Welcome to our book review site go-pdf.online!
You may have to Search all our reviewed books and magazines, click the sign up button below to create a free account.
An Investigation of Atmospheric Density Between Altitudes of 180 Km and 300 Km
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).
Variability of Atmospheric Density in the Middle Atmosphere
An analysis of the time and space variability of density in the middle atmosphere has been developed in this report, affording a means to determine density changes that occur over distances out to 200 nmi and time periods of 1 to 72 hr. Spatial variations - The rms differences between densities at locations 50, 100, and 200 nmi apart are provided in Tables 4, 8 and 11 for low- and middle- latitude stations at altitudes from 20 through 60 km. These rms values are estimates of the day-to-day variability around the mean density gradients given in Table 5 for low latitudes and Tables 9 and 12 for middle latitudes. Time variations - The rms variability of density for time periods from 1 to 12 hr ...
Range of Density Variability from Surface to 120 Km Altitude
A re-entry space vehicle development program, such as Project Apollo, requires a knowledge of the variability of atmospheric density from the surface of the earth to re-entry altitude (120 km). This report summarizes the data on density given in the most recent literature on the subject. The range of atmospheric density with respect to the ARDC 1959 Model Atmosphere is determined and shown graphically. From the surface to 30 km altitude abundant information on density is available. From 30 to 90 km altitude the summarized reports of observations made at a limited number of stations have been used. Between 90 and 120 km altitude the density is somewhat speculative, there being but few measurements available. Therefore, the qualitative values for the variability of density above 30 km must be considered tentative. Variations of atmospheric density by latitude and seasons made it necessary to develop a family of curves rather than a single profile. Three curves are presented to show the range of density deviation versus altitudes with respect to the ARDC 1959 Model Atmosphere. Each curve is used for a specific latitude range and season.
Atmospheric Density Variations in the Southern Hemisphere at Low Satellite Altitudes
Accurate density measurements are required to develop predictive atmospheric models. Of particular concern is the altitude region below 250 km. Few measurements are presently available in this region and data are urgently required by the Air Force for accurate ephemeris, trajectory, and reentry predictions. Profiles of neutral atmospheric density obtained at low satellite altitudes in the southern hemisphere during geomagnetically quiet conditions are described in this report.
Atmospheric Density Results Derived from the SPADES Satellite Accelerometer Data
The report describes density results obtained from the ultrasenstive triaxial accelerometer system flown on the Air Force low-altitude density research satellite OV 1-15 (SPADES). A description of the spacecraft operation, the accelerometers, and the data reduction procedure is also given. The accelerometers measured the satellite deceleration induced by aerodynamic drag. Profiles of the neutral atmospheric density were derived directly from the drag data. Measurements were made from an altitude of 250 km down to perigee, nominally 160 km. Density profiles acquired from 14 July 1968 to 28 September 1968 are presented as Appendix A. Comparison of the density results to the appropriate Jacchia 1971 model atmosphere is given in Appendix B. (Author Modified Abstract).
