Module frames 

High-accuracy frame transforms (Skyfield-compatible, 0-ULP).

The precise frame-transform substrate that used to be pub(crate) inside orbis_nif, now a public part of the core crate. It exposes:

• nutation - IAU 2000A nutation in longitude/obliquity, mean obliquity, the nutation rotation matrix, and the equation-of-equinoxes complementary terms. Depends on crate::astro::data::iau2000a + crate::astro::math::mat3.
• precession - IAU 2006 precession matrix and the ICRS->J2000 frame bias. Depends on crate::astro::math::mat3.
• transforms - the transform engine: TEME->GCRS, GCRS->ITRS, ITRS->geodetic (WGS84), geodetic->ITRS, and topocentric az/el/range. Depends on nutation, precession, crate::astro::math::mat3, and crate::astro::time::scales.

The numerics are byte-for-byte identical to the orbis_nif originals so the existing Skyfield 0-ULP parity (test/skyfield_parity_test.exs) holds. The only changes on relocation are visibility (pub(crate) -> pub) and import paths; the operation order, summation order, transcendental sequence, and the single sanctioned mul_add site are preserved exactly.

Per the crate-boundary invariant, the Rustler decode/encode shims (*_impl, parse_datetime_tuple) stay in orbis_nif; only the pure float-producing compute functions live here.

Modules

nutation

IAU 2000A nutation computation, ported from the C++ Skyfield-compatible implementation.

precession

IAU 2006 precession matrix and ICRS-to-J2000 frame bias, ported from the C++ Skyfield-compatible implementation.

transforms

Coordinate transformation pipeline.