J2

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Constant / Last modified by eng on 2017/09/11 02:08

The `J_2` constant is the Earth's second dynamic form factor used in computing the `J_2` perturbation of the inverse square formulation of the gravitational effect on the force due to a perfect spherical body of uniform density.

The MATH AND SCIENCE

This factor can be calculated as:

`J_2 = (2 epsilon_E/3) -  (R_E^3 omega_E^2) / (3 G M_E)`

where

  • `epsilon_E` is the central body's oblateness (in this case Earth's oblateness)
  • `R_E` is the central body's equatorial radius (in this case the Earth's mean equatorial radius)
  • `omega_E` is the central body's rotational rate (in this case Earth's rotation rate is `7.292115 X 10^-5` rad/sec
  • `G` is the universal gravitational constant
  • `M_E` is the mass of the central body (in this case the Earth's mass)

REFERENCE

Equation section of Nodal Precession article

SEE ALSO