlin. "A STUDY ON METEOR ECHOES USING THE ARECIBO AND JICAMARCA HIGH POWER LARGE APERTURE RADARS." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1547218801600341.
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Leech, Steven. "Echoes from the recent past : an archaeological ethnography of historic Cold War radar sites in the UK." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/echoes-from-the-recent-past-an-archaeological-ethnography-of-historic-cold-war-radar-sites-in-the-uk(39f78976-c8ec-40c8-835f-242b76d59792).html.
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This thesis is an archaeological and ethnographic exploration of historic military sites associated with the Cold War. It takes a multi-sited approach to former radar installations in the UK and examines the range of meanings and values that surround them, as well as their mediation, management and curation in the contemporary landscape. This thesis provides a detailed study of a range of related (although not necessarily overlapping) practices, which have accumulated around these places since the 1990s. Much has been written about the ruined-aesthetic of abandoned military sites. Moreover, conservation professionals have undertaken extensive research and granted heritage status to a number of key sites. However, little academic research has been carried out concerning the contemporary social life of former military installations. Furthermore, despite valuable archaeological research concerning the character and form of Cold War historic sites, little attention has been given to the ways in which they are involved in the production of ideas surrounding the Cold War and Cold War heritage in the present; this thesis aims to cover both of these issues. Each of the main chapters in this thesis focuses on a particular set of practices or relationships surrounding historic radar sites, which have been treated in a relatively sporadic and uneven fashion â some have been demolished, others left in ruination and limbo, whereas as a few have been designated as nationally important heritage sites. Therefore, a number of heritage and memory practices are covered, including conservation management, militarisation and nostalgia, as well as the museumification of Cold War sites and objects and the (often) disparate memory practices of former radar veterans. Principally, the analysis in this thesis focuses on extensive ethnographic research undertaken by the author at a number of sites in the UK. This includes semi-structured interviews, participant observation and archival research undertaken in England and Scotland. The key case-studies are the listed and scheduled monuments at RAF Neatishead in Norfolk; the Air Defence Radar Museum, which is located on the same site; and a former early warning site at Saxa Vord in Unst, Shetland. Research conducted at a number of other Cold War sites and museums is also discussed. The principal aim of this thesis is to contribute a set of nuanced and detailed accounts surrounding the archaeology and heritage of the recent past. The Cold War was a varied and complex phenomenon â one which is much debated. Manifold legacies of the Cold War also continue to shape and influence the contemporary world. In a similar manner, concepts and practices surrounding heritage and memory are widely studied, but remain slippery and resist straightforward interpretation. Therefore, the complexities surrounding these phenomena are magnified when they are combined in the present through the notion of Cold War heritage. In order to add some specificity to these related issues, this thesis focuses on two main questions (which are really two-sides of the same coin): what kind of heritage emerges in relation to historic Cold War radar sites? And, what kind of Cold War is produced in the context of heritage and memory practices? Throughout the thesis, it is argued that the Cold War is an uneven, complex and occasionally difficult heritage to deal with in the UK. Mostly, this relates to practical problems such as the complexities surrounding the ownership of former military sites, as well as a number of other conceptual and philosophical issues. For example, in the context of designation and management, this emerges as a tension between the idea of the Cold War as avant-garde heritage and modern conservation principles that underpin contemporary heritage management practices. Furthermore, the emphasis placed on materiality, place and continuity in heritage and memory practices are also brought into relief. At times, these are shown to be complicated by the (at times) elusive, unpredictable and uncertain character of the Cold War in the present. Using radar sites as a microcosm, it is argued that former Cold War sites are seldom the product of coherent or unified approaches to heritage and memory. Instead, they are often at the centre of a variety of converging, conflicting and confounding agendas. Practices surrounding radar sites also present a number of ethical and political challenges. Moreover, it is also argued that radar sites, despite their billing as Cold War heritage, cannot simply be reduced or collapsed into the concept of the Cold War. Nonetheless, the author argues that this kind of fragmentation and complexity might form the basis of a more comprehensive approach to the Cold War and the recent past in the present. Therefore, in the conclusions to this thesis, the author presents a number of avenues for future research and examines the implications of his findings.
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Miao, Qun. "Fine-scale vertical structure of clear-air echoes during the International H₂O Project as detected by an airborne Doppler radar." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1296094731&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Viberg, Andreas. "Remnant echoes of the past : Archaeological geophysical prospection in Sweden." Doctoral thesis, Stockholms universitet, Institutionen för arkeologi och antikens kultur, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-79239.
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The aim of this thesis has been to investigate the benefits, pitfalls and possibilities of using geophysical methods in archaeological projects. This is exemplified by surveys carried out at archaeological sites in different geographical and chronological contexts. The thesis also aims at investigating the cause for the under-use of the methods in Swedish archaeology by looking at previously conducted surveys. The methods used during these surveys have been Ground-penetrating radar (GPR), magnetometer, slingram and a kappameter. The surveys in the mountain tundra region of Lapland show that magnetic susceptibility surveys is a valuable aid in discovering heaps of fire-cracked stones and when combined with magnetometry, also hearths. GPR and magnetometer surveys within the Migration Period ringfort Sandbyborg provided the spatial layout of the fort and indicated, along with results from recent excavations and metal detections, many similarities with the ringfort Eketorp II. The non-magnetic character of the sedimentary bedrock on Öland and Gotland is suitable for magnetometer surveys and the method is also highly appropriate for the detection of the remains of high-temperature crafts. GPR surveys at St. Mary’s Dominican convent in Sigtuna produced the spatial layout of the central cloister area. The investigations also show that the geology, pedology, land use and the character of commonly occurring prehistoric remains in Sweden, in certain circumstances and in certain areas, have restricted the possibility of successfully carrying out geophysical surveys. Care must therefore be taken to choose the right instrument for the survey and to tailor the sampling density of each geophysical survey, according to the character and size of the expected archaeological remains, in order to maximize their information return. To increase the use of geophysical methods in Sweden the educational opportunities, both for surveyors and professional archaeologists, need to improve.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript.
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Foster, James A. "A Comparison of Mobile Radar-Inferred Rain-Drop Size Estimates between Tornadic and Non-Tornadic Supercell Hook Echoes." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou157832340334202.
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Kero, Johan. "High-resolution meteor exploration with tristatic radar methods." Doctoral thesis, Umeå universitet, Fysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1602.
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A meteor observed with the naked eye is colloquially called a shooting star. The streak of light is generated by an extra-terrestrial particle, a meteoroid, entering the Earth’s atmosphere. The term meteor includes both luminosity detectable by optical means and ionization detectable by radar. The radar targets of meteor head echoes have the same motion as the meteoroids on their atmospheric flight and are relatively independent of aspect angle. They appear to be compact regions of plasma created at around 100 km altitude and have no appreciable duration. This thesis reviews the meteor head echo observations carried out with the tristatic 930 MHz EISCAT UHF radar system during four 24h runs between 2002 and 2005, and a 6h run in 2003 with the monostatic 224 MHz EISCAT VHF radar. It contains the first strong observational evidence of a submillimeter-sized meteoroid breaking apart into two distinct fragments. This discovery promises to be useful in the further understanding of the interaction processes of meteoroids with the Earth’s atmosphere and thus also the properties of interplanetary/interstellar dust. The tristatic capability of the EISCAT UHF system makes it a unique tool for investigating the physical properties of meteoroids and the meteor head echo scattering process. The thesis presents a method for determining the position of a compact radar target in the common volume of the antenna beams and demonstrates its applicability for meteor studies. The inferred positions of the meteor targets are used to estimate their velocities, decelerations, directions of arrival and radar cross sections (RCS) with unprecedented accuracy. The head echoes are detected at virtually all possible aspect angles all the way out to 130° from the meteoroid trajectory, limited by the antenna pointing directions. The RCS of individual meteors simultaneously observed with the three receivers are equal within the accuracy of the measurements with a very slight trend suggesting that the RCS decreases with increasing aspect angle. A statistical evaluation of the measurement technique shows that the determined Doppler velocity agrees with the target range rate. This demonstrates that no contribution from slipping plasma is detected and that the Doppler velocities are unbiased within the measurement accuracy. The velocities of the detected meteoroids are in the range of 19-70 km/s, but with very few detections at velocities below 30 km/s. The thesis compares observations with a numerical single-body ablation model, which simulates the physical processes during meteoroid flight through the atmosphere. The estimated meteoroid masses are in the range of 10-9 - 10-5.5 kg.Meteorer är ljusfenomen på natthimlen som i vardagligt tal kallas fallande stjärnor. Ljusstrimmorna alstras av meteoroider, små partiklar på banor genom solsystemet, som kolliderar med jordens atmosfär. Förutom ljus genererar meteoroider regioner av joniserat plasma, som är detekterbara med radar. Meteoriska huvudekon tycks komma från kompakta radarmål på ungefär 100 km höjd och rör sig genom atmosfären med de infallande meteoroidernas hastighet. Huvudekons signalstyrka förefaller oberoende av vinkeln mellan radarmålens rörelseriktning och riktningen från vilken radiovågorna infaller och sprids. Avhandlingen sammanfattar huvudekoobservationer från fyra 24-timmarsmätningar mellan 2002 och 2005 med det trestatiska 930 MHz EISCAT UHF-radarsystemet och en 6-timmarsmätning under 2003 med den monostatiska 224 MHz EISCAT VHF-radarn. Avhandlingen innehåller den första observationella bekräftelsen på att en meteoroid av sub-millimeterstorlek faller sönder i två distinkta fragment i atmosfären. Upptäckten är betydelsefull för studier av meteoroiders växelverkansprocesser med atmosfären och interplanetärt/interstellärt stofts materialegenskaper. EISCAT UHF-systemet består av tre vitt åtskilda mottagarstationer, vilket gör det till ett unikt mätinstrument för studier av meteoroiders egenskaper och hur radiovågor sprids från de radarmål som ger upphov till huvudekon. Avhandlingen presenterar en metod med vilken ett radarmåls position kan bestämmas om det detekteras simultant med de tre mottagarna. Metoden används till att med hög noggrannhet beräkna meteorers radartvärsnitt samt meteoroiders hastighet och atmosfärsinbromsning. De detekterade huvudekona genereras av meteoroider med i princip alla av mätgeometrin tillåtna rörelseriktningar i förhållande till radarstrålen, ända ut till 130° från radiovågornas spridningsriktning. Enskilda meteorers radartvärsnitt är likvärdiga inom mätnoggrannheten i de tre mottagarstationernas dataserier, men en svag trend antyder att radartvärsnittet minskar med ökande vinkel mellan meteoroidernas rörelseriktning och spridningsriktningen. En statistisk utvärdering av mättekniken visar att den uppmätta dopplerhastigheten stämmer överens med radarmålens flygtidshastighet. Detta innebär att dopplerhastigheterna är väntevärdesriktiga och opåverkade av bidrag från det spår av plasma som meteoroiderna lämnar efter sig. De uppmätta hastigheterna är 19-70 km/s, men bara ett fåtal detekterade meteoroider är långsammare än 30 km/s. Meteoroidmassorna är uppskattade till 10-9 – 10-5.5 kg genom jämförelser av observationerna med simuleringar av meteoroiders färd genom atmosfären i en numerisk ablationsmodell.
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Li, Li. "On the use of variational analysis for determining the motion, growth and decay of radar echoes over complex orography /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10823.
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Andersen, Arne Helge. "Suppression of Radar Echoes produced below the Liquid Surface close to the Base of a Storage Container for LNG." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-8794.
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Malhotra, Garima. "HF Radar Observations of Inter-Annual variations in Mid-Latitude Mesospheric Winds." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78084.
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The equatorial Quasi Biennial Oscillation (QBO) is known to be an important source of inter-annual variability at mid and high latitudes in both hemispheres. Coupling between QBO and the polar vortex has been extensively studied over the past few decades, however, less is known about QBO influences in the mid-latitude mesosphere. One reason for this is the relative lack of instrumentation available to study mesospheric dynamics at mid-latitudes. In this study, we have used the mid-latitude SuperDARN HF radar at Saskatoon (52.16 N, -106.53 E) to study inter-annual variation in mesospheric winds. The specific aim was to determine whether or not a Quasi Biennial signature could be identified in the Saskatoon mesosphere, and if so, to understand its relationship with the equatorial stratospheric QBO. To achieve this goal, a technique has been developed which extracts meteor echoes from SuperDARN near-range gates and then applies least-squares fitting across all radar beam directions to calculate hourly averages of the zonal and meridional components of the mesospheric neutral wind. Subsequent analysis of 13 years (2002-2014) of zonal wind data produced using this technique indicates that there is indeed a significant QBO signature present in Saskatoon mesospheric winds during late winter (Jan-Feb). This mesospheric QBO signature is in opposite phase with the equatorial stratospheric QBO, such that when QBO (at 50 hPa) is in its easterly (westerly) phase, the late winter winds in Saskatoon mesosphere become more (less) westerly. To further examine the source of the signature, we also analyzed winds in the Saskatoon stratosphere between 5 hPa and 70 hPa using the ECMWF ERA-Interim reanalysis data set, and found that the late winter stratospheric winds become less (more) westerly when QBO is easterly (westerly). This QBO signature in the mid-latitude stratospheric winds is essentially the same as that observed for the polar vortex in previous studies but it is opposite in phase to the mid-latitude mesospheric QBO. We therefore conclude that filtering of gravity waves through QBO-modulated stratospheric winds plays a major role in generating the mesospheric QBO signature we have identified in the Saskatoon HF radar data. When the Saskatoon stratospheric winds are anomalously westward during easterly QBO, the gravity waves having westward momentum might be filtered out, depositing a net eastward momentum in the mesosphere as they propagate upwards. This would result in increased westerly mesospheric winds at Saskatoon. The opposite would happen when the equatorial QBO is westerly.Master of Science
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Duncan, Mike R. (Mike Ross). "The universal multifractal nature of radar echo fluctuations." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41364.
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The intensity returns obtained by a radar from precipitation are well known to fluctuate violently in space and time. We present a systematic study of the resolution dependence time series with overlapping time resolutions spanning 10 orders of magnitude (0.77 ms to 4 months), of the fluctuating radar echo from precipitation. The results undermine the current assumptions of homogeneity of rainfield at scales smaller than the radar resolution, due to Marshall and Hitschfeld (1953), by showing that the only length scales identifiable in the time series are those of the radar pulse volume, the wavelength, and a very small inner scale of the order of millimeters. An analysis of the multiscaling nature of the time series of echo fluctuations reveals multiscaling behaviour at scales down to the resolution or pulse volume scale. Since there are no a priori scales in the rainfield we proceed to model the fluctuating radar echo by assuming a multiscaling model of rainfield variability which extends to sub-resolution scales. A systematic analysis of the statistical behaviour of computed reflectivities from this variability gives a full statistical description of reflectivity originating from multiscaling variability, and solves the scalar multifractal radar observer's problem. Computation of time series of reflectivities from a time-space representation of this variability reveals quantitative and qualitative behaviours consistent with those of observed echo fluctuation time series. We conclude that a multiscaling model of the rainfield which extends to the smallest scales of the rainfield is consistent with observation.
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Luce, Hubert. "Interpretation des echos radar st vhf a l'aide de mesures a haute resolution de la temperature." Toulon, 1996. http://www.theses.fr/1996TOUL0004.
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L'origine du renforcement des echos radar vhf (30-300 mhz) st (stratosphere-troposphere) en incidence verticale par rapport a l'oblique est toujours sujet a controverses. En effet, plusieurs mecanismes ont ete proposes tels que la reflexion partielle sur des couches stables horizontalement stratifiees ou la diffusion par la turbulence anisotrope. La campagne rasci-ba90 (aire sur l'adour, france, 1990) realisee conjointement par le laboratoire de sondages electromagnetiques de l'environnement terrestre (l. S. E. E. T), le service d'aeronomie du c. N. R. S de verrieres le buisson et le departement d'astrophysique de nice (u. N. S. A) a permis de reunir des donnees ballon complementaires a celles des radars vhf provence 45 mhz et insu meteo 72. 5 mhz. Les mesures de temperature a haute resolution verticale (20 cm) ont revele la presence de feuillets, gradients positifs intenses de temperature confines sur de faibles epaisseurs (quelques metres) jusque dans la stratosphere moyenne (27 km au moins) et coexistant avec des fluctuations turbulentes aux memes echelles. Il est montre, d'une part, que le modele de reflexion partielle applique a ces feuillets de temperature est suffisant pour reproduire l'essentiel des caracteristiques des echos en incidence verticale et, d'autre part, que le modele de diffusion par la turbulence isotrope est satisfaisant pour reproduire les profils de puissance recue en incidence oblique (15 du zenith). Bien que la validation des modeles passe par une description encore plus complete des structures atmospheriques aux petites echelles, ces etudes ont apporte des resultats decisifs sur l'interpretation des echos radar vhf
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Furumoto, Jun-ichi. "Observation of Turbulence Echo Characteristics and Humidity Profiles with the MU Radar-RASSObservation of turbulence echo characteristics and humidity profiles with the MU radar-RASS." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/68897.
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Mecklenburg, Susanne Martha. "Nowcasting precipitation in an alpine region with a radar echo tracking algorithm /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13608.
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Williams, Taylor P. "Compressive Sensing for Tomographic Echo Imaging in Two Dimensions." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338330434.
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Belhadj, Zied. "Apport de la polarisation multifréquence pour la classification en télédétection radar." Nantes, 1995. http://www.theses.fr/1995NANT2056.
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Le but du travail réalisé dans cette thèse est l'étude des informations acquises par un capteur polarimétrique multifréquence. L'objectif vise d'une part la modélisation statistique d'échos radar et d'autre part la discrimination et la classification polarimétrique multifréquence. La distinction fine entre les couverts à divers stades de croissance illustre l'apport spécifique de la polarimétrie multifréquence. Des images multipolarisées, multifréquences acquises en 1989 par le système ROS de la Nasa/JPL concernant la forêt des Landes ont été exploitées dans laquelle les diverses sections différent par leurs paramètres intrinsèques (biomasse, hauteur, âge, densité,). La modélisation polarimétrique d'échos radar consiste à trouver les lois de distribution décrivant au mieux les amplitudes absolues, les rapports d'amplitude et les différences de phase. La distribution K s'est révélée être la mieux adaptée pour décrire les amplitudes absolues des données aussi bien monovues que multivues. La méthode dite Bootstrap minimisant, voire éliminant l'interdépendance des données, a été introduite afin d'améliorer la confiance du test d'adéquation confirmant le choix de la distribution K. Un nouveau discriminateur fréquentiel, issu de la distribution k et étroitement lié à l'hétérogénéité du couvert, a été développé. La non symétrie azimutale, classiquement négligée, a été mise en évidence par une représentation équi-amplitude des signatures polarimétriques. L'algorithme de classification de Van Zyl et celui de décomposition de Freeman ont été exploités pour classifier les terrains. De plus, un algorithme de classification de pixels vérifiant la non symétrie azimutale a été développé permettant d'introduire une nouvelle classe la non symétrie azimutale pour une interprétation plus réaliste des terrains. Une extension des algorithmes de Novak concernant la réduction du speckle, a été proposée et appliquée sur des données réelles et sur des données synthétisées, en utilisant la propriété de non symétrie azimutale. Le travail de thèse réalisé représente une contribution non seulement à l'évaluation de l'apport de la polarimétrie multifréquence, mais aussi au développement des méthodes d'analyse et de traitement de données en télédétection radar.
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LE, HELLARD DANIEL. "Modelisation des echos de sol radar en eclairement rasant, de 1 ghz a 10 ghz, a partir d'un modele numerique de terrain." Rennes 1, 1997. http://www.theses.fr/1997REN10025.
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Cette these est consacree a la modelisation et la simulation du fouillis de sol en eclairement rasant, dans les bandes de frequence l (1 ghz) a x (10 ghz). Apres une synthese des modeles de fouillis existants, nous procedons a l'analyse de mesures de fouillis de sol. Cette analyse montre que, en eclairement rasant, les echos de fouillis proviennent principalement du sursol. Nous developpons ensuite un modele de fouillis de sol base sur une distribution verticale de reflecteurs elementaires. Ce modele est mis en uvre dans un logiciel de generation de cartes de reflectivite de fouillis de sol a partir d'un modele numerique de terrain. L'analyse des parametres statistiques de la reflectivite simulee et la correlation de cartes d'echos simules avec les cartes de fouillis enregistrees par un radar nous permettent de valider le modele propose.
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BERTOLDO, SILVANO. "X-band mini weather radar network and other wireless sensor networks for environmental monitoring." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2535714.
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The main section of the present Ph. D. thesis is related to X-band radars. Since 2005 the Remote Sensing Group of Department of Electronics and Telecommunications of Politecnico di Torino developed an X-band mini weather radar as a standalone sensor to measure rain. Some early results have been presented until 2011 showing the proper functioning and it has been decided to realize an experimental and operative integrated network of X-band radar devoted to rain measurement. The network structure deployed during the Ph. D. period is presented, together with the analysis, the study and the realizations of some operative services, calibration procedures (including Quantitative Precipitation Estimation, QPE) and software and applications developed for the institutions which support the network realizations. The design of an innovative and low cost method to check the radar stability and proper functioning is presented: by simply acquiring a large number of ground clutter echoes during clear sky days and computing some analysis, it is shown it is possible to identify some statistical indicators that allow users and radar operators to know if the radar equipments suffered some degradations of failure.
The second part of the thesis is dedicated to Wireless Sensor Networks (WSNs). After a study on WSN technologies for environmental monitoring, a first developed prototypal DGPS network is presented. Using the same multipurpose node designed for such network (or its updated releases with very small differences) and varying only their firmware, other two prototypal and fully operative WSNs are described. The designed choices are described for what concern both hardware and software.
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Newman, T. "Application of synthetic aperture techniques to radar echo soundings of the Pine Island Glacier, Antarctica." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1318098/.
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In this PhD I have developed a Synthetic Aperture Radar (SAR) processing algorithm and applied it to airborne radar sounding data collected during the 2004/05 austral summer season over Pine Island Glacier (PIG) West Antarctica. The SAR processing algorithm is one-dimensional and non-symmetrical and is applied in MATLAB® . Phase corrections are calculated and applied on a trace-by-trace basis, and are based on pre-calculated lookup tables. The section of the survey that I concentrated on was that of the main PIG glacier trunk, which was flown at a terrain clearance of between 110 m and 260 m. The flights over the trunk were sub-divided into 4 along-flow flight sections (L 1 -L4) and 13 cross-flow flight sections (X1-X13). After SAR processing the levels of surface clutter are reduced allowing for the imaging of englacial layering and the bed-interface, even in areas of heavy surface crevassing. In addition the SAR processor improves the along-track resolution from hundreds of metres to metres allowing for the imaging of small-scale subglacial and englacial features. Using SAR processed data in proximity to the grounding line I constrained the grounded ice interface material by inverting the radar equation. 0n the PIG ice shelf I observed bottom crevassing extending from the base of the ice shelf into the ice mass. By performing a stress analysis using published velocity fields I estimated the maximum height a bottom crevasse can reach and the strain rates required for their formation. I also observed undulations on the ice shelf base and using spectral analysis techniques I show these undulations to have a dominant periodicity of around a year. I therefore link the genesis of these undulations to localised melting at the grounding line forced by an annual influx of circumpolar deepwater into the ice shelf cavity. These undulations decrease in amplitude away from their grounding line formation site which I attribute to a combination of melting by modified circumpolar deep water escaping the cavity and viscous relaxation of ice operating on a decadal timescale.
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Weertman, Bruce Randall. "Interpretation of ice sheet stratigraphy : a radio-echo sounding study of the Dyer Plateau, Antarctica /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/6822.
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Kerbiriou, Corinne. "Développement d'une méthode d'étalonnage d'un radar transhorizon basée sur une analyse fine du fouillis de mer." Rennes 1, 2002. http://www.theses.fr/2002REN1A003.
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Le but de cette thèse était de développer une méthode d'étalonnage dans le cadre du radar transhorizon NOSTRADAMUS afin d'établir sa capacité de détection en s'affranchissant des limitations liées à la propagation dans l'ionosphère. Cette méthode est fondée sur une analyse spectrale du fouillis de mer et permet d'estimer un paramètre étalon : le coefficient de réflectivité de la mer. La connaissance de ce coefficient permet de déterminer la surface équivalente radar d'une cible susceptible d'être détectée par transposition du bilan énergétique de la mer à celui de cette cible. Ce processus permet alors de prédire les performances du radar en terme de détectabilité. Outre l'analyse spectrale de l'écho de mer, l'étude de l'ionosphère a été indissociable des travaux à mener. En effet, l'ionosphère est un milieu instable qui peut dégrader le spectre.
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Gonçalves, Micheli Fernandes. "Previsão de chuva com auxílio de radar de tempo visando a um sistema de alerta antecipado de cheias em áreas urbanas." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-27042010-133924/.
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Para reduzir as perdas humanas e materiais durante as inundações, é possível realizar estudo conciso da previsão de chuva, etapa principal de um sistema de alerta antecipado de inundação. O uso de informações de radar de tempo, quando acopladas a modelos de previsão de precipitação baseados fisicamente, pode contribuir para o monitoramento e previsão de episódios de chuva intensa. Desta forma, a previsão de chuva, baseada no uso de informações de radar, juntamente com um modelo conceitual de previsão hidrometeorológica, foi descrita neste trabalho. Teve-se por objetivo aperfeiçoar as previsões de chuva de curtíssimo prazo (poucos minutos), que acopladas a um modelo chuva-vazão, podem ser usadas em sistemas de alerta antecipado. O modelo hidrometeorológico adotado, que considera uma nuvem hipotética unidimensional vertical, foi inicialmente desenvolvido por Georgakakos e Bras (1984a) e ampliado, neste trabalho. Para tal, adotou-se o uso das informações de Topo dos Ecos para determinação da altura das nuvens e considerou-se que a componente do modelo relativa à massa de água líquida no interior da nuvem corresponde à estimativa do conteúdo de água líquida integrado verticalmente (VIL) efetuada por radar. Para eventos de natureza frontal quente e convectiva, o modelo geralmente antecipou o início do processo de chuva, embora tenha conseguido simular seu comportamento e o instante em que o pico da precipitação ocorreu. Para os eventos frontais frios, o pico simulado registrou atraso. Para episódios de simulação com VIL maior que 3 Kg/\'M POT.2\', a chuva simulada acompanhou o comportamento temporal do VIL, mas com influências das variáveis meteorológicas pressão, temperatura e umidade relativa. As lâminas simuladas tornaram-se entrada para o modelo chuva-vazão do SCS, parcialmente calibrado com algoritmo genético. Para a escala de uma pequena bacia hidrográfica urbana brasileira, com estação fluviométrica experimental, preliminarmente, alguns resultados indicam vazões um pouco inferiores e com atrasos na previsão da vazão máxima. A antecedência proporcionada pelo modelo é de 15 minutos e, apesar da simplicidade, conseguiu-se prever o início do processo de precipitação que gerou inundação do córrego urbano.To reduce human and material losses during floods it is feasible to concisely study the rainfall forecast as the main part of an early warning system. The use of weather radar information, when linked to physically-based forecast models, can contribute for monitoring and forecasting of intense rainfall episodes. Thus, the rainfall forecast, based on using of radar information along with a conceptual model of hydrometeorological forecast, was outlined in this dissertation. One goal of the study was to improve very short term rainfall forecasts, named as a \'nowcasting\' process throughout few minutes, coupled with a rainfall-runoff generation model to be used in early warning system. The hydrometeorological model, a hypothetical vertical 1-D cloud, was initially developed by Georgakakos and Bras (1984a) and further developed in this study to profit signals from radar tracking control volumes of moisture storage. Either \'Echo Top\' radar information was addressed to determinate the cloud height, and the vertically-integrated liquid (\'VIL\') water mass content inside the cloud, estimated by other radar signal, was considered into the model. On the one hand, during rainfall events of hot and convective front genesis monitored with on-field pluviometers, the model results generally anticipated the beginning of the rain process; however the model was capable of not only simulating well the behavior but also the time-step when rainfall monitored peak occurred. On the other hand, and for cold-front events, the simulating peaks depicted a time delay. For simulation episodes with VIL greater than 3 Kg/\'M POT.2\', the simulated rainfall accompanied the time behavior of VIL, but with influences from weather variables of pressure, temperature and relative humidity. These rainfall depths became inputs of a simple SCS rainfall-runoff model, partially calibrated with genetic algorithms. At the scale of a small brazilian urban river basin with experimental gauging station, some preliminary results modeled streamflows a bit lower than, and with some delay of maximum flow forecasts, observed discharges. The advanced lad time period used by model was of about 15 min and, besides its simplicity, it was quite able to anticipate the beggining of the rainfall process that generated the flood formation at the urban creek.
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Gan, Tong. "Study to improve measurement accuracy and resolution of atmospheric radars." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202819.
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Turchetti, Gabriele. "Search for subsurface liquid water in MARSIS data." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
After the first evidence of subglacial liquid water in the subsurface near the Martian South Pole the search for further evidence of liquid water in that area has become a driver in the analysis of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) data. If this discovery is not an isolated case it could be possible to find a liquid water system in the subsurface.
In this work data of Martian South Pole collected by
MARSIS are analysed.
These echoes are used to map the characteristics of Mars ground and underground topography because their power values change with the composition of the soil. The power values of the echoes depend on the altitude of the spacecraft and on distortion due to
ionosphere. Ionospheric distortions can’t be completely eliminated, then a precise data
calibration is not possible.
These problems are addressed with an empirical calibration of surface and subsurface reflected data based on
the assumption that different orbits passing above the same point have to collect
the same value of surface echo power.
After these operations the calibrated maps of the Southern Residual Ice Cap (SRIC)
and of the South Polar Layered Deposits (SPLD) show that their surface reflectivity
are significantly different, while their subsurface characteristics seem to be similar.
The comparison of these two areas confirms the previous studies about the surface
composition of the Polar Cap covered by few meters thick layer of CO2 ice responsible for weak reflections. The analysis of the SPLD highlights the presence of bright
reflectors near the subglacial lake, already found by recent studies and additional
zones with high basal echoes undetected before. These could be the target for future
investigation since they are likely to host small liquid water bodies in subsurface.
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Gades, Anthony M. "Spatial and temporal variations of basal conditions beneath glaciers and ice sheets inferred from radio echo-sounding measurements /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/6845.
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Platzer, Florestan. "Etude de la signature radar de la surface de la mer en incidence rasante." Electronic Thesis or Diss., Toulon, 2020. http://www.theses.fr/2020TOUL0006.
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Ces travaux proposent une analyse de l’écho radar de mer grâce au traitement d’une base de données issue de campagnes de mesures en zone côtière. L'analyse de l'amplitude de l’onde rétrodiffusée montre qu’elle respecte un modèle à deux échelles, combinaison de deux composantes nommées texture et speckle. La texture restitue les variations de la puissance rétrodiffusée associées aux grandes vagues, tandis que le speckle caractérise les variations rapides de la phase. Un traitement Doppler met alors en évidence la relation entre « spikes » de mer (événements ponctuels à forte rétrodiffusion) et vitesses Doppler élevées (diffuseurs rapides). La composante basse-fréquence présente sur les spectres 2D des cartes temps-distance de puissance rétrodiffusée, appelée « group line », est ensuite modélisée. Il apparaît que, contrairement à une hypothèse répandue, le déferlement n’est pas la cause principale de la présence de la « group line ». Une proposition de modélisation de l’écho de mer basée sur les observations expérimentales est finalement proposée, permettant de restituer des cartes spatio-temporelles dont les caractéristiques sont proches des mesuresThis work proposes an analysis of the sea radar echo through the processing of a database resulting from measurement campaigns in the coastal zone. The analysis of the amplitude of the backscattered wave shows that it follows a two-scale model, a combination of two components called texture and speckle. The texture component captures the variations in backscattered power associated with large waves, while the speckle component characterizes rapid phase variations. A Doppler processing then highlights the relationship between sea spikes (localized events with strong backscattering) and high Doppler velocities (fast scatterers). The lowfrequency component present on the 2D spectra of the time-distance maps of backscattered power, called "group line", is then modelled. It appears that, contrary to a common assumption, wave breaking is not the main cause of the presence of the group line. Finally, a sea echo modeling based on experimental observations is proposed, allowing the restitution of space-time maps whose characteristics are close to the measurements
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Gharib, Ahmad. "Diffusiomètre micro-onde en vue de caractériser la diffusion électromagnétique par une houle contrôlée dans un bassin de houle." Nantes, 2011. http://archive.bu.univ-nantes.fr/pollux/show.action?id=fced2534-8f29-4cad-8ee9-6fb59f043e77.
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Cette thèse s’inscrit dans le contexte de l’étude de la diffusion électromagnétique par une houle contrôlée. L’écho radar monostatique d’une houle générée dans un bassin de houle est étudié expérimentalement et théoriquement. La réponse électromagnétique de la houle dépend de sa forme, de ses caractéristiques diélectriques et des caractéristiques des antennes. Des comparaisons sont réalisées entre des données expérimentales, issues d’un diffusiomètre monostatique, et des résultats de simulation de modèles électromagnétiques, basés sur l’approximation de l’optique physique (asymptotique) et la méthode des moments (rigoureuse). Les houles traitées par le simulateur sont données à partir de la simulation du mouvement du batteur. Le bon accord, observé entre les résultats de calcul par les deux méthodes, permet de valider l’OP. Aussi, Un assez bon accord est observé entre les résultats théoriques et les mesures du champ. La différence observée est due à la présence des vaguelettes qui se propagent sur le bassin expérimental et qui ne sont pas prise en compte dans les simulations des houles. Ces vaguelettes sont dues à la réflexion sur la plage absorbante non idéale et aux intervalles existant entre les volets du batteur. Par suite, les vaguelettes observées sur la surface du bassin, sont modélisées et ajoutées sur l’exemple d’une houle régulière déjà étudiée. La réponse électromagnétique calculée de la houle régulière perturbée est plus cohérente avec celle issue de la mesureIn this work we focused on the electromagnetic wave scattering by a controlled swell. The microwave signal backscattered by a controlled swell in a wave basin is studied both theoretically and experimentally. The electromagnetic response of such a surface depends on its shape, its dielectric characteristics, and antennas characteristics and positions. Measurements acquired with a monostatic microwave scatterometer installed above a wave basin, in which regular and irregular waves are generated, are compared with simulation results obtained from two electromagnetic models, based on the Physical Optics approximation (PO) and the Method of Moments (MoM). The swells studied by the electromagnetic simulator are given by the paddle movement simulation. From both methods, a good agreement is observed between the results. Also, a good agreement is observed between theoretical and experimental results around the inclination angle 0°. Nevertheless, a difference is observed between results for highest angles. This is due to the propagation of short ripples on top of the desired long waves. Those ripples are generated both by the gaps existing between the wavemaker paddles and by the beach located at the end of the wave tank, where waves break in order to avoid reflection. These short ripples are modeled and added to an example of a regular surface. For regular surfaces with additional ripples, better agreement is then observed between the results
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Lindbäck, Katrin. "Hydrology and Bed Topography of the Greenland Ice Sheet : Last known surroundings." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-259076.
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The increased temperatures in the Arctic accelerate the loss of land based ice stored in glaciers. The Greenland Ice Sheet is the largest ice mass in the Northern Hemisphere and holds ~10% of all the freshwater on Earth, equivalent to ~7 metres of global sea level rise. A few decades ago, the mass balance of the Greenland Ice Sheet was poorly known and assumed to have little impact on global sea level rise. The development of regional climate models and remote sensing of the ice sheet during the past decade have revealed a significant mass loss. To monitor how the Greenland Ice Sheet will affect sea levels in the future requires understanding the physical processes that govern its mass balance and movement. In the southeastern and central western regions, mass loss is dominated by the dynamic behaviour of ice streams calving into the ocean. Changes in surface mass balance dominate mass loss from the Greenland Ice Sheet in the central northern, southwestern and northeastern regions. Little is known about what the hydrological system looks like beneath the ice sheet; how well the hydrological system is developed decides the water’s impact on ice movement. In this thesis, I have focused on radar sounding measurements to map the subglacial topography in detail for a land-terminating section of the western Greenland Ice Sheet. This knowledge is a critical prerequisite for any subglacial hydrological modelling. Using the high-resolution ice thickness and bed topography data, I have made the following specific studies: First, I have analysed the geological setting and glaciological history of the region by comparing proglacial and subglacial spectral roughness. Second, I have analysed the subglacial water drainage routing and revealed a potential for subglacial water piracy between adjacent subglacial water catchments with changes in the subglacial water pressure regime. Finally, I have looked in more detail into englacial features that are commonly observed in radar sounding data from western Greenland. In all, the thesis highlights the need not only for accurate high-resolution subglacial digital elevation models, but also for regionally optimised interpolation when conducting detailed hydrological studies of the Greenland Ice Sheet.De ökade temperaturerna i Arktis påskyndar förlusten av landbaserad is lagrad i glaciärer och permafrost. Grönlands inlandsis är den största ismassan på norra halvklotet och lagrar ca 10% av allt sötvatten på jorden, vilket motsvarar ca 7 meter global havsnivåhöjning. För ett par decennier sedan var inlandsisens massbalans dåligt känd och antogs ha liten inverkan på dagens havsnivåhöjning. Utvecklingen av regionala klimatmodeller och satellitbaserad fjärranalys av inlandsisen har under de senaste decenniet påvisat en betydande massförlust. För att förutse vilken inverkan inlandsisen har på framtida havsnivåhöjningar krävs en förståelse för de fysikaliska processerna som styr dess massbalans och isrörelse. I de sydöstra och centrala västra delarna av inlandsisen domineras massförlusten av dynamiska processer i isströmmar som kalvar ut i havet. Massförlusten i de centrala norra, sydvästra och nordöstra delarna domineras av isytans massbalans. Ytterst lite är känt om hur det hydrologiska systemet ser ut under inlandsisen; hur väl det hydrologiska systemet är utvecklat avgör vattnets påverkan på isrörelsen. I denna doktorsavhandling har jag använt markbaserade radarmätningar för att kartlägga den subglaciala topografin för en del av den västra landbaserade inlandsisen. Denna kunskap är en viktig förutsättning för att kunna modellera den subglaciala hydrologin. Med hjälp av rumsligt högupplöst data över istjockleken och bottentopografin har jag gjort följande specifika studier: Först har jag analyserat de geologiska och glaciologiska förhållandena i regionen genom att jämföra proglacial och subglacial spektralanalys av terrängens ytojämnheter. Sedan har jag analyserat den subglaciala vattenavrinningen och påvisat en potential för att avrinningsområdena kan ändras beroende på vattentryckförhållandena på botten. Slutligen har jag tittat mer i detalj på englaciala radarstrukturer som ofta observerats i radardata från västra Grönland. Sammanfattningsvis belyser avhandlingen behovet av inte bara noggranna rumsligt högupplösta subglaciala digitala höjdmodeller, utan även regionalt optimerad interpolering när detaljerade hydrologiska studier ska utföras på Grönlands inlandsis.
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GUO, WAN-YI, and 郭萬益. "Analysis and simulation of MST radar echoes." Thesis, 1986. http://ndltd.ncl.edu.tw/handle/84638683372999392780.
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wang, Jian-Lin, and 王健霖. "Effective Estimation of the Radar Echoes for Offshore Wind Turbines." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/2j59vk.
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碩士國立臺灣海洋大學
電機工程學系
105
In order to assess the impact of offshore wind farm on marine and aircraft radar systems, it is important to predict the RCS (Radar Cross Section) and the scattering electric field of wind turbines. It was found that the tower scattering constitutes approximately 80% of the turbine, as the blades scattering is approximately 15%. The main purpose of this thesis is to calculate the RCS and the scattering electric field of wind turbine tower and blade quickly and effectively . The tower is divided into n sections so that each section can be analyzed by the far-field approximation, and the RCS of each section can be evaluated analytically. Adding up all the contributions from each section yields the RCS for the wind turbine tower. A mesh made of bi-quadratic patches are used to model the blades of wind turbine. The PO(physical optics) approximation is utilized to calculate the far-field scattering electric field of the blades and/or its RCS. In the process of calculating the field, we set up some approximate conditions, so that the surface integral can be simplified into a product of two one-dimensional integrals, which reduces the computational complexity. This approach is very efficient to calculate RCS and the scattering electric field for electrically large wind turbine blades with irregular curvilinear surface. It greatly reduces computing time and memory requirement. If suitable patch size is selected for meshing and the aforementioned approximation approach is adopted, the calculation time can be reduced to a half of that by the commercial software FEKO, and also the required memory is cut down by a half. Separately calculating the scattered field for the wind tower and blades, we then linearly superimpose both contributions to obtain the total radar echo field from the wind turbine.
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Lai, Pei-Chen, and 賴珮晨. "The study of QP echoes observed by the Chung-Li Radar." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/19207540789186079501.
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碩士國立中央大學
太空科學研究所
92
Sporadic E (Es) layers are ionization enhancements in the E region at altitude between 90 and 120 km. The density can be up to an order of magnitude greater than that in the background and the major species in the layer are metallic. High-resolution observations of quasi-periodic (QP) structures of the midlatitude E region irregularities made with the MU radar were presented in 1991. The structures were found to display striations with periods close to the Brunt Vaisala period. After then, the Chung-Li radar observed the same phenomenon, too. The physical mechanisms proposed for the generation of QP echoes are associated with gravity wave and wind shear. In this study we present an optimum postulate for the QP echoes observed at the Chung-Li VHF radar.
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Yu-RuChen and 陳禹儒. "Identification and Direction Finding of Ship Echoes with SeaSonde HF Radar." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/zvt79z.
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碩士國立成功大學
海洋科技與事務研究所
104
Enhancing near-real-time surveillance capability for complex vessel movements within an exclusive economic zone (EEZ) is an important issue for maritime management. High-frequency (HF) radar’s over the horizon property can effectively extend detection range to cover most of an EEZ area, making it suitable for a long-range vessel monitoring system. An island-wide HF radar network has been established in Taiwan primarily to monitor ocean surface currents and other oceanic parameters. The purpose of this study is to develop a technique for detecting and tracing vessel echoes using the radar sea returns from HF radar stations without interfering with existing system functions. The proposed technique integrates two algorithms, namely an adaptive signal identification algorithm, which is used to extract ship positions and radial velocity information of ship echoes, and a multiple signal classification algorithm, which is used to retrieve ship bearing information. The ship information retrieved from HF radar data was verified against automatic identification system data. Finally, the accuracy and usefulness of the proposed technique are demonstrated by case studies for the Suao HF radar station.
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Yun-YunHo and 何雲筠. "Investigating on the Estimation of Rainfall and Slope Groundwater Table by Radar Echoes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4u39ec.
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碩士國立成功大學
土木工程學系
103
This study used the Alishan Highway at Chia-I and Pong-Ping-Keng at Chia-Hsien, Kaohsiung as the research sites to build a dBZ-I Power Law Relationship equation. The investigation shows the requirements to modify the dBZ-I relationship because the radar rainfall data (dBZ) overestimate the rainfall intensity (I). Then, by involving the slope groundwater table variation data Alishan Highway 86.95K in 2014, the groundwater table variation has linear relationship to the accumulated rainfall, and the accumulated dBZ. At a specified point, the radar reflectivity (dBZ) one-hour ago can be used to estimate the rainfall intensity. Therefore, the process can be used to predict the maximum rainfall intensity, the occurrence time, and predict the groundwater table increased time. The groundwater table can be a useful parameter to evaluate the slope stability. Therefore, the new dBZ-I Power Law Relationship equation has practical usage to ensure the safety of mountain highway during a rainfall.
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Cheng, Chao-Tuan, and 程昭團. "Interferometry investigation of long-live meteor trail echoes made with Chung-Li VHF radar." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/56682196223452937796.
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碩士國立中央大學
太空科學研究所
93
The horizontal wind velocity from 90 km to 110 km can be estimated through the drift of meteor trail echoes observed by Chung-Li VHF radar with spatial interferometery method. The observed meteor echoes included both from meteor head and meteor trail echo. The averaged fall velocity and deceleration of meteor head were estimated to be 51 km/s and 17.7 km / , respectively. The horizontal wind vectors in the height range from 96 km to 109 km rotated a clockwise with the increase of height, strongly implying an upward (downward) propagation of gravity energy (phase).
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"Occurrence and Causes of F-region Echoes for the Canadian PolarDARN/SuperDARN Radars." Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-03-949.
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This thesis has two major objectives. The first objective is to investigate the seasonal and diurnal variations in occurrence of HF coherent echoes. We assess F-region echo occurrence rates for the PolarDARN HF radars at Inuvik (INV) and Rankin Inlet (RKN) and the auroral zone SuperDARN radars at Saskatoon (SAS) and Prince George (PGR) for the period of 2007-2010. We show that the INV and RKN PolarDARN radars show comparable rates of echo occurrence all the time and they detect 1.5-2.5 times more echoes through ½-hop propagation mode (MLATs=80°-85°) than the SAS and PGR SuperDARN radars through 1½-hope propagation mode (MLATs=75°-80°). For all four radars, the winter occurrence rates are about ~2 times higher than the summer rates. For observations in the dusk, midnight and dawn sectors, equinoctial maxima are evident. The pattern of echo occurrence in terms of MLT/season is about the same for all radars with clear maxima near noon during winters and summers and enhanced (as compared to other time of the day) occurrence rates during equinoctial dusk and dawn hours. Additionally, to investigate the effect of solar cycle on occurrence of F-region echoes, we consider the near noon and near midnight echo occurrence rates for the Saskatoon radar over the period of 1994-2010. We show that there is a strong, by a factor of ~10, increase in SAS night-side echo occurrence towards solar maximum. The effect does not exist for the dayside echoes; moreover, a decrease in number of echoes, by a factor of ~2, was discovered for the declining phase of the solar cycle.
The second objective is to evaluate the electron density and the electric field as factors controlling the occurrence of F-region echoes. We use observations of these two ionospheric parameters measured by CADI ionosonde and RKN observations of echo occurrence rates over Resolute Bay (MLAT=83°). We show that there is a correlation in changes of echo occurrence and electron density changes for 3 years of radar-ionosonde joint operation (2008-2010). The comparison of radar-ionosonde data shows that the enhanced echo occurrence at near noon hours during summer months correlate with the enhanced electric field during these periods.
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"On the Origin of Close-Range E Region Echoes Observed by SuperDARN HF Radars in the Mid- and High Latitudes." Thesis, 2016. http://hdl.handle.net/10388/ETD-2016-04-2517.
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The Super Dual Auroral Radar Network (SuperDARN) is a global network of coherent high frequency (HF) radars located in the polar, high- and mid-latitudes of both the Northern and Southern hemispheres. This thesis deals with close-range SuperDARN echoes (oblique HF backscatter from the lower part of the ionosphere). The aim of this thesis is to shed light on the origin of these echoes. Previous studies have been content to propose explanations for the origin of these echoes without thorough checking of the proposed mechanisms against constraints available from various radars and other important information. For the purpose of clarifying the situation, a chain of SuperDARN radars in the Northern and Southern hemispheres and several years of daily statistics have been used. This has allowed for several findings. Notably, the close-range SuperDARN echoes show diurnal and seasonal variations and their properties with respect to signal-to-noise-ratio, Doppler velocity and Doppler width vary. Three distinct populations of close-range HF backscatter have been established: (1) a morning population (0400-0700 LT), (2) a midday summer population (0800-1300 LT) and (3) a pre-midnight (2100-2300 LT) population. The morning population is associated with meteor trails which are observed to be peaking near local dawn as expected, and already suggested by previous research. High latitude SuperDARN radars also had echoes (pre-midnight population) with higher Doppler velocities than the others yet the Doppler velocities are smaller than that expected from auroral E region echoes. Given the time and location of this population of echoes, it has been concluded that they are a special class of high latitude E region echoes at high aspect angle which have been termed ``high aspect irregularity region" echoes in the past. Lastly, the midday summer population was found to be too high for polar mesosphere summer echoes and too early for plasma instabilities. It is proposed that these SuperDARN echoes are produced either from contribution from meteors trails or by neutral turbulence which is suspected (from other work) to be present near 100 km. The properties of the midday summer population resembles those of meteor trails as they have the same power, and the same altitude and have high summer occurrence as expected for meteors. Their late morning occurrence could be due to particular look direction of individual radars which may change the occurrence statistics in the presence of meteor showers. With respect to neutral turbulence, the drift of the midday summer population is similar to that of neutral wind.
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Li, Yen-huang, and 李彥篁. "Image Processing Approaches to Dice Counting and Radar Echo Center Locating." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/32961290459055231004.
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碩士朝陽科技大學
資訊工程系碩士班
96
In this thesis, we propose image processing approaches to LED die counting and radar echo center locating. The die counting process is very important in LED manufacture. Two common approaches are used in LED die counting. One is by human inspection for cost down. The other employs high-end automatic equipment for high throughput. In this thesis, two low cost approaches to LED die counting based on zonal autocorrelation and grid arrangement are proposed. The challenge in die counting with image processing schemes is low contrast image. To deal with the problem, we employ histogram equalization to enhance the contrast between pixels of dice and background. Then, an automatic approach for determining the threshold is used to separate die pixels from background pixels. With the binary image, two schemes to count LED dice are given. In the first approach, autocorrelation scheme is applied to LED die image and the correlation coefficients are computed. Then, count the number of LED die image which correlation coefficients are larger than a given threshold. The second approach is based on grid arrangement. Through the binary image, determine the possible LED dice pixels after noise removal. Given a threshold, count the total number of LED dice whose number of pixels is above the threshold. In the experimental results, thirty LED die samples are given to verify the proposed counting approaches. The results show the two die counting approaches are able to find the number of LED dice perfectly. The grid arrangement based approach is better than the zonal autocorrelation approach in terms of automation in LED die counting. The automatic determination of threshold for a binary image in LED die counting is extended to radar echo center locating. Since the information of echo centers can be of great use to examine the scattering mechanisms and the dynamics of the atmosphere. Hence, we need an approach to locate the radar echo centers angle of arrival. In this thesis, we propose two approaches to locate radar echo centers: (a) watershed based approach and (b) grey clustering approach. In the watershed based approach, we employ a FIR low-pass filter to smoothen the radar echo image. Then, find the maximum value within working window and locate the echo centers. In the grey clustering approach, a threshold is determined to separate the echo and background and its corresponding binary image is found. Then, the grey clustering algorithm is employed to coordinates of radar echo pixels and the clustering centers are found. Eight radar echo images with different types of structure are given to verify the proposed locating schemes. The results show that the two locating schemes are able to find the echo centers efficiently and accurately.
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GIU, JIAN-GING, and 丘建青. "Echo analysisfor Chung-li radar using the spaced antenna drift method." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/11441201235304183020.
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Yu-JenChung and 鍾育仁. "Echo Identification of Vessel Activities Using HF Radar and Relevant Threat Evaluation." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/54078032465040639724.
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博士國立成功大學
海洋科技與事務研究所
104
There is a growing need to deal with threats to national security coming from the ocean. Compared to conventional radar, high-frequency (HF) ground wave radar transmits low-power radar waves that can extend the detection distance up to several hundred kilometers with little attenuation. Moreover, HF radar has various advantages, such as active, continuous monitoring and near real-time performance. It is thus worth developing a vessel detection algorithm based on the HF radar system for large area surveillance. The present study aims to achieve three objectives. The first is to analyze the local environmental noise to understand its distribution and effects. The second is to extract ship echoes from the HF radar system’s sea-returns by applying a simple procedure to the cross-spectra series of the signals of the SeaSonde HF radar system. An adaptive detection technique (ADT) is used to build a threshold surface which can be adaptive to the local environmental noise. In this work the ship information retrieved from the HF radar data was validated against the automatic identification system (AIS) data. The final aim is to explore the potential use of this system for maritime management, with a focus on threat evaluation of non-cooperative targets. Since environmental noise may contain the complex irregular variations, this study first explores this noise to understand the regional characteristics and system limits. Appropriate observations in range and time intervals are derived from the spatial and temporal variations of the environmental noise, which can help develop a better detection scheme. The results show that the background noise levels during the nighttime are significantly higher than those during the daytime. Similar to the regularities of the ionosphere, the diurnal variations of time series can be derived by spectral analysis. Furthermore, the results of the environmental noise analysis show that the better time period and scope for vessel detection is from 02:00 to 07:00 (UTC) and the range cells from 4 to 12, within which the targets can be easily identified. Based on ADT, a two-dimensional moving average filter is applied to build an adaptive threshold surface in the region of interest to extract ship motion data. Actual information for the vessels collected from the AIS database closely matched that derived from the HF radar sea echoes, which confirms the vessel signal detection capabilities of this HF radar. In addition, the main advantage of ADT is the decision process applied to find the optimal window, which may change based on the properties pof the environmental noise. The process of optimal window determination in ADT is not a tradeoff check, and this can be decided according to the spatial and temporal characteristics of the environmental noise. Furthermore, the unidentified targets, which may be the non-cooperative ones, are determined by ADT and checked against the AIS. The proposed threat evaluation procedure is a preliminary idea which not only provides an initial and rapid classification of possible targets, but also helps the command system to take the appropriate actions using the related information. The threat levels can thus be computed to obtain the related information, which can be regarded as part of the decision support system to better understand the reaction time of the command system with regard to maritime security.