mean_obliquity_of_ecliptic_iau1980 Function

public pure function mean_obliquity_of_ecliptic_iau1980(et) result(e)

Mean obliquity of the ecliptic, IAU 1980 formula.

Note

This equation is consistent with the one from the SPICE zzmobliq routine.

Arguments

Type IntentOptional Attributes Name
real(kind=wp), intent(in) :: et

ephemeris time (sec)

Return Value real(kind=wp)

obliquity of ecliptic (deg)


Called by

proc~~mean_obliquity_of_ecliptic_iau1980~~CalledByGraph proc~mean_obliquity_of_ecliptic_iau1980 obliquity_module::mean_obliquity_of_ecliptic_iau1980 proc~mean_ecliptic_to_equatorial_rotmat obliquity_module::mean_ecliptic_to_equatorial_rotmat proc~mean_ecliptic_to_equatorial_rotmat->proc~mean_obliquity_of_ecliptic_iau1980 proc~equatorial_to_mean_ecliptic_rotmat obliquity_module::equatorial_to_mean_ecliptic_rotmat proc~equatorial_to_mean_ecliptic_rotmat->proc~mean_ecliptic_to_equatorial_rotmat proc~get_c_cdot_ecliptic transformation_module::ecliptic_frame%get_c_cdot_ecliptic proc~get_c_cdot_ecliptic->proc~mean_ecliptic_to_equatorial_rotmat proc~get_c_cdot_ecliptic->proc~equatorial_to_mean_ecliptic_rotmat proc~transformation_module_test transformation_module::transformation_module_test proc~transformation_module_test->proc~get_c_cdot_ecliptic

Source Code

    pure function mean_obliquity_of_ecliptic_iau1980(et) result(e)

    implicit none

    real(wp),intent(in) :: et  !! ephemeris time (sec)
    real(wp)            :: e   !! obliquity of ecliptic (deg)

    real(wp) :: t  !! time in centuries from the J2000 epoch

    real(wp),dimension(0:3),parameter :: c = [84381.448_wp,&
                                              -46.8150_wp,&
                                              -0.00059_wp,&
                                              +0.001813_wp] !! coefficients

    ! convert input time to centuries:
    t = et*sec2day*day2century

    ! use horner's rule:
    e = (c(0)+t*(c(1)+t*(c(2)+t*c(3))))*arcsec2deg

    end function mean_obliquity_of_ecliptic_iau1980