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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
The Earth's atmosphere is often portrayed as a thin and finite blanket covering our planet, separate from the emptiness of outer space. In reality, the transition is gradual and a tiny fraction of the atmophere gases is still present at the altitude of low orbiting satellites. The very high velocities of these satellites ensure that their orbital motion can still be considerably affected by air density and wind. This influence can be measured using accelerometers and satellite tracking techniques. The opening chapters of this thesis provide an excellent introduction to the various disciplines that are involved in the interpretation of these observations: orbital mechanics, satellite aerodynamics and upper atmospheric physics. A subsequent chapter, at the heart of this work, covers advances in the algorithms used for processing satellite accelerometry and Two-Line Element (TLE) orbit data. The closing chapters provide an elaborate analysis of the resulting density and wind products, which are generating many opportunities for further research, to improve the modelling and understanding of the thermosphere system and its interactions with the lower atmosphere, the ionosphere-magnetosphere system and the Sun.
Atmospheric density measurements obtained by the satellite accelerometer experiment provide data over a wide range of solar and geophysical conditions. These results are used in a preliminary evaluation of several atmospheric models. The model accuracies are compared by their mean values and standard deviations relative to the accelerometer data. Sources of model uncertainties and problems in reducing them are described. Long-term programs involving coordinated measurements, analyses of available data and theoretical studies are required along with development of more accurate indicators of solar and geomagnetic activity before models can show significant improvement. Keywords include: Satellite, Accelerometers, Atmospheric density measurements, Thermospheric model evaluations, Thermospheric density variability.
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 201. Modeling the Ionosphere-Thermosphere System brings together for the first time a detailed description of the physics of the IT system in conjunction with numerical techniques to solve the complex system of equations that describe the system, as well as issues of current interest. Volume highlights include discussions of: Physics of the ionosphere and thermosphere IT system, and the numerical methods to solve the basic equations of the IT system The physics and numerical methods to determine the global electrodynamics of the IT system The response of the IT system to forcings from below (i.e., the lower atmosphere) and from above (i.e., the magnetosphere) The physics and numerical methods to model ionospheric irregularities Data assimilation techniques, comparison of model results to data, climate variability studies, and applications to space weather Providing a clear description of the physics of this system in several tutorial-like articles, Modeling the Ionosphere-Thermosphere System is of value to the upper atmosphere science community in general. Chapters describing details of the numerical methods used to solve the equations that describe the IT system make the volume useful to both active researchers in the field and students.
The Earth's atmosphere is often portrayed as a thin and finite blanket covering our planet, separate from the emptiness of outer space. In reality, the transition is gradual and a tiny fraction of the atmophere gases is still present at the altitude of low orbiting satellites. The very high velocities of these satellites ensure that their orbital motion can still be considerably affected by air density and wind. This influence can be measured using accelerometers and satellite tracking techniques. The opening chapters of this thesis provide an excellent introduction to the various disciplines that are involved in the interpretation of these observations: orbital mechanics, satellite aerodynamics and upper atmospheric physics. A subsequent chapter, at the heart of this work, covers advances in the algorithms used for processing satellite accelerometry and Two-Line Element (TLE) orbit data. The closing chapters provide an elaborate analysis of the resulting density and wind products, which are generating many opportunities for further research, to improve the modelling and understanding of the thermosphere system and its interactions with the lower atmosphere, the ionosphere-magnetosphere system and the Sun.
This book shows the state-of-the-art in Europe on a very new discipline, Space Weather. This discipline lies at the edge between science and industry. This book reflects such a position with theoretic papers and applicative papers as well. Each chapter starts with a short introduction, which shows the coherence of a given domain. Then, four to five contributions written by the best specialists in Europe give detailed hints of a hot topic in space weather.
Spatial information technology and its integration, such as remote sensing, geographic information systems (GIS), and global navigation satellite systems (GNSS), known as 3S technology, have been extensively utilized in managing and monitoring natural disasters. This book illustrates the 3S integrated applications in the field of meteorology and promotes the role of 3S in developing precise and intelligent meteorology. It presents the principles of 3S technology and the methods for monitoring different meteorological disasters and hazards as well as their application progress. The case studies from the United States, Japan, China, and Europe were conducted to help all countries understand the 3S technology functions in handling and monitoring severe meteorological hazards. FEATURES Presents integral observations from GNSS, GIS, and remote sensing in estimating and understanding meteorological changes Explains how to monitor and retrieve atmospheric parameter changes using GNSS and remote sensing Shows three-dimensional modelling and evaluations of meteorological variation processing based on GIS Helps meteorologists develop and use space-air-ground integrated observations for meteorological applications Illustrates the practices in monitoring meteorological hazards using space information techniques and case studies This book is intended for academics, researchers, and postgraduate students who specialize in geomatics, atmospheric science, and meteorology, as well as scientists who work in remote sensing and meteorology, and professionals who deal with meteorological hazards.
In February 2009, the commercial communications satellite Iridium 33 collided with the Russian military communications satellite Cosmos 2251. The collision, which was not the first recorded between two satellites in orbit-but the most recent and alarming-produced thousands of pieces of debris, only a small percentage of which could be tracked by sensors located around the world. In early 2007, China tested a kinetic anti-satellite weapon against one of its own satellites, which also generated substantial amounts of space debris. These collisions highlighted the importance of maintaining accurate knowledge, and the associated uncertainty, of the orbit of each object in space. These data are needed to predict close approaches of space objects and to compute the probability of collision so that owners/operators can decide whether or not to make a collision avoidance maneuver by a spacecraft with such capability. The space object catalog currently contains more than 20,000 objects, and when the planned space fence radar becomes operational this number is expected to exceed 100,000. A key task is to determine if objects might come closer to each other, an event known as "conjunction," and the probability that they might collide. The U.S. Air Force is the primary U.S. government organization tasked with maintaining the space object catalog and data on all space objects. This is a complicated task, involving collecting data from a multitude of different sensors-many of which were not specifically designed to track orbiting objects-and fusing the tracking data along with other data, such as data from atmospheric models, to provide predictions of where objects will be in the future. The Committee for the Assessment of the U.S. Air Force's Astrodynamic Standards collected data and heard from numerous people involved in developing and maintaining the current astrodynamics standards for the Air Force Space Command (AFSPC), as well as representatives of the user community, such as NASA and commercial satellite owners and operators. Preventing collisions of space objects, regardless of their ownership, is in the national security interested of the United States. Continuing Kepler's Quest makes recommendations to the AFSPC in order for it to create and expand research programs, design and develop hardware and software, as well as determine which organizations to work with to achieve its goals.
Density data from the Satellite Electrostatic Triaxial Accelerometer (SETA) experiment were spectrally analyzed by the Maximum Entropy Method (MEM). The purpose is to make available a technique by which the occurrence of wavelike structures in thermospheric densities can be quantitatively analyzed and correlated with various geophysical conditions, including the deposition of energy at high latitudes during geomagnetically disturbed conditions. Spectra were computed for typical magnetically quiet and active days during July 1983, and the relative occurrence of spectral peaks in wavelength ranges of large-scale (hundreds to thousands of kilometers) and medium-scale (tens to hundreds of kilometers) traveling ionospheric disturbances is examined as a function of local time and latitude.