The gravitational field of the earth

Perturbations in Perigee Height of Vanguard I

“…The applications of the results of this theory to the Vanguard I satellite indicate that solar radiation pressure will produce a variation in the perigee height of this satellite with a period of ~850 days and an amplitude of 1 or 2 km. This effect accounts almost completely for the observed variations in perigee height when combined with the previously determined solar and lunar gravitational perturbations (3) and the effect of the third harmonic (4).…”

Perturbations of a Hyperbolic Orbit by an Oblate Planet

“…Member ARS. 3 Numbers in parentheses indicate References at end of paper. 4 Since 1960, when this report was originally prepared, there have been two additional papers published concerning the perturbing effects of an oblate planet upon a vehicle on a hyperbolic trajectory (7,8).…”

Recent Advances in Astrodynamics 1960

“…Furthermore, O'Keefe notes that the basic theory of Musen and Herget does not make use of osculating elements and that the misleading short-period terms (periods less than the orbital period) have been eliminated just as Brenner advocates. O'Keefe's argument seems to have been amply confirmed by the work of Cohen and Anderle (42) who verified the third harmonic by a reduction of Transit IB data by a method entirely different from that originally used by O'Keefe, Eckels and Squires (199). O'Keefe in another article (198) discusses the hypothesis about Earth's gravitational field made by Heiskanen and Vening Meinesz in light of recent satellite findings.…”