Crate celestial_core 

Low-level astronomical calculations for coordinate transformations.

celestial-core provides the mathematical building blocks for celestial mechanics: rotation matrices, nutation/precession models, angle handling, and geodetic conversions. It implements IAU 2000/2006 standards in pure Rust with no runtime FFI.

Modules

Module	Purpose
angle	Angle types, parsing (HMS/DMS), normalization, validation
matrix	3×3 rotation matrices and 3D vectors
nutation	IAU 2000A/2000B/2006A nutation models
precession	IAU 2000/2006 precession (Fukushima-Williams angles)
cio	CIO-based GCRS↔CIRS transformations
obliquity	Mean obliquity of the ecliptic (IAU 1980, 2006)
location	Observer geodetic coordinates, geocentric conversion
constants	Astronomical constants (J2000, WGS84, unit conversions)
errors	AstroError and AstroResult

Coordinate Transformation Pipeline

GCRS → CIRS transformation (CIO-based):

// 1. Compute precession-nutation-bias matrix
let fw = FukushimaWilliamsAngles::iau2006a(tt_centuries);
let nutation = NutationIAU2006A::new().compute(jd1, jd2)?;
let npb = fw.build_npb_matrix(nutation.delta_psi, nutation.delta_eps);

// 2. Extract CIO quantities
let cio = CioSolution::calculate(&npb, tt_centuries)?;

// 3. Build GCRS→CIRS matrix
let matrix = gcrs_to_cirs_matrix(cio.cip.x, cio.cip.y, cio.s);

Re-exports

Common types are re-exported at the crate root for convenience:

use celestial_core::{Angle, Vector3, RotationMatrix3, Location};
use celestial_core::{AstroError, AstroResult, MathErrorKind};

Design Notes

• Two-part Julian Dates: Functions accepting (jd1, jd2) preserve precision by splitting the date. Typically jd1 = 2451545.0 (J2000.0) and jd2 is days from epoch.

• Radians internally: All angular computations use radians. The Angle type provides conversion methods for degrees/HMS/DMS display.

• No implicit state: Models like NutationIAU2006A are stateless calculators. Call compute(jd1, jd2) with any epoch.

Re-exports

pub use angle::Angle;

pub use cio::gcrs_to_cirs_matrix;

pub use cio::CioLocator;

pub use cio::CioSolution;

pub use cio::CipCoordinates;

pub use cio::EquationOfOrigins;

pub use errors::AstroError;

pub use errors::AstroResult;

pub use errors::MathErrorKind;

pub use location::Location;

pub use matrix::RotationMatrix3;

pub use matrix::Vector3;

Modules

angle

cio

Celestial Intermediate Origin (CIO) based celestial-to-terrestrial transformations.

constants

errors

Error types for astronomical calculations.

location

Observer location on Earth.

math

matrix

3D rotation matrices and vectors for coordinate transformations.

nutation

Nutation models for computing oscillations in Earth’s rotational axis.

obliquity

Mean obliquity of the ecliptic.

precession

Precession models for transforming coordinates between epochs.

test_helpers

utils

Utility functions for time and angle conversions.

Macros

assert_ulp_lt