/*
 * sidereal_time.h -- Greenwich sidereal time (mean and apparent)
 *
 * Clean-room implementation from published standards:
 *   IERS Conventions (2010), IERS Technical Note 36, Ch. 5.
 *   Capitaine, Guinot & McCarthy (2000), "Definition of the
 *   Celestial Ephemeris Origin and of UT1 in the International
 *   Celestial Reference Frame", A&A 355, 398-405.
 *
 * No PostgreSQL dependencies -- pure math, suitable for standalone use.
 */

#ifndef PG_ORBIT_SIDEREAL_TIME_H
#define PG_ORBIT_SIDEREAL_TIME_H

/*
 * get_mean_sidereal_time -- Greenwich Mean Sidereal Time
 *
 * Computes GMST using the classical polynomial in UT1,
 * consistent with IAU 2006 precession.
 *
 *   JD  = Julian Date (UT1 timescale)
 *   JDE = Julian Ephemeris Date (TDB/TT timescale)
 *
 * For pg_orbit Phase 2, JD and JDE are treated as identical
 * (delta-T correction not yet applied; the difference is <1s
 * for recent epochs).
 *
 * Returns GMST in radians, normalized to [0, 2*pi).
 */
double get_mean_sidereal_time(double JD, double JDE);

/*
 * get_apparent_sidereal_time -- Greenwich Apparent Sidereal Time
 *
 * GAST = GMST + equation of the equinoxes.
 *
 * The equation of the equinoxes accounts for nutation:
 *   EqEq = delta_psi * cos(epsilon_A)
 * where delta_psi is nutation in longitude and epsilon_A is
 * the mean obliquity, both from precession.h.
 *
 * Returns GAST in radians, normalized to [0, 2*pi).
 */
double get_apparent_sidereal_time(double JD, double JDE);

#endif /* PG_ORBIT_SIDEREAL_TIME_H */