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Importance of SLR in the Determination of the ITRF

Importance of SLR in the Determination of the ITRF. SLR Strength : its contribution to the ITRF Origin Scale SLR Weakness : its current network configuration Conclusions. Zuheir Altamimi IGN, France. Geoscience Australia, Canberra, August 2 9 , 2005.

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Importance of SLR in the Determination of the ITRF

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  1. Importance of SLR in the Determinationof the ITRF • SLR Strength: its contribution to the ITRF • Origin • Scale • SLR Weakness: its current network configuration • Conclusions Zuheir Altamimi IGN, France Geoscience Australia, Canberra, August 29, 2005

  2. International Terrestrial Reference System (ITRS) Adopted by IUGG in 1991 for all Earth Science Applications • Realized and maintained by the International Earth Rotation and Reference Systems Service (IERS) • Its Realization is called International Terrestrial Reference Frame (ITRF) • Set of station positions and velocities, estimated by combination of VLBI, LLR, SLR, GPS and DORIS individual TRF solutions More than 800 stations located on more than 500 sites Available: ITRF88, 89,…,97 Latest: ITRF2000 http://www.ensg.ign.fr/ITRF/

  3. ITRF Datum Definition • Origin : SLR • Scale : VLBI & SLR • Orientation : Conventional • Orientation time evolution: NNR condition • Science Requirement : 0.1mm/yr

  4. Current ITRF Status • ITRF2000: ~ 4 years old • New GPS & DORIS stations since 2000 • Longer histories ==> Improve velocities • Methods for time series combination recently developed

  5. ITRF Origin comes from SLR

  6. ITRF Scale comes from VLBI&SLR

  7. SLR Network Since 93 From 99 on

  8. Current Co-locations (1999 on) (9) (59) (16) (2)

  9. Current VLBI-SLR Co-locations (1999 on) (9) Inhomogeneous distribution of VLBI&SLR Networks and their Co-locations ITRF Scale in danger !!!

  10. Current SLR-GPS Co-locations (1999 on) (25)

  11. Current SLR-DORIS Co-locations (1999 on) (7) Only 7 SLR-DORIS Co-locations

  12. ITRF2004 • For 1st time, use Time Series of Station Positions : • Daily (VLBI) • Weekly (GPS, SLR & DORIS) • and Earth Orientation Parameters: Polar Motion (xp, yp) Universal Time (UT1) (Only from VLBI) Length of Day (LOD)

  13. SLR Origin and Scale Variations from time series analysis

  14. VLBI Scale Variations

  15. Quality of SLR GEOS time series With Yarragadee Without Yarragadee

  16. SLR Origin and Scale Time Series

  17. SLR Origin and Scale time series wrt ITRF2000 With & Without Yarragadee

  18. SLR Origin and Scale time series wrt ITRF2000 With & Without Yarragadee

  19. SLR GEOS Origin & Scale Diff. (With - W/out Yar. Data)

  20. Geodetic Signal ? SLR

  21. Geodetic Signal ? SLR GPS

  22. Conclusions • SLR is the unique technique currently capable to ‘’see’’ the Earth CoM • But SLR suffers from its weak network geometry • SLR stations with long history are absolutely needed for the long term maintenance of the ITRF origin • Effect when Yarragadee observations are not used: • Results seem to be slightly more scattered when Yarragadee data is removed • Drift changes: • Delta TX = 0.6 mm/yr • Delta TY = 1.0 mm/yr larger than science requirement • Delta TZ = 1.0 mm/yr • No significant change in the scale

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