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Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Atmospheric density modeling has long been one of the greatest uncertainties in the dynamics of low Earth satellite orbits. Accurate density calculations are required to provide meaningful estimates of the atmospheric drag perturbing satellite motion. These effects increase with lower altitude orbits and also with higher effective area and lower mass satellites. Both of these conditions are usually met by the new class of small satellites being developed around the world as low-cost ventures into space. Early atmospheric models consisted of simple exponential functions with scale height factors that allowed the user to estimate a constant density at a given altitude. From these approaches and estimated density conditions, standard atmospheres were developed that were meant to represent the average conditions at any given point in time for a particular altitude. However, it was soon obvious that the atmosphere was far too dynamic to be adequately represented by static approaches. The 1990s brought a new approach to improving atmospheric density modeling. Dynamic Calibration of the Atmosphere (DCA) involves estimating density corrections to a given atmospheric density model based upon the observed motion of satellites. The goal of atmospheric density dynamics research is to understand and characterize the dynamic nature of the extreme upper atmosphere and develop improved orbital prediction algorithms based upon this new understanding. Many indicators suggest that the extreme upper atmosphere is far more dynamic than what is accounted for in atmospheric density models used in orbit propagation. This paper explores the impact these dynamics have on the motion of satellites. Simulations show that unmodeled atmospheric density dynamics can greatly impact the orbit determination process and add kilometers of error to orbit predictions. (10 figures, 8 refs.).
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Atmospheric density modeling has long been one of the greatest uncertainties in the dynamics of low Earth satellite orbits. Accurate density calculations are required to provide meaningful estimates of the atmospheric drag perturbing satellite motion. These effects increase with lower altitude orbits and also with higher effective area and lower mass satellites. Both of these conditions are usually met by the new class of small satellites being developed around the world as low-cost ventures into space. Early atmospheric models consisted of simple exponential functions with scale height factors that allowed the user to estimate a constant density at a given altitude. From these approaches and estimated density conditions, standard atmospheres were developed that were meant to represent the average conditions at any given point in time for a particular altitude. However, it was soon obvious that the atmosphere was far too dynamic to be adequately represented by static approaches. The 1990s brought a new approach to improving atmospheric density modeling. Dynamic Calibration of the Atmosphere (DCA) involves estimating density corrections to a given atmospheric density model based upon the observed motion of satellites. The goal of atmospheric density dynamics research is to understand and characterize the dynamic nature of the extreme upper atmosphere and develop improved orbital prediction algorithms based upon this new understanding. Many indicators suggest that the extreme upper atmosphere is far more dynamic than what is accounted for in atmospheric density models used in orbit propagation. This paper explores the impact these dynamics have on the motion of satellites. Simulations show that unmodeled atmospheric density dynamics can greatly impact the orbit determination process and add kilometers of error to orbit predictions. (10 figures, 8 refs.).
Author: Eelco Doornbos Publisher: Springer Science & Business Media ISBN: 3642251293 Category : Science Languages : en Pages : 192
Book Description
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.
Author: R. W. Bruce Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Various model atmospheres are examined with regard to their effect upon the prediction of (1) satellite lifetime and (2) satellite orbit ephemerides. High speed computer results based upon the empirical dynamic model atmospheres of Paetzold and Jacchia are compared to corresponding results based on the ARDC 1959 static model atmosphere that has been in wide use in the United States. For the sake of completeness the atmospheric density profiles and dynamic models of Nicolet, King-Hele, Harris, and Priester are described together with static models such as CIRA 1961 and the U.S. Standard Atmosphere, . 1962. It is shown for near-earth altitude regions that predicted values of satellite lifetime may differ by a factor of 30 depending upon whether use is made of a static or a dynamic model atmosphere. This is primarily due to the fact that the large long-term influence of the 11-year solar cycle can introduce appreciable differences between static models, which are patterned after a given time period, and dynamic models, which vary with time. In the case of satellite ephemeris prediction, short-term effects such as those due to geomagnetic disturbances which are not accountable with static models become important as well. It is shown that the predicted in-track position of a typical satellite may be in error by approximately 10 kilometers (5 nautical miles) after a 12-hour time period if an intense but unpredictable magnetic storm occurs in that interval. (Author).
Author: G.E.O. Giacaglia Publisher: Springer Science & Business Media ISBN: 3642463193 Category : Technology & Engineering Languages : en Pages : 385
Book Description
This volume includes original papers presented at the 4th Symposium on Satellite Dynamics held at the XII Annual Plenary Meeting of COSPAR. At a time where it might be thought that very few problems were left un solved in celestial mechanics, we discover that new and more challenging questions must be answered. The pre cision of observations reaches the centimeter level and physical phenomena which had been disregarded come into play. We need a better treatment of atmospheric drag, radiation forces, and a better knowledge of the earth's gravitational field. Time has to be precisely defined as well as reference systems, including improved values for precision and nutation. The question of resonances introduced by nonzonal harmonics was to be carefully in vestigated. Numerical integration techniques must be optimized and means of controlling their errors improved. Analytical techniques must be made appropriate for com puter processing. Presently existing methods of solu tions of differential equations of interest to celestial mechanics are getting cumbersome as all these new facts come to light. It is clear that entirely new and more effective methods are necessary. These methods must, among other requirements, take into account the essential nonlinear character of the equations. Finally, the mo tion about the center of mass of a satellite is becoming an essential need for the thorough understanding and de scription of the orbital motion.
Author: James N. Bass Publisher: ISBN: Category : Artificial satellites Languages : en Pages : 68
Book Description
Atmospheric densities are computed from analysis of Doppler beacon satellite data. Modifications to Doppler beacon data processing program CELEST necessary for this study are described. Results obtained for satellites DB-7(6382), DB-8(6727), and DB-9(6928) are found to be in good agreement with those obtained by analysis of skin track data for the same satellites using program CADNIP. (Author).
Author: Leonard L. DeVries Publisher: ISBN: Category : Artificial satellites Languages : en Pages : 140
Book Description
A knowledge of atmospheric density and its variation at satellite altitudes is needed for operational support of several military activities. Atmospheric density data computed from the decay rates of more than 40 satellites orbited during a five-year period were analyzed during this investigation. Multiple regression equations were derived to specify the density at 10-km intervals at altitudes from 180 to 300 km as a function of solar activity, time of day, time of year, and combinations of these variables. Density values depicted by these regression equations were then compared with density data which had not been used during the derivation of the equations. The results of this investigation indicate that multiple regression analysis and the associated screening procedure can produce equations from which computed density values are in close agreement with observed density data. The results lead to a conclusion that no single density model can meet all needs. These results also indicate that characteristics of a density model should be selected to fit the purpose for which the model is intended. Four possible density models designed for different purposes are suggested. (Author).
Author: John Marshall Publisher: ISBN: 9780123749246 Category : Science Languages : en Pages : 344
Book Description
For advanced undergraduate and beginning graduate students in atmospheric, oceanic, and climate science, Atmosphere, Ocean and Climate Dynamics is an introductory textbook on the circulations of the atmosphere and ocean and their interaction, with an emphasis on global scales. It will give students a good grasp of what the atmosphere and oceans look like on the large-scale and why they look that way. The role of the oceans in climate and paleoclimate is also discussed. The combination of observations, theory and accompanying illustrative laboratory experiments sets this text apart by making it accessible to students with no prior training in meteorology or oceanography. * Written at a mathematical level that is appealing for undergraduates and beginning graduate students * Provides a useful educational tool through a combination of observations and laboratory demonstrations which can be viewed over the web * Contains instructions on how to reproduce the simple but informative laboratory experiments * Includes copious problems (with sample answers) to help students learn the material.
Author: Bruno Morando Publisher: Springer Science & Business Media ISBN: 3642999662 Category : Technology & Engineering Languages : en Pages : 319
Book Description
This book gathers the proceedings of a symposium on Dynamics of satellites which took place in Prague in May 1969 during the twelfth COSPAR meeting. This symposium was sponsored by the International Astronomical Union, the International Association of Geodesy, the International Union of Theoretical and Applied Mechanics and COSPAR (Committee on Space Research). The organizing committee was composed of Dr. KOVALEVSKY chair man, Dr. Yu. V. BATRAKOV representing IAU, Dr. A. H. COOK for lAG, Dr. D. KING-HELE for COSPAR, Prof. M. Roy for IUTAM and Dr. ROSENBERG. I wish to take advantage of the opportunity to thank, on behalf of all the participants, the organizing committee members, Prof. BUCHAR, Dr. RAJSK:I and Dr. SEHNAL, for the kindness and efficiency of their welcome. The interpreters who translated with virtuosity during the whole symposium also deserve our gratitude. I am grateful also for the care and skill with which Springer-Verlag has printed this volume.
Author: 
Author: 
Author: Eelco Doornbos
Author: R. W. Bruce
Author: G.E.O. Giacaglia
Author: Robert Clifton Duncan
Author: International Union of Theoretical and Applied Mechanics
Author: James N. Bass
Author: Leonard L. DeVries
Author: John Marshall
Author: Bruno Morando