[time-nuts] Project GREAT - Galloping Galileo version

[Bob kb8tq]

Hi

You might be surprised by how well the CSAC does in orbit. There have been a lot of cases
over the years where a device has done much better once it is away from “poking fingers” 
like pressure and other semi-random stuff ….

Bob

> On Dec 8, 2018, at 1:49 PM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 12/8/18 10:12 AM, Peter Monta wrote:
>> If a little eccentricity makes for a good test of relativity, wouldn't a
>> lot of eccentricity be even better?  :-)
>> Does anyone know what clock facilities are on the Parker solar probe?
>> Atomic clock?  And a drag-free mode would have been great too, but I doubt
>> that was included.
> 
> Extremely unlikely.. I know one of the PIs for Parker, I'll ask him.
> If anything, they would fly a USO (a really good crystal in a temperature stabilized enclosure).
> 
> I'm flying an atomic clock (a CSAC), launching next week, but it will be in a circular orbit, and I'll bet the gravity variations are small enough that they are less than the uncertainty.
> 
> The other problem is that you need to *measure* that atomic clock against something. The best I can do with my CSAC is compare its 1pps against a Novatel OEM-6 single frequency GPS 1pps, and an onboard 100 MHz oscillator - none of them are outstanding by timenuts standards.
> 
> (CSAC is around 1E-12 at 1000-10000 seconds - see
> http://www.leapsecond.com/pages/csac/
> 
> It's about an order of magnitude worse than a PRS-10 Rb)
> 
> Tom, with his herd of clocks, can leave some at home and take some with him, and compare them upon return.
> 
> I would imagine that someone looks at the behavior of the atomic clocks on the GPS satellites in excruciating detail.  The signals from GPS are incredibly well studied, and have been recorded at carefully maintained ground sites for decades with high quality reference clocks.
> 
> 
> There are folks developing and flying a Deep Space Atomic Clock (DSAC), a trapped Hg-ion, which is substantially better.  Launch is currently March 2019 (on the Falcon Heavy) It's a bit of a beast: 17.5kg, 17.4 liters (a bit bigger than their original goal of 1kg, 1 liter, <grin>) and 44 watts.
> 
> It's supposedly going to be in the 1E-14 range at 1000 seconds, and 1E-15 at 100,000 seconds.
> 
> It will be in LEO, but maybe you can see the variation from the Moon and Sun?
> 
> 
> 
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