/******************************************************************************* *$ Component_name: * FKEP_NODE *$ Abstract: * Calculates the nodal regression rate as a function of distance from a * planet. *$ Keywords: * KEPLER, ORBITAL_MOTION * FORTRAN, PUBLIC *$ Declarations: * real*8 function FKEP_NODE( a ) * real*8 a *$ Inputs: * a mean orbital radius in km. *$ Outputs: * none *$ Returns: * nodal regression rate in radians/second (generally a negative number). *$ Detailed_description: * This FORTRAN-callable function returns the nodal regression rate of a * body at the given radius. The planetary field must have been defined * previously using subroutine FKEP_SETPLANET(). *$ External_references: * Kep_Node(), fKep_Planet *$ Examples: * none *$ Error_handling: * none *$ Limitations: * Result should be exact for infinitesimal perturbations to a small body * on a circular orbit about an oblate planet. Perturbations from the sun * and any other moons and rings are not included. Nonzero eccentricity * or inclination would introduce relative errors of order e^2 and * sin^2(i). *$ Author_and_institution: * Mark R. Showalter * NASA/Ames Research Center *$ Version_and_date: * 1991 June 18 *$ Change_history: * none *******************************************************************************/ #include "fortran.h" #include "kepler.h" extern KEP_PLANET fKep_Planet; double FORTRAN_NAME(fkep_node) ( a ) double *a; { return Kep_Node( &fKep_Planet, *a ); } /******************************************************************************/