Subject: [ids.analysis.forum] GFZ SLCCI precise orbits of altimetry satellites ERS-1, ERS-2 and Envisat in ITRF2008
From: Sergei Rudenko <[email-masked]>
To: "[email-masked]" <[email-masked]>
Cc: "[email-masked]" <[email-masked]>, Pascal Willis <[email-masked]>, Carey Noll <[email-masked]>, "Frank G. Lemoine" <[email-masked]>, Bruno Garayt <[email-masked]>, Pascale Ferrage <[email-masked]>, John Ries <[email-masked]>, Laurent Soudarin <[email-masked]>, Chopo Ma <[email-masked]>,Tilo Schöne <[email-masked]>, Sergei Rudenko <[email-masked]>
Date: Fri, 25 May 2012 18:00:38 +0200

Dear colleagues,

I would like to inform you that new precise orbits of altimetry satellites
ERS-1 (August 1, 1991 - July 5, 1996), ERS-2 (May 16, 1995 - February 
27, 2006)
and Envisat (April 12, 2002 - January 3, 2011) were derived at the time 
spans given
at Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences
within the Sea Level project of the European Space Agency (ESA)
Climate Change Initiative using "Earth Parameter and Orbit System -
Orbit Computation (EPOS-OC)" software and the Altimeter Database
and processing System (ADS, http://adsc.gfz-potsdam.de/ads/) developed 
at GFZ.
The orbits were computed in the same (ITRF2008) terrestrial reference frame
for all satellites using common, most precise models and standards 
available
and described below.

The ERS-1 orbit is computed using satellite laser ranging (SLR) and 
altimeter
crossover data, while the ERS-2 orbit is derived using additionally
Precise Range And Range-rate Equipment (PRARE) measurements. The Envisat 
orbit
is based on Doppler Orbitography and Radiopositioning Integrated by 
Satellite
(DORIS) and SLR observations.

The orbit files are available in the Extended Standard Product 3 Orbit 
Format
(SP3-c, ftp://igscb.jpl.nasa.gov/igscb/data/format/sp3c.txt) via ftp at

ftp://slcci:[email-masked]/Data/WP2200/GFZ_SLCCI_ER1_V2/  for 
ERS-1 orbit,
ftp://slcci:[email-masked]/Data/WP2200/GFZ_SLCCI_ER2_V2/  for 
ERS-2 orbit,
ftp://slcci:[email-masked]/Data/WP2200/GFZ_SLCCI_ENV/     for 
Envisat orbit,

Files are gzip-compressed. File names are given as sate_YYYYMMDD_SP3C.gz,
where "sate" is the abbreviation (ERS1, ERS2, ENVI) of the satellite name,
YYYY stands for 4-digit year, MM stands for month and DD stands for day
of the beginning of the file.

To reference these orbits in publications please use (for the moment)
the following citation:

Rudenko, S., Schoene, T., Esselborn, S. and Storr, H.
Computation and evaluation of new consistent orbits
of Envisat, ERS-1 and ERS-2 in the ITRF2008 reference frame,
Geophysical Research Abstracts, Vol. 14, EGU2012-5894-1, 2012.

The list of the main models used to compute these orbits follows.

Terrestrial Reference Frame             ITRF2008 (Altamimi et al., 2011),
                                         SLRF2008 (Pavlis, 2009) and 
DPOD2008
                                         (Willis, 2011) are used for 
stations
                                         missing in ITRF2008
Polar motion and UT1                    IERS EOP 08 C04 (IAU2000A) series
                                         with IERS daily and sub-daily 
corrections
Precession and Nutation model           IERS Conventions (2010)
Gravity field (static)                  EIGEN-GL04S-ANNUAL (Lemoine et 
al., 2007)
Gravity field (time varying)            Annual and semi-annual variation
                                         up to degree and order 50 from
                                         EIGEN-GL04S-ANNUAL gravity 
field model
                                         (Lemoine et al., 2007)
Solid Earth tides                       IERS Conventions (2010)
Pole tide                               IERS Conventions (2010)
Ocean tides                             EOT10A (Savcenko and Bosch, 
2010), all
                                         constituents up to degree and 
order 50
Atmospheric tides                       Biancale and Bode (2006)
Atmospheric gravity                     ECMWF 6-hourly fields up to degree
                                         and order 50 (Flechtner,  2007)
Third bodies                            Sun, Moon, Mercury, Venus, Mars, 
Jupiter,
                                         Saturn, Uranus, Neptune and Pluto
                                         (DE-421) (Folkner et al., 2009)

More details will be given in a peer-reviewed paper under preparation.

Use of data from the International Laser Ranging Service, the 
International DORIS
Service, the International Earth Rotation and Reference Systems Service is
acknowledged. Radar Altimetry data were provided by ESA for ERS-1, ERS-2 
and
Envisat. I would like to acknowledge the contributions of the colleagues
Tilo Schoene, Helmut Storr and Jean-Claude Raimondo, as well as useful 
discussions
with the colleagues of GFZ Section 1.2 "Geomonitoring and Gravity Field".
This research was performed within the ESA Climate Change Initiative
Sea Level project that is gratefully acknowledged.

In case of questions please contact Sergei Rudenko or Tilo Schoene:
[email-masked]
[email-masked]

With kind regards,
Sergei Rudenko
(On behalf of the co-authors)

---
Dr. Sergei Rudenko
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Department 1: Geodesy and Remote Sensing
Section 1.2: Global Geomonitoring and Gravity Field
Telegrafenberg
D-14473 Potsdam
Germany

E-mail: [email-masked]
Phone:  +49-8153-281578
Fax:    +49-8153-281735
http://www.gfz-potsdam.de/portal/-?$part=GFZ&$event=profile&username=rudenko