Subject: [ids.analysis.forum] Sensitivity of GRACE vs LAgeos for deg 2 terms (forwarded)
From: "Lemoine, Frank G. (GSFC-6980)" <[email-masked]>
To: "[email-masked]" <[email-masked]>
Date: Tue, 8 Feb 2011 15:25:42 -0600

Dear IDS Analysis Forum.

I forward the following email on the same thread as earlier
today.

F. Lemoine
**************************************************************
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________________________________________
De : John C. Ries [[email-masked]]
Date d'envoi : mardi 8 février 2011 15:18
À : E Schrama; Lemoine Jean-Michel
Objet : Re: RE : Long term trends in the gravity field

At 12:46 PM +0100 2/8/11, E Schrama wrote:
>Dear all,
>
>This is a most interesting discussion. Is a GRACE+Lageos solution
>for C21/S21 not the same as saying that you have a Lageos only
>solution for these terms? Is GRACE capable of observing these degree
>2 order 1 terms at all?
>
>Ernst
>

Hi Ernst,

My impression is that SLR and GRACE both do well for C21/S21. GRACE
only seems to have problems with C20, not the other degree-2 terms.
We've done a number of SLR solutions for C21/S21. We've used 5
satellites to determine a 3x3 and 5x5 gravity field (Minkang Cheng
did these) and I've done individual and combined LAGEOS-1 and
LAGEOS-2 solutions. C21/S21 are so well observed now that even a
single LAGEOS satellite provides credible results. I found that
individually, LAGEOS-1 and LAGEOS-2 gave identical results for S21,
and similar results for C21 except for a difference in slope (this
was in my 2009 Fall AGU poster).

Best regards,
John

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