Date: Thu, 14 Nov 2002 10:18:49 -0800
From: Pascal Willis <Pascal.R.Willis@jpl.nasa.gov>
To: Jean-Paul Berthias <jean-paul.berthias@cnes.fr>
Cc: "John C. Ries" <ries@csr.utexas.edu>,
    Bruce J Haines <bjh@cobra.jpl.nasa.gov>,
    Yoaz Bar-Sever <Yoaz.Bar-Sever@jpl.nasa.gov>,
    nzelensk@geodesy.gsfc.nasa.gov, sluthcke@xyz.gsfc.nasa.gov,
    krchoi@csr.utexas.edu, Martine Feissel <feissel@ensg.ign.fr>
Subject: JASON phase center estimation using DORIS + new preprocessing issue

Hi Jean-Paul,

I have reprocessed the first 20 cycles of JASON looking for a 
possible phase center offset in the radial component.

I am presently getting some very strange results: large value (12 cm) 
with a nice 120-day period and a possible drift only at the beginning 
of the data (until day 50).

Was there a change in the preprocessing strategy around cycle 4?

On the other hand, it is not clear that the difference between the 
"yaw fixed mode" and the "sinusoidal mode" is visible in these 
results (as shown in GPS results by other contributors).

Finally, what seems to be more worrying is that when I use the new 
preprocessed data (cycle 18 and 20 at AVISO) instead of the regular 
DORIS data at CDDIS, I get the same results but shifted by 2.6 cm 
(the total estimated value getting closer to 0).

I will continue this study but estimating my own phase center 
correction, either using the attitude file or the quaternions when 
available. But I don't think it is going to change those results.

Best regards
Pascal

NB: The R axis in my computations is pointing in direction of the 
Earth, so the sign is coherent with the GPS results (we all try to 
put the phase center much higher in altitude).