[time-nuts] Re: gravity fields affect time keeping?

[Lux, Jim]

On 1/31/23 10:38 PM, Hal Murray via time-nuts wrote:
>>> Anybody studied the influence of the Sun's gravity on clocks in GNSS
> satellites?
>
> Steve Allen said:
>> This particular effect is small, and I am not sure that the GPS clocks are
>> stable enough to reveal it.
> I was at an astronomy talk last night.  One of the interesting comments by the
> speaker is that the JWST is wonderfully stable.  It is constantly cold as
> compared to the Hubble that goes into the Earth's shadow every hour with the
> associated thermal swing.
>
> I assume the guys in the GPS control room have lots of stability data.  Are
> there times when a satellite will stay in the sun for several orbits?  Any
> published data?

Here:
https://gssc.esa.int/navipedia/index.php/Satellite_Eclipses

they say every satellite has 2 eclipse seasons/year lasting 7 weeks.

And interestingly, the satellites lose attitude control during that 
time, and shouldn't be used during that time.  I guess I never thought 
about this, I would have thought they were 3 axis stabilized with a star 
tracker or similar, so they could Nadir point all the time.


>
> Picking an orbit to maximize the sun's gravity delta will go into the shade.
>
>