[time-nuts] Spacecraft Timekeeping

jimlux jimlux at earthlink.net
Wed Mar 9 14:14:07 UTC 2011


On 3/8/11 9:08 PM, Kevin Watson wrote:
> Hi All. Thanks for responding. There are quite a few GPS receivers that
> will work outside of the usual commercial-grade GPS limitations, but I'm
> not too sure I need such a receiver. As my application is to just
> accuratly time-tag messages for a data recorder, my thinking is to allow
> a ruggedized GPSDO to stabilize on the pad before launch, and then just
> before launch force the GPSDO into holdover mode and act as the PTP
> grandmaster for the onboard computers until we reach orbit. Once on
> orbit I have other means to synchronize the PTP grandmaster.

I'd start by not worrying about discipline.. look up companies like 
Wenzel or Vectron or Q-tech and find an oscillator that is "good enough" 
to hold your timing performance over the environment you need.

That oscillator and some logic to make a suitable clock would probably 
do you.

You probably don't even have a particularly wide range of temperatures 
during the flight (although you probably do have a wide test range, to 
make sure it works)






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