[time-nuts] CCTF Survey on redefinition of the Second and UTC

[Magnus Danielson]

Hal,

Many thanks. I was unaware of this, but now got an opportunity to file a
reply.

Most of it actually is not as much related to the SI redefinition, but
covers a wider set of questions. View it more as a survey to the use of
frequency and time in various ways. It has a taint of NMI related
world-view, which more reflects what is typically discussed in the
conferences and workshops they usually participate in. As long as they
reach outside of that and get input on things they are missing, fine.
This survey can to some degree serve that purpose and I tried to
contribute some of that to aid them.

One particular angle they where missing is the angle what a vendor of
equipment see. What I do in my company when testing and designing is not
necessarily the relevance to what my customers experience and as we help
them with that. Thus, it not as much as what I operate as what I help my
customers operate.

Cheers,
Magnus

On 2021-01-14 14:12, Hal Murray wrote:
> This is from the time-zone list.
> I dropped the HTML version and the PDF letter.
> Archived version here:
>   http://mm.icann.org/pipermail/tz/2021-January/029692.html
>
> Survey here:
>   https://www.surveymonkey.com/r/CCTF_Survey_2020
> It has infoductory/background stuff that I haven't checked out yet.
>
> -------
>
> Subject: Re: [tz] CCTF survey on Time and Frequency Metrology - Telecom
> From: "Gertsvolf, Marina" <Marina.Gertsvolf at nrc-cnrc.gc.ca>
> Date: Tue, 12 Jan 2021 17:14:24 +0000
> To: "Gertsvolf, Marina" <Marina.Gertsvolf at nrc-cnrc.gc.ca>
> Cc: MILETI Gaetano <gaetano.mileti at unine.ch>,
>         Frédéric Meynadier <Frederic.Meynadier at bipm.org>
>
> Dear Colleague,
>
> The last time the definition of the SI second was changed was in 1967 when =
> Caesium atom hyperfine frequency transition was chosen as the reference val=
> ue.
>
> Since then first the primary thermal beam caesium clocks and then caesium f=
> ountains have been providing the SI second realization values to steer the =
> International Atomic Timescale. The current fountain uncertainties are at t=
> he low 1E-16 level.
>
> The frequency metrology research in recent years has surpassed the microwav=
> e clocks, and optical frequency standards based on trapped ions and atoms n=
> ow provide frequency measurements with evaluated uncertainties at the level=
>  1E-18.
>
> The frequency comparisons have also been advancing both through improved te=
> chniques in Global Navigation Satellite Systems signal analysis and the Two=
>  Way satellite Time and Frequency transfer as well as with fibre based freq=
> uency links and portable optical clocks.
> Frequency combs used to compare frequencies between clock lasers of differe=
> nt optical clocks and also between optical frequencies and microwave 133Cs =
> frequency of 9.192631770 GHz are now routine laboratory equipment and are c=
> ommercially readily available.
>
> These factors now provide a solid foundation to prepare for the redefinitio=
> n of SI second based on the optical frequency standard. The exact approach =
> is currently under discussion and it may be selecting one atomic candidate =
> or building an ensemble. The specific requirements and the conditions for t=
> he redefinition to take place are also being finalized.
>
> The Consultative Committee for Time and Frequency (CCTF) has started prelim=
> inary work on this subject, to investigate possible scenarios and their pos=
> sible impact. It is within this framework that we contact you an expert in =
> the field of Telecommunications, in order to make sure that the needs and w=
> ishes of your community are integrated into the general debate that will ta=
> ke place and may, eventually, lead to the redefinition of the second.
>
> With the new definition, the frequency measurement accuracy will surpass th=
> at of Caesium-based timescale by at least one order of magnitude and will p=
> rovide an adequate tool for current and future research into fundamental ph=
> ysics as well as technology exploitation.
> The redefinition is not expected to affect any of the existing commercial f=
> requency standard uncertainties such as those of caesium beam clocks or hyd=
> rogen masers, because their uncertainties are generally orders of magnitude=
>  higher than the expected accuracy of the new definition. Same is true for =
> caesium fountains. The computation and dissemination of UTC will also not c=
> hange, but UTC will become more stable and accurate based on the improved o=
> ptical realizations of the SI second.
>
> We would like to ask your expert opinion on whether the redefinition may ha=
> ve any impact be it negative or positive on your field of study and operati=
> on. The issues we would like you to consider are not just scientific and te=
> chnological, but also regulatory and legislative. Your answers will be care=
> fully examined and taken into account by CCTF in their analysis of Time and=
>  Frequency metrology current and future needs and SI second and UTC evoluti=
> on.
>
>
> You can find the survey at https://www.surveymonkey.com/r/CCTF_Survey_2020 =
> and in the attached letter from CCTF president No=EBl Dimarcq you will find=
>  additional information on other activities at CCTF for your reference.
>
>
> Best regards,
> The CCTF Task Force on the redefinition of the second, subgroup A
>
> Co-chairs:
> Marina Gertsvolf (marina.gertsvolf at nrc-cnrc.gc.ca<mailto:marina.gertsvolf at n=
> rc-cnrc.gc.ca>)
> Gaetano Mileti (gaetano.mileti at unine.ch<mailto:gaetano.mileti at unine.ch>)
>
> Secretary:
> Frederic Meynadier(frederic.meynadier at bipm.org<mailto:frederic.meynadier at bi=
> pm.org>)
>
>
>