Did you know that a probe is an unmanned spacecraft? These probes which monitor the planets in the sky help us to determine the complexity of our solar system. They are used when manned spacecrafts are not sufficient in bringing back knowledge. The paths of the interplanetary space probes are plotted against the orbit of the planets themselves. That is why timing of each individual launch is important in minimizing the distance it will have to travel in order to fly by its moving target.