[time-nuts] NIST

[Magnus Danielson]

Hi Hal,

On 08/31/2018 08:17 PM, Hal Murray wrote:
> 
> attila at kinali.ch said:
>> I have somewhere a paper (which i cannot find currently, sorry) that used a
>> dish trained at one of the EGNOS satellites and used it as the only source
>> for timing. IIRC the results were promising, but not spectacular. The problem
>> being that all the ionospheric and tropospheric ...
> 
> There is another problem in that area.  How accurately is the location of the 
> satellite known?  published?
> 
> Geo-sync satellites actually wander around their nominal positions.  How much 
> does that effect timing?  I've seen figure-8 pictures of the pattern, but I 
> don't remember any data on elevation changes.

The figure of 8 is just one of the artifacts of the elliptic orbit, and
it does cause distance changes and hence affect timing. Correct
ephimeris data is needed for good compensation. We do that for GPS
satellites too, which is part of the systems capability that the
receiver can do these compensations unaided with anything but the
signals from space segment.

Cheers,
Magnus