Name

CL_mod_precessionAngles — Precession angles (Lieske 1976)

Calling Sequence

   [K[,KP[,KPP]]]=CL_mod_precessionAngles(jj_tai,sec_tai[,flag])
   
   

Description

  • Calculate precession angles according to Lieske precession theory.

    if P0 is the pole of J2000 equator, and P is the pole of the equator at date t; if G0 is the equinox of J2000 and G is the equinox at date t:

    zetaa : angle between the meridians (pole P0) P0-P and P0-G0

    thetaa: angle between the equateur J2000 and the equateur t

    za : angle between the meridians (pole P) P-P0 and P-G

  • Last update : 19/09/2007

Parameters

jj_tai :

CNES Julian day (TAI time) (1xN)

ss_tai :

seconds (TAI time) (1xN)

flag :

(optional) "n" -> K; "p" -> K and Kp; "s" -> K, Kp, Kpp (default depends on number of outputs)

K :

precession angles K = [zetaa;tetaa;za] [rad] (3xN)

KP:

(optional) first time derivative of K [rad/s] (3xN)

KPP :

(optional) second time derivative of K [rad/s^2] (3xN)

Authors

CNES - DCT/SB

Bibliography

1 IERS Conventions (1996), Dennis D. McCarthy

2 Explanatory Supplement to the Astronomical Almanac, Seidelman (1992)

See also

CL_mod_nutationAngles

Examples

jj_tai = [19500:1:20500];
ss_tai = 43200*ones(jj_tai);
[K,KP,KPP]=CL_mod_precessionAngles(jj_tai,ss_tai,"s");
plot(jj_tai'+ss_tai'/86400,K');