4,053 research outputs found

    Aerometry instrumentation study Final report

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    Techniques and instruments for meteorological measurements in Mars and Venus atmosphere

    A unified approach to cooperative and non-cooperative sense-and-avoid

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    Cooperative and non-cooperative Sense-and-Avoid (SAA) capabilities are key enablers for Unmanned Aircraft Vehicle (UAV) to safely and routinely access all classes of airspace. In this paper state-of-the-art cooperative and non-cooperative SAA sensor/system technologies for small-to-medium size UAV are identified and the associated multi-sensor data fusion techniques are introduced. A reference SAA system architecture is presented based on Boolean Decision Logics (BDL) for selecting and sorting non-cooperative and cooperative sensors/systems including both passive and active Forward Looking Sensors (FLS), Traffic Collision Avoidance System (TCAS) and Automatic Dependent Surveillance - Broadcast (ADS-B). After elaborating the SAA system processes, the key mathematical models associated with both non-cooperative and cooperative SAA functions are presented. The analytical models adopted to compute the overall uncertainty volume in the airspace surrounding an intruder are described. Based on these mathematical models, the SAA Unified Method (SUM) for cooperative and non-cooperative SAA is presented. In this unified approach, navigation and tracking errors affecting the measurements are considered and translated to unified range and bearing uncertainty descriptors, which apply both to cooperative and non-cooperative scenarios. Simulation case studies are carried out to evaluate the performance of the proposed SAA approach on a representative host platform (AEROSONDE UAV) and various intruder platforms. Results corroborate the validity of the proposed approach and demonstrate the impact of SUM towards providing a cohesive logical framework for the development of an airworthy SAA capability, which provides a pathway for manned/unmanned aircraft coexistence in all classes of airspace

    In situ sensors for measurements in the global trosposphere

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    Current techniques available for the in situ measurement of ambient trace gas species, particulate composition, and particulate size distribution are reviewed. The operational specifications of the various techniques are described. Most of the techniques described are those that have been used in airborne applications or show promise of being adaptable to airborne applications. Some of the instruments described are specialty items that are not commercially-available. In situ measurement techniques for several meteorological parameters important in the study of the distribution and transport of ambient air pollutants are discussed. Some remote measurement techniques for meteorological parameters are also discussed. State-of-the-art measurement capabilities are compared with a list of capabilities and specifications desired by NASA for ambient measurements in the global troposphere

    Lunar and planetary instruments

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    Folding rotating cup anemometer for hard landing Mars probe, and instruments for measuring wind velocity on Mars surfac

    Forcing and Dynamics of Seafloor-Water Column Exchange on a Broad Continental Shelf

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    Relict sediments of elevated permeability characterize the majority of continental shelves globally (Emery, 1968). In these settings, interactions between benthic boundary layer (BBL) flows and seabed topography generate pressure fluctuations that drive advective and dispersive porewater transport, dramatically increasing the magnitude and variability of porewater solute and particulate exchange across the sediment-water interface (Huettel et al., 1996; Huettel and Rusch, 2000). On broad shallow shelves with a relatively large area-to-volume ratio, the seafloor’s role is magnified. Energetic events may reorganize bedforms across a significant fraction of the shelf, leading to altered exchange dynamics that may persist long after the organizing event. Ecosystem-based management of both resources and environmental status requires improved fundamental understanding of dynamic benthic exchange processes. Scattered, short-time-scale observations are unlikely to capture the full spectrum of events that affect sediment-water exchanges; a persistent observational presence on the seafloor is required

    Two-layer particle filter for multiple target detection and tracking

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    This paper deals with the detection and tracking of an unknown number of targets using a Bayesian hierarchical model with target labels. To approximate the posterior probability density function, we develop a two-layer particle filter. One deals with track initiation, and the other with track maintenance. In addition, the parallel partition method is proposed to sample the states of the surviving targets

    Publications of the Jet Propulsion Laboratory, July 1961 through June 1962

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    Jpl bibliography on space science, 1961-196

    Sensors for Desert Surveillance

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    Various types of sensors-visible, passive night vision, infrared, synthetic aperture radar, etc can be used for desert surveillance. The surveillance capability of these sensors depends to a large extent, on various atmospheric effects, viz., absorption, scattering, aerosol, turbulence, and optical mirage. In this paper, effects of various atmospheric phenomena on the transmission of signals, merits and demerits of different means of surveillance under desert environmental conditions are discussed. Advanced surveillance techniques, ie, multisensor fusion, multi and hyperspectral imaging, having special significance for desert surveillance, have also been discussed

    Advances in Sonar Technology

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    The demand to explore the largest and also one of the richest parts of our planet, the advances in signal processing promoted by an exponential growth in computation power and a thorough study of sound propagation in the underwater realm, have lead to remarkable advances in sonar technology in the last years.The work on hand is a sum of knowledge of several authors who contributed in various aspects of sonar technology. This book intends to give a broad overview of the advances in sonar technology of the last years that resulted from the research effort of the authors in both sonar systems and their applications. It is intended for scientist and engineers from a variety of backgrounds and even those that never had contact with sonar technology before will find an easy introduction with the topics and principles exposed here
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