Subject: preliminary comparisons of weekly DORIS solutions : LCA et IGN/JPL - weekly coordinates
From: Pascal Willis <[email-masked]>
To: IDS_Analysis_Forum <[email-masked]>
Date: Tue, 4 Jan 2005 10:06:32 -0800

(end of the previous email)

2.2) weekly coordinate residuals

Residuals mean values (weekly WRMS in mm)

(see also plots)

North (WRMS)	mean value (mm)		standard dev (mm)
LCA		16.5			6.7
IGN/JPL		19.8			6.2

On the plot, it seems that the LCA solutions are slightly better in 
north for the most recent solutions (after week 1260), approaching 
the 10 mm limit.

East (WRMS)	mean value (mm)		standard dev (mm)
LCA		21.1			6.3
IGN/JPL		19.4			4.7

Vertical (WRMS)	mean value (mm)		standard dev (mm)
LCA		23.5			4.0
IGN/JPL		20.1			4.2

On the plot, this time it seems that the IGN/JPL solutions are better 
in vertical for the most recent solutions (after week 1240), reaching 
15 mm.

3) Here are my preliminary conclusions (for discussion through the 
IDS Analysis Forum)

LCA and IGN/JPL weekly solutions seem to be almost at the same level 
of quality. The IGN/JPL solution seem to be better in vertical, 
probably due to the way we estimate the tropospheric delay (to be 
confirmed), while the LCA solutions seems to be better in North.

LCA has a scale factor toward ITRF2000 that is almost three times 
larger as IGN/JPL but of opposite sign. This will require some 
further investigation (see also Position Paper at the last IDS 
meeting from P. Willis and J.-F Cretaux at the following Web site 
http://lareg.ensg.ign.fr/IDS/events/prog_2004.html).

Changes in satellite constellation seem to be visible in the scale 
(but with opposite sign again). This may give us a hint to look for 
systematic errors in the DORIS scale.

Best regards
Pascal
-- 
Pascal Willis
Jet Propulsion Laboratory, MS 238-646     Ph : 1-818-393-4748
4800 Oak Grove Drive                      FAX: 1-818-393-4965
Pasadena CA 91109                         Em : [email-masked]