Subject: solution for week 05016 / SPOT2 - January 21, 2005 ?
From: Pascal Willis <[email-masked]>
To: IDS_Analysis_Forum <[email-masked]>
Date: Thu, 10 Mar 2005 10:29:01 -0800

Dear colleagues,

I am having some problems computing the DORIS data for January 21, 2005

Do other groups see similar problems for POD or for positioning results ?

Any hints about what could be the cause ?

The only thing that I was able to detect is a small increase in the 
SPOT2 residuals for this specific day and a large outlier value for 
polar motion (XP) for the multi-satellite satellite (see below). I 
tried different processing strategies but I could not get rid of the 
problem.

The table below provides the polar motion differences between the 
DORIS/IGN-JPL solution and the GPS/JPL solution. Typical differences 
have a 0.6 to 1.5 mas RMS so the -20.89 mas value for January 21, 
2005 is quite a large outlier.

DATE           XP(mas)   YP(mas)
---------------------------------
16-JAN-2005     -0.79     -1.33
17-JAN-2005      6.65      1.64
18-JAN-2005     -2.98     -1.68
19-JAN-2005      3.74      0.04
20-JAN-2005     -0.56     -0.90
21-JAN-2005    -20.89     -8.74
22-JAN-2005      0.95     -0.78

The DORIS coordinates derived from the multi-satellite solution for 
this week are also slightly degraded compared to typical weekly 
solutions but not too much.

You can also see on the following plot that the DORIS/EOP value for 
this specific day differ quite a lot from the GPS/JPL solution :

You can also see that the formal error are not much bigger for this 
specific day so it is not related with the amount of DORIS data 
available but more with a systematic error in the processing.

Looking forward hearing some feed-back from other DORIS Analysis groups

Thanks in advance for your help
Pascal

NB: the next 2 weeks (without ENVISAT data presently) do not seem to 
be affected at all by this problem. It is really specific to this 
specific day (21-JAN-2005).
-- 
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]