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sci.geo.satellite-nav (Global Satellite Navigation) (sci.geo.satellite-nav) Discussion of global navigation satellite systems (GNSS). Topics include the technical aspects of GNSS operation, user experiences in the use of GNSS, information regarding GNSS products and discussion of GNSS policy (such as GPS selective availability).

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Latest on fixing PRN01 (SVN49)



 
 
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  #1  
Old June 20th 09, 02:45 AM posted to sci.geo.satellite-nav
HIPAR
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Posts: 95
Default Latest on fixing PRN01 (SVN49)

A report from the front lines:

http://sidt.gpsworld.com/gpssidt/Lat...ategoryId=1385
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  #2  
Old June 20th 09, 03:50 AM posted to sci.geo.satellite-nav
Wolfgang S. Rupprecht[_4_]
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Default Latest on fixing PRN01 (SVN49)


HIPAR writes:
http://sidt.gpsworld.com/gpssidt/Lat...ategoryId=1385


That is a great explanation. A big thank-you to the folks that made it
happen!

So it sounds like the theory that it was a connector is starting to look
darn good. The one question in my mind is, if they do have to move the
description of the phase center by adjusting the navigation message (I
assume the SV's orbital ephemeris), wouldn't that be a good thing in
terms of keeping the exact position of the SV a bit secret? (Or put a
different way, isn't a miss by 150 meters by a hostile object as good as
a miss by a mile?) And no, I'm not really expecting *that* to be
answered publicly.

-wolfgang
--
Wolfgang S. Rupprecht Android 1.5 (Cupcake) and Fedora-11
  #3  
Old June 20th 09, 02:49 PM posted to sci.geo.satellite-nav
HIPAR
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Posts: 95
Default Latest on fixing PRN01 (SVN49)

From an earlier topic:

On Jun 19, 9:45*pm, HIPAR wrote:
A report from the front lines:

http://sidt.gpsworld.com/gpssidt/Lat...-Story-What-We...


On Jun 19, 7:10 pm, Mike Jr wrote:

Obviously nobody can go 'up there' and disconnect the L5 transmitter
from the antenna farm so yes, the root problem cannot be fixed.


My guess is the 'work around' will adjust the navigation message
parameters that estimate the ionospheric time delay. There's a user
equipment equation that accepts these parameters and the satellite
elevation and azimuth as variables.


--- CHAS


Chas,
I am rusty on my end user nav algorithms but if I remember correctly,
ionospheric delay is calculated every ten days or so and applies to
the entire constellation. It is useless for correcting a single
bird. A more useful approach may be to look at turning off coarse
acquisition on the L1 signal. Makes IIR-20(M) useless to the low end
users who rely on it for, well, coarse acquisition. But it will not
hurt them either.

--Mike Jr


Your correct, they aren't going to adjust the ionospheric
parameters.

The Air Force no longer includes the PRN01 satellite error in its
daily performance report. I occasionally checked it during the last
two weeks (or so) before they stopped reporting it. PRN01 was well
below a meter so their 'tuning' appears to be working. As a
navigator, I'd be happy with those results but those who rely on GPS
for precision survey should be skeptical until the testing is
complete.

My experience with 'work arounds' has been they restore basic
functionality but often leave or introduce higher order problems ..
like the initial attempts to computer correct the images from Hubble
Space Telescope.

--- CHAS



 




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