 Why is Jakdane going to Earth?
For some reason she decided against telling him that the assignment on which she had come to the Jupiter system was to gather his own father's notebooks and take them back to Earth. The ship that they boarded on Moon Nine was one of the newer ships that could attain a hundred-mile-per-second velocity and take a hyperbolic path to Earth, but it would still require fifty-four days to make the trip. She told him only that she was a messenger, sent out to Ganymede to pick up some important papers and take them back to Earth. When it was found at last, he sent Trella, his most trusted secretary, to Ganymede to bring back to him the notebooks found there.
 Jakdane is the captain of the ship that Trella and Quest are taking to earth.
 Jakdane is a corporate spy from Moon 5 on a mission to infiltrate Dom Blessing's organization.  Jakdane is following Trella to Earth because he is stalking her.  Jakdane is transferring from his company's office on Ganymede to the corporate headquarters on Earth.  Jakdane is the captain of the ship that Trella and Quest are taking to earth.