Two Earth-orbiting satellites move on circular geodesics of radius km (altitude km)…

PHYSICS · Multi-part · Fermi University Physics · Relativity & Gravitation · Differential geometry of curved spacetime · Einstein's field equations

The Geometry of Gravity, Ch Curvature: the Riemann tensor, geodesic deviation and the Einstein tensor

Problem

Two Earth-orbiting satellites move on circular geodesics of radius r=7178r = 7178 km (altitude 800800 km) whose orbital planes are tilted with respect to one another by Δι=0.02∘\Delta\iota = 0.02^\circ. In the Newtonian limit the entry of Ri0j0R^i{}_{0j0} normal to the orbital plane is GM⊕/(r3c2)GM_\oplus/(r^3c^2), so the out-of-plane separation SS between the satellites obeys S¨=−GM⊕r3S,\ddot S = -\frac{GM_\oplus}{r^3}S, with initial condition S=0S=0 at a node (where the planes cross) and growing towards a maximum a quarter-period later. Take GM⊕=3.986×1014 m3 s−2GM_\oplus = 3.986\times10^{14}\ {\rm m^3\,s^{-2}} (equivalently GM⊕/c2=4.44GM_\oplus/c^2 = 4.44 mm). ((a)) Find the orbital period TorbT_{\rm orb}. ((b)) Find the tidal rate GM⊕/r3GM_\oplus/r^3 and confirm it equals the square of the orbital angular frequency. ((c)) Find the amplitude of the out-of-plane separation and the time after the node at which it is reached.

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