Date: Fri, 09 Jul 2004 08:54:40 +0200
From: Jean-Jacques Valette <valette@cls.fr>
To: Frank.Lemoine@gsfc.nasa.gov
Cc: martine Feissel-Vernier <feissel@ensg.ign.fr>,
    gilles Tavernier <Gilles.Tavernier@cnes.fr>,
    sabine houry <sabine.houry@cnes.fr>,
    laurent Soudarin <Laurent.Soudarin@cls.fr>
Subject: Re: attitude for SPOT-2 and Envisat

Dear Frank,

>Would it be possible to obtain a clarification as
>to what attitude algorithm is used on SPOT-2 and
>ENVISAT?  The documentation for SPOT-2 which is online
>says geocentric.

For the Spot satellite series, it is geocentric. The constraint for the 
camera is less strong than the one for the altimeters.

>  Now Topex follows a *geodetic* profile
>(ie +Z, nadir, is geodetic). My guess is that ERS/ENVISAT
>must as well.

We think so. The official document we have is referenced in 
ftp://ftp.cls.fr/pub/ids/satellites/en1att.txt

>  If so what ellipsoid and what flattening
>do they use in flying the spacecraft? Same question for
>SPOT-2.

We're going to see how to get these information and also try to get 
quaternions for ENVISAT what would be the best.

Sorry for not being more precise.

JJacques and Sabine