view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Diurnal Atmospheric Bulge and Its Effect on Satellite Motions. Wyatt, Stanley P. Abstract Several authors have derived expressions for the secular acceleration of a satellite moving through the high atmosphere and giving away momentum to the air. The simplest assumptions one can make are that the atmosphere is spherically symmetric, stationary, and of constant scale height. The resulting drag formula then permits one to use the observed accelerations to deduce the product of air density times the square root of scale height at the perigee level of the satellite. Analyses by a number of authors have revealed primary facts concerning the structure of the outer atmosphere. First, the scale height of the atmosphere increases with height above ground throughout all strata traveled by satellites. Second, on the daytime hemisphere the atmospheric density correlates strikingly with solar activity. Third, at heights of 500 km and more the atmosphere bulges conspicuously toward the sun. In October of 1958, when Vanguard I was passing through perigee at local time 13 or 14 hr the air density at 650 km was some 10 times greater than from mid-1959 to mid-1960 when its perigee passage occurred during the nighttime hours. At any geographic position this variation amounts to a diurnal rise and fall of the high atmosphere, with maximum expansion occurring an hour or two after noon. Jacchia has used the accelerations of four satellites to construct a model of the atmosphere in the 200-600 km range, incorporating all three of these effects (Jacchia, L. G., Smithsonian Astrophys. Obs. Spec. Rept. No. 39,1960). Because the atmosphere has neither spherical symmetry nor an exponential decrease of density, the present work is addressed to the derivation of a new and more complex drag formula relating perigee density and scale height to the observed acceleration of a satellite moving through a Jacchia-type atmosphere. The essential results are twofold. First, use of the earlier and simpler drag equation may yield atmospheric densities that are systematically incorrect by as much as 50 or 60%, the sign and amount of the error depending on the orbital elements and the orientation of the orbit relative to the bulge on any given date. Second, and provisionally, the new formula indicates that the diurnal bulge is even sharper than previously thought. This work was partly done at the Smithsonian Astrophysical Observatory. Publication: The Astronomical Journal Pub Date: September 1961 DOI: 10.1086/108429 Bibcode: 1961AJ.....66..299W full text sources ADS |