Subject: [ids.analysis.forum] Error in CoM correction field of Cryosat-2 DORIS 2.2 files
From: "Cerri Luca" <[email-masked]>
To: <[email-masked]>
Cc: "Couhert Alexandre" <[email-masked]>, "Houry Sabine" <[email-masked]>, "Flavien Mercier" <[email-masked]>, "E Schrama" <[email-masked]>, <[email-masked]>
Date: Mon, 11 Apr 2011 17:49:04 +0200

Dear all, 

We have recently discovered a bug in our processing of DORIS 2.2 
measurements files for the CRYOSAT-2 satellite. 
The bug concerns a wrong configuration file describing the phase 
center position of DORIS antenna. 
This error affects the CoM correction and the ionospheric correction 
fields in the DORIS measurement files between arc 031 and arc 048 . 
The correct file has been restored and measurement files frome arc 
049 onward will be correct. 

Wrong files will be replaced as soon as possible, within two weeks. 

The impact on the orbit is completely negligible, however the impact on
station 
positioning is not negligible. 
The error committed in the phase center position is 

2 GHz phase center : 
Correct value : 0.312 m 
Wrong Value   : 0.319 m
Error         : 0.007 m

400 MHz phase center:
Correct value : 0.158 m
Wrong value   : 0.155 m
Error         :-0.003 m

The impact on the ionospheric correction field is expected to be 
negligible : ~(7 mm + 3 mm)/(25-1) ~ 0.4 mm 
(25 is the square of doris frequency ratio) 

However the impact on the CoM correction field is in the order of 7 mm, 
and users of CoM correction field should see the impact in their scale
factor. 

Please, let me know if you spot any discontinuity in your Cryosat-2
series 
starting from arc 031, 

On behalf of the CNES POD Team, I apologize for the inconvenience that
this error
might have caused to your processing, and will give you as soon as
possible further 
updates. 

Best regards

Luca 

__________________________________
Luca CERRI
Centre National d'Etudes Spatiales
DCT\SB\OR
18, av Edouard Belin
31401  Toulouse Cedex 09 - FRANCE
tel.   +33 (0)5 61283549
fax    +33 (0)5 61281855
bpi    1323
email  [email-masked]

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