swiftest.shgrav.clm_from_ellipsoid

swiftest.shgrav.clm_from_ellipsoid(mass, density, a, b=None, c=None, lmax=6, lref_radius=False, ref_radius=None)

Creates and returns the gravity coefficients for an ellipsoid with principal axes a, b, c upto a certain maximum degree lmax. Uses pyshtools. No units necessary for a, b, & c. However, they need to be in the same units (DU).

Parameters:

• mass (float) – mass of the central body

• density (float) – density of the central body

• a (float) – length of the pricipal axis aligned with the x axis

• b (float, optional, default = a) – length of the pricipal axis aligned with the y axis

• c (float, optional, default = b) – length of the pricipal axis aligned with the z axis

• lmax (int, optional, default = 6) – The maximum spherical harmonic degree resolvable by the grid.

• lref_radius (boolean, optional, default = False) – Boolean value to return the reference radius calculated by SHTOOLS

• ref_radius (float, optional, default = None) – Reference radius to scale the gravitational coefficients to

Returns:

clm (ndarry, shape (2, lmax+1, lmax+1)) – numpy ndarray of the gravitational potential spherical harmonic coefficients. This is a three-dimensional array formatted as coeffs[i, degree, order], where i=0 corresponds to positive orders and i=1 to negative orders.