Re: [time-nuts] would an optical primary standard provide any general benefit?
On 04/03/2012 01:10 PM, Jim Lux 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, bealebe...@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 ...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. I wonder if they have really reached the measurement limit possible in fibre systems. If one is serious about pushing fibre based TT systems down, there is a number of techniques one could apply as an ensemble, but I have not seen any serious work, only working on different pieces of the puzzle. Hence, I think the article may be premature in this respect. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] would an optical primary standard provide any general benefit?
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 be...@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 ...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? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] would an optical primary standard provide any general benefit?
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 jim...@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, bealebe...@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.pdfhttp://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.htmlhttp://www.nasa.gov/mission_pages/tdm/clock/clock_overview.html __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] would an optical primary standard provide any general benefit?
On 4/3/12 5:22 AM, Azelio Boriani wrote: Agreed. My consideration was general but, yes, money is necessary so a decision is a must to properly allocate the financial resources. Well.. we could hope for a fabulously wealthy patron who thinks that it would be a good thing to fund time-nuts of all kinds to tinker. grin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] would an optical primary standard provide any general benefit?
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 ...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? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
