[LEAPSECS] Metrologia on time
Tom Van Baak
tvb at LeapSecond.com
Thu Aug 4 23:31:03 EDT 2011
> Hi Tom,
>> I'd guess that any person or any system that needs DUT1 has long since switched over to telephone, fax, or the
>> internet to obtain this information.
> "I'd guess" is not an inventory.
OK, you're welcome to poll your astronomical sources then and
see how many still get DUT1 from broadcast services like WWV.
I'm not saying it's zero.
>> Few tears were shed when GOES went away. Or Loran-C. Or CHU. Or pop-corn. Or when analog TV time/frequency went off
>> the air. It's time for DUT1 at 1 baud to make its exit as well.
> "The tire didn't come off with the first four lug nuts, so why should it with number five?"
Look carefully at your tire. Faster than you can remove old rusty
lug nuts shiny new ones show up. They are more accurate than
the old ones.
Time services come and go. Western Union & USNO had a nice
telegraph system decades ago. I can send you photos. Loran-C
was useful, but even it got phased out. CHU (Canada) changed
frequency. HBG (Switzerland) is going away this year. WWVB
changed its modulation format. Half of JJY got too hot for a few
months. The GOES timecode is gone. GPS has/will have new
bands and ICD. CDMA is still a great source of atomic time (while
it's still around). Omega is long gone. But for every one of these
old systems there is new technology or new protocols. There's
really no shortage of precise time these days.
> I deployed and operated an automated feed of GOES data from the 9600 baud UNIDATA stream in the 1990's (as well as a
> more direct whole-disk mbone feed from the AF via Maui). This was just before they transitioned to the 3-axis
> stabilized spacecraft. There was a period of time when the U.S. fleet was down to one GOES and they parked it due
> south of Arizona, very handy for astronomers in the Southwest (though our risk of hurricanes is quite low). Reports
> of GOES's demise are greatly exaggerated:
It's the NIST timecode part of GOES I was talking about.
> On the other hand, there is a nice retrospective of the GOES time code service:
I followed the demise of GOES timecode to the end. Tried to log
the last timecode byte it sent. It was another case of an expensive
service and almost no users. Sad to see it go, partly because I
have a boatload of old GOES antennas and timing receivers in
the lab. But the range, reception, and performance was horrible
compared with more modern systems like NTP or GPS.
Interestingly, the GOES timecode was turned off more than once.
Users were given plenty of time (years?) to convert to other time
sources (e.g., cellular or GPS). As I recall when final day came
a phone call or two came in and NIST restarted it a few days later
for the remaining user(s). This happened more than once, making
it hard to "capture the last bit". Eventually after a couple of months
it went silent for good.
> Is the notion described here safe? How would one test such an assertion? Is the operational system the correct
Good question. The transition out of GOES provides an example.
I think NIST handled that very well. There's a lesson to be learned
with how power companies are handling the TEC proposal too.
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