A new atomic clock being developed for navigation satellites will perform better than previous devices. The Clock will use a new microwave cavity design to provide a compact and lightweight package and new electronic techniques to maintain long-term stability. The clock can provide precise navigation information because it is stable to one second in three million years. The differences in the time when signals from four satellites arrive at one location can be used to calculate that position to within a few yards. It can be inferred from the passage that the new clock will be-