earth equatorial radius in meters

earth flattening (unitless)

earth J2 coefficient (unitless)

earth J3 coefficient (unitless)

earth J4 coefficient (unitless)

earth J5 coefficient (unitless)

earth J6 coefficient (unitless)

earth mean radius in meters

earth gravitational parameter in m^3/s^2

Calculate the IAU 1980 nutation angles for the earth, in radians.

coeffs is how many terms of the 106-term series to sum, longest-period first; the default is all of them. Truncating to the leading 4 costs about 0.14 arcseconds, which is larger than everything else in this chain.

@spec polarMotion(DateTime.t()) :: {float(), float()}

Polar motion angles at an epoch, as {xp, yp} in radians.

These orient the true celestial pole against the ITRF pole and are the W in the W * R * N * P chain from J2000 to Earth-fixed. They are tabulated by the IERS in arcseconds and are worth up to about 15 m at the Earth's surface.

Returns {0.0, 0.0} when no EOP record covers the epoch, which degrades the Earth-fixed frame to the true-of-date pole rather than failing.

earth polar radius in meters

Calculate the IAU 1976 precession angles for the earth, in radians.

The angles are defined on Julian centuries of Terrestrial Time since J2000.0, not UTC.

earth sidereal rotation period in seconds

earth sidereal rotation rate in rad/s