FRB–FORTRAN routines for the exact computation of free rigid body motions

We present two algorithms and their corresponding FORTRAN routines for the exact computation of free rigid body motions. The methods use the same description of the angular momentum part m by Jacobi elliptic functions, and suitably chosen frames for the attitude matrix/quaternion Q/q respectively. The frame transformation requires the computation of elliptic integrals of the third kind. Implementation and usage of the routines are described, and some examples of drivers are included. Accuracy and performance are also tested to provide reliable numerical results.