The DSN has to ship a sign and the spaceship has to ship it again. The trajectory cannot be calculated and if a maneuver is to be made, the DSN should ship maneuver instructions to the spacecraft. If a probe is in Earth orbit, the processing time is often lower than one second, however in the event you attempt to speak to a probe by Jupiter, the sign takes 45 minutes to get there, and 45 minutes to return, and extra At the moment, the spacecraft had maybe traveled a substantial distance: the Cassini-Huygens mission sure for Saturn had reached a prime pace of greater than 100,000 kilometers on the time relative to the Solar. It's as if a ship at sea, fairly than sporting her personal stopwatch, needed to depend on the time indicators of a clock going again to her port, and additional, indicators that would not touring, say, that's on the pace of sound. (The port might have, for instance, the strongest gun on this planet at midday). You can also make it work, however it could be significantly better for the ship – and the spaceship – to have an correct on-board clock.