Subject: Re: estimating DORIS pole motion rates? 1-week preliminary results
From: "Erricos C. Pavlis" <[email-masked]>(au lieu de Laurent Soudarin <[email-masked]>)
To: [email-masked]
Date: Thu, 23 Mar 2006 11:33:19 +0100

Frank,

The ILRS AWG tackled this issue more than two years ago and after
some deliberations, tests, and comparisons, we came to the conclusion
that Daniel is now finding out about DORIS and GPS rates. Without
taking the time to go too deep in the reasons why satellite
techniques do not get the rates correctly, I can assure you that you
will destroy your polar motion estimates if you allow the
simultaneous estimation of rates. This is different for LOD, where we
DO estimate LOD (the rate of UT1), rather than UT1 itself (which is
confounded with the errors in our definition of the node). Make sure
that when you estimate LOD, you do let UT1 loose, because if you do
not allow for that, Geodyn will use it as is in the tables, i.e. fix
it, thereby delivering LOD which is indistinguishable from that of
the tables!

ecp

On Mar 3, 2006, at 8:05 PM, Frank Lemoine wrote:

>Erricos and Ron
>  Did the ILRS come to any conclusion about the estimation of pole
>rates?
>  Is this done as a matter of routine?
>Frank-
>
>------ Forwarded Message
>From: "Daniel Gambis" <[email-masked]>
>Date: Fri, 17 Feb 2006 12:25:52 +0100
>To: "Pascal Willis" <[email-masked]>, "Laurent
>Soudarin" <[email-masked]>, "Frank Lemoine"
><[email-masked]>
>Cc: "Daniel Gambis" <[email-masked]>, "Richard Gross"
><[email-masked]>, "Zuheir Altamimi" <[email-masked]>,
>"Gilles Tavernier" <[email-masked]>, "Jean-Jacques
>Valette" <[email-masked]>, "Jayles Christian"
><[email-masked]>, "Ron Noomen"
><[email-masked]>, "Markus Rothacher" <rothache@gfz- potsdam.de>
>Subject: RE: estimating DORIS pole motion rates? 1-week preliminary
>results
>
>Dear colleagues
>
>The discussions we had last year within the GPS community showed
>that pole rates
>were not useful to improve EOPs. According to the analyses I made,
>for interpolation
>it is better to use a linear fit than using estimated pole rates.
>The situation is as you imagin
>not better with DORIS than with GPS.
>I attach thereafter 2 plots showing polar rates. You can see that
>DORIS pole rates are very noisy.
>In DORIS data processing, there is probably a significant
>correlation between estimates of pole
>and pole rates. I thus guess that estimating pole rates leads to a
>degradation of the pole components
>derived and I would recommend NOT to estimate anymore pole rates.
>
>Regards
>
>Daniel
>
>
>
>------ End of Forwarded Message
><pdorisx.ps>
><pdorisy.ps>

   +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   Dr. Erricos C. Pavlis                       Phone:    +1 (410)
455-5832
   Research Associate Professor         FAX:    +1 (410) 455-5868

   Joint Center for Earth Systems Technology, (JCET/UMBC)
   University of Maryland Baltimore County & NASA Goddard
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   U S A    21250           [email-masked]

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