The length of the packet is limited by the broadcast frequency and the time to update .. so the packet was kept tight.
The satellites drift (orbital decay, magnetic torque, solar wind, random particle pressure) and live in a different gravity (aka relativistic time) .. their 'self' data (position | time) is regularly updated from ground stations and their internal epochs only need to operate for some low N number of expected update cycles .. if they lack an accurate sense of 'self' they lack function as waypoints.
Adding clock data widths that count nanoseconds for the lifetime of the sun would be pointless: it makes the data packet longer and it doesn't change the hard requirement for regular time|position updates from the ground.
They were designed with short epoch counters with an understanding of functional constraints.
Still surprised, every time I see it mentioned, to have a cultural construct like a week in the data model. Likely a deliberate break from SI to avoid ambiguity between monotonously increasing counters and calendaric time, but surprising nonetheless.
* GPS depends upon acurate timing and positions.
* GPS broadcasts a data packet.
The length of the packet is limited by the broadcast frequency and the time to update .. so the packet was kept tight.
The satellites drift (orbital decay, magnetic torque, solar wind, random particle pressure) and live in a different gravity (aka relativistic time) .. their 'self' data (position | time) is regularly updated from ground stations and their internal epochs only need to operate for some low N number of expected update cycles .. if they lack an accurate sense of 'self' they lack function as waypoints.
Adding clock data widths that count nanoseconds for the lifetime of the sun would be pointless: it makes the data packet longer and it doesn't change the hard requirement for regular time|position updates from the ground.
They were designed with short epoch counters with an understanding of functional constraints.