pkg/radtrans/radtrans_nutate.F

C $Header$
C $Name$

#include "RADTRANS_OPTIONS.h"

CBOP
C     !ROUTINE: RADTRANS_NUTATE

C     !INTERFACE: ======================================================
      subroutine radtrans_nutate (radeg, t, xls, gs, xlm, omega,
     O                            dpsi, eps)

C     !DESCRIPTION:
c  This subroutine computes the nutation in longitude and the obliquity
c  of the ecliptic corrected for nutation.  It uses the model referenced
c  in The Astronomical Almanac for 1984, Section S (Supplement) and 
c  documented in Exact closed-form geolocation algorithm for Earth 
c  survey sensors, by F.S. Patt and W.W. Gregg, Int. Journal of 
c  Remote Sensing, 1993.  These parameters are used to compute the 
c  apparent time correction to the Greenwich Hour Angle and for the 
c  calculation of the geocentric Sun vector.  The input ephemeris 
c  parameters are computed using subroutine ephparms.  Terms are 
c  included to 0.1 arcsecond.

c  Calling Arguments

c  Name         Type    I/O     Description
c
c  t            R*8      I      Time in days since January 1, 2000 at 
c                                12 hours UT
c  xls          R*8      I      Mean solar longitude (degrees)
c  gs           R*8      I      Mean solar anomaly   (degrees)
c  xlm          R*8      I      Mean lunar longitude (degrees)
c  Omega        R*8      I      Ascending node of mean lunar orbit 
c                                (degrees)
c  dPsi         R*8      O      Nutation in longitude (degrees)
c  Eps          R*8      O      Obliquity of the Ecliptic (degrees)
c                                (includes nutation in obliquity)
c
c
c       Program written by:     Frederick S. Patt
c                               General Sciences Corporation
c                               October 21, 1992
c
c       Modification History:
c
C     !USES: ===========================================================
      IMPLICIT NONE

C     !INPUT PARAMETERS: ===============================================
      _RL radeg, t, xls, gs, xlm, omega
c     INTEGER myThid

C     !OUTPUT PARAMETERS: ==============================================
      _RL dpsi, eps

C     !FUNCTIONS: ======================================================

C     !LOCAL VARIABLES: ================================================
      _RL epsm, deps
CEOP


c  Nutation in Longitude
      dpsi = - 17.1996D0*sin(omega/radeg) 
     * + 0.2062D0*sin(2.0D0*omega/radeg)
     * - 1.3187D0*sin(2.0D0*xls/radeg) 
     * + 0.1426D0*sin(gs/radeg) 
     * - 0.2274D0*sin(2.0D0*xlm/radeg) 

c  Mean Obliquity of the Ecliptic       
      epsm = 23.439291D0 - 3.560D-7*t 

c  Nutation in Obliquity 
      deps = 9.2025D0*cos(omega/radeg) + 0.5736D0*cos(2.0D0*xls/radeg)

c  True Obliquity of the Ecliptic 
      eps = epsm + deps/3600.0D0

      dpsi = dpsi/3600.0D0

      return
      end
c
1	C $Header$
2	C $Name$
3
4	#include "RADTRANS_OPTIONS.h"
5
6	CBOP
7	C !ROUTINE: RADTRANS_NUTATE
8
9	C !INTERFACE: ======================================================
10	subroutine radtrans_nutate (radeg, t, xls, gs, xlm, omega,
11	O dpsi, eps)
12
13	C !DESCRIPTION:
14	c This subroutine computes the nutation in longitude and the obliquity
15	c of the ecliptic corrected for nutation. It uses the model referenced
16	c in The Astronomical Almanac for 1984, Section S (Supplement) and
17	c documented in Exact closed-form geolocation algorithm for Earth
18	c survey sensors, by F.S. Patt and W.W. Gregg, Int. Journal of
19	c Remote Sensing, 1993. These parameters are used to compute the
20	c apparent time correction to the Greenwich Hour Angle and for the
21	c calculation of the geocentric Sun vector. The input ephemeris
22	c parameters are computed using subroutine ephparms. Terms are
23	c included to 0.1 arcsecond.
24
25	c Calling Arguments
26
27	c Name Type I/O Description
28	c
29	c t R*8 I Time in days since January 1, 2000 at
30	c 12 hours UT
31	c xls R*8 I Mean solar longitude (degrees)
32	c gs R*8 I Mean solar anomaly (degrees)
33	c xlm R*8 I Mean lunar longitude (degrees)
34	c Omega R*8 I Ascending node of mean lunar orbit
35	c (degrees)
36	c dPsi R*8 O Nutation in longitude (degrees)
37	c Eps R*8 O Obliquity of the Ecliptic (degrees)
38	c (includes nutation in obliquity)
39	c
40	c
41	c Program written by: Frederick S. Patt
42	c General Sciences Corporation
43	c October 21, 1992
44	c
45	c Modification History:
46	c
47	C !USES: ===========================================================
48	IMPLICIT NONE
49
50	C !INPUT PARAMETERS: ===============================================
51	_RL radeg, t, xls, gs, xlm, omega
52	c INTEGER myThid
53
54	C !OUTPUT PARAMETERS: ==============================================
55	_RL dpsi, eps
56
57	C !FUNCTIONS: ======================================================
58
59	C !LOCAL VARIABLES: ================================================
60	_RL epsm, deps
61	CEOP
62
63
64	c Nutation in Longitude
65	dpsi = - 17.1996D0*sin(omega/radeg)
66	* + 0.2062D0sin(2.0D0omega/radeg)
67	* - 1.3187D0sin(2.0D0xls/radeg)
68	* + 0.1426D0*sin(gs/radeg)
69	* - 0.2274D0sin(2.0D0xlm/radeg)
70
71	c Mean Obliquity of the Ecliptic
72	epsm = 23.439291D0 - 3.560D-7*t
73
74	c Nutation in Obliquity
75	deps = 9.2025D0cos(omega/radeg) + 0.5736D0cos(2.0D0*xls/radeg)
76
77	c True Obliquity of the Ecliptic
78	eps = epsm + deps/3600.0D0
79
80	dpsi = dpsi/3600.0D0
81
82	return
83	end
84	c