DORIS AWG MeetingParis, France - 23 March 2009 1

Analysis Analysis IssuesIssuesFrank Lemoine (NASA/GSFC)

Doug Chinn (NASA/GSFC - SGT Inc.)

DORIS AWG MeetingParis, France - 23 March 2009 2

OutlineOutline

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1. Newest orbit differences (GAU vs GSFC)2. Modelling summary for AC’s.3. Paper Proposal for ASR.4. Perspectives, Challenges, and Future work.

DORIS AWG MeetingParis, France - 23 March 2009 3

Gravity Gravity & & Tide SummaryTide Summary

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¶ wd20 dsc file and Nov. AWG Presentation do not match.# From June 2008 AWG Presentation; Does not reflect latest.

GOT00IERS2003?No?GGM02CGGM02CNCL

GOT00IERS2003Yes.Yes/NCEP50x50.

GGM02CGGM02CGAU

GOT4.7IERS2003Yes.Yes. ECMWF50x50.

+ annual20x20fromGRACE

Eigen-Gl04s(120x120)

GSC(wd09)

FES2004IERS2003?Yes. NCEP,20x20.

+seasonalto 50x50

Eigen-GL05C orEIGEN-GL04s?(?x?)

ESA

CSR3IERS2003?Yes. ECMWF?x?.

+ratesEigen-GL04S(100x100)

GOP

CSR3IERS2003No?NoGGM01CGGM01CINA#

FES2004IERS2003YesYes,ECMWF?x?

+rates? +periodic

Eigen-Gl04

LCA¶

??Wahr ?NoNoGGM03sGGM03S(120x120)

IGN

OceanTides

EarthTides

Airtides

Atmosph.Gravity

Time-VaryingGravity

StaticGravity

Center

DORIS AWG MeetingParis, France - 23 March 2009 4

Nonconservative Nonconservative ForcesForces

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?NoYes.@6hrsMSIS83NCL

Yes/YesYes.Yes@6hrsSp245ENV

MSIS86GAU

Yes/YesYes. TOP.UCL(ENV,JA1)SP2

Yes. Source?@6hrsSp245ENV

MSIS86GSC(wd09)

Yes, Model?Angara(ENV only)

Yes.@2.4hrsSp245ENV

MSIS90ESA

NoN/AGOP

Yes/Yes.Top.Others?

Yes. Source??DTM94INA#

Models orECMWF?

?Yes. Not CNES? @4hrsSp245ENV

DTM94LCAwd20

Yes/No?NoYes. Source? @1hrSp245ENV

DTM94IGNwd08

Albedo/IRSat.SpecificModels

MacromodelsCd Freq.Atmos.Model

Center

DORIS AWG MeetingParis, France - 23 March 2009 5

Troposphere ModellingTroposphere Modelling

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Wet??GPT?NCL

Wet+DryNoNeill (wasHopfield)

Doris Met12ºGAU

Wet+DryNoNeill (wasHopfield)

GPT (wasDoris met)

10ºGSC(wd09)

WetNoGMFGPT10ºESA

Wet?GMFGPT 15º?GOP

WetNo??15ºINA#

WetDownwt ftnapplied <20 deg

Guo andLangley

< 2002DORIS met> 2002ECMWF

12º fromdsc file.No toFGL

LCAwd20

WetNo?Lanyi?GPT?FromCNES

IGNwd08

AdjustLow Elevdownwt.

MappingFunction

ModelApriori

ElevCutoff

Center

DORIS AWG MeetingParis, France - 23 March 2009 6

Model Comparison CommentsModel Comparison Comments1. Description files for SINEX don’t match presention information

(from November IDS workshop, for example).2. Information is Incomplete.3. Information or Description files do not exist.

DORIS AWG MeetingParis, France - 23 March 2009 7

Joint Paper Proposal for ASRJoint Paper Proposal for ASR1. Orbit Comparison, 2003?, 1 year all centers, all satellites (+

another year, 1995 for Spot 3). Orbits should correspond to finalSINEX submission or an archived SINEX submission.

2. Intercompare Residual empirical opr amplitude (along & cross-track), one year, all satellites.

3. Troposphere comparison: 1 week, 4? stations; Total Zenith delay(see next slide as example)

4. Paper would include modelling summary to show status ofmodelling at the centers ….

DORIS AWG MeetingParis, France - 23 March 2009 8

Troposphere comparisonsTroposphere comparisons

Hartebeesthoek Kokee Park

Preliminary (example) comparisonsfrom VLBI & GPS (Johannes Boehm)and DORIS (Pascal Willis).

• DORIS, like VLBI & GPS must estimate troposphere corrections.• Corrections are estimated pass-by-pass (typically 10-15 min, ~2Xper satellite & DORIS station, and per day).

DORIS AWG MeetingParis, France - 23 March 2009 9

Perspectives and Challenges.Perspectives and Challenges.

1. What do we need to do to complete the IERS submission?2. What is the impact of data distribution, elevation cutoffs, troposphere

modelling, mapping functions on scale? Is it possible to have an absoluteDORIS scale?

3. What is impact of offsets? How do improper cgmass/offset knowledge affectCOM corrections?

4. Second Order Ionosphere. How important is this effect?5. What are the impact of software changes on the Level 1B DORIS data? (Eg

ENVISAT Late 2004).6. Atmospheric Loading? What is impact on DORIS processing? Are we ready

for this?7. Operational time series: Will we soon have three centers making weekly

deliveries?8. Improvements in Nonconservative Force modelling; UCL-type models for

SPOT satellites; Availability of quaternions for TP & Jason-1,2; Improvementsto atmosphere modelling from GRACE+CHAMP Accelerometer data?

9. Open issue. Define orbit format for deliveries by AC’s. sp3 or sp1? (Mixture offormats at CDDIS).

DORIS AWG MeetingParis, France - 23 March 2009 10

Thank you for your attention!