[time-nuts] a link to a explanation of Rb vs Cs?

[Magnus Danielson]

Hi,

On 04/12/2017 01:17 PM, Bob kb8tq wrote:
> Hi
>
> If you take a look at the standard weekly publications, the GPS system runs on Rb’s.
> There is always one sat that has a Cs turned on. That’s been true as long as they
> have been running the system. The simple answer for that choice is that the Rb’s
> are easier to predict (better short term to medium term performance).
>
> The Cs standards were originally on board to allow operation in the event that the ground control
> system was unable to upload to the constellation. There also was concern in the 80’s
> about the reliability of the Rb’s. The configuration has stayed the same, despite the
> Rb’s being the main standard used.
>
> Number of standards on board in the block IIF sats was 2 Rb’s and 2 Cs’s. That is a
> petty typical “redundant” approach.

For the block IIR they new cesium failed to get space-qualification, so 
those birds only fly rubidium.

Cheers,
Magnus