Subject: Re: proposed JASON campaign
From: Martine Feissel-Vernier <[email-masked]>
To: [email-masked]
Cc: Jean-Paul Berthias <[email-masked]>, [email-masked], [email-masked], [email-masked], Jean-Jacques Valette <[email-masked]>, Laurent Soudarin <[email-masked]>, Pascal Willis <[email-masked]>, [email-masked]
Date: Fri, 8 Nov 2002 15:14:19 +0100 (Paris, Madrid)

Dear colleague

I have a few short comments on your plan.

- Proposed statistics (2B, p.2). Statistics in the three directions would
  be more informative than 3D statistics (if I did not misunderstand your 
  wording).

- 2C, p. 2: you could use version numbers as part of the filenames.

- It seems to me that having a number of solutions obtained by three
  techniques allows you to go a little further in the comparison
  statistics. You could estimate the variances of the individual solutions
  (all techniques), and the covariances between solutions from the same
  technique, by the "three-corner hat technique", i.e. a least square
  inversion of equations of the type 

       "variance(A-B)=variance(A)+variance(B)+covariance(A,B)"

  where variance (A-B) is derived from the orbit differences analysis, and
  covariance(A,B) is assumed to be zero if solutions A and B are
  obtained by different techniques. The latter hypothesis may be not
  rigorously verified (common modelling error effetcs may exist), but
  that's life...

What do you expect to be the timetable of the project?

I am glad to see the progress in the JASON orbit comparison campaign. 
We view the consideration of DORIS in the game as extremely important. 
As you know, we would like to develop orbit comparisons in the framework
of the future IDS. We are sure to learn much from your analysis campaign.
 
With my best wishes.

Martine Feissel-Vernier
Analysis coordinator,
DORIS Pilot Experiment
-- 
  Martine Feissel-Vernier               Internet:     [email-masked]
  Observatoire de Paris and
  Institut Geographique National        Telephone:    33 (0) 1 64 15 32 83
  ENSG/LAREG     			Fax:          33 (0) 1 64 15 32 53
  8 Av. Blaise Pascal, Champs sur Marne
  77455 Marne la Vallee Cedex 2, France
--