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Using cosmic radio sources to measure the deformation of the Australian plate: the AuScope VLBI project Oleg Titov Australian Government Geoscience Australia.

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Presentation on theme: "Using cosmic radio sources to measure the deformation of the Australian plate: the AuScope VLBI project Oleg Titov Australian Government Geoscience Australia."— Presentation transcript:

1 Using cosmic radio sources to measure the deformation of the Australian plate: the AuScope VLBI project Oleg Titov Australian Government Geoscience Australia 20 June 2012

2 Leap second! Additional second to increase the length of day 20 June 2012 will be introduced on 1, July, 2012 From 24 hours to 24 hours 00 minutes 01 seconds We’ll stay in offices 1 seconds longer!

3 Geoscience Australia 20 June 2012 Now 10 billon years

4 UT1-UTC Geoscience Australia 20 June The Earth slows down due to tidal friction and energy dissipation; 2.Two time scales: UT1 – connected with real Earth (does not flow uniformly) UTC – connected to atomic clock (TAI)

5 UT1-UTC 20 June 2012 When difference UT1-UTC exceeds 0.9 seconds, new leap second is introduced by IERS (International Earth Rotation Service)

6 Geoscience Australia 20 June 2012 UTC TIME STEP on the 1st of July 2012 A positive leap second will be introduced at the end of June The sequence of dates of the UTC second markers will be: 2012 June 30, 23h 59m 59s 2012 June 30, 23h 59m 60s 2012 July 1, 0h 0m 0s

7 Geoscience Australia 20 June 2012

8 How IERS measures UT1-UTC? 20 June 2012 Using VLBI V ery L ong B aseline I nterferometry – special astronomical technique

9 Geoscience Australia 20 June 2012 Hobart – two telescopes

10 Geoscience Australia 20 June 2012

11 Geoscience Australia 20 June 2012 B   B = km,  = 0.03 cos  sec

12 Geoscience Australia 20 June 2012 Parkes

13 Geodetic VLBI network 20 June 2012 When the number of stations is more than 2, we could convert (B, φ) to station positions and coordinates of reference radio sources (quasars)

14 Quasars (“quasi-stellar”) are very distant radio sources 20 June 2012 They are used to be at the cosmological distances, their light was emitted when the Universe was young, so their position are expected to be stable. Observed in GHz wavelengths 2.3 GHz and 8.4 GHz – to calibrate ionosphere Typical flux: 0.1  10 Jy

15 Quasar 3C273B 20 June 2012 Point-like core and extended jet Typical structure:

16 Quasars 20 June 2012 Positions are known with accuracy up to 10 microseconds of arc

17 For comparison 20 June 2012 Moon: 30’ Darling Harbour on the Moon: 1” 50c coin: ~ 15 microseconds of arc A man on the Moon: 0”.001 = 1 milliarcsecond

18 Local tie Geoscience Australia 20 June 2012

19 Geoscience Australia 20 June 2012 We observe distant objects from the moving platform

20 Precession, nutation, EOP 1.Precession P=26000 years Amplitude ~ 23° 2.Nutation P=18.6 year Amplitude ~ 9” 3.Pole motion P=1 & 1.2 year Amplitude ~ 0”.15 (9 meters) 4.Universe Time P=1 & 0.5 year Amplitude ~ 0.01 sec 20 June 2012

21 Three major areas Geoscience Australia 20 June International Celestial Reference Frame (ICRF) - positions of reference radio sources (VLBI only!) 2.International Terrestrial Reference Frame (ITRF) - positions of the reference point on Earth 3.Earth Orientation Parameters (link between ICRF and ITRF), UT1-UTC is measured by VLBI only!

22 VLBI in Australia Geoscience Australia 20 June meter dish in Hobart has been erected extension of the geodetic VLBI network was started to discuss 2007 – funding within NCRIS has been approved 2011 – network of three 12-meter telescopes started operations

23 AuScope project densification 20 June 2012

24 Geoscience Australia 20 June 2012

25 Australian – New Zealand network Geoscience Australia 20 June 2012

26 12m Antenna at Patriot 5 deg/sec in azimuth, 1.5 deg/sec in elevation 20 June 2012

27 The 64-meter “dish” at work 20 June 2012

28 AuScope network Hobart12 – started operation in tag along mode in October 2010; in full mode – January, 2011 Yarragadee – since 26 May, 2011 Katherine – since 16 June, 2011; 20 June 2012

29 Hobart12 Geoscience Australia 20 June 2012 Participates mostly in international programs to estimate Earth Orientation Parameters (prepared by IVS); Astrometry (IVS); Regional geodesy (GA + UTAS) In total we have 78 ‘good’ session From 50 to 635 observations per session

30 Geoscience Australia 20 June 2012 ITRF2005 Velocity field

31 Hobart12 – X component Geoscience Australia 20 June 2012

32 Hobart12 – Y component Geoscience Australia 20 June 2012

33 Hobart12 – Z component Geoscience Australia 20 June 2012

34 Hobart12 (ITRF2005) Geoscience Australia 20 June 2012 ComponentVLBI GPS + local tie (26-Nov-09) VLBI - GPS X (meter) / / / Y (meter) / / / Z (meter) / / / Reference epoch T =

35 Hobart12 (ITRF2005) Geoscience Australia 20 June 2012 Component Hobart26 (ITRF2005) Hobart12 Hobart26- Hobart12 VX (cm/y) / /- 0.8 VY (cm/y) / /- 0.5 VZ (cm/y) / /- 0.8 Tectonic velocities

36 Hobart12: error budget? Geoscience Australia 20 June 2012 ComponentXYZ σ (cm) Weighted rms (cm) External errors (positions of radio sources) contribute to the total geodetic error budget! internal external

37 Kath12M Geoscience Australia 20 June 2012 In total we have 24 ‘good’ session From 104 to 700 observations per session Not properly tied to ITRF2005

38 Kath12M – X component Geoscience Australia 20 June 2012

39 Kath12M – Y component Geoscience Australia 20 June 2012

40 Kath12M – Z component Geoscience Australia 20 June 2012

41 Yarra12M Geoscience Australia 20 June 2012 In total we have 12 ‘good’ session From 28 to 452 observations per session Not properly tied to ITRF2005

42 Yarra12M – X component Geoscience Australia 20 June 2012

43 Yarra12M – Y component Geoscience Australia 20 June 2012

44 Yarra12M – Z component Geoscience Australia 20 June 2012

45 Geoscience Australia 20 June 2012

46 Internal vs external accuracy Geoscience Australia 20 June 2012 Baseline lengths are sensitive to selection of the reference radio sources For X, Y, Z components – external accuracy looks worse then internal

47 First catalogue (Ma et al., 1990)

48 ICRF1 defining sources Geoscience Australia 20 June 2012

49 ICRF1 catalogue (1998) Geoscience Australia 20 June /3 in the northern hemisphere 2.1/3 in the southern hemisphere 608 sources

50 ICRF2 sources

51 ICRF2 catalogue (2009) Geoscience Australia 20 June “defining” sources with the positional accuracy ~0.04 mas 922 “non-defining” sources 1217 VCS sources 3414 sources separated into 3 groups For the sake of homogeneity, less accurate radio sources in the southern hemisphere were included

52 ICRF2 defining sources (295) Geoscience Australia 20 June 2012

53 ICRF2 non-defining sources (922) Geoscience Australia 20 June 2012

54 ICRF in the South Geoscience Australia 20 June Positional accuracy of the “defining” and “non-defining” sources in the southern hemisphere is 2-3 times worse; 2.More resources to be spent for improvement (in collaboration with key stakeholders – ATNF, UTAS).

55 Tectonic impact on the Earth rotation Geoscience Australia 20 June Boxing day earthquake and tsunami, 26-Dec Feb 2010, Chile. VLBI site Tigoconc was shifted on 3 meters 3.11-Mar 2011, Japan, First big earthquake during the VLBI network operation

56 Earthquake in Japan – 11 March June 2012

57 UT1-UTC during March June 2012

58 Earthquake, 11 March June 2012 P = 1.5 hours P = 3 hours

59 Conclusion Geodesy (positive) Astrometry (negative) 20 June 2012

60 Geodesy AuScope network operates successfully in spite of some technical problems; Geodetic positions for Hobart12 were calculated (ITRF2005) with accuracy ~ 4 mm; A good consistency with independent (GPS + local tie) results; 20 June 2012

61 Astrometry Number of the ICRF2 reference radio sources in the southern hemisphere in sufficient, but positional accuracy needs to improved; Astrometric problems are likely to contribute to the total error budget We should keep an eye on the observational schedules and, particularly, on the source selection 20 June 2012

62 Short-term strategy To run more sessions (AuScope + Parkes + Warkworth + Hartrao) to get more observations of the reference radio sources and extend the list (AuScope expires since 1, July 2013); To revise the existing list of reference radio sources (in cooperation with IVS-IERS-IAU); 20 June 2012

63 Long-term strategy Running scheduling inside GA Making correlation inside GA To build up fourth 12-meter dish in north NSW or south Queensland 20 June 2012

64 Thank you! 20 June 2012

65 P.S. Don’t forget asking your manager for the leap second allowance 20 June 2012

66 Baseline Hobart12 - Kath12M (ICRF2 reference radio sources) Geoscience Australia 20 June 2012

67 Hobart12 - Katherine (alternative list of reference radio sources) Geoscience Australia 20 June 2012

68 Hobart - Katherine, GPS data Geoscience Australia 20 June 2012

69 Hobart12 - Katherine Geoscience Australia 20 June 2012 Reference sources Baseline rate (cm/year) ICRF2 list ( ) /- 1.3 The alternative list ( ) /- 1.9 GPS ( ) /- 0.7 Baseline rate estimates

70 Tectonic impact on the Earth rotation Geoscience Australia 20 June Boxing day earthquake and tsunami, 26-Dec Feb-2010, Chile. VLBI site Tigoconc was effected – shifted on 3 meters

71 Earthquake in Chile – 27-Feb October 2010


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