[time-nuts] GPS disciplined Mars clock
jimlux
jimlux at earthlink.net
Sat Jul 9 17:59:54 EDT 2016
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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