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Author: Jules Aarons
Publisher:
ISBN:
Category : Artificial satellites in telecommunication
Languages : en
Pages : 40
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Book Description
Author: Jules Aarons
Publisher:
ISBN:
Category : Artificial satellites in telecommunication
Languages : en
Pages : 40
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Book Description
Author: Sunanda Basu
Publisher:
ISBN:
Category : F region
Languages : en
Pages : 32
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Book Description
In situ measurements of F-region irregularity amplitude and ambient electron density made by the retarding potential analyzer (RPA) on OGO-6 near perigee altitude of 400 km have been utilized to derive the variation of electron density deviation over the equatorial region. Based on these measured electron density deviations and other assumed model parameters, including a three-dimensional power-law form of irregularity spectrum of index 4, a model of equatorial scintillations is developed in the framework of diffraction theory. The percentage occurrence contours of estimated equatorial scintillations greater than or equal to 4.5 dB at 140 MHz during 1900 to 2300 LMT for the period November to December 1969 and 1970 have been derived. The model is found to depict a pronounced longitude variation with the scintillation belt width and percentage occurrence being maximum over the African sector. The latitude extent of the spatial scintillation belt narrows over the American sector without much decrease in the scintillation occurrence whereas over the Indian and Far Eastern sectors both the extent and the occurrence are found to decrease. The percentage occurrence of scintillations estimated from this model is found to be consistent with VHF scintillation measurements at Ghana, Huancayo, and Calcutta. In addition, the model was found to be in qualitative agreement with GHz observations at various longitudes made by the COMSAT group. The effect of varying model parameters on scintillation estimates at VHF, UHF and GHz are discussed. Implications of the observed longitudinal variation of scintillations on current theories of equatorial irregularity formation are indicated. (Author).
Author: Jules Aarons
Publisher:
ISBN:
Category : Geostationary satellites
Languages : en
Pages : 48
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Book Description
Amplitude fluctuations produced by small irregularities in electron density in the F-layer of the ionosphere (at 300 to 400 km height) can be a problem to communication and navigation systems in the VHF-UHF range. Recent measurements, primarily by AFCRL, are shown with emphasis on results at high and equatorial latitudes. At high latitudes an irregularity region exists whose lower boundary reaches 57 degrees invariant latitude near midnight. During magnetic storms the boundary descends to lower latitudes and the fading becomes deeper. Over the polar cap scintillations are somewhat diminished. When observing synchronous satellites through the irregularity region, deep and fast fading is frequently seen, with fade rates to one per second. Irregularities produce deep scintillations in the VHF range plus or minus 15 degrees from the geomagnetic equator. In equatorial regions maximum occurrence of high level scintillations takes place between 2100 and 2400 local time during the equinoxes; a minimum occurrence is observed during the solstices. When the sunspot number decreases, the equatorial irregularity region spreads and becomes larger. The data for various latitudes has been placed in statistical form, that is, distribution of amplitudes for 15-min samples as well as for periods of 1 yr and longer. (Author).
Author: Richard Frank Donnelly
Publisher:
ISBN:
Category : Cosmic physics
Languages : en
Pages : 736
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Author: Richard Frank Donnelly
Publisher:
ISBN:
Category : Geophysics
Languages : en
Pages : 744
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Book Description
Author: H. E. Whitney
Publisher:
ISBN:
Category : Backscattering
Languages : en
Pages : 146
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Book Description
A large scale test program was developed jointly by AFGL and AFAL to evaluate the effects of equatorial ionospheric irregularities on UHF (250 MHz) satellite communications to map the temporal and spatial extent of the equatorial scintillation region, and to determine the geophysical mechanisms leading to the formation of irregularities in the equatorial ionosphere and thus to scintillations. Of specific interest were scintillation characteristics and effects observed by airborne terminals and their relation to simultaneously obtained results from ground based terminals. The test results are based on radio propagation and geophysical measurements conducted from ground and airborne stations and show the general scintillation patterns, latitudinal dependence, heading dependence and signal statistics. Backscatter measurements from the Jicamarca radar and optical observations from the all sky imaging photometer show the development and motion of the irregularity structure. Scintillation plots for several satellites received at the ground stations and on the aircraft are included. (Author).
Author: Dogan Ugur Sanli
Publisher: BoD – Books on Demand
ISBN: 178984925X
Category : Technology & Engineering
Languages : en
Pages : 152
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Book Description
Following the GPS, new GNSS techniques are emerging today. Various surveying and processing methods are available for the analysis of GNSS data. Equipment and software are also varied. The orbit quality, controlled by the system designer, and the IGS are continuously improved. The user is mainly interested in the quality of position and of the deformation rates produced by the GNSS. Hence, research needs to guide the user in terms of selecting the best combination of the available methods and instrumentation to produce the desired accuracy. This book reviews the current available accuracy obtainable using the GNSS methods. In fact, the main aim of this book is to make an impact on young researchers so that they keep updating the accuracy of GNSS for future generations.
Author:
Publisher:
ISBN:
Category : Geophysics
Languages : en
Pages : 32
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Book Description
Author:
Publisher:
ISBN:
Category : Astronautics
Languages : en
Pages : 522
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Author: John Edmond Jackson
Publisher:
ISBN:
Category : Geophysical observatories
Languages : en
Pages : 150
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Book Description
