Subject: Jason DORIS version 2 data (From Nikita Zelensky)
From: "Frank G. Lemoine" <[email-masked]>
To: <[email-masked]>
Date: Thu, 05 Jul 2007 15:52:06 +0000

------ Forwarded Message
From: "Nikita Zelensky" <[email-masked]>
Date: Tue, 3 Jul 2007 17:53:55 -0400
To: "Frank G. Lemoine" <[email-masked]>, "jries"
<[email-masked]>, <[email-masked]>, "Cerri Luca"
<[email-masked]>, "Pascal Willis" <[email-masked]>
Cc: <[email-masked]>, <[email-masked]>
Subject: Jason DORIS version 2 data

Hi everyone,
 
Jason  DORIS data has been re-processed over cycles 1-195 for improving the
ionosphere correction and to include more data previously missing in version
1 due to the effect of the  SAA degradation. The reprocessed data is called
here version 2, and its performance in the SLR/DORIS ITRF2000 dynamic orbit
solutions is compared to using the previous version 1 data over cycles
1-190. DORIS data have been corrected for SAA using the Lemoine/Capdeville
2006 model.
 
The attached plots illustrate the following:
1)      version 2 provides about 20% more data over cycles 1-140, and from
cycle 140 about 5% more data.
2)      Version 2 residuals are about 3.3 % higher, which is expected with
the new ionosphere correction
3)      Version 2 time tag adheres much closer to SLR time, as indicated by
the estimated DORIS time biases.
4)      Independent crossover residuals indicate the orbit based on version
2 is slightly more accurate.
5)      Over cycles 1-90 there is a mean Z orbit drift of +1.71 mm/year
between SLR/DORIS version 2  version 1 orbits; over cycles 92-190 the mean
Z drift is near zero. When compared to independent SLR/Crossover orbits, the
mean Z drift over cycles 1-90 for version 2 is 2.22 mm/year, significantly
higher than the +1.44 mm/year seen between the ITRF2005  ITRF2000 SLR/DORIS
orbits.
 
Although the SLR/DORIS version 2 orbits are slightly more accurate per
cycle, the apparent increase in the Mean Z trend over cycles 1-90 is of
concern. I¹m wondering if anyone else has noticed an increased mean Z trend
using the version 2 data?
 
bye,
Nikita

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