[time-nuts] GPS disciplined Mars clock

Bob Camp kb8tq at n1k.org
Sat Jul 9 19:56:11 EDT 2016


Hi

Obviously time for a Kickstarter campaign to put a set of observatories on Mars ….

Bob

> On Jul 9, 2016, at 5:59 PM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 7/9/16 1:40 PM, Joe Fitzgerald wrote:
>> 
>> 
>> On 7/9/2016 3:00 PM, jimlux wrote:
>>> 
>>> TAI my friend, TAI...
>>> 
>> Hmm,  gravitational time dilation it might complicate things ...  I
>> suppose it depends on whether your Mars clock is on the surface of Mars,
>> Earth or somewhere else.
>> 
>> 
>> On 7/9/2016 3:34 PM, Hal Murray wrote:
>>> 
>>> How good is the data on the rotation rate for Mars?  Is it good enough so
>>> that they would need leap seconds?
>>> 
>>> 
>> 
>> Without an ocean or significant atmosphere I bet the rotation rate would
>> be more predictable than Earth - once good measurements were made.  The
>> dearth of observatories on Mars suggests the current error bars on
>> current rate estimates pretty wide.
> 
> 
> I'd guess the rate estimate is quite good.  Wikipedia says
> 88,775.24409 seconds/sol
> 
> We can do very good ranging to MER and MSL.  Phoenix didn't carry a direct to earth transponder.
> 
> We can also do ranging from rovers to MRO, and then from MRO to Earth. I don't know how much ranging we've done at UHF, though.  The radio wasn't really designed for it, so the math gets a bit complex, and I'm not sure you can back out all the higher order terms.  The UHF radio on MRO does have a USO driving it, so it's timing performance should be quite good in "open loop record" mode.
> 
> The uncertainty in the MRO range & range rate is probably less than for the rovers, because the SNR is much better (big multi-meter antenna on MRO helps a lot).
> 
> 
>> 
>> Fun to think about that's for sure.
>> 
>> -Joe
>> 
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