Retrieving "Equatorial Bulging" from the archives

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1. Orbital Mechanics

   Linked via "equatorial bulging"

   Oblateness Perturbations ($J_2$ Effect)
   Celestial bodies, especially those with rapid rotation like Earth, exhibit equatorial bulging, described mathematically by the gravitational potential expansion coefficients. The dominant non-spherical term is the second zonal harmonic, $J_2$.
   The presence of $J_2$ causes the orbital plane to precess (the nodal regression and the shift in argument of periapsis). The secular rate of precession of the ar…