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DORIS positioning: performance assessment from the last data processing at CNES/CLS

Analysis CenterL. Soudarin 1, H. Capdeville 1, J.-M. Lemoine 2 , P. Schaeffer 1

1 CLS, Collecte Localisation Satellites, Ramonville, France2 CNES, Toulouse, France

1. About the data processing

2. Positioning performances assessment

3. Contribution of each generation of instruments

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Overview

3. Contribution of each generation of instruments

4. Summary

Reprocessing :In the second half of 2011, the CNES/CLS Analysis C enter (LCA) has entirely re-processed the whole DORIS data set for orbit determination and tracking station coordinate estimation.

Motivations :-revised attitude laws for Topex/Jason-1/Jason-2, En visat and Cryosat-2-fixed bug related to the frequency bias

Current series: lcawd32Page 3

-fixed bug related to the frequency bias-new macro-model tuned by GRGS for Jason-2

Changes in standards (wrt previous processing set up for IDS-3): -DPOD2008 as a priori instead of DPOD2005-IERS EOP series aligned on ITRF2008-GMF/GPT tropospheric model instead ECMWF + Guo&Lang ley MF -EIGEN-6S gravity model instead of EIGEN-GL04S

New SINEX series:lcawd32 including Jason-2, Cryosat-2, HY-2A

Station position time seriesPage 4

Time series are availableon IDS web site:-files of data (STCD format) and plots (GIF format)

They can be displayed

Kokee Park : KOKA + KOLB

They can be displayedwith STCDtool

http://ids-doris.org/plottool/stcdtool.php

Comparison to DPOD2008Page 5

3D RMS of the weekly LCA solutions wrt DPOD2008 (1993 -2012)

•1008 weeks(1993/01/03 – 2012/06/02)•44 stations by weekly solutionon average

RMS average value (mm) �

3D N E Uwholeperiod 18,4 14,3 22,9 16,4

1993-2002 23,0 17,6 29,0 20,6

2002-2008 14,4 11,3 18,3 12,5

2008-2012 12,9 11,1 15,1 12,1

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Repeatability of the time series

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•1008 weeks (1993/01/03 – 2012/06/02)•148 stations: from 6.1 mm (ADFB, 2.7 yrs) to 21.2 mm (MORA, 4.9 yrs)

- 3D wrms: mean value 12.3 mm / median value 11.1 mm- amount of analyzed data: mean value 5.08 years / median values 4.69 years

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North residuals WRMS

Precision of the positioning

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East residuals wrms

Precision of the positioning

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Up residuals WRMS

Precision of the positioning

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yearmm 3D WRMS (biais removed) and installation time span

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Positioning precision and installation

1989

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20001 cm

Improvement of LCA time seriesPage 11

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3D wrms (bias removed)Previous (lcawd24) vs Current processing (lcawd32)

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lcawd24 lcawd32

unit: mm 3D North East Up

lcawd24 (1) 9,51 8,44 13,22 9,18

lcawd32 (2) 8,23 7,63 11,50 7,52

(2)-(1)/(1) -13,52% -9,66% -13,04% -18,11%

2009/01-2010/0750 stations

Decreasing of the residuals �

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1st & 2nd vs DGXX instruments

48 stations27 weeks2011/10/02 – 2012/04/07

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unit: mm 3D North East Up

6 satellites 6,64 6,23 9,53 6,16

Spot4+ Spot5+Env = 1 st & 2nd Gen. 9,71 9,18 15,56 8,47

Jason2+Cryosat2+HY-2A = DGXX 7,45 6,75 10,74 7,33

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Contribution of DGXX instruments

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3D wrms constellation 5 sat. -Jason-2 or -Cryosat-2 or -HY-2A compared to Spot-4+Spot-5+Jason-2+Cryosat-2+HY-2A

w/o Jason-2 w/o HY-2A w/o Cryosat-2

unit: mm 3D North East Up

5 sat. constellation 6,07 5,33 8,95 6,01

w/o Jason-2 6,51 5,64 10,31 6,62

w/o HY-2A 6,59 5,84 9,80 6,44

w/o Cryosat-2 6,80 5,98 9,98 6,66

Most important DGXX contributors: Cryosat-2 (717 km, 92°) for North and Up, Jason-2(130 0km, 66°) for East

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48 stations15 weeks2012/04 – 2012/07

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Current constellation without SPOT -4

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3D wrms Spot-4 contribution

48 stations15 weeks2012/04/08 – 2012/07/21

unit: mm 3D North East Up

with Spot4 6,07 5,33 8,95 6,01

w/o Spot4 6,31 5,57 9,14 6,29

(2)-(1)/(1) +3,92% +4,51% +2,16% +4,64%

Small increasing of the residuals �

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constellation w/o SPOT4 - constellation with SPOT4

• Current LCA positionning solutions better by 10 to 18%(up) wrt to processing for ITRF2008

• Positionning < 1cm since DGXX

• Time series improved by DGXX data and installation renovation

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Summary

• Time series improved by DGXX data and installation renovation

• Most important DGXX contributor: Cryosat-2 for North and Up, Jason-2 for East

• End of SPOT-4 mission will have a small impact. It will likely belargely balanced with SARAL (12/12/2012).