Simple ballistics. The probe is still subject to gravity and it can receive trajectory adjustments as needed. It's not like it was launched ten years ago and th

Simple ballistics. The probe is still subject to gravity and it can receive trajectory adjustments as needed. It's not like it was launched ten years ago and then it was on its own: it's been piloted remotely from the Earth as necessary. It's a remarkable achievement but the science behind it has been known and used successfully for decades.