On 03/09/2011 03:15 PM, jimlux wrote:
On 3/8/11 11:05 PM, Magnus Danielson wrote:
On 03/09/2011 06:08 AM, 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.
Why carry the dead weight of something unusable in orbit.
Drop the receiver and antenna out of the equation and just provide a
timing signal on launch pad...
I'm going to guess that you want a GPS receiver on orbit for other
reasons (like to know where you are, if your IMU or star tracker dies)
Notice his last sentence...
I agree that there are many uses for a GPS onboard a sat... and if one
wants one it needs to handle the altitude, speed, different amount of
atmospheric shift, etc. etc. etc.
But if he only wants a GPS for launch pad synchronisation and then
reverts to other methods, it seems like dead weight to bring it all the
way up.
Cheers,
Magnus
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