408 research outputs found

    Signals of Opportunity for Atmospheric Remote Sensing

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    Atmospheric propagation effects on radio interferometry

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN.Bibliography: leaves 278-284.by James Louis Davis.Ph.D

    Atmospheric refraction and turbulence in VLBI data analysis

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    The progress in further improving the quality of results derived by space-geodetic techniques observing in the radio frequency domain, such as Very Long Baseline Interferometry (VLBI) or Global Navigation Satellite Systems (GNSS), is limited by rapid changes in the neutral part of the atmosphere. In particular, insufficient knowledge of the temporal and spatial refractivity variations restrict the attainable accuracy of the derived VLBI and GNSS target parameters. In the current model describing the additional propagation delay due to the neutral part of the atmosphere, only annual to hourly long periodic variations are taken into account. In contrast, small-scale fluctuations mainly originating from turbulent motions are generally neglected, although they form a serious error source for electromagnetic wave propagation. Dynamic processes in the neutral atmosphere additionally induce physical correlations in space and time, which are also largely ignored so far. Particularly with regard to future requirements, as, for instance, defined within the framework of the Global Geodetic Observing System established by the International Association of Geodesy, the current tropospheric model is not sufficient and needs to be improved. High rate GNSS data of 1 Hz sampling and below, and the VLBI Global Observing System with faster telescopes result in a better sampling of the atmosphere. However, new challenges emerge with respect to improved and proper analysis strategies, in particular to model the stochastic properties of atmospheric refraction, which represents a crucial issue in research and the main objective of this thesis. Quantifying and assessing the small-scale behavior of atmospheric refraction is extremely challenging, since small-scale characteristics of atmospheric refraction cannot be analyzed without sufficient knowledge of the stability of the VLBI observing system. An optimal experimental setup for both, investigations in atmospheric refraction and system stability issues, emerges from the commissioning phase of the twin radio telescope at the Wettzell Geodetic Observatory in Germany. Specially designed so-called WHISP sessions are scheduled, observed and analyzed within this thesis allowing to quantify the individual components of the observing system, in part for the first time. On this basis, refractivity fluctuations are quantified which are found to be in the range of 1-3 millimeters. A number of noteworthy conclusions has been drawn which would not have been possible without the novel observing approach. Special emphasis is also given to the development of an atmospheric turbulence model, which stochastically describes small-scale refractivity fluctuations due to turbulent motions in the neutral atmosphere. The results have produced an important contribution to the modeling of refraction effects in the neutral atmosphere now considering temporal and spatial correlations between the observations in a physical and meteorological way. By analyzing 2700 VLBI sessions including traditional and local observing networks, it is demonstrated that the incorporation of the newly devised model into the VLBI data analysis leads to an improvemen of the solutions compared to the standard strategies of the International VLBI Service for Geodesy and Astrometry, or other strategies refining the stochastic model of VLBI observations. Compared to other approaches addressing the issue of atmospheric turbulence, the model developed within this thesis has the advantage to be operationally efficient for routine mass analysis of VLBI observing sessions. Since the current atmospheric model reveals severe deficiencies with respect to the estimation of atmospheric parameters, new modeling and adjustment strategies are introduced to better describe the behavior of the neutral atmosphere. It is demonstrated that, in particular, the least squares collocation method ensures an improved modeling of the stochastic properties of the neutral atmosphere, which allows a zenith wet delay estimation in more meaningful and appropriate sense. The main achievements of this thesis are the development of an atmospheric turbulence model to improve the stochastic model of VLBI observations and the quantification of local atmospheric refraction variations in space and time. Both allows for new interpretations and model improvements in a stochastic and deterministic sense.AtmosphĂ€rische Refraktion und Turbulenzin der VLBI-Auswertung Die stetige Weiterentwicklung und QualitĂ€tsverbesserung von Ergebnissen aus weltraum-geodĂ€tischen Verfahren im Radiofrequenzbereich, wie beispielsweise VLBI (Very Long Baseline Interferometry) oder GNSS (Global Navigation Satellite Systems), ist durch schnelle VerĂ€nderungen in der neutralen AtmosphĂ€re limitiert. Die zu erreichende Genauigkeit von Stationskoordinaten, Erdrotationsparametern oder anderen Zielparametern wird durch die unzureichende Kenntnis rĂ€umlicher oder zeitlicher Variationen in der RefraktivitĂ€t maßgeblich begrenzt. Das aktuelle AtmosphĂ€renmodell in der Auswertung weltraum-geodĂ€tischer Verfahren sieht ausschließlich die BerĂŒcksichtigung langperiodischer Signale vor. Kleinskalige, ĂŒberwiegend durch turbulentes Verhalten in der AtmosphĂ€re hervorgerufene Fluktuationen werden hingegen weitestgehend vernachlĂ€ssigt, obwohl sie einen nicht unerheblichen Einfluss auf die Ausbreitung elektromagnetischer Wellen haben. Des Weiteren induzieren dynamische Prozesse in der neutralen AtmosphĂ€re sowohl rĂ€umliche als auch zeitliche Korrelation zwischen den Beobachtungen, die ebenfalls weitestgehend ignoriert werden. Insbesondere im Hinblick auf die von der IAG (International Association of Geodesy) formulierten GGOS (Global Geodetic Observing System) Ziele genĂŒgt das aktuelle AtmosphĂ€renmodell nicht den zukĂŒnftigen Anforderungen. Zwar fĂŒhren hoch aufgelöste GNSS-Daten mit Abtastfrequenzen von bis zu 1 Hz und eine neue Generation von schnelleren und prĂ€ziseren sogenannten VGOS (VLBI Global Observing System) Radioteleskopen zu einer besseren Abtastung der AtmosphĂ€re, jedoch entstehen auch neue Herausforderungen hinsichtlich einer verbesserten und geeigneteren Modellierung der stochastischen Eigenschaften atmosphĂ€rischer Refraktion, welche allgemein eine zentrale Fragestellung darstellt und folglich die wesentliche Aufgabe dieser Arbeit reprĂ€sentiert. Die Quantifizierung und Bewertung des Verhaltens der atmosphĂ€rischen Refraktion stellt eine große Herausforderung dar. Da insbesondere das kleinskalige Verhalten der atmosphĂ€rischen Refraktion eng mit den StabilitĂ€tseigenschaften des VLBI-Beobachtungssystems zusammenhĂ€ngt, mĂŒssen diese ausreichend gut bekannt sein. Durch die Inbetriebnahme des weltweit ersten Twin-Teleskops am GeodĂ€tischen Observatorium Wettzell in Deutschland entstanden optimale Voraussetzungen fĂŒr die Detektion der StabilitĂ€tseigenschaften des Beobachtungssystems sowie der atmosphĂ€rischen Refraktion. In dieser Arbeit wurden spezielle WHISPExperimente entworfen, die es erlauben, einzelne Komponenten des Beobachtungssystems zum Teil erstmalig zu quantifizieren. Auf dieser Grundlage wird auch der Einfluss von Variationen in der RefraktivitĂ€t bestimmt, dem eine GrĂ¶ĂŸenordnung von 1-3 Millimetern zugerechnet wird. Ein besonderer Fokus liegt außerdem auf der Entwicklung eines Turbulenzmodells, welches zum einen zeitliche und rĂ€umliche Korrelationen zwischen den Beobachtungen berĂŒcksichtigt und zum anderen kleinskalige Fluktuationen in der RefraktivitĂ€t stochastisch sowie physikalisch und meteorologisch sinnvoll beschreibt. Auf Basis der Auswertung von 2700 VLBI-Beobachtungssessionen unterschiedlicher NetzwerkgrĂ¶ĂŸe wird gezeigt, dass die EinfĂŒhrung des neuen Turbulenzmodells in die VLBI-Auswertung fĂŒr die operationelle Auswertung geeignet ist und zu Verbesserungen gegenĂŒber der Standardlösung des IVS (International VLBI Service for Geodesy and Astrometry) sowie alternativer AnsĂ€tze zur Verfeinerung des stochastischen Modells fĂŒhrt. Da das routinemĂ€ĂŸig verwendete AtmosphĂ€renmodell einige Defizite hinsichtlich der SchĂ€tzung atmosphĂ€rischer Parameter aufweist, werden in dieser Arbeit einige Modellierungs- und Ausgleichungsstrategien eingefĂŒhrt, um die neutrale AtmosphĂ€re besser zu charakterisieren. Es wird gezeigt, dass insbesondere die Kleinste-Quadrate-Kollokation eine verbesserte Modellierung der stochastischen Eigenschaften der neutralen AtmosphĂ€re erlaubt und somit zu einer aussagekrĂ€ftigeren und geeigneteren SchĂ€tzung der AtmosphĂ€renparameter fĂŒhrt. Die Haupterrungenschaften dieser Arbeit sind die Entwicklung eines Turbulenzmodells zur Verbesserung des stochastischen Modells sowie die verbesserte Quantifizierung lokaler Refraktionseigenschaften in Raum und Zeit. Beides resultiert in neuen Interpretationsmöglichkeiten und Modellverbesserungen in deterministischer und stochastischer Hinsicht

    Atmospheric refraction and turbulence in VLBI data analysis

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    The progress in further improving the quality of results derived by space-geodetic techniques observing in the radio frequency domain, such as Very Long Baseline Interferometry (VLBI) or Global Navigation Satellite Systems (GNSS), is limited by rapid changes in the neutral part of the atmosphere. In particular, insufficient knowledge of the temporal and spatial refractivity variations restrict the attainable accuracy of the derived VLBI and GNSS target parameters. In the current model describing the additional propagation delay due to the neutral part of the atmosphere, only annual to hourly long periodic variations are taken into account. In contrast, small-scale fluctuations mainly originating from turbulent motions are generally neglected, although they form a serious error source for electromagnetic wave propagation. Dynamic processes in the neutral atmosphere additionally induce physical correlations in space and time, which are also largely ignored so far. Particularly with regard to future requirements, as, for instance, defined within the framework of the Global Geodetic Observing System established by the International Association of Geodesy, the current tropospheric model is not sufficient and needs to be improved. High rate GNSS data of 1 Hz sampling and below, and the VLBI Global Observing System with faster telescopes result in a better sampling of the atmosphere. However, new challenges emerge with respect to improved and proper analysis strategies, in particular to model the stochastic properties of atmospheric refraction, which represents a crucial issue in research and the main objective of this thesis. Quantifying and assessing the small-scale behavior of atmospheric refraction is extremely challenging, since small-scale characteristics of atmospheric refraction cannot be analyzed without sufficient knowledge of the stability of the VLBI observing system. An optimal experimental setup for both, investigations in atmospheric refraction and system stability issues, emerges from the commissioning phase of the twin radio telescope at the Wettzell Geodetic Observatory in Germany. Specially designed so-called WHISP sessions are scheduled, observed and analyzed within this thesis allowing to quantify the individual components of the observing system, in part for the first time. On this basis, refractivity fluctuations are quantified which are found to be in the range of 1-3 millimeters. A number of noteworthy conclusions has been drawn which would not have been possible without the novel observing approach. Special emphasis is also given to the development of an atmospheric turbulence model, which stochastically describes small-scale refractivity fluctuations due to turbulent motions in the neutral atmosphere. The results have produced an important contribution to the modeling of refraction effects in the neutral atmosphere now considering temporal and spatial correlations between the observations in a physical and meteorological way. By analyzing 2700 VLBI sessions including traditional and local observing networks, it is demonstrated that the incorporation of the newly devised model into the VLBI data analysis leads to an improvement of the solutions compared to the standard strategies of the International VLBI Service for Geodesy and Astrometry, or other strategies refining the stochastic model of VLBI observations. Compared to other approaches addressing the issue of atmospheric turbulence, the model developed within this thesis has the advantage to be operationally efficient for routine mass analysis of VLBI observing sessions. Since the current atmospheric model reveals severe deficiencies with respect to the estimation of atmospheric parameters, new modeling and adjustment strategies are introduced to better describe the behavior of the neutral atmosphere. It is demonstrated that, in particular, the least squares collocation method ensures an improved modeling of the stochastic properties of the neutral atmosphere, which allows a zenith wet delay estimation in more meaningful and appropriate sense. The main achievements of this thesis are the development of an atmospheric turbulence model to improve the stochastic model of VLBI observations and the quantification of local atmospheric refraction variations in space and time. Both allows for new interpretations and model improvements in a stochastic and deterministic sense

    VUV emission and absorption spectroscopy with a multichannel near normal incidence spectrometer

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    An experiment for vacuum UV emission and photoabsorption spectroscopy usmg a normal incidence multi-channel spectrometer is described. Two detection configurations were used in the experiments, one a Channel Electron Multiplier Anay with Photo Diode Array readout ( CEMA / PDA), the other a directly illuminated back thmned Charge Coupled Device ( CCD ). Emission spectra of plasmas of a number of low and high Z target matenals were recorded covering the majority of the vacuum UV spectral region ( 35 to 200 nm ). These experiments were designed mainly to study the nature of the emission ( line versus continuum) and it’s dependence on atomic number. The use of two detection configurations allowed for mter comparisons to be made on resolution, efficiency and dynamic range of the two multi-channel detector and spectrometer systems. Experiments were also performed on photoabsorption by helium gas. The spectra thus obtamed were used to help charactense the system’s application to absorption studies around the He principal series limit at - 50 43 nm. In addition, for the first time the instrument was used to study photoabsorption using the dual laser plasma technique ( DLP ). Results on the relative photo absorption cross sections of barium and barium ions using a samarium continuum back-light are presented which indicate that the instrument is well suited to absorption experiments m the range of 35 to 80 nm where second order of the contmuum is mainly absent and the grating is being used close to it’s blaze wavelength ( 80 nm ). Finally, the work concludes with details on the design, construction and preliminary testmg of a vacuum-optical beamlme which should both improve the aperture matchmg ability of the instrument and allow spatially resolved studies of the laser plasma light source to be made. The spectrometer with the additional spherical mirror was modelled by means of simple geometric optic calculations as well as with ray tracing software m order to estimate improvements in throughput

    GSFC Heliophysics Science Division 2008 Science Highlights

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    This report is intended to record and communicate to our colleagues, stakeholders, and the public at large about heliophysics scientific and flight program achievements and milestones for 2008, for which NASA Goddard Space Flight Center's Heliophysics Science Division (HSD) made important contributions. HSD comprises approximately 261 scientists, technologists, and administrative personnel dedicated to the goal of advancing our knowledge and understanding of the Sun and the wide variety of domains that its variability influences. Our activities include Lead science investigations involving flight hardware, theory, and data analysis and modeling that will answer the strategic questions posed in the Heliophysics Roadmap; Lead the development of new solar and space physics mission concepts and support their implementation as Project Scientists; Provide access to measurements from the Heliophysics Great Observatory through our Science Information Systems, and Communicate science results to the public and inspire the next generation of scientists and explorers

    Modeling and Simulation in Engineering

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    This book provides an open platform to establish and share knowledge developed by scholars, scientists, and engineers from all over the world, about various applications of the modeling and simulation in the design process of products, in various engineering fields. The book consists of 12 chapters arranged in two sections (3D Modeling and Virtual Prototyping), reflecting the multidimensionality of applications related to modeling and simulation. Some of the most recent modeling and simulation techniques, as well as some of the most accurate and sophisticated software in treating complex systems, are applied. All the original contributions in this book are jointed by the basic principle of a successful modeling and simulation process: as complex as necessary, and as simple as possible. The idea is to manipulate the simplifying assumptions in a way that reduces the complexity of the model (in order to make a real-time simulation), but without altering the precision of the results

    Wet Path Delay Corrections from Line-of-Sight Observations of Effelsberg’s Water Vapour Radiometer for Geodetic VLBI Sessions

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    Water vapour induced excess path lengths in electromagnetic waves have been one of the most unmanageable errors in space geodesy, such as GPS and VLBI. The difficulty mainly comes from the highly variable distribution of atmospheric water vapour both in time and space. In general, these wet path delays cannot be estimated accurately by atmospheric models that are conventionally used in space geodetic applications. In the last few decades, water vapour radiometry has shown great potential for measuring atmospheric water vapour content. However, the wet path delay retrieval processes are strongly dependent on radiosonde data, although periodic radiosonde observations are rarely available in the vicinity of water vapour radiometers (WVRs). Radiosonde observations are weather profiles from balloon starts which are transmitted by radio signals. On the other hand, the possibility of using a numerical weather model (NWM) instead of a radiosonde has been on the increase in recent years. NWM can provide meteorological profiles for those places where radiosonde data is not available. The focus of this thesis is mainly on the improvement of the wet path delay corrections in geodetic VLBI sessions using the WVR observations at the 100m Effelsberg radio telescope. Compared to other WVRs, the Effelsberg one has a great advantage in terms of observation. It always points at the same direction as the VLBI antenna because it has been installed on the prime focus cabin of the telescope. However the Effelsberg station does not make periodic radiosonde observations. To overcome this weakness, the numerical weather model of the European Centre of Medium Range Weather Forecasts (ECMWF) was introduced. It provides meteorological profiles over Effelsberg such as atmospheric pressures, temperatures, and water vapour pressures. Those profiles were processed by a radiative transfer model, which calculates theoretical measurements of brightness temperature and converts them into wet path delays. These two models were combined to be compared with WVRobserved wet path delays. For a better comparison between wet path delays from the WVR and the models, zenith wet delays (ZWDs) were used. As the results of the comparison illustrate, ZWDs from the models showed higher values than the WVR-measured ones by roughly 30 mm. For comparison with GPS-derived values, average offsets and standard deviations of the models and the WVR were -4.3±11.0 mm and -44.8±24.0 mm, respectively. From these ZWD comparisons it was found that further corrections to the WVR ZWDs are necessary. In addition, the noisy behaviour of the raw WVR ZWD measurements should be smoothed by a running mean method before application. In addition, averaged offsets between the models and the WVR measurements should be determined for the correction of individual sessions. However, already at this step it became obvious that the instrumental calibrations of the radiometer are far from being mature resulting in erroneous absorption profiles. ZWDs from the WVR measurements with different levels of corrections were applied as corrections to the wet components of the atmospheric refraction in the five geodetic VLBI sessions. Impacts on baseline repeatability and height precision by these were investigated. As the results show, the baseline repeatability was improved in terms of Root Mean Squared Error (RMS) when the offset correction was applied. However, the improvement was less than one percent. Although the repeatability of the height component was improved in terms of Weighted RMS (WRMS) with respect to the short term mean height by a factor of 2, the height component itself showed a larger deviation from the original value than that expected from the ZWD corrections. A possible reason is that the estimation of the many parameters in the least squares adjustment can easily affected the height parameter. The conclusion of this study is that the Effelsberg WVR observations are not perfectly suited for wet path delay corrections yet. This is mainly due to the imperfectness of instrumental calibration. Further studies based on an increased number of WVR data with better internal calibrations seems to be necessary to make a final judgment regarding the usefulness of the WVR for wet path delay corrections in geodetic VLBI.Zur Korrektur von feuchtebedingten Laufzeitverzögerungen mit dem co-linearen Wasserdampfradiometer in Effelsberg fĂŒr geodĂ€tische VLBI-Messungen Wasserdampfinduzierte Refraktionseffekte der elektromagnetischen Wellen stellen die zurzeit grĂ¶ĂŸte Fehlerquelle bei Messverfahren der SatellitengeodĂ€sie, wie z.B. GPS und VLBI, dar. Die Problematik rĂŒhrt hauptsĂ€chlich her von der stark variierenden Verteilung von atmosphĂ€rischem Wasserdampf sowohl in der Zeit als auch im Raum. Im Allgemeinen können diese Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re nicht exakt genug durch atmosphĂ€rische Modelle berechnet werden, die herkömmlich in SatellitengeodĂ€sieanwendungen genutzt werden. In den vergangenen Jahrzehnten hat die Wasserdampfradiometrie ein großes Potential entwickelt, um den atmosphĂ€rischen Wasserdampfbestandteil zu messen. Allerdings ist der Prozess der Umrechnung von gemessenen Helligkeitstemperaturen in Laufzeitverzögerungen stark von gleichzeitig durchgefĂŒhrten Radiosondenmessungen abhĂ€ngig. Dabei werden die Messergebnisse von an aufsteigenden Ballons befestigten Wettersensoren fĂŒr verschiedene Druckstufen per Radiosignal ausgesendet. Leider werden periodische Radiosondenbeobachtungen aber nur selten in der NĂ€he des Wasserdampfradiometers (WVR) durchgefĂŒhrt. Dem gegenĂŒber besteht seit einigen Jahren die Möglichkeit, ein numerisches Wettermodell anstelle der Radiosondenergebnisse zu nutzen. Ein numerisches Wettermodell kann meteorologische Profile fĂŒr solche Orte liefern, wo eine Radiosonde nicht verfĂŒgbar ist. Der Schwerpunkt dieser Dissertation liegt hauptsĂ€chlich auf der verbesserten Bestimmung der Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re in der geodĂ€tischen VLBI, wobei die Wasserdampfradiometerbeobachtungen am Radioteleskop in Effelsberg genutzt werden. Verglichen mit anderen Wasserdampfradiometern hat dieses Instrument große Vorteile hinsichtlich der Messwertgewinnung. Es zeigt immer in dieselbe Richtung wie die VLBI-Antenne, weil es im PrimĂ€rfokus des Teleskopes installiert ist. In oder in der NĂ€he von Effelsberg werden jedoch keine Radiosondenbeobachtungen durchgefĂŒhrt. Um diese SchwĂ€che zu beheben, wurde ein numerisches Wettermodell des European Centre for Medium Range Weather Forecasts (ECMWF) fĂŒr die Bestimmung von Kalibrierwerten herangezogen. Es liefert fĂŒr das Radioteleskop in Effelsberg meteorologische Daten wie z.B. Druck, Temperatur und Wasserdampfdruck. Solche Profile wurden in einem StrahlungsĂŒbertragungsmodell verarbeitet, welches theoretische Messungen der Helligkeitstemperatur ermittelt und diese in Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re umwandelt. Um die Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re aus Wasserdampfradiometermessungen und die Modelle besser vergleichen zu können, wurden alle Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re auf die Zenitrichtung (Zenith Wet Delays, ZWD) bezogen. Der Vergleich hatte zum Ergebnis, dass die ZWDs der Modelle einen um ca. 30 mm höheren Wert zeigten als jene, die mit einem Wasserdampfradiometer gemessen wurden. Im Vergleich zu GPS-abgeleiteten ZWDs betrugen die durchschnittlichen Offsets der Modelle und des Wasserdampfradiometers -4.3±11.0 mm beziehungsweise -44.8±24.0 mm. Diese ZWDVergleiche haben gezeigt, dass eine Korrektur der WVR ZWDs erforderlich ist. Außerdem hatte es den Anschein, dass die rohen WVR-ZWD-Messungen geglĂ€ttet werden sollten, um das Rauschen des Instruments zu reduzieren. FĂŒr die Fehlerkorrektur wurden außerdem in jeder einzelnen Session durchschnittliche Offsets zwischen den Modellen und den Wasserdampfradiometern berechnet und angesetzt. Allerdings zeigte sich schon hier, dass die interne Kalibrierung des Instruments einige Defizite aufwies und die Ergebnisse dadurch in ihrer Genauigkeit eingeschrĂ€nkt waren. Die Korrekturen an den Laufzeitverzögerungen in Zenitrichtung aus verschiedenen AnsĂ€tzen wurden in fĂŒnf geodĂ€tischen VLBI-Sessionen verwendet und die Auswirkungen auf die Basislinienwiederholbarkeit und Höhengenauigkeit untersucht. Es stellte sich heraus, dass die Basislinienwiederholbarkeit bei manchen Basislinien verbessert werden konnte, wenn Offsets an den gemessenen WVR-Ergebnissen angebracht wurden. Die Verbesserung war jedoch kleiner als 1 Prozent. Obwohl die Höhengenauigkeit, ausgedrĂŒckt als Root Mean Squared Error (RMS) und Weighted RMS (WRMS), um den Faktor 2 verbessert werden konnte, zeigte die Höhenkomponente selbst eine grĂ¶ĂŸere Ablage von den Ursprungswerten als erwartet. Als Ursache dafĂŒr wurde die Vielzahl der zu schĂ€tzenden Parameter und ihre zum Teil hohen Korrelationen identifiziert. Die Schlussfolgerung dieser Untersuchung ist somit, dass die Waserdampfradiometerbeobachtungen in Effelsberg noch nicht gĂ€nzlich fĂŒr die Fehlerbehebung der Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re geeignet sind, was hauptsĂ€chlich auf die Unvollkommenheit einer instrumentellen Kalibrierung zurĂŒckzufĂŒhren ist. Es werden weitere Studien mit einer grĂ¶ĂŸeren Zahl von WVR- Messwerten mit einer verbesserten Kalibrierung des WVR notwendig sein, um die ZweckmĂ€ĂŸigkeit des Wasserdampfradiometers fĂŒr die Fehlerbehebung der Laufzeitverzögerungen durch den feuchten Anteil der AtmosphĂ€re in der geodĂ€tischen VLBI abschließend nachweisen zu können

    Remote Sensing

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    This dual conception of remote sensing brought us to the idea of preparing two different books; in addition to the first book which displays recent advances in remote sensing applications, this book is devoted to new techniques for data processing, sensors and platforms. We do not intend this book to cover all aspects of remote sensing techniques and platforms, since it would be an impossible task for a single volume. Instead, we have collected a number of high-quality, original and representative contributions in those areas

    Solar System Remote Sensing : September 20-21, 2002, Pittsburgh, Pennsylvania

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    This international meeting presents the current state of research over a wide range of topics including:; Photometric theory; Spectroscopic modeling; Laboratory exploration of scattering phenomena; Space weathering processes throughout the inner solar system; Photometric and spectroscopic studies of the Moon, Mars, Mercury, and asteroids; Photometric and spectroscopic studies of cold, icy places such as comets and outer planet satellites.This international meeting presents the current state of research over a wide range of topics including:; Photometric theory; Spectroscopic modeling; Laboratory exploration of scattering phenomena; Space weathering processes throughout the inner solar system; Photometric and spectroscopic studies of the Moon, Mars, Mercury, and asteroids; Photometric and spectroscopic studies of cold, icy places such as comets and outer planet satellites.sponsors, University of Pittsburgh ... [and others]conveners, William Cassidy, Deborah Domingue, Robert M. Nelson ; scientific organizing committee William Cassidy ... [and others].PARTIAL CONTENTS: Interpreting Photometry of Planetary Regoliths: Progress and Problems as Seen from Kharkov / Yu.G. Shkuratov--Toward an Improved Single-Particle Model for Large, Irregular Grains / W.M. Grundy, B. Schmitt, S. Doute--A New Method for Estimating the Single Scattering Phase Functions of Regolith Grains / P. Helfenstein--The Opposition Effect: A Very Unusual Case / R.M. Nelson--Coherent Backscattering by Random Particulate Media in the Solar System / K. Muinonen--The Diverse Surface Compositions of the Galilean Satellites / R.W. Carlso
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