Subject: DORIS time biases and orbit differences & the SAA correction (forwarded from Nikita Zelensky)
From: "Frank G. Lemoine" <[email-masked]>
To: <[email-masked]>
Date: Fri, 09 Feb 2007 20:02:15 +0000

------ Forwarded Message
From: "Nikita Zelensky" <[email-masked]>
Date: Fri, 9 Feb 2007 14:47:45 -0500
To: "Cerri Luca" <[email-masked]>, "John C. Ries" <[email-masked]>,
"Frank G. Lemoine" <[email-masked]>
Cc: <[email-masked]>, "Mercier Flavien"
<[email-masked]>, "Houry Sabine" <[email-masked]>, "Perrachon
Pascal" <[email-masked]>,
<[email-masked]>, "Bruce J Haines" <[email-masked]>,
"Lemoine Jean-Michel" <[email-masked]>, <[email-masked]>,
<[email-masked]>, <[email-masked]>,
<[email-masked]>, "Nikita Zelensky" <[email-masked]>
Subject: RE: RE : ITRF2000 orbits and SAA model

Hi Luca,
 
The DORIS time-biases estimated in my SLR/DORIS orbit solutions support your
2) Long term frequency variations observation. The 1.4 microsecond
difference in the time biases following the oscillator change with cycle 91
corresponds to about a 1-cm mean along-track orbit difference between the
SAA corrected-uncorrected orbits. This is shown in the html plot below. The
corrected orbit time bias series change at cycles 30, 92, and 137.
 
Also I wanted to confirm your 3) SAA and network degradation observation.
The 2nd plot below shows the DORIS network degradation appears to augment,
or perhaps even drive, the mean Z difference trend between the SLR/DORIS SAA
corrected-uncorrected orbits up to cycle 91.
 
What do you think of John's point about the potential degradation to the
DORIS measurement caused by application of the frequency drift in the CNES
preprocessing which has not been corrected for the SAA effect? It may not be
easy to identify such degradation by simply looking at orbit differences.
 
bye,
Nikita

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