Date: Mon, 28 Jun 2004 19:11:19 +0000 (GMT)
From: flemoine@bowie.gsfc.nasa.gov
Reply-To: Frank.Lemoine@gsfc.nasa.gov
To: Jean-Jacques Valette <valette@cls.fr>, feissel@ensg.ign.fr
Cc: flemoine@bowie.gsfc.nasa.gov, ramesh.govind@ga.gov.au,
    john.dawson@ga.gov.au
Subject: Re: attitude for SPOT-2 and Envisat

Dear Jean-Jacques and Martine,

Greetings from the Northern Hemisphere.

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. Now Topex follows a *geodetic* profile
(ie +Z, nadir, is geodetic). My guess is that ERS/ENVISAT
must as well. If so what ellipsoid and what flattening
do they use in flying the spacecraft? Same question for
SPOT-2.

The rationale behind my question is the verify that we have
the correct pointing for these spacecraft in GEODYN.
This would affect the measurement offset correction that
we compute and might have a bearing on the problems which
we see on Envisat that I mentioned last week while still
in Canberra.

SPOT-2 modelling in GEODYN is definitely geocentric.
I'm still deciphering the ERS/ENvisat routine in
GEODYN.

Thanks

A+,
Frank