Skip to main content

Module iau2000a

celestial_core::nutation

Module iau2000a 

Source
Expand description

IAU 2000A nutation model.

Implements the IAU 2000A nutation model as defined by the International Astronomical Union. This model computes the nutation in longitude (delta_psi) and nutation in obliquity (delta_eps) for a given epoch.

§Model Specification

IAU 2000A is a nutation model based on the MHB2000 (Mathews, Herring, Buffett 2002) rigid-Earth series with:

  • 678 lunisolar terms: Trigonometric series based on 5 fundamental arguments (Moon’s mean anomaly, Sun’s mean anomaly, Moon’s argument of latitude, mean elongation of Moon from Sun, longitude of Moon’s ascending node)
  • 687 planetary terms: Additional terms involving planetary mean longitudes (Mercury through Neptune) and general precession in longitude

§Precision

  • Formal precision: ~0.1 microarcsecond (μas) for epochs near J2000.0
  • Accuracy degrades for epochs far from J2000.0 due to polynomial approximations
  • Suitable for applications requiring sub-milliarcsecond precision

§Reference

  • IERS Conventions (2010), Chapter 5
  • Mathews, Herring & Buffett (2002), J. Geophys. Res. 107, B4

Structs§

NutationIAU2000A
IAU 2000A nutation calculator.