asteroid.c

Examples of how to use asteroid functions.

/*
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 

Copyright (C) 2003 Liam Girdwood <liam@gnova.org>


A simple example showing the asteroid Pallas.

*/

#include <stdio.h>
#include <libnova/asteroid.h>
#include <libnova/julian_day.h>
#include <libnova/rise_set.h>
#include <libnova/transform.h>
#include <libnova/elliptic_motion.h>

/* just prints the date */
void print_date (char * title, struct ln_zonedate* date)
{
        printf ("\n%s\n",title);
        printf (" Year    : %d\n", date->years);
        printf (" Month   : %d\n", date->months);
        printf (" Day     : %d\n", date->days);
        printf (" Hours   : %d\n", date->hours);
        printf (" Minutes : %d\n", date->minutes);
        printf (" Seconds : %f\n", date->seconds);
}

int main (int argc, char * argv[])
{
        struct ln_rst_time rst;
        struct ln_zonedate rise, set, transit;
        struct ln_lnlat_posn observer;
        struct ln_hrz_posn hrz;
        struct ln_ell_orbit orbit;
        struct ln_rect_posn posn;
        double JD, M_JD;
        double l,V,dist;
        struct ln_equ_posn equ_posn;
        double H, G;
        double mag, elong, ph;
        char* M_epoch = "K036A";
        
        /* observers location (Edinburgh), used to calc rst */
        observer.lat = 55.92; /* 55.92 N */
        observer.lng = -3.18; /* 3.18 W */
        
        /* get Julian day from local time */
        JD = ln_get_julian_from_sys();  
        printf ("JD (sys) %f\n", JD);
        
        /* Pallas orbital parameters 
        * Taken from MPCORB.DAT
        * 00002    4.13  0.11 K036A 260.69458  310.45917  173.16479
        * 34.84989  0.2299839  0.21343771   2.7730346    MPC 24084
        * 5482  63 1839-1993 0.55 M-c 28  Bowell     0000     (2) Pallas          
        */
        orbit.a = 2.7730346;
        orbit.e = 0.2299839;
        orbit.i = 34.84989;
        orbit.omega =  173.16479;
        orbit.w = 310.45917;
        orbit.n =0.21343771;
        H = 4.13;
        G = 0.11;
        
        /* calc last passage in Perihelion, in julian day  */
        M_JD = ln_get_julian_from_mpc(M_epoch);
        orbit.JD = ln_get_ell_last_perihelion (M_JD, 260.69458, orbit.n);
        printf ("JD (Perihelion) %f\n", orbit.JD);

        /* calc the earth centered position */
        ln_get_ell_geo_rect_posn (&orbit, JD, &posn);
        printf ("(Geocentric Rect Coords X) for Pallas   %f\n", posn.X);
        printf ("(Geocentric Rect Coords Y) for Pallas   %f\n", posn.Y);
        printf ("(Geocentric Rect Coords Z) for Pallas   %f\n", posn.Z);
        
        /* calc the sun centered position */
        ln_get_ell_helio_rect_posn (&orbit, JD, &posn);
        printf ("(Heliocentric Rect Coords X) for Pallas   %f\n", posn.X);
        printf ("(Heliocentric Rect Coords Y) for Pallas   %f\n", posn.Y);
        printf ("(Heliocentric Rect Coords Z) for Pallas   %f\n", posn.Z);
        
        /* get the RA and Dec */
        ln_get_ell_body_equ_coords (JD, &orbit, &equ_posn);
        printf ("(RA) for Pallas   %f\n", equ_posn.ra);
        printf ("(Dec) for Pallas   %f\n", equ_posn.dec);
        
        /* get Alt, Az */
        ln_get_hrz_from_equ (&equ_posn, &observer, JD, &hrz);
        printf ("Az %f\n",hrz.az);
        printf ("Alt %f\n", hrz.alt);
        
        /* orbit length */
        l = ln_get_ell_orbit_len (&orbit);
        printf ("(Orbit Length) for Pallas in AU   %f\n", l);
        
        /* orbit velocities */
        V = ln_get_ell_orbit_pvel (&orbit);
        printf ("(Orbit Perihelion Vel) for Pallas in kms   %f\n", V);
        V = ln_get_ell_orbit_avel (&orbit);
        printf ("(Orbit Aphelion Vel) for Pallas in kms   %f\n", V);
        V = ln_get_ell_orbit_vel (JD, &orbit);
        printf ("(Orbit Vel JD) for Pallas in kms   %f\n", V);
        
        /* earth and solar distance */
        dist = ln_get_ell_body_solar_dist (JD, &orbit);
        printf ("Solar Dist (AU)  : %f\n", dist);
        dist = ln_get_ell_body_earth_dist (JD, &orbit);
        printf ("Earth Dist (AU)  : %f\n", dist);
        
        /* phase angle, elongation */
        ph = ln_get_ell_body_phase_angle(JD, &orbit);
        printf ("Phase angle      : %f\n",ph);
        elong = ln_get_ell_body_elong(JD, &orbit);
        printf ("Elongation       : %f\n",elong);
        
        /* magnitude */
        mag = ln_get_asteroid_mag (JD, &orbit, H, G);
        printf ("Magnitude        : %f\n", mag);
        
        /* rise, set and transit time */
        if (ln_get_ell_body_rst (JD, &observer, &orbit, &rst) == 1) 
                printf ("Pallas is circumpolar\n");
        else {
                ln_get_local_date (rst.rise, &rise);
                ln_get_local_date (rst.transit, &transit);
                ln_get_local_date (rst.set, &set);
                print_date ("Rise", &rise);
                print_date ("Transit", &transit);
                print_date ("Set", &set);
        }
        
        return 0;
}