c2ixys¶

erfa.c2ixys(x, y, s)[source]¶

Form the celestial to intermediate-frame-of-date matrix given the CIP X,Y and the CIO locator s.

Parameters:

xdouble array
ydouble array
sdouble array

Returns:

rc2idouble array

Notes

Wraps ERFA function eraC2ixys. The ERFA documentation is:

- - - - - - - - - -
 e r a C 2 i x y s
- - - - - - - - - -

Form the celestial to intermediate-frame-of-date matrix given the CIP
X,Y and the CIO locator s.

Given:
   x,y      double         Celestial Intermediate Pole (Note 1)
   s        double         the CIO locator s (Note 2)

Returned:
   rc2i     double[3][3]   celestial-to-intermediate matrix (Note 3)

Notes:

1) The Celestial Intermediate Pole coordinates are the x,y
   components of the unit vector in the Geocentric Celestial
   Reference System.

2) The CIO locator s (in radians) positions the Celestial
   Intermediate Origin on the equator of the CIP.

3) The matrix rc2i is the first stage in the transformation from
   celestial to terrestrial coordinates:

      [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), ERA is the Earth
   Rotation Angle and RPOM is the polar motion matrix.

Called:
   eraIr        initialize r-matrix to identity
   eraRz        rotate around Z-axis
   eraRy        rotate around Y-axis

Reference:

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

This revision:  2021 May 11

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

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c2ixys¶