Showing papers on "Total electron content published in 1973"

Total Electron Content Studies of the Ionosphere

Abstract: : Radio waves that pass through the earth's ionosphere travel more slowly than their free space velocity due to the group path delay of the ionosphere. This group path delay, directly proportional to the total electron content of the ionosphere, can be an important source of error to VHF, UHF and L-band satellite detection radars and satellite navigation systems. In this report, the current state of knowledge of ionospheric total electron content is outlined, with special emphasis placed on the North Atlantic region of the world due to NATO special requirements of this region. A numerical model of total electron content, valid over the European continent under certain conditions, is presented for systems engineering use for an average background total electron content correction. Typical values of total electron content are also given at various locations in the high, middle, and equatorial latitudes. If the results presented here seem incomplete, it is only because the state of knowledge of the total electron content parameter is still incomplete. With more observational data being taken at many locations, an over-all satisfactory picture of the world-wide behavior of this important parameter is beginning to emerge.

Total electron content studies of the ionosphere. Air Force survey in geophysics

Abstract: Radio waves that pass through the ionosphere travel more slowly than their free space velocity due to the group path delay of the ionosphere. This group path delay, directly proportional to the total electron content of the ionosphere, can be an important source of error to vhf, uhf, and L-band satellite detection radars and satellite navigation systems. In this report, the current state of knowledge of ionospheric total electron content is outlined, with special emphasis placed on the North Atlantic region of the world due to NATO special requirements of this region. A numerical model of total electron content, valid over the European continent under certain conditions, is presented for systems engineering use for an average background total electron content correction. Typical values of total electron content are also given at various locations in the high, middle, and equatorial latitudes. If the results presented seem incomplete, it is only because the state of knowledge of the total electron content parameter is still incomplete. With more observational data being taken at many locations, an overall satisfactory picture of the world-wide behavior of this important paramcter is beginning to emerge. (auth)

Numerical Models of Total Electron Content over Europe and the Mediterranean and Multi-station Scintillation Comparisons.

Abstract: : The addendum to AGARDograph 166 on Total Electron Content and Scintillation Studies of the Ionosphere is concerned with two subjects: (1) A Numerical Model of Total Electron Content which has been validated for Europe and the Mediterranean for specific periods of time, and (2) Multi-station observations of scintillations over relatively short time spans - in one study five months and in the other seven days.

Plasma column changes at small solar elongations

Abstract: The differenced range versus integrated Doppler (DRVID) technique was used to study charged particle changes in the ray path between earth and Mariner 9. For plasma activity near the sun, DRVID data were obtained from August 10 to October 24, 1972, surrounding the Mariner 9 superior conjunction on September 7. If the records are viewed in terms of range change or range change rate, the day-to-day fluctuations in these quantities mask the changes expected due to the varying solar elongation. Thus, while the steady-state total electron content varies by a factor of 4, the columnar content changes show no systematic variations.

Ionospheric effects on one-way timing signals

Abstract: A proposed navigation concept requires that a user measure the time-delay that satellite-emitted signals experience in traversing the distance between satellite and user. Simultaneous measurement of the propagation time from four different satellites permits the user to determine his position and clock bias if satellite ephemerides and signal propagation velocity are known. A pulse propagating through the ionosphere is slowed down somewhat, giving an apparent range that is larger than the equivalent free space range. The difference between the apparent range and the true range, or the free space velocity and the true velocity, is the quantity of interest. This quantity is directly proportional to the total electron content along the path of the propagating signal. Thus, if the total electron content is known, or is measured, a perfect correction to ranging could be performed. Faraday polarization measurements are continuously being taken at Fort Monmouth, N. J., using beacon emissions of the ATS-3 (137.35 MHz) satellite. Day-to-day variability of the diurnal variation of total electron content values is present with differences of up to 50% or more not being uncommon. In addition, superposed on the overall diurnal variation are smaller scale variations of approximately 5 to 10% of the total content which are attributed to ionospheric density irregularities.

Corrections of Satellite Positions in Near-Real Time

Abstract: The influence of sudden increases of electron content on the accurate determination of the position of a satellite is investigated based on a spherically stratified ionospheric model. Using the total electron content information from Faraday rotation measurements, a procedure is presented whereby the corrections of satellite position due to the unpredicted electron increase can be accounted for without the need to know the spatial distribution of the additional electrons.