Signal Processing Techniques and Concept of Operations for Polarimetric Rotating Phased Array Radar

The Weather Surveillance Radar 1988 Doppler (WSR-88D) network has been operational for over 30 years and is still the primary observational instrument employed by the National Weather Service (NWS) forecasters to support their critical mission of issuing severe weather warnings and forecasts in the United States. Nevertheless, the WSR-88Ds have exceeded their engineering design lifespan and are projected to reach the end of operational lifetime by 2040. Technological limitations may prevent the WSR-88D to meet demanding functional requirements for future observational needs. The National Oceanic and Atmospheric Administration (NOAA) has started considering radar systems with advanced capabilities for the eventual replacement of the WSR-88D. Unique and flexible capabilities offered by Phased Array Radar (PAR) technology support the required enhanced weather surveillance strategies that are envisioned to improve the weather radar products, making PAR technology an attractive candidate for the next generation of weather radars. If PAR technology is to replace the operational WSR-88D, important decisions must be made regarding the architecture that will be needed to meet the functional requirements. A four-faced planar PAR (4F-PAR) is expected to achieve the requirements set forth by NOAA and the NWS, but deploying and maintaining an operational network of these radars across the U.S. will likely be unaffordable. A more affordable alternative radar system is based on a single-face Rotating PAR (RPAR) architecture, which is capable of exceeding the functionality provided by the WSR-88D network. This dissertation is focused on exploring advanced RPAR scanning techniques in support of meeting future radar functional requirements. A survey of unique RPAR capabilities is conducted to determine which ones could be exploited under an RPAR Concept of Operations (CONOPS). Three capabilities are selected for further investigation: beam agility, digital beamforming, and dwell flexibility. The RPARs beam agility is exploited to minimize the beam smearing that results from the rotation of the antenna system over the collection of samples in the coherent processing interval. The use of digital beamforming is investigated as a possible way to reduce the scan time and/or the variance of estimates. The RPAR's dwell flexibility capability is explored as a possible way to tailor the scan to meteorological observations with the goal of improving data quality. Three advanced RPAR scanning techniques are developed exploiting these capabilities, and their performance in support of meeting the radar functional requirements is quantified. The proposed techniques are implemented on the Advanced Technology Demonstrator (ATD), a dual-polarization RPAR system at the National Severe Storms Laboratory (NSSL) in Norman, OK. Data collection experiments are conducted with the ATD to demonstrate the performance of the proposed techniques for dual-polarization observations. Results are verified by quantitatively comparing fields of radar-variable estimates produced using the proposed RPAR techniques with those produced by a well-known collocated WSR-88D radar simultaneously collecting data following an operational Volume Coverage Pattern (VCP). The techniques introduced are integrated to operate simultaneously, and used to design an RPAR CONOPS that can complete a full volume scan in about one minute, while achieving other demanding functional requirements. It is expected that the findings in this dissertation will provide valuable information that can support the design of the future U.S. weather surveillance radar network

On Small Satellites for Oceanography: A Survey

The recent explosive growth of small satellite operations driven primarily from an academic or pedagogical need, has demonstrated the viability of commercial-off-the-shelf technologies in space. They have also leveraged and shown the need for development of compatible sensors primarily aimed for Earth observation tasks including monitoring terrestrial domains, communications and engineering tests. However, one domain that these platforms have not yet made substantial inroads into, is in the ocean sciences. Remote sensing has long been within the repertoire of tools for oceanographers to study dynamic large scale physical phenomena, such as gyres and fronts, bio-geochemical process transport, primary productivity and process studies in the coastal ocean. We argue that the time has come for micro and nano satellites (with mass smaller than 100 kg and 2 to 3 year development times) designed, built, tested and flown by academic departments, for coordinated observations with robotic assets in situ. We do so primarily by surveying SmallSat missions oriented towards ocean observations in the recent past, and in doing so, we update the current knowledge about what is feasible in the rapidly evolving field of platforms and sensors for this domain. We conclude by proposing a set of candidate ocean observing missions with an emphasis on radar-based observations, with a focus on Synthetic Aperture Radar.Comment: 63 pages, 4 figures, 8 table

Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 2: Final report

The results are presented of a study which identifies over 100 new and highly capable space systems for the 1980-2000 time period: civilian systems which could bring benefits to large numbers of average citizens in everyday life, much enhance the kinds and levels of public services, increase the economic motivation for industrial investment in space, expand scientific horizons; and, in the military area, systems which could materially alter current concepts of tactical and strategic engagements. The requirements for space transportation, orbital support, and technology for these systems are derived, and those requirements likely to be shared between NASA and the DoD in the time period identified. The high leverage technologies for the time period are identified as very large microwave antennas and optics, high energy power subsystems, high precision and high power lasers, microelectronic circuit complexes and data processors, mosaic solid state sensing devices, and long-life cryogenic refrigerators

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

China Near Seas Combat Capabilities

The capstone U.S. Defense Department study on the future operational environment declares, China\u27s rise represents the most significant single event on the international horizon since the collapse of the Cold War. Understanding and assessing changes in China\u27s traditionally defensive naval strategy, doctrine, and force structure are of obvious importance to the U.S. Navy (USN) and other Pacific navies concerned with the possible security implications of that rise. This chapter examines the development of the Chinese navy\u27s Houbei (Type 022) fast-attack-craft force and its roles and missions in China\u27s near seas and discusses implications for the U.S. Navy and other navies in the region.https://digital-commons.usnwc.edu/cmsi-red-books/1010/thumbnail.jp

Characterising Spatial and Temporal Ionospheric Variability with a Network of Oblique Angle-of-arrival and Doppler Ionosondes

Ionospheric variability exists on a broad range of scales, and routinely impacts skywave propagation modes of high frequency radio waves, to the detriment of radar and communication systems. In order to better understand the electron density structures associated with such variability at mid-latitudes, a network of oblique angle-of-arrival (AoA) and Doppler ionosondes were installed in central and northern Australia as part of the ELOISE campaign in 2015. This thesis analyses observations from the ELOISE AoA ionosondes, with a focus on characterising the influence of medium- to large- scale gradients and signatures of travelling ionospheric disturbances (TIDs). Following an overview of the experiment, the design and calibration of the new ionosonde system is described. With multi-channel receivers connected to each element of two twin-arm arrays, a total of eleven AoA paths of between 900 and 2700 km were collected, including nine with interleaved Doppler measurements using a special channel scattering function (CSF) capability. On-board signal processing was developed to perform real-time clear channel evaluation and CSF scheduling, and generate the AoA ionograms and delay-Doppler images with fitted electron density profiles. In further offline analysis, peak detection and mode classification was carried out, to support reflection point mapping and tilt estimation. Significant testing and validation of the new ionosonde before and after the experiment revealed AoA uncertainties on the scale of 0.2–0.5° in bearing and 0.4–0.9° in elevation. Having identified a low-elevation bias, models of tropospheric refraction and antenna mutual coupling effects were considered as possible correction strategies, but ultimately an empirical approach based on aggregated ionospheric returns was implemented. Small-scale (intra-dwell) ionospheric variability also has the potential to compromise results, through unresolved multi-mode mixing, and this has been investigated using a combination of spatial and temporal variability metrics derived from the CSF data. The analysis of large quantities of F2 peak data shows persistent diurnal patterns in the oblique AoA observables that are also well-captured by a conventional data-assimilative ionospheric model, even without the benefit of AoA and Doppler inputs. Furthermore, Doppler measurements are reproduced remarkably well using just the midpoint fitted profiles. A statistical study has quantified the level of consistency between observations and model, to provide greater confidence in the results. Many of the geophysical features can be interpreted as ionospheric gradients, as evident in the tilt estimates, and horizontally moving structures such as TIDs, using a form of Doppler-based drift analysis. While signatures of TIDs vary considerably, two simple wave-like perturbation models have been evaluated to help classify quasi-periodic behaviour in the AoA observations, as well as understand the directional filtering effect imposed by the path geometry. In some cases, a set of TID parameters can be determined by eye, but in others automatic parameter inversion techniques may be more viable. Two such techniques were implemented but results using both real and synthetic data demonstrated some significant limitations. Finally, attempts to relate TID signatures across multiple paths shows promise, but there still appears to be a strong dependence on path geometry that is difficult to eliminate.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 202

Restless bandit index policies for dynamic sensor scheduling optimization

This dissertation addresses two complex stochastic and dynamic resource allocation problems, with application in modern sensor systems: (i) hunting multiple elusive hiding targets and (ii) tracking multiple moving targets. These problems are naturally formulated as Multi-armed Restless Bandit Problems (MARBPs) with real-state variables, which introduces technical difficulties that cause its optimal solution to be intractable. Hence, in this thesis we focus on designing tractable and well-performing heuristic policies of priority-index type. We consider the above MARBPs as Markov Decision Processess (MDPs) with special structure, and we deploy recent extensions to the unifying principle to design a dynamic priority index policy based on a Lagrangian relaxation and decomposition approach. This approach allows to design an index rule based on a structural property of the optimal solution to the decomposed parametric-optimization subproblems. The resulting index is a measure of the Marginal Productivity (MP) of resources invested in the subproblems, and it is then used to define a heuristic priority rule for the original intractable problems. For each of the problems under consideration we perform such a decomposition, to analyze the conditions under which the index recovering the optimal policies for the subproblems exists. We further obtain formulae for the indices which do not admit a closed form expression, but which are approximately computed by a tractable evaluation method. Apart from the practical contribution of deriving the tractable sensor scheduling polices which improve on existing heuristics, the main contributions of this thesis are the following: (i) deploying the recent extensions of Sufficient Indexability Conditions (SIC) to the real state case, for two problems in which direct verification of the SIC and obtaining a closed-form index formula are not possible, (ii) addressing the technical difficulties to analyze PCL-indexability introduced by the uncountable state space of the MARBPs of concern, and the state evolution over it given by non-linear dynamics by exploiting the special structure of the trajectories of the state and the action processes under a threshold policy using properties of M¨obius Transformations, and (iii) providing with a tractable approximate evaluation method for the resulting index policies._________________________________________________________________________________________________________________________________Esta tesis estudia dos problemas dinámicos y estocásticos de asignación de recursos, con aplicación a sistemas modernos de sensores: (i) localización de múltiples objetivos evasivos que se ocultan y (ii) el rastreo de múltiples objetivos que se mueven. Estos problemas son modelizados naturalmente como problemas de “Multi-armed Restless Bandit” con variable de estado real, lo que introduce dificultades técnicas que causan que su solción óptima no sea computacionalmente tratable. Debido a esto, en esta tesis nos concentramos en cambio en diseñar políticas heurísticas de prioridad que sean computacionalmente tratables y cuyo rendimento sea casi óptimo. Modelizamos los problemas arriba mencionados como problemas de decisión Markovianos con estructura especial y les aplicamos resultados existentes en la literatura, los que constituyen un principio unificador para el diseño de políticas de índices de prioridad basadas en la relajación Lagrangiana y la descomposición de esos problemas. Este enfoque nos permite considerar una propiedad de los subproblemas: la indexabilidad, por la cual podemos resolverlos de manera óptima mediante una política índice. El índice resultante es una medida de productividad de los recursos invertidos en los subproblemas, y es usado luego como medidad de la prioridad dinámica para los problemas originales intratables. Para cada uno de los problemas bajo estudio realizamos tal descomposición, y analizamos las condiciones bajo las que una política índice que recupere la solución óptima de los subproblemas existe. Además obtenemos fórmulas para los índices, las que a pesar de no admitir una expresión cerrada, son calculadas aproximadamente de manera eficiente meadiante un método tratable. Aparte de la contribución práctica de obtener reglas heurísticas de índices de prioridad para el funcionamiento de sistemas de múltiples sensores en el contexto de los dos problemas analizados, las principales contribuciones teóricas son las siguientes: (i) la aplicación de las extensiones recientes de las condiciones suficientes de indexabilidad para el caso de variable de estado real, para dos problemas en los que tanto la verificación directa de ellas como la obtención de fórmulas cerradas no son posibles, (ii) el tratamiento de las dificultades técnicas para establecer la indexabilidad introducidas por el espacio de estado infinito de los problemas bajo consideración, y por la evolución sobre este estado dada por dinámicas no lineales, explotando propiedades estructurales de los procesos de la variable de estado y trabajo bajo políticas de umbral como recursiones de Transformaciones de Möbius, and (iii) un método aproximado de evaluación de las políticas de índices resultantes