The onboard passive hydrogen maser clocks' precision is four times better than the onboard rubidium atomic clocks and estimated at 1 second per 3 million years (a timing error of a nanosecond or 1 billionth of a second (10 −9 or 1 / 1,000,000,000 s) translates into a 30 cms positional error on Earth's surface), and will provide an accurate timing signal to allow a receiver to calculate the time that it takes the signal to reach it.