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.gertsv...@nrc-cnrc.gc.ca> Date: Tue, 12 Jan 2021 17:14:24 +0000 To: "Gertsvolf, Marina" <marina.gertsv...@nrc-cnrc.gc.ca> Cc: MILETI Gaetano <gaetano.mil...@unine.ch>, Frédéric Meynadier <frederic.meynad...@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.gertsv...@nrc-cnrc.gc.ca<mailto:marina.gertsvolf@n= rc-cnrc.gc.ca>) Gaetano Mileti (gaetano.mil...@unine.ch<mailto:gaetano.mil...@unine.ch>) Secretary: Frederic Meynadier(frederic.meynad...@bipm.org<mailto:frederic.meynadier@bi= pm.org>) -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.