How Precise is the Orbit of (99942) Apophis and how Probable is its Collision with the Earth in 2036? ... At present the orbit of asteroid (99942) Apophis and the forces acting on it are not known with sufficient accuracy to predict with certainty its motion after the close approach to the Earth in April of 2029. As a result of this approach the current heliocentric orbit of the asteroid will be changed by Earth's gravity. ...