NASA Ocean Color

ocssw V2022

 /*
  *----------------------------------------------------------------------
  * @(#) obliq.c     1.0 20 Oct 93   <shc>
  * Copyright (c) 1993, CSIRO Division of Oceanography
  *----------------------------------------------------------------------
  *
  * obliq --
  *
  *  Calculate mean obliquity of date.
  *
  * Results:
  *
  *  Given a modified Julian dynamical time TJD, this function
  *  returns the mean obliquity of date of the ecliptic and its
  *  time derivative in radians per second.  Each value pointer
  *  can be NULL if the particular value is not required.
  *
  * Side effects:
  *  None.
  *
  * References:
  *  "Astronomical Algorithms", Jean Meeus, Willmann-Bell Inc, 1991,
  *  Chapter 45.
  *
  * History:
  *  1.0 20 Oct 93   <shc>
  *     Initial version.
  *
  *----------------------------------------------------------------------
  */
  
 #include "orbit.h"
  
 void
 obliq(tjd, mood, dmood)
 double tjd;
 double *mood, *dmood;
 {
     double t, a0, a1;
  
     /* Julian centuries from 2000 Jan 1.5 TDB */
     t = (tjd - J2000) / 36525.0;
  
     if (mood != (double *) NULL) {
         a0 = ((1.813e-3 * t - 5.9e-4) * t - 46.8150) * t + 84381.4119;
         *mood = DTOR(a0 / 3600.0);
     }
  
     if (dmood != (double *) NULL) {
         a1 = (3 * 1.813e-3 * t - 2 * 5.9e-4) * t - 46.8150;
         *dmood = DTOR(a1 / 3600.0) / 36525.0;
     }
  
     return;
 }

data_t t[NROOTS+1]

Definition: decode_rs.h:77

NULL

#define NULL

Definition: decode_rs.h:63

DTOR

#define DTOR

Definition: get_ctht.c:1633

orbit.h

obliq

void obliq(double tjd, double *mood, double *dmood)

Definition: obliq.c:35

J2000

#define J2000

Definition: orbit.h:72