[LEAPSECS] Reliability

[Adi Stav]

On Sun, Jan 04, 2009 at 08:36:31AM -0700, Rob Seaman wrote:

> Adi Stav wrote:

>>

>> I'm trying to understand this position. I have a question.

>

> I appreciate both the question and the polite way it was asked :-)


Thanks for that, and for your answer :)


> I remain flabbergasted that of all the postings I've made to this list  

> over the years - postings like the recent one that speculated 5 billion 

> years into the future - that of all these, the ones to generate 

> full-throated outrage as a result are when I humbly suggest that normal 

> system engineering protocols be followed.


Maybe because discussing possible solutions is much more interesting
than talking about funding long-term requirements research, after all.


> Which is to say that I can speculate on an acceptable maximum value for 

> DUT1, but that misses the point.


But surely there's some value in exploration of the problem and
solution spaces beforehand. In can help guide subsequent efforts and
decisions.


> I could say, for example, that 4 seconds wouldn't make me gag too badly 

> (even though this corresponds to a full arc-minute at the equator).  If 

> we feed this into some Bayesian simulation using historical values from 

> Bulletin A to predict the baseline truth of Bulletin B, this seems likely 

> to give us a decade or more lead time on announcing a leap second 

> schedule.


Then why 4 seconds? Because they could be predicted a decade in advance?
Isn't that putting the cart before the horses? I think the "lead time"
is a different requirement altogether. (Although, for some values you might 
not be able to satisfy both at the same time.)

If I reckon correctly, people on this list specified 20 or 60 minutes as
their guesses for the limit, based on current human tolerance as witnessed 
by our indifference towards the Equation of Time and our own design of 
the time zone system. Clearly, you think DUT should be smaller. Why? For
practical reasons of astronomy? For other reasons?

Or, perhaps, it's not the *magnitude* of DUT but its permanence? Maybe
civil time can correct for the secular drift and ignore the decade
noise? (*That* could be predicted millenia in advance.)