Ryan Malloy
0544a78276
Phase 1 — Stars, comets, Keplerian propagation: - star_observe() / star_observe_safe(): fixed star alt/az via IAU 1976 precession, equatorial-to-horizontal transform - kepler_propagate(): two-body Keplerian orbit propagation for elliptic, parabolic, and hyperbolic orbits - comet_observe(): observe comets/asteroids from orbital elements - heliocentric type: ecliptic J2000 position (x, y, z in AU) Phase 2 — VSOP87 planets, ELP82B Moon, Sun: - planet_heliocentric(): VSOP87 heliocentric ecliptic J2000 positions for Mercury through Neptune (Bretagnon & Francou, MIT) - planet_observe(): full observation pipeline for any planet - sun_observe(): Sun position from negated Earth VSOP87 - moon_observe(): ELP2000-82B lunar position (Chapront-Touzé, MIT) - Clean-room precession (IAU 2006) and sidereal time (IERS 2010) - elliptic_to_rectangular utility (Stellarium, MIT) All Stellarium extractions are MIT-licensed, thread-safe (static caching removed for PARALLEL SAFE), zero external data files. All 9 regression tests pass (90ms total).
48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
/*
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* sidereal_time.h -- Greenwich sidereal time (mean and apparent)
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*
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* Clean-room implementation from published standards:
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* IERS Conventions (2010), IERS Technical Note 36, Ch. 5.
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* Capitaine, Guinot & McCarthy (2000), "Definition of the
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* Celestial Ephemeris Origin and of UT1 in the International
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* Celestial Reference Frame", A&A 355, 398-405.
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*
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* No PostgreSQL dependencies -- pure math, suitable for standalone use.
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*/
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#ifndef PG_ORBIT_SIDEREAL_TIME_H
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#define PG_ORBIT_SIDEREAL_TIME_H
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/*
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* get_mean_sidereal_time -- Greenwich Mean Sidereal Time
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*
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* Computes GMST using the classical polynomial in UT1,
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* consistent with IAU 2006 precession.
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*
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* JD = Julian Date (UT1 timescale)
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* JDE = Julian Ephemeris Date (TDB/TT timescale)
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*
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* For pg_orbit Phase 2, JD and JDE are treated as identical
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* (delta-T correction not yet applied; the difference is <1s
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* for recent epochs).
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*
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* Returns GMST in radians, normalized to [0, 2*pi).
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*/
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double get_mean_sidereal_time(double JD, double JDE);
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/*
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* get_apparent_sidereal_time -- Greenwich Apparent Sidereal Time
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*
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* GAST = GMST + equation of the equinoxes.
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*
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* The equation of the equinoxes accounts for nutation:
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* EqEq = delta_psi * cos(epsilon_A)
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* where delta_psi is nutation in longitude and epsilon_A is
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* the mean obliquity, both from precession.h.
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*
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* Returns GAST in radians, normalized to [0, 2*pi).
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*/
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double get_apparent_sidereal_time(double JD, double JDE);
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#endif /* PG_ORBIT_SIDEREAL_TIME_H */
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