Clean-room DE binary reader (~400 lines C) with Chebyshev/Clenshaw
evaluation — no GPL dependency on jpl_eph. Per-backend lazy
initialization preserves PARALLEL SAFE. Existing VSOP87/ELP82B
functions stay IMMUTABLE; new _de() variants are STABLE with
automatic fallback to compiled-in ephemerides on any DE failure.
Implementation:
- de_reader.c: header parse, record seek, Clenshaw recurrence
- eph_provider.c: GUC (pg_orbit.ephemeris_path), lazy init,
ICRS-to-ecliptic frame rotation, on_proc_exit cleanup
- de_funcs.c: 11 new SQL functions (_de variants + diagnostics)
- Constant chain of custody rules 6-8 (frame rotation,
same-provider, AU consistency)
Extract observe_from_geocentric() to astro_math.h for shared use
by planet_funcs.c, moon_funcs.c, and de_funcs.c.
57 → 68 functions, 11 → 12 regression test suites, all passing.
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).
6 custom types (tle, eci_position, geodetic, topocentric, observer,
pass_event), 67 SQL functions, 2 operators (&&, <->), and a GiST
operator class for altitude-band indexing. Wraps Bill Gray's sat_code
for SGP4/SDP4 propagation with WGS-72 constants for propagation and
WGS-84 for coordinate output. All 5 regression tests pass on PG 18.
