Polarization techniques for mitigation of low grazing angle sea clutter

Maritime surveillance radars are critical in commerce, transportation, navigation, and defense. However, the sea environment is perhaps the most challenging of natural radar backdrops because maritime radars must contend with electromagnetic backscatter from the sea surface, or sea clutter. Sea clutter poses unique challenges in very low grazing angle geometries, where typical statistical assumptions regarding sea clutter backscatter do not hold. As a result, traditional constant false alarm rate (CFAR) detection schemes may yield a large number of false alarms while objects of interest may be challenging to detect. Solutions posed in the literature to date have been either computationally impractical or lacked robustness. This dissertation explores whether fully polarimetric radar offers a means of enhancing detection performance in low grazing angle sea clutter. To this end, MIT Lincoln Laboratory funded an experimental data collection using a fully polarimetric X-band radar assembled largely from commercial off-the-shelf components. The Point de Chene Dataset, collected on the Atlantic coast of Massachusetts’ Cape Ann in October 2015, comprises multiple sea states, bandwidths, and various objects of opportunity. The dataset also comprises three different polarimetric transmit schemes. In addition to discussing the radar, the dataset, and associated post-processing, this dissertation presents a derivation showing that an established multiple input, multiple output radar technique provides a novel means of simultaneous polarimetric scattering matrix measurement. A novel scheme for polarimetric radar calibration using a single active calibration target is also presented. Subsequent research leveraged this dataset to develop Polarimetric Co-location Layering (PCL), a practical algorithm for mitigation of low grazing angle sea clutter, which is the most significant contribution of this dissertation. PCL routinely achieves a significant reduction in the standard CFAR false alarm rate while maintaining detections on objects of interest. Moreover, PCL is elegant: It exploits fundamental characteristics of both sea clutter and object returns to determine which CFAR detections are due to sea clutter. We demonstrate that PCL is robust across a range of bandwidths, pulse repetition frequencies, and object types. Finally, we show that PCL integrates in parallel into the standard radar signal processing chain without incurring a computational time penalty

Statistical Analysis of Coherent Monostatic and Bistatic Radar Sea Clutter

Radar sea clutter analysis has been an important area of radar research for many years. Very limited research has been carried out on coherent monostatic sea clutter analysis and even less on bistatic sea clutter. This has left a significant gap in the global scientific knowledge within this area. This thesis describes research carried out to analyse, quantify and model coherent sea clutter statistics from multiple radar sources. The ultimate goal of the research is to improve maritime radars' ability to compensate for clutter and achieve effective detection of targets on or over the sea surface. The first analyses used monostatic data gathered during the fight trials of the Thales Searchwater 2000 AEW radar. A further sea clutter trials database from CSIR was then used to investigate the variation of clutter statistics with look angle and grazing angle. Finally simultaneous monostatic and bistatic sea clutter data recorded in South Africa using the S-band UCL radar system NetRAD were analysed. No simultaneous monostatic and bistatic coherent analysis has ever been reported before in the open literature. The datasets recorded included multiple bistatic angles at both horizontal and vertical polarisations. Throughout the analysis real data have been compared to accepted theoretic models of sea clutter. An additional metric of comparison was investigated relating to the area of information theoretic techniques. Information theory is a significant subject area, and some concepts from it have been applied in this research. In summary this research has produced quantifiable and novel results on the characteristics of sea clutter statistics as a function of Doppler. Analysis has been carried out on a wide range of monostatic and bistatic data. The results of this research will be extremely valuable in developing sea clutter suppression algorithms and thus improving detection performance in future maritime radar designs

Sensor and data fusion of remotely sensed wide-area geospatial targets

This thesis consists of the examination of methodologies for sensor fusion and data fusion of remotely sensed, sparse geospatial targets. Methods for attaining an increased awareness of targets in both tactical and strategic roles are proposed and examined. The example methodologies are demonstrated, and areas for further research noted. Discussions of the proposed methods are carried forth in the context of iceberg detection. -- Amongst the difficulties associated with the combination of sensor parameters and sensor data are the wide variety of technologies, performance ability, coverage, and reliability that are available to those users of remote sensing technology. Typical sensors include airborne search radars, marine search radars, surface wave radar, and satellite synthetic aperture radar. The ability to mitigate the related parametric variances is the test of an appropriate sensor or data fusion algorithm. -- Documented herein are the efforts to find such an algorithm using various statistical methods. Primary among these is Bayes Theorem combined with tracking systems such as the multiple hypothesis tracker. This and other methodologies are explored and evaluated, where appropriate. It will be demonstrated that such a methodology can combine sensor data returns to provide high performance, wide-area, situational awareness with sensors considered to have poor performance

Counter Unmanned Aircraft Systems Technologies and Operations

As the quarter-century mark in the 21st Century nears, new aviation-related equipment has come to the forefront, both to help us and to haunt us. (Coutu, 2020) This is particularly the case with unmanned aerial vehicles (UAVs). These vehicles have grown in popularity and accessible to everyone. Of different shapes and sizes, they are widely available for purchase at relatively low prices. They have moved from the backyard recreation status to important tools for the military, intelligence agencies, and corporate organizations. New practical applications such as military equipment and weaponry are announced on a regular basis – globally. (Coutu, 2020) Every country seems to be announcing steps forward in this bludgeoning field. In our successful 2nd edition of Unmanned Aircraft Systems in the Cyber Domain: Protecting USA’s Advanced Air Assets (Nichols, et al., 2019), the authors addressed three factors influencing UAS phenomena. First, unmanned aircraft technology has seen an economic explosion in production, sales, testing, specialized designs, and friendly / hostile usages of deployed UAS / UAVs / Drones. There is a huge global growing market and entrepreneurs know it. Second, hostile use of UAS is on the forefront of DoD defense and offensive planners. They are especially concerned with SWARM behavior. Movies like “Angel has Fallen,” where drones in a SWARM use facial recognition technology to kill USSS agents protecting POTUS, have built the lore of UAS and brought the problem forefront to DHS. Third, UAS technology was exploding. UAS and Counter- UAS developments in navigation, weapons, surveillance, data transfer, fuel cells, stealth, weight distribution, tactics, GPS / GNSS elements, SCADA protections, privacy invasions, terrorist uses, specialized software, and security protocols has exploded. (Nichols, et al., 2019) Our team has followed / tracked joint ventures between military and corporate entities and specialized labs to build UAS countermeasures. As authors, we felt compelled to address at least the edge of some of the new C-UAS developments. It was clear that we would be lucky if we could cover a few of – the more interesting and priority technology updates – all in the UNCLASSIFIED and OPEN sphere. Counter Unmanned Aircraft Systems: Technologies and Operations is the companion textbook to our 2nd edition. The civilian market is interesting and entrepreneurial, but the military and intelligence markets are of concern because the US does NOT lead the pack in C-UAS technologies. China does. China continues to execute its UAS proliferation along the New Silk Road Sea / Land routes (NSRL). It has maintained a 7% growth in military spending each year to support its buildup. (Nichols, et al., 2019) [Chapter 21]. They continue to innovate and have recently improved a solution for UAS flight endurance issues with the development of advanced hydrogen fuel cell. (Nichols, et al., 2019) Reed and Trubetskoy presented a terrifying map of countries in the Middle East with armed drones and their manufacturing origin. Guess who? China. (A.B. Tabriski & Justin, 2018, December) Our C-UAS textbook has as its primary mission to educate and train resources who will enter the UAS / C-UAS field and trust it will act as a call to arms for military and DHS planners.https://newprairiepress.org/ebooks/1031/thumbnail.jp

Bowdoin Orient v.67, no.1-25 (1937-1938)

https://digitalcommons.bowdoin.edu/bowdoinorient-1930s/1008/thumbnail.jp

Change and continuity in Asymmetric Alliances in the Asia Pacific: Japanese and Australian security alliances with the Unites States of America

This dissertation examines the development of military alliances in the Asia-Pacific after the end of the Cold War. The research focuses on US alliances with Japan and Australia and tracks the central developments in these two alliances since the late Cold War period until the end of the 2010s. The research is designed as a comparative case study of these two alliance relations. The research framework is constructed around four theoretical approaches to military alliances derived from the Realist School of International Relations: the framework of threats, the alliance security dilemma, the influence of domestic politics on alliances and, lastly, the asymmetric alliance framework. This study provides comprehensive and historical parallel narratives of the two alliances. The developments in the alliances are considered from the perspectives of institutional and political structures, international military operations, defense procurement, and technological cooperation. The cases are divided into three periods that are designed to roughly correspond to the different dynamics of power relations in the region, beginning from the period of uncontested US unipolarity in the Asia-Pacific and ending with the increased military rivalry in the region and the rise of China. While different theoretical frameworks are determined to have their own strengths and weaknesses, the longer time perspective used in this study clearly demonstrates that the asymmetric nature of these alliances is simply the strongest explanatory factor behind the persistent lines of development witnessed in the alliances. These long-term trends are, in turn, consistently found to explain several singular events better than short term focus on more immediate factors such as changing domestic circumstances. The asymmetric framework has arguably been underutilized in the contemporary International Relations discipline, but the results of this work show that it can provide valuable insights for future research on military alliances, especially given the nature of today’s world, characterized by increasingly fluid power relations.Tämä väitöstyö käsittelee Aasian ja Tyynenmeren alueen sotilasliittojen kehittymistä kylmän sodan päättymisen jälkeisenä aikana. Tutkimus keskittyy Yhdysvaltojen sotilasliittoihin Japanin ja Australian kanssa ja seuraa niiden keskeisiä kehityslinjoja kylmän sodan viimeisistä vuosista aina 2010-luvun loppupuolelle. Tutkimus on suunniteltu vertailevaksi tapaustutkimukseksi näiden kahden liittosuhteen välillä. Tutkimuksen viitekehys rakentuu kansainvälisen politiikan Realismin tutkimus-perinteestä johdettuihin neljään keskeiseen sotilasliittojen tutkimuksen malliin. Nämä ovat uhkien, liittodilemman, valtion sisäpolitiikan ja asymmetristen sotilasliittojen teoreettiset viitekehykset. Työ tarjoaa kokonaisvaltaisen historiallisen narratiivin sen kohteena olevista sotilasliitoista. Sotilasliittojen kehitystä käsitellään institutionaalisten rakenteiden, kansainvälisten sotilasoperaatioiden sekä puolustushankintojen ja teknologisen yhteistyön kautta. Tapaustutkimukset on jaettu kolmeen ajanjaksoon, jotka on määritelty vastaamaan Aasian-Tyynenmeren alueen kansainvälisen järjestelmän voimasuhteissa tapahtuneita muutoksia, alkaen Yhdysvaltojen kiistattoman taloudellisen ja sotilaallisen valta-aseman kaudesta 1990-luvun alussa ja päättyen 2010-luvun kiihtyvän sotilaallisen vastakkainasettelun ja nousevan Kiinan aikaan. Tutkimus löytää sekä vahvuuksia että heikkouksia kaikista neljästä käytetystä teoreettisesta viitekehyksestä. Kuitenkin, pidemmällä aikaperspektiivillä tarkasteltuna, sotilasliittojen asymmetristä luonnetta painottava viitekehys selittää selvästi parhaiten liittojen pitkään jatkuneita kehityslinjoja. Pitkän linjan kehityslinjat puolestaan selittävät myös yksittäiset tapahtumat vakuuttavammin kuin lyhemmällä tähtäimellä muuttuvat tekijät, kuten valtioiden sisäiset poliittiset olosuhteet. Asymmetristä viitekehystä ei ole aiemmin kattavasti käytetty sotilasliittojen tutkimuksessa. Tämän tutkimuksen tulosten valossa on kuitenkin selvää, että viitekehyksen kautta voidaan saada arvokasta tietoa Aasian-Tyynenmeren alueen sotilasliittojen mahdollisista kehityslinjoista. Tällainen tieto on erityisen arvokasta nykyisen, nopeasti muuttuvan kansainvälisen voimatasapainon aikana

Bowdoin Orient v.117, no.1-24 (1987-1988)

https://digitalcommons.bowdoin.edu/bowdoinorient-1980s/1008/thumbnail.jp

MX Missile Basing

A study by the Office of Technology Assessment (OTA) that examines a new intercontinental ballistic missile known as the MX, identifies MX basing modes and assesses "the major advantages, disadvantages, risks, and uncertainties of each" (p. 3)

Bowdoin Orient v.116, no.1-27 (1986-1987)

https://digitalcommons.bowdoin.edu/bowdoinorient-1980s/1007/thumbnail.jp