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.
-Kevin
----- Original Message -----
From: "ehydra" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Tuesday, March 08, 2011 3:02 PM
Subject: Re: [time-nuts] Spacecraft Timekeeping
There are is a list on a ballooner website with GPS devices working beyond
export rules.
- Henry
--
ehydra.dyndns.info
Magnus Danielson schrieb:
First thing to consider is that standard GPSes will not meet your needs,
since they have to obey the height and speed limits for export rules.
The side-effect is that doppler frequencies may be much higher and both
tracking and acquisition needs to include these more extremer doppler
frequencies.
Use of PTP within a rocket or spacecraft may or may not be a good thing.
NMEA + PPS may suffice and be less power-hungry. IRIG may also be an
option.
If timing and frequency needs strict correlation with ground, relativity
comes into play due to altitude alone shifts frequency.
Cheers,
Magnus
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