[time-nuts] Using GPS for space-based instrument

Lux, James P james.p.lux at jpl.nasa.gov
Mon Nov 10 18:04:45 EST 2008


I'd suggest giving the GPS folks at JPL a call.  They've probably looked into all the issues you're interested in, and can make suitable suggestions where to go for answers (subject to the usual export control restrictions).Jim Zumberge is the Section Manager of the Tracking Systems and Applications Section (which does the GPS stuff). Try James.F.Zumberge at jpl.nasa.gov

http://iono.jpl.nasa.gov/ might give you a start.
http://www.gdgps.net/


There have been proposals, for instance, to receive GPS signals at the moon, based, as another poster mentioned, on the GPS signal from a satellite that is not occulted by the Earth.  The GPS satellites are fairly high up and the overall beam is fairly broad, so if you're almost in line with the Earth and the satellite, you might get decent signal strengths.

James Lux, P.E.
Task Manager, SOMD Software Defined Radios
Flight Communications Systems Section
Jet Propulsion Laboratory
4800 Oak Grove Drive, Mail Stop 161-213
Pasadena, CA, 91109
+1(818)354-2075 phone
+1(818)393-6875 fax

> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Strauss, Karl F
> Sent: Monday, November 10, 2008 2:28 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] Using GPS for space-based instrument
>
> I've been tasked (or was it I was volunteered?) to do some
> basic design & definition work on an ultra-stable master
> frequency system for a proposed instrument that is currently
> planned to be in an Earth-trailing orbit.   Given the first
> order accuracy requirement of 1 part in 1E-10, my first
> thought was to grab the GPS timing signal.
>
> Sorry for the newbie questions here:    a) Do all satellites
> in the constellation broadcast a signal into space  (as
> opposed to, say,  bouncing off some ionospheric boundary
> layer); and b) is there some website/technical paper
> describing expected signal strength for these space-radiated signals?
>
> Again, apologies to all for the Newbie Q's.  Hopefully this
> will be a fun topic of discussion
>
> Thanks
>
> Karl
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