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Air Force Polls Receiver Makers for Solutions to Satellite Problems

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Sam Wormley

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Jun 30, 2009, 10:08:32 PM6/30/09
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Air Force Polls Receiver Makers for Solutions to Satellite Problems
http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=607645

Jun 30, 2009
GPS World

The U.S. Air Force GPS Wing seeks comments from receiver manufacturers regarding the
SVN-49 signal anomaly and the Air Force’s proposed solution. The Air Force has been
investigating the cause and effects of signal distortions, observed as an
elevation-dependent bias in ranging measurements, from the GPS IIR-20(M) spacecraft
launched on March 24, 2009 and not yet set operational. As recently as June 19, the GPS
Wing outlined solutions it planned to implement to compensate for the pseudorange errors,
but now it states that “it is not possible for the Air Force to evaluate the myriad of
civilian products and applications. Your help is urgently requested to […] evaluate […],
conduct tests […], and provide recommendations and advice to the Air Force.”

Worldwide GPS users are not affected by the signal distortion, since this satellite is
still in early-orbit checkout and has not been introduced into the operational constellation.

A presentation currently being made to GPS manufacturers includes a detailed technical
explanation of the problem, with copious charts and figures, preceded by the language:

See: http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=607645

claudegps

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Jul 2, 2009, 5:55:00 AM7/2/09
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On 1 Lug, 04:08, Sam Wormley <sworml...@mchsi.com> wrote:
> Air Force Polls Receiver Makers for Solutions to Satellite Problems
>    http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=607645
>
> Jun 30, 2009
> GPS World
>
> The U.S. Air Force GPS Wing seeks comments from receiver manufacturers regarding the
> SVN-49 signal anomaly and the Air Force’s proposed solution. The Air Force has been
> investigating the cause and effects of signal distortions, observed as an
> elevation-dependent bias in ranging measurements, from the GPS IIR-20(M) spacecraft
> launched on March 24, 2009 and not yet set operational. As recently as June 19, the GPS
> Wing outlined solutions it planned to implement to compensate for the pseudorange errors,
> but now it states that “it is not possible for the Air Force to evaluate the myriad of
> civilian products and applications. Your help is urgently requested to […] evaluate […],
> conduct tests […], and provide recommendations and advice to the Air Force.”

I wonder which problems may rise for Ephemeris Extension solutions.
The computation of client-based or server-based long term ephemeris
maybe affected by the fix of the problem.

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