Earth’s rotation: observations and theory - Earth Dynamics: Deformations and Oscillations of the Rotating Earth - page 311

the 18.6-year, 9.3-year, annual and semi-annual periodic terms as well as the lin-
ear and constant terms, as determined by least squares fits with coe cients given

in Table 4.1. The nutation residuals cover a time span of 8615.276389 days. We
take the record length to be 8617 days, the first point to be 0.8618055 days into
the record, and the last point to be 0.8618055 days before the end of the record.
After subtraction of the foregoing terms, the time base is reset to have its origin
0.8618055 days before the first point. The resulting nutation residuals are returned
in the file nutres.dat.

C PROGRAMME NUTRES.FOR

C
C Programme NUTRES removes 18.6 yr term, 9.3 yr term, annual,
C and semi-annual terms, and the linear and constant terms from
C the nutation co-ordinates, taking the time origin to be the original
C 44,089.99375 days.
C

IMPLICIT DOUBLE PRECISION(A-H,O-Z)
OPEN(UNIT=1,FILE='nut.dat',STATUS='OLD')
OPEN(UNIT=2,FILE='nutres.dat',STATUS='UNKNOWN')
C Set constants.
PI=3.14159265358979D0
W=2.D0*PI/6798.58D0
W9=2.D0*W
WA=2.D0*PI/365.25971D0
WSA=2.D0*WA
AX=2.4496D0
AY=1.9026D0
BX=1.9307D0
BY=-2.3741D0
CX=-0.37214D0
CY=-0.18244D0
DX=-0.24779D0
DY=0.13710D0
EX=-1.0785D0
EY=1.6863D0
FX=1.7798D0
FY=1.2533D0
GX=0.82405D0
GY=-0.17113D0
HX=0.19983D0
HY=0.71118D0
AIX=-0.00324337D0
AIY=-0.000665044D0
AJX=150.02D0
AJY=29.144D0
DO 10,I=1,3343
READ(1,11)J,DAY,XNUT,SEX,YNUT,SEY
11 FORMAT(1X,I4,F15.6,4F10.3)
C Reset time origin.
DAY=DAY+44089.99375D0
C Subtract 18.6 yr term, 9.3 yr term, annual, and semi-annual terms,
C as well as linear and constant terms.
XNUT=XNUT-AX*DCOS(W*DAY)-BX*DSIN(W*DAY)

1 -CX*DCOS(W9*DAY)-DX*DSIN(W9*DAY)

2 -EX*DCOS(WA*DAY)-FX*DSIN(WA*DAY)

3 -GX*DCOS(WSA*DAY)-HX*DSIN(WSA*DAY)

4 -AIX*DAY-AJX