int DLL_FUNC calc_planet_orientation( int planet_no, int system_no, double jd, double *matrix) #endif { static int prev_planet_no = -1, prev_system_no = -1, prev_rval = 0; static double prev_jd = -1.; static double prev_matrix[9]; int i, rval, is_retrograde; double pole_ra, pole_dec, omega; if( planet_no == prev_planet_no && system_no == prev_system_no && jd == prev_jd) { memcpy( matrix, prev_matrix, 9 * sizeof( double)); return( prev_rval); } prev_planet_no = planet_no; prev_system_no = system_no; prev_jd = jd; if( planet_no == 3) /* handle earth with "normal" precession: */ { const double J2000 = 2451545.; /* 1.5 Jan 2000 = JD 2451545 */ const double t_cen = (jd - J2000) / 36525.; int i; setup_precession( matrix, 2000., 2000. + t_cen * 100.); for( i = 3; i < 6; i++) matrix[i] = -matrix[i]; spin_matrix( matrix, matrix + 3, green_sidereal_time( jd)); memcpy( prev_matrix, matrix, 9 * sizeof( double)); prev_rval = 0; return( 0); } /* For everybody else, we use TD. Only the earth uses UT. */ /* (This correction added 5 Nov 98, after G Seronik pointed */ /* out an error in the Saturn central meridian.) */ jd += td_minus_ut( jd) / 86400.; /* correct from UT to TD */ rval = get_cospar_data_from_text_file( planet_no, system_no, jd, &pole_ra, &pole_dec, &omega, &is_retrograde); pole_ra *= PI / 180.; pole_dec *= PI / 180.; polar3_to_cartesian( matrix, pole_ra - PI / 2., 0.); polar3_to_cartesian( matrix + 3, pole_ra - PI, PI / 2. - pole_dec); polar3_to_cartesian( matrix + 6, pole_ra, pole_dec); spin_matrix( matrix, matrix + 3, omega * PI / 180. + PI); if( is_retrograde) for( i = 3; i < 6; i++) matrix[i] *= -1.; memcpy( prev_matrix, matrix, 9 * sizeof( double)); prev_rval = rval; return( rval); }
int fill_planet_data( PLANET_DATA *pdata, const int planet_no, const double jd, const double observer_lat, const double observer_lon, const char *vsop_data) { double loc_sidereal_time = green_sidereal_time( jd) + observer_lon; double t_centuries = (jd - J2000) / 36525.; double obliquity = mean_obliquity( t_centuries); double loc[3]; pdata->jd = jd; if( planet_no == 10) /* get lunar data, not VSOP */ { double fund[N_FUND]; lunar_fundamentals( vsop_data, t_centuries, fund); lunar_lon_and_dist( vsop_data, fund, &pdata->ecliptic_lon, &pdata->r, 0L); pdata->ecliptic_lon *= pi / 180.; pdata->ecliptic_lat = lunar_lat( vsop_data, fund, 0L) * pi / 180.; } else { /* What we _really_ want is the location of the sun as */ /* seen from the earth. VSOP gives us the opposite, */ /* i.e., where the _earth_ is as seen from the _sun_. */ /* To evade this, we add PI to the longitude and */ /* negate the latitude. */ pdata->ecliptic_lon = calc_vsop_loc( vsop_data, planet_no, 0, t_centuries, 0.) + pi; pdata->ecliptic_lat = -calc_vsop_loc( vsop_data, planet_no, 1, t_centuries, 0.); pdata->r = calc_vsop_loc( vsop_data, planet_no, 2, t_centuries, 0.); } polar3_to_cartesian( loc, pdata->ecliptic_lon, pdata->ecliptic_lat); memcpy( pdata->ecliptic_loc, loc, 3 * sizeof( double)); /* At this point, loc is a unit vector in ecliptic */ /* coords of date. Rotate it by 'obliquity' to get */ /* a vector in equatorial coords of date: */ rotate_vector( loc, obliquity, 0); memcpy( pdata->equatorial_loc, loc, 3 * sizeof( double)); /* The following two rotations take us from a vector in */ /* equatorial coords of date to an alt/az vector: */ rotate_vector( loc, -loc_sidereal_time, 2); /* printf( "LST: %lf\n", fmod( loc_sidereal_time * 180. / pi, 360.)); */ pdata->hour_angle = atan2( loc[1], loc[0]); rotate_vector( loc, observer_lat - pi / 2., 1); memcpy( pdata->altaz_loc, loc, 3 * sizeof( double)); return( 0); }