[ntp:questions] National time standard differences

David J Taylor david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid
Wed Feb 10 09:05:34 UTC 2010

"David Woolley" <david at ex.djwhome.demon.invalid> wrote in message 
news:hksmaf$1cm$2 at news.eternal-september.org...
> David J Taylor wrote:
>> I remember the flying of caesium or other atomic clocks round the 
>> world, and that folks had to invoke relativistic corrections.  Were 
>> these better than microseconds as well?
> That's called Navstar (GPS) and GPS position solutions do have to 
> include a general relativity correction to the satellite clocks.

Not today's GPS, but some forty or more years ago:



"The highly accurate HP 5060A cesium-beam atomic clocks gain worldwide 
recognition as the "flying clocks" when they are flown from Palo Alto to 
Switzerland to compare time as maintained by the U.S. Naval Observatory in 
Washington, D.C. to time at the Swiss Observatory in Neuchatel. The atomic 
clock was designed to maintain accuracy for 3000 years with only one 
second of error. The cesium-beam standard becomes the standard for 
international time."

I had wondered what accuracy was obtained - i.e. how far was each nation 
out - and whether relativistic corrections had been needed for these 
"flying clock" tests.


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