Crate spacelab_eop 

Earth-orientation parameters, as published by the IERS.

The Earth is not a clock and its pole is not fixed. Turning a celestial frame into a terrestrial one needs three measured quantities that no theory supplies: the position of the pole (xp, yp), and how far the planet’s rotation has drifted from atomic time (ΔUT1). They are observed, published daily, and predicted a year ahead with rapidly decaying confidence.

Two things this crate refuses to do quietly

Predicted values are not final values. A ΔUT1 predicted a month ahead carries millisecond error, which is metres of longitude. EopQuality is part of every sample and every interpolation result, so the distinction cannot be lost by accident.

Bulletin B is preferred over Bulletin A when it exists. finals2000A carries both: the rapid service (columns 17–134) and the final combined solution (columns 135–185). Most implementations read only the first. Before 2000 the two disagree by tens of milliarcseconds.

The frame is read, not assumed. finals2000A has no header, so it cannot say which ITRF its pole coordinates are in. The IERS EOP 20 C04 series can, on its second line, and EopSeries::parse_c04 reads it into EopSeries::frame: an orbit product’s frame is then checked against the chain’s with ReferenceFrame::agrees_with rather than stated in prose.

Interpolation and sub-daily corrections

The daily series is interpolated with four-point Lagrange, as the IERS Conventions prescribe (a ΔUT1 leap-second step is undone first so it is never smeared across the window). On top of that, the Conventions add diurnal and semidiurnal corrections for ocean tides and lunisolar libration (ortho_eop, pmsdnut2, utlibr). These live in subdaily and are exposed as subdaily_correction — a caller with better-than-mas inputs adds them to the interpolated Eop; for TLE-scale work they are far below the input error and can be ignored.

Re-exports

pub use subdaily::SubdailyCorrection;

pub use subdaily::subdaily_correction;

Modules

subdaily

IERS 2010 sub-daily (diurnal and semidiurnal) EOP corrections.

Structs

Eop

Earth orientation at one instant.

EopSample

One tabulated day.

EopSeries

A parsed finals2000A or C04 series.

Enums

EopError

Why an EOP record could not be read, or a query answered.

EopQuality

Whether a value was measured or predicted.