1. 03/000 VLBI network design Australian Government Geoscience Australia NGRS Workshop, 1-2 February, Canberra

2. Geoscience Australia 17 August 2005

3. ICRF catalogue (1998) Geoscience Australia 17 August 2005 1.212 defining sources with position accuracy ~0.4 mas 2.294 candidate sources 3.102 other sources 608 sources separated into 3 groups

4. Radiotelescopes in Australia Geoscience Australia 28 June 2004

5. ICRF defining sources Geoscience Australia 17 August 2005

6. ICRF source instability (quasar 2145+067) Geoscience Australia 17 August 2005 Instability ~0.2 mas ( 6 mm )

7. ICRF source instability Geoscience Australia 17 August 2005 It is important to monitor all radiosources to mitigate the effect of instability About 60 defining sources from the ICRF catalogue are appeared to be unstable! New ICRF realization wanted now

8. Geoscience Australia 17 August 2005

9. Radiotelescopes in Australia Geoscience Australia 17 August 2005

10. Geoscience Australia 17 August 2005 Hobart, 26-meter antenna Too far from all other telescopes; Limited amount of defining sources in southern hemisphere – problems with scheduling; Slow slew rate (1 deg/sec) – little data

11. Problem Geoscience Australia 17 August 2005 - set of radiosources to be fixed (212 defining sources); - if unstable radiosources are fixed the geodetic results will be corrupted; - effect of the instability of the fixed radiosources on the TRF solution has never been studied!

12. Procedure Geoscience Australia 17 August 2005 - two global VLBI solutions have been obtained by identical way; - Solution 1: 207 ICRF defining sources; - Solution 2: 199 ‘stable’ sources (Feissel-Vernier); - daily TRF solutions have been obtained for Sol #1 and #2 providing two sets of time series of VLBI site geodetic positions; - differences of the daily geodetic positions were calculated; - measure of discrepancy between two solution

13. TRF daily difference time series Geoscience Australia 17 August 2005

14. Geoscience Australia 17 August 2005 TRF daily difference time series

15. Geoscience Australia 17 August 2005 TRF daily difference time series

16. Geoscience Australia 17 August 2005 TRF daily difference time series

17. wrms and offset of the TRF solution Geoscience Australia 17 August 2005 StationLatitude (º) wrms (mm) Offset (mm) heightlatitudelongitudeheightlatitudelongitude Algopark465.53.02.10.9 +/- 0.30.2 +/- 0.20.1 +/- 0.1 DSS45-3513.59.74.63.0 +/- 1.7-0.5 +/- 1.2-0.7 +/- 0.6 Fortaleza-48.64.73.7-1.2 +/- 0.4-0.5 +/- 0.20.0 +/- 0.2 Hartrao-2515.47.25.2-1.6 +/- 0.9-1.4 +/- 0.50.2 +/- 0.3 Hobart26-4320.410.29.310.6 +/- 1.4-3.9 +/- 0.7-0.8 +/- 0.6 Kokee224.83.13.4-0.2 +/- 0.20.6 +/- 0.10.1 +/- 0.1 Medicina453.52.71.70.6 +/- 0.40.1 +/- 0.3-0.3 +/- 0.2 Ny-Alesund793.51.41.5-0.3 +/- 0.30.0 +/- 0.1-0.2 +/- 0.1 O’Higgins-6311.86.25.91.9 +/- 1.81.9 +/- 0.9-0.6 +/- 0.9 Onsala60573.22.02.10.0 +/- 0.10.1 +/- 0.1-0.1 +/- 0.1 Seshan25317.22.73.3-0.2 +/- 1.80.3 +/- 0.7-0.2 +/- 0.8 Svetloe604.43.91.6-6.9 +/- 7.6-6.9 +/- 7.5-3.1 +/- 3.0 Tigoconc-3716.39.44.924.3 +/- 8.5-17.8 +/- 4.42.7 +/- 2.9 Westford435.42.92.61.0 +/- 0.10.5 +/- 0.10.0 +/- 0.1 Wettzell494.73.02.40.0 +/- 0.10.6 +/- 0.1-0.4 +/- 0.1

18. Geoscience Australia 17 August 2005 Effect on the TRF quality (wrms vs latitude)

19. Geoscience Australia 17 August 2005 Hobart daily difference time series

20. Hobart’s problem Geoscience Australia 17 August 2005 - poor reference sources due to geographical location - insufficient amount of data due to low slew rate

21. Hobart’s problem solution Geoscience Australia 17 August 2005 -

22. Conclusion Geoscience Australia 17 August 2005 - ICRF deficiency causes uncertainties in geodetic positions as much as 10-20 mm for VLBI sites in Southern hemisphere; - more good radiosources for schedule - more radiosources - more VLBI stations with high slew rate 5 deg/sec - potentially we can reach ~ 1 mm or better by 2010

23. criteria Geoscience Australia 17 August 2005

24. Geoscience Australia 17 August 2005 ICRF instability (wrms vs declination)