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Analysis of the Errors Associated with the Determination of Planetary Atmosphere Structure from Measured Accelerations of an Entry Vehicle

出版	National Aeronautics and Space Administration, 1965
URL	http://books.google.com.hk/books?id=B-wQAQAAIAAJ&hl=&source=gbs_api
EBook	FULL_PUBLIC_DOMAIN

註釋An analytic method is developed for estimating the errors in the density and pressure structure of a planetary atmosphere constructed from measurements of accelerations experienced by an entry body. Among the sources of error considered both singly and collectively are the measured accuracy of the accelerometers, the uncertainties in entry speed, entry angle, and aerodynamic coefficients, the frequency of data measurements, and the uncertainty of the attitude of entry bodies having nonzero lift-to-drag ratios. Results of sample calculations are presented to show the accuracy with which the extremes of a range of postulated model atmospheres for Mars can be defined from measurements of accelerations experienced by a spherically shaped entry body. It is found that if the accelerometer method were used only over that portion of the atmosphere traversed at speeds greater than sonic speed, then any of the atmospheres postulated for Mars can be defined reasonably well even when errors from all sources are combined in the most unfavorable manner. Some of the results obtained by the analytic method are compared with those from more precise numerical calculations and the agreement is found to be excellent.