era.c2tcio.md

eraC2tcio

rc2t = ERFA.c2tcio(rc2i, era, rpom)

Assemble the celestial to terrestrial matrix from CIO-based components (the celestial-to-intermediate matrix, the Earth Rotation Angle and the polar motion matrix).

Given:

   rc2i     double[3][3]    celestial-to-intermediate matrix
   era      double          Earth rotation angle (radians)
   rpom     double[3][3]    polar-motion matrix

Returned:

   rc2t     double[3][3]    celestial-to-terrestrial matrix

Notes:

1. This function constructs the rotation matrix that transforms vectors in the celestial system into vectors in the terrestrial system. It does so starting from precomputed components, namely the matrix which rotates from celestial coordinates to the intermediate frame, the Earth rotation angle and the polar motion matrix. One use of the present function is when generating a series of celestial-to-terrestrial matrices where only the Earth Rotation Angle changes, avoiding the considerable overhead of recomputing the precession-nutation more often than necessary to achieve given accuracy objectives.

2) The relationship between the arguments is as follows:

      [TRS] = RPOM * R_3(ERA) * rc2i * [CRS]

            = rc2t * [CRS]

where [CRS] is a vector in the Geocentric Celestial Reference System and [TRS] is a vector in the International Terrestrial Reference System (see IERS Conventions 2003).

Called:

   eraCr        copy r-matrix
   eraRz        rotate around Z-axis
   eraRxr       product of two r-matrices

Reference:

McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003), IERS Technical Note No. 32, BKG

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.