1. ILRS Workshop, Poznan, Poland, October 2008 1 Status of ITRF Development and SLR Contribution Zuheir Altamimi Xavier Collilieux David Coulot IGN France Key Word: Vertical Velocities and GIA

2. ILRS Workshop, Poznan, Poland, October 2008 2 Warning Preliminary analysis SLR Analyzed Solutions are not official ILRS products ILRS reprocessed combined solution not yet available

3. ILRS Workshop, Poznan, Poland, October 2008 3 Outline Focus on SLR contribution –Origin & Scale –Vertical Velocities & GIA model (?) Analyzed solutions: –IVS official combined time series –ASI-12 –GRGS-11 –NCL (Philip Moore): Not yet an Official ILRS AC –Test SLR solutions (David Coulot): Solution per satellite (L1 & L2)

4. ILRS Workshop, Poznan, Poland, October 2008 4 ITRF and Science Requirement Long-term stable ITRF: 0.1 mm/yr Stable: linear behaviour of the TRF parameters, i.e. with no discontinuity : –Origin Components: 0.1 mm/yr –Scale0.01 ppb/yr (0.06 mm/yr) Current situation: probably not better than 1 mm/yr

5. ILRS Workshop, Poznan, Poland, October 2008 5 Current ITRF Derivation TRF (X, V)+ EOP (SINEX) Local Ties Combination ITRF Stacking S1 S2S3Sn… VLBI SLR GPS DORIS TRF (X, V)+ EOP (SINEX) Step 1 Step 2 W1W2Wn… W1W2Wn… W1W2Wn…

6. ILRS Workshop, Poznan, Poland, October 2008 6 Intrinsic Conditions Preserve the intrinsic origin of SLR –Seen as No-Net-Translation condition –Preserve/Realize the long-term CoM as sensed by SLR Preserve the intrinsic scale of SLR & VLBI &

7. ILRS Workshop, Poznan, Poland, October 2008 7 Origin and Scale wrt ITRF2005

8. ILRS Workshop, Poznan, Poland, October 2008 8 Origin and Scale wrt ITRF2005

9. ILRS Workshop, Poznan, Poland, October 2008 9 Origin and Scale wrt ITRF2005

10. ILRS Workshop, Poznan, Poland, October 2008 10 IGN SLR Origin & Scale ITRF2005 Contribution by David Coulot

11. ILRS Workshop, Poznan, Poland, October 2008 11 IGN SLR Origin & Scale ITRF2005 Contribution by David Coulot 4.3 mm1.0 mm 1.4 mm 0.36 ppb

12. ILRS Workshop, Poznan, Poland, October 2008 12 IGN SLR Origin & Scale ITRF2005 Contribution by David Coulot

13. ILRS Workshop, Poznan, Poland, October 2008 13 IVS Scale (ppb) wrt ITRF2005 Mean Pole Tide Corrected

14. ILRS Workshop, Poznan, Poland, October 2008 14 IVS and SLR (ASI-12) Scale (ppb) wrt ITRF2005

15. ILRS Workshop, Poznan, Poland, October 2008 15 Origin, Scale & Vertical Velocities Vertical velocities depend on –Z-Translation rate: –Scale rate: ratio 1 to 1 But Vertical velocities should reflect geophysics (GIA)

16. ILRS Workshop, Poznan, Poland, October 2008 16 Illustration of Origin, Scale drift on Vertical Velocities Impact of 1.8 mm/yr Tz drift (VLBI Network) Impact of -0.2 ppb/yr Scale drift (SLR Network)

17. ILRS Workshop, Poznan, Poland, October 2008 17 VLBI and SLR Co-located (with GPS) Sites Two different network shapes

18. ILRS Workshop, Poznan, Poland, October 2008 18 Peltier, ICE-5G V1.2, Earth VM4 UP velocities at ITRF2005 sites

19. ILRS Workshop, Poznan, Poland, October 2008 19 UP Velocitity Differences ASI-12 -IVS (ITRF2005 origin)

20. ILRS Workshop, Poznan, Poland, October 2008 20 ASI-12 UP velocities at Co-location sites Intrinsic Origin and Scale Mean = - 0.36 mm/yr Weighted Mean = - 0.24

21. ILRS Workshop, Poznan, Poland, October 2008 21 ASI-12 UP velocities & GIA corrected at Co-location Sites (Intrinsic Origin and Scale) Mean = - 0.32 mm/yr Weighted Mean = +0.16

22. ILRS Workshop, Poznan, Poland, October 2008 22 IVS UP velocities at Co-location sites Intrinsic Scale, Origin from SLR(ITRF2005) Mean = +0.96 mm/yr Weighted Mean = +0.89

23. ILRS Workshop, Poznan, Poland, October 2008 23 IVS UP velocities & GIA corrected at Co-location Sites Intrinsic Scale, Origin from SLR(ITRF2005) Mean = +0.94 mm/yr Weighted Mean = +1.26

24. ILRS Workshop, Poznan, Poland, October 2008 24 IVS UP velocities at Co-location sites Intrinsic Scale, Origin from SLR(ITRF2000) Mean = +0.19 mm/yr Weighted Mean = -0.24

25. ILRS Workshop, Poznan, Poland, October 2008 25 IVS UP velocities & GIA corrected at Co-location Sites Intrinsic Scale, Origin from SLR(ITRF2000) Mean = +0.18 mm/yr Weighted Mean = +0.13

26. ILRS Workshop, Poznan, Poland, October 2008 26 Concluding Remarks Preliminary analysis: to be repeated with official ILRS reprocessed solution Vertical velocity differences ( and hence scale rate diff. ) btw IVS and ASI-12 are most likely due to: –Different network shapes to infer similar GIA effect –ITRF origin (ITRF2005 vs ITRF2000 ?) Accuracy of vertical velocities is probably not better than 1 mm/yr GPS/IGS dense network is useless without SLR & VLBI Continuous observations by space techniques are fundamental Equally fundamental is the improvement of the geodetic infrastructure