ASTEROIDS APPROACHING THE EARTH FROM DIRECTIONS AROUND THE SUN

We have estimated close asteroid encounters with the Earth by numerica l integrations of a system with the Sun, 9 planets, and 188 near-earth -asteroids during the period 1994-4600. Asteroids approach the Earth f rom directions within 30 degrees around the Sun in more than 20% of en counters with the closest distance less than 0.01 AU. Since groundbase d observations cannot detect these objects, we should develop space-bo rne and/or lunar observatories in a short time to allow enough warning time before a catastrophic collision.