celestial-eop-data

Bundled IERS Earth Orientation Parameter data for Rust. Ships real EOP data as compressed binary, embedded at compile time — no network access needed at runtime.

Used by celestial for coordinate transformations, precession-nutation corrections, and UT1-UTC lookups.

Data sources

• C04 series — IERS EOP 20 C04 (observed values, 1962–present)
• finals2000A — IERS finals (observed + ~1 year predictions)

Raw data files live in data/ and are updated weekly by a GitHub Action.

Usage

use celestial_eop_data::{c04_data, finals_data, combined_data, data_time_span};

// Lazy-loaded on first access, cached for the process lifetime
let c04 = c04_data();
let finals = finals_data();

// C04 preferred, finals appended for dates beyond C04 coverage
let all = combined_data();

let (start_mjd, end_mjd) = data_time_span();

Each EopEntry contains:

Field	Unit
mjd	days
x_p	arcseconds
y_p	arcseconds
ut1_utc	seconds
lod	seconds
dx	milliarcseconds
dy	milliarcseconds

How it works

build.rs parses the raw IERS text files from data/, packs them into a binary format (7 × f64 per record), and compresses with zstd. The compressed blobs are embedded via include_bytes! and decompressed lazily on first access using OnceLock.

Data updates

A weekly GitHub Action downloads fresh IERS files, runs the test suite, and if the data changed, bumps the patch version and publishes to crates.io. Downstream crates pick up new data with cargo update -p celestial-eop-data.

License

MIT OR Apache-2.0