[time-nuts] would an optical primary standard provide any general benefit?

Azelio Boriani azelio.boriani at screen.it
Tue Apr 3 12:22:16 UTC 2012


Agreed. My consideration was general but, yes, money is necessary so a
decision is a must to properly allocate the financial resources.

On Tue, Apr 3, 2012 at 1:10 PM, Jim Lux <jimlux at earthlink.net> wrote:

> On 4/3/12 12:49 AM, Azelio Boriani wrote:
>
>> Yes, but nonetheless why not develop more stable primary clock sources? We
>> can always take care of the dissemination in the meantime and try to
>> develop a more precise time transfer method.
>>
>> On Tue, Apr 3, 2012 at 2:39 AM, beale<beale at bealecorner.com>  wrote:
>>
>>  Having read this NIST review paper by Thomas E. Parker, "The uncertainty
>>> in the realization and dissemination
>>> of the SI second from a systems point of view"
>>> http://tf.boulder.nist.gov/**general/pdf/2564.pdf<http://tf.boulder.nist.gov/general/pdf/2564.pdf>
>>>
>>> ...it seems that any potential improvement in frequency standards (Cs
>>> fountain ->  optical clocks) will not benefit most time/frequency users,
>>> because existing long-range time-transfer methods (TWSTFT and GPS carrier
>>> phase) are still limited to at best 2E-16 for 30-day averaging, and there
>>> is no generally practical way to improve them currently in sight.  (Laser
>>> ranging of satellites being considered not generally practical). Just
>>> curious what people think, is this too pessimistic a view, or is it fair
>>> to
>>> say that having a 10x improved primary standard would not improve
>>> stability
>>> or accuracy for anyone outside of stabilized optical-fiber distance from
>>> such a standard?
>>>
>>>
>>>
>
> In general, as a technology developer, I agree with you, but the sources
> of money with which to develop technology often have a slightly different
> view.
>
> If one has limited resources, there's a desire to spend the resources
> where they will produce something that is usable.  Since there are more
> things to spend money on than there is money to spend, the money has to get
> allocated, and that allocation process cannot be done in a truly objective
> way.
>
> In my own field of space telecommunications, it seems self evident to me
> that faster data links are better, but from the perspective of a national
> funding source, they have to decide where to spend their money: faster
> telecom; new science instruments; precision pinpoint landing, etc.   So
> what they do is look for places to spend money that are "enabling" new
> science.
>
> there is a sort of circular argument.. you need scientists to stand up and
> say "I need communication technology Y to do my science" (creating what is
> known as a "validated requirement"), but, on the other hand, the scientists
> have a very strong incentive to say "I can do my science with existing
> communication technology X", because that makes their mission proposal
> lower risk (or, at least, reduces  the risk in "infrastructure" sorts of
> ways.  That is, they'd rather spend their risk budget on the science
> measurement, not on getting the data back to Earth.
>
>
> So, the comment from Parker is quite relevant.  If you have no way to
> distribute your incredibly precise time, there's no way to get it to users,
> so it's not clear whether you should spend your money getting the precise
> time, or spend your money on trying to figure out a way to distribute it,
> first.  Or, should you make your really accurate clock small and portable,
> so you can effective distribute it by making lots of them (they are
> *primary* standards, after all)
>
> This is why there is interest in a 1kg, 1 liter Hg+ ion clock for
> spacecraft, of course.  And you too can have a demonstration of one in
> space for around $100M.
>
> http://www.nasa.gov/mission_**pages/tdm/clock/clock_**overview.html<http://www.nasa.gov/mission_pages/tdm/clock/clock_overview.html>
>
>
>
>
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