public List<NaturalSatellite> getNaturalSatellites() {
        List<NaturalSatellite> returnedSatellites = new ArrayList<NaturalSatellite>();

        for (Satellite satellite : satellites) {
            if (satellite.getClass() == NaturalSatellite.class) {
                returnedSatellites.add((NaturalSatellite) satellite);
            }
        }
        return returnedSatellites;
    }