| Ionospheric Corrections to Precise Time Transfer Using GPS, |
02 DEC 1993 |
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| Authors:
Robert W. Snow; Allen W. Osborne III; John A. Klobuchar; HAHNEMANN UNIV SCHOOL OF MEDICINE PHILADELPHIA PA
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 | The free electrons in the earth's ionosphere can retard the time of reception of GPS signals received at a ground station, compared to their time in free space, by many tens of nanoseconds, thus limiting the accuracy of time transfer by GPS. The amount of the ionospheric time delay is proportional to the total number of electrons encountered by the wave on its path from each GPS satellite to a ... |
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| Computerized Ionospheric Tomography, |
03 MAY 1990 |
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| Authors:
Jeffrey R. Austen; Timothy D. Raymund; John A. Klobuchar; J. Stalker; C. H. Liu; TENNESSEE TECHNOLOGICAL UNIV COOKEVILLE DEPT OF ELECTRICAL ENGINEERING
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| In this paper the background of computerized tomography (CT) and its application to the ionosphere is reviewed. CT techniques, using only total electron content (TEC) data, can be used to reconstruct a two-dimensional image of the electron density in the ionosphere. The limitations of this technique are discussed and examples showing the limitations and capabilities are presented. Simulation results for two applications are presented: imaging the high latitude trough, and ... |
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| Evaluation of Six Ionospheric Models as Predictors of TEC, |
03 MAY 1990 |
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| Authors:
Lincoln D. Brown; Robert E. Daniell Jr.; Matthew W. Fox; John A. Klobuchar; Patricia H. Doherty; BOSTON UNIV MA CENTER FOR SPACE PHYSICS
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| We have gathered TEC data from a wide range of latitudes and longitudes for a complete range of solar activity. This data was used to evaluate the performance of six ionospheric models as predictors of Total Electron Content (TEC). The TEC parameter is important in correcting modern DoD space systems, which propagate radio from the earth to satellites, for the time delay effects of the ionosphere. The TEC data were ... |
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| Ionospheric Time-Delay Algorithm for Single-Frequency GPS Users |
MAY 1987 |
9 pages |
| Authors:
John A. Klobuchar; AIR FORCE SYSTEMS COMMAND HANSCOM AFB MA GEOPHYSICS LAB
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 | The goal in designing an ionospheric time-delay correction algorithm for the single-frequency global positioning system user was to include the main features of the complex behavior of the ionosphere, yet require a minimum of coefficients and user computational time, while still yielding an rms correction of at least 50 percent. The algorithm designed for this purpose, and implemented in the GPS satellites, requires only eight coefficients sent as part of ... |
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| Correlation Distance of Mean Daytime Electron Content |
22 AUG 1977 |
24 pages |
| Authors:
John A. Klobuchar; J. M. Johanson; AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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| In the total electron content (TEC) monitoring station network, an important parameter is the required number of stations for a given percentage improvement over the use of monthly median predicted values. Using data from nine TEC stations, taken a pair at a time, values are computed for the correlation coefficient for the 10 to 16 hour local time period when the diurnal values of TEC are generally highest. Little consistent ... |
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| A First-Order, Worldwide, Ionospheric, Time-Delay Algorithm |
SEP 1975 |
26 pages |
| Authors:
John A. Klobuchar; AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
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| A first-order model algorithm designed to reduce ionospheric time- delay errors by approximately 50% rms on a world-wide basis for single frequency users of the Global Positioning System/NAVSTAR is described. The algorithm was designed for greatest accuracy during times of day when ionospheric time-delay errors are expected to be largest. The algorithm is available in several options from one which requires only a monthly mean solar-flux value to one which ... |
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