[IGSMAIL-6407] ESA/ESOC Analysis Changes

[Tim.Springer at esa.int]

Author: Tim Springer
Subject: ESA/ESOC Analysis Changes


Today, starting with our Ultra-Rapid solutions of 12 o'clock (day 151 of 
2011), we are switching all our IGS GNSS analysis to use the latest 
release of our NAPEOS software, version 3.6.  NAPEOS version 3.6 offers 
several enhanced processing features which are now (partly) used in our 
IGS analysis. 

NAPEOS version 3.6 and the corresponding changes for our IGS processing 
have been carefully tested but if you notice anything strange please let 
us know ASAP.


The main features now used in our IGS analysis are:
Estimation of tropospheric gradients. Linear (offset and drift) over 24 
hours for each station.
Increased time resolution of the tropospheric zenith delays. Changed from 
every 2 hours to every hour using piece wise linear estimates.
Eclipse Attitude model for the GLONASS satellites (according to: Dilssner, 
F, T. Springer, G. Gienger, J. Dow, The GLONASS-M satellite yaw-attitude 
model, Advances in Space Research, Volume 47, Issue 1, p 160-171)
Eclipse attitude model for GPS not activated as our testing has revealed 
that it gives significantly worse results compared to using the "nominal" 
attitude. Both the nominal rotation rates as well as the "averaged" 
rotation rates (published by Kouba) lead to degraded results compared to 
using the "nominal" attitude. The only proper solution seems to be the 
estimation of the actual yaw rate and in particular the direction of the 
post-eclipse rotation.

IMPORTANT: Please note that the usage of the eclipse attitude model for 
GLONASS is important for all PPP users of our GNSS clocks. You will have 
to make sure that your PPP software also applies the correct attitude for 
the GLONASS satellites during eclipse!

We would like to remind you that all our IGS products are true GNSS 
products, i.e., based on a fully combined analysis of the GPS and GLONASS 
observations including clocks for both systems. For those people who want 
to use our ESA GNSS products directly you will find them on our anonymous 
ftp:
ftp://dgn6.esoc.esa.int/products

Our products are of course also available from the normal IGS archives.

We hope the GNSS community can make good use of our products! If you have 
any comments and or questions please do not hesitate to contact us! If you 
use our products please make sure to properly acknowledge our efforts, 
see, e.g., ftp://dgn6.esoc.esa.int/products/000readme.esoc for an example 
of a proper reference.

Many greetings,
The ESOC IGS Team.

ps. An updated AC summary file will been send to the IGSCB shortly

---------------------
Tim Springer
Navigation Support Office, OPS-GN (nng.esoc.esa.de)
European Space Operations Centre
Robert Bosch Strasse 5
64293 Darmstadt
Germany
Tel: +49-6151-90-2029  Fax: +49-6151-90-3129
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.igs.org/pipermail/igsmail/attachments/20110531/503429ed/attachment.html>