[time-nuts] seeking a time/clock software architecture

[Jim Lux]

On 9/23/11 10:25 AM, Jim Lux wrote:
>
>
> One aspect of why at least a standardized second order model would be
> nice is that it allows you to make smooth non-discontinuous changes in
> rate. the transformation from count to time would be discontinuous in
> rate of rate (i.e. it would go from zero, to something, to zero), but
> continuous in terms of rate.
>

The other thing that crops up all the time in the spacecraft world is 
that you're always taking into account the light time propagation delay 
between two ends of a link, which is varying fairly quickly.  Since the 
problem of doing something like "I want my signal to arrive at a 
particular time over there" crops up a lot, as does the general "I want 
to measure my oscillator against the one on that other spacecraft", 
something that provides a consistent computational framework (as opposed 
to specifically designed for the application) might be useful.

For instance, GPS receivers have to do this calculation already, so the 
whole range/range rate estimation process is built in, in order to do 
the nav solution.  Each implementation probably does it a different way, 
but at least the observables are reported in a standard way as RINEX 
(tailored to the needs of GPS, e.g carrier phase is measured in cycles)