# Our analysis strategy summary

## Method

We use GINS/DYNAMO software package for the satellites orbit determination and for the computation of 3.5-day NEQ residuals. Weekly station positions and daily ERP are solved together from 7-day NEQ systems.

## Models and standards

The table below gives the list of models and standards applied for the processing of the grgwd40 series for the contribution to the ITRF2014.

Data Analysis Summary of the DORIS weekly SINEX series used in the IDS combination for the realization of ITRF2014 |
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Sinex Series |
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Name | grgwd40 | |||||

Description form | TBD | |||||

Analysis Center |
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Name | CNES/CLS | |||||

Contact | H. Capdeville | |||||

Additionnal contacts | J.M. Lemoine, L. Soudarin | |||||

Software |
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Name and version | GINS v 13.2d1 | |||||

SINEX Method (NEQ or COV) | COV | |||||

Data weights (data reduction) | 0.3 mm/s | |||||

If COV, Station Constraint | 10 m | |||||

If COV, EOP Constraint | 15 m | |||||

Satellite |
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satellites included in weekly SINEX | start-end | |||||

SPOT2 | 03/01/1993 - 18/07/2009 | |||||

SPOT3 | 30/01/1994 - 16/11/1996 | |||||

SPOT4 | 03/05/1998 - 22/06/2012 | |||||

SPOT5 | 16/06/2002 - 31/12/2013 | |||||

TOPEX | 03/01/1993 - 30/10/2004 | |||||

ENVISAT | 21/07/2002 - 07/04/2012 | |||||

JASON1 | 31/10/2004 - 12/07/2008 | |||||

JASON2 | 13/07/2008 - 31/12/2013 | |||||

CRYOSAT2 | 20/06/2010 - 31/12/2013 | |||||

HY2A | 02/10/2011 - 31/12/2013 | |||||

SARAL | TBD | |||||

Arc cut |
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Arc lengths | 3.5 days nominally (minimum 1 day) | |||||

Handle of Manoeuvers | Break arc and Restart at 12am or 12pm; estimated from 2012/01/01 | |||||

Handle of Data gaps | Arcs truncated for large data gaps and Restarted. | |||||

Additional margins | 6hrs before and 6 hrs after for POD but not in SINEX | |||||

Reference System |
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Earth reference system | DPOD2008v12 | |||||

Celestial reference system | inertial J2000 | |||||

Polar motion and UT1 | IERS C04 08 | |||||

Background C21, S21 | ||||||

Pole model | ||||||

Precession/Nutation | IERS 2010 using NRO origin | |||||

Station coordinates | DPOD2008v12 | |||||

Displacement of reference points |
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Solid Earth tidal displacement | IERS 2010 Conventions | |||||

Ocean loading | FES 2012 | |||||

Tidal atmospheric loading | S1/S2 Ray & Ponte (2003) | |||||

Non tidal atmospheric loading | none | |||||

Solid pole tide displacement | IERS 2010 Conventions | |||||

Ocean pole tide displacement | none | |||||

Tidal Geocenter | ||||||

Satellite reference |
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Mass and center of gravity | initial values and time evolution from IDS files "sat"mass.txt | |||||

Attitude Model | nominal laws | |||||

Gravity |
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Gravity field (static) | EIGEN-6S2 | |||||

Gravity field (time varying) | EIGEN-6S2 up to degree 95 including time variable terms up to degree 50 (bias & drift per yr from 2002 to 2012, periodic 18.6, 1, 0.5yrs) | |||||

Solid Earth tides | IERS 2010 conventions | |||||

Ocean tides | FES 2012 (32 principal waves, + 60 admittance waves) up to degree 50 | |||||

Atmospheric gravity | 3hr ERA-interim / ECMWF up to degree 50 | |||||

Air Tides | ||||||

Non tidal oceanic gravity | TUGO R12 up to degree 50 TUGO R12 up to degree 50 | |||||

Atmospheric tides | none (considered through the ECMWF atmospheric data) | |||||

Earth pole tide | IERS 2010 conventions | |||||

Ocean pole tide | Desai 2002 up to degree 12 | |||||

Third bodies | Sun, Moon, Mars, Venus, Jupiter, Saturn, Uranus and Neptune ephemeris : DE421 (JPL) | |||||

Surface forces and empiricals |
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Radiation Pressure model | Thermo-optical coefficient from pre-launch box and wing model, with smoothed Earth shadow model; models from CNES document for all satellites except tuned macromodels for Spot-2, -3, -4, Jason2 | |||||

Radiation pressure scale coefficient | 1 coef/day but strongly constrainted (1. e-4) to: 1.03 for Topex; 1.07 for Spot-2; 1.07 for Spot-3; 1.16 for Spot-4; 1.05 for Spot-5; 1.05 for Envisat; 0.94 for Jason-1, 0.97 for Jason-2; 1.00 for Cryosat-2; 1.13 for HY-2A | |||||

Earth radiation | Albedo and IR pressure values interpolated from ECMWF 6hr grids | |||||

Atmospheric density model | DTM 94, with best available solar activity | |||||

Drag coefficients | Adjusted; Spots, Envisat, Cryosat2, HY-2A: 1 coef/4 hours (1/1hr in high solar activity periods) ; Topex,Jasons: 1 coef/half day | |||||

1/rev empiricals | 2 coeff cos-sin /orbital period in normal direction ; 2 coeff cos-sin /orbital period in tangential direction ; per arc | |||||

DORIS measurements |
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Troposphere Model | GPT2/VMF1 | |||||

Weather (meteorological data) | ||||||

Troposphere mapping function | ||||||

Troposphere correction | One zenith delay/pass (wet tropo scale factor adjusted) + one daily tropospheric gradient per station in North & East directions | |||||

2nd order ionosphere | Not applied | |||||

Frequency | 1 frequency bias adjusted per pass | |||||

Relativity | Schwarzschild model + Lense-Thirring + geodesic precession | |||||

Weight | models: 0.3 mm/s; measurements: derived from observation standard deviation in data files | |||||

Elevation angle cutoff | 12 degrees | |||||

Downweighting law | Downweighting law for elevation <= 20 deg; Weight of the observation is multiplied by the factor elevation**2/400 with elevation in degrees) | |||||

Satellite system | Center of mass - antenna phase center vector computed from macro model + attitude law; no phase law applied | |||||

Ground system | Phase centre / reference point vector from manufacturer values; phase law applied (Alcatel, Starec version 2013) | |||||

DORIS System Time Bias | ||||||

South Atlantic Anomaly | Corrective model for Jason-1; corrected measurements for Spot-5 from 2006 only |