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).
56 lines
2.0 KiB
C
56 lines
2.0 KiB
C
/*
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* precession.h -- IAU 2006 precession and simplified nutation
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*
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* Clean-room implementation from published standards:
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* Precession: Capitaine, Wallace & Chapront (2003), A&A 412, 567
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* (IAU 2006 polynomial expressions)
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* Nutation: Simplified 4-term model from fundamental arguments
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* documented in IERS Technical Note 32, Ch. 5.
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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_PRECESSION_H
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#define PG_ORBIT_PRECESSION_H
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/*
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* get_precession_angles_vondrak -- IAU 2006 precession angles
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*
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* Computes the four fundamental precession quantities at JDE:
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* psi_A -- luni-solar precession (arcsec)
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* omega_A -- inclination of equator on J2000 ecliptic (arcsec)
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* chi_A -- planetary precession (arcsec)
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* epsilon_A -- obliquity of the ecliptic (arcsec)
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*
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* These are the IAU 2006 polynomial expressions valid to ~1 mas
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* for several centuries around J2000. The full Vondrak (2011)
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* periodic terms are not included here; they extend validity
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* to +/-200,000 years but add sub-arcsecond corrections that
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* are negligible for our use case.
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*
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* Output is in arcseconds.
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*/
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void get_precession_angles_vondrak(double jde,
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double *epsilon_A,
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double *chi_A,
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double *omega_A,
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double *psi_A);
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/*
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* get_nutation_angles_iau2000b -- simplified nutation
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*
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* Computes nutation in longitude (delta_psi) and nutation in
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* obliquity (delta_epsilon) using the dominant 4 lunisolar terms.
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*
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* This matches the level of nutation correction used in SGP4
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* coordinate transforms and is suitable for "what's up?" queries
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* where ~1 arcsecond accuracy is sufficient.
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*
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* Output is in arcseconds.
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*/
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void get_nutation_angles_iau2000b(double jde,
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double *delta_psi,
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double *delta_epsilon);
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#endif /* PG_ORBIT_PRECESSION_H */
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