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Australian Government Geoscience Australia. VLBI network design. NGRS Workshop, 1-2 February, Canberra. 03/000. Geoscience Australia. 17 August 2005. ICRF catalogue (1998). 608 sources separated into 3 groups. 212 defining sources with position accuracy ~0.4 mas 294 candidate sources

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03/000

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

  2. Geoscience Australia 17 August 2005

  3. ICRF catalogue (1998) 608 sources separated into 3 groups • 212 defining sources with position accuracy ~0.4 mas • 294 candidate sources • 102 other sources Geoscience Australia 17 August 2005

  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) Instability ~0.2 mas ( 6 mm ) Geoscience Australia 17 August 2005

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

  8. Geoscience Australia 17 August 2005

  9. Radiotelescopes in Australia Geoscience Australia 17 August 2005

  10. 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 Geoscience Australia 17 August 2005

  11. Problem • 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! Geoscience Australia 17 August 2005

  12. Procedure • 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 Geoscience Australia 17 August 2005

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

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

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

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

  17. wrms and offset of the TRF solution Geoscience Australia 17 August 2005

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

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

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

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

  22. Conclusion • 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 Geoscience Australia 17 August 2005

  23. criteria Geoscience Australia 17 August 2005

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

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