Function lupnt::spice::GetPlanetOrientation

Function Documentation

Vec3d lupnt::spice::GetPlanetOrientation(BodyId id, Real t_tdb)

Get a planet’s orientation as the (alpha0, delta0, W) IAU rotation-pole right ascension/declination and prime-meridian angle [rad], derived from SPICE’s "IAU_<body>" -> "J2000" rotation at t_tdb.

Provides a SPICE-based cross-check / alternative source for the (alpha0, delta0, W) IAU body-orientation angles used elsewhere to build body-fixed <-> inertial rotation matrices for non-Earth/Moon bodies.

Parameters:

  • id – Body whose orientation is requested (resolved to "IAU_<bodyname>" via bodc2n_c)

  • t_tdb – Epoch [s, TDB seconds since J2000]

Returns:

(alpha0, delta0, W) [rad]: right ascension and declination of the body’s rotation pole in J2000, and the prime-meridian rotation angle