1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
/// Extract from the bias-precession-nutation matrix the X,Y coordinates
/// of the Celestial Intermediate Pole.
///
/// Given:
/// * rbpn celestial-to-true matrix (Note 1)
///
/// Returned:
/// * x,y Celestial Intermediate Pole (Note 2)
///
/// # Notes:
///
/// 1) The matrix rbpn transforms vectors from GCRS to true equator (and
/// CIO or equinox) of date, and therefore the Celestial Intermediate
/// Pole unit vector is the bottom row of the matrix.
///
/// 2) The arguments x,y are components of the Celestial Intermediate
/// Pole unit vector in the Geocentric Celestial Reference System.
///
/// # Reference:
///
/// "Expressions for the Celestial Intermediate Pole and Celestial
/// Ephemeris Origin consistent with the IAU 2000A precession-
/// nutation model", Astron.Astrophys. 400, 1145-1154
/// (2003)
///
/// n.b. The celestial ephemeris origin (CEO) was renamed "celestial
/// intermediate origin" (CIO) by IAU 2006 Resolution 2.
///
/// This revision: 2021 May 11
pub fn bpn2xy(rbpn: &[[f64; 3]; 3], x: &mut f64, y:&mut f64)
{
/* Extract the X,Y coordinates. */
*x = rbpn[2][0];
*y = rbpn[2][1];
/* Finished. */
}