On Sun 2019-01-20T06:22:58-0800 Tom Van Baak hath writ: > I'm curious how your findings compare with this random link I ran across [1]: > > https://koka-lang.github.io/koka/doc/std_time_utc.html > > See especially section "1.3. UTC before 1961"
It was 1959 July or August (recollections differ) when H.M. Smith of the Greenwich time department had some UK and US folks in his living room for tea. The UK and US were already independently regulating their time broadcasts using cesium, with USNO and US NBS using different strategies. That tea-time was the impetus for coordination, and it was following a recommendation for frequency stability from the 1959 CCIR meeting in Los Angeles which basically said that VLF transmitters had to be calibrated using cesium. USNO Time Service Notice no 9 (1960-12-21) says that US and UK started coordinating in 1959, and the author of that was at the tea-time meeting. Without transcribing and plotting the BIH records it is hard to say when exactly the US and UK coordination started, but one memoire says the official US/UK agreement was forged during 1960. It is clear that during 1960 the URSI meeting recommended that every transmitter should coordinate using cesium, and that BIH should have the job of choosing the coordination starting with 1961. Really there can be nothing called UTC before 1960. Everything before then in that github project applies to one particular source of broadcast time signals, or is a wishful reconstruction based on no actual source at all. And as I noted recently, everything in that github between 1970-01-01 and 1972-01-01 does not apply to anyone in Europe who was getting time stamps using DCF77 after they decided it was illegal to broadcast rubber-second old UTC. > and also the link: > https://books.google.com/books?id=uJ4JhGJANb4C&lpg=PA87&vq=wwv&pg=PA87#v=onepage&q=wwv&f=false USNO Time Service Notice no 8 (1959-11-18) disagrees and says that for 1959 the USNO cesium offset was -170e-10 and for 1960 the offset was -150e-10. This is not the only place where contemporary documents differ from McCarthy and Seidelmann and their books. All of the USNO broadcast peculiarities and changes were indicated in the circulars issues by the time division. A complete collection of the USNO time division circulars may not exist because most recipients did not save them, and in any case the acid of the paper they used has turned most of them to dust. Usually the circulars served as announcements in advance so that navigators would not be surprised by changes, and usually the circulars give the rationale for the changes. Time signal broadcasts have always been extrapolations of time based on the local clocks at the station and algorithms for that extrapolation which have particular strategies. According to Bulletin Horaire WWV was using a different strategy than USNO until the era when coordination began. Before coordination most observatories kept an internal astronomical time scale and noted the difference between that and the radio broadcast time signals that they controlled. Bulletin Horaire shows how the UK broadcasts were providing Provisional Uniform Time regulated using quartz by the early 1950s, and very clearly shows when the Greenwich observatory decided to change their official internal time from the direct astronomical observations to the readings from the quartz chronometers. In the very old Bulletin Horaire from around 1930 it is noted that WWV was particularly good for the purposes of geodesy. Up until the era of coordination the USNO broadcasts had a systematic difference from other broadcasts because USNO was for navigators. USNO broadcast time that was self-consistent with longitudes on the navigational charts, and those charts were based on an old value for the longitude of Washington. USNO Time Service Notice no 9 (1960-12-21) indicates that on 1961-01-01 they changed the time at the USNO observatories by 30 to 40 ms in order to fix the longstanding time offset between the USNO observatories and the global average notion of longitude. > Give it some thought. I don't have a quick answer and would > appreciate your instr. If you've ever worked with raw UTC(k) data, > present or historical, you know there's no one right time. So in the > late 1950's, making claims about Paris vs. Washington / Gaithersburg > / Boulder might not be as clear as you hope. > In my home museum the earliest cesium standard is 9,192,631,840 Hz > not 9,192,631,770 [2]. I've learned that re-interpreting > international time & frequency history is not always simple. Almost every writeup of the history of time ignores details which are evident in the issues of Bulletin Horaire and the bulletins issued by the various national time service bureaus. The dirty laundry of timing for all the received radio signals is there in Bulletin Horaire. There are hundreds of thousands of turgid numbers giving the timing of exactly when each signal was received, and then followup publications indicating how wrong each station clock was. Some of the discussions in Bulletin Horaire make references to changes made by observatories and transmitters, but most of the particular decisions and rationale made by the folks doing the broadcasting are lost to history. Transcribing and plotting Bulletin Horaire would allow for the reconstruction of a lot of when changes happened and good guesses at what the underlying strategy was. And, alas, reading through Bulletin Horaire also calls into question some content in the historical writeups. I will admit that it borders on insanity to actually read through Bulletin Horaire and pick out details. I suppose Guinot must have agreed, and I think that is why the precise records of earth rotation that the IERS inherited from the BIH begin at the transition from FK3 to FK4 on 1962-01-01. -- Steve Allen <[email protected]> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m _______________________________________________ LEAPSECS mailing list [email protected] https://pairlist6.pair.net/mailman/listinfo/leapsecs
