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

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!

Geoscience Australia 20 June 2012 Now 10 billon years

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)

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

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

Geoscience Australia 20 June 2012

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

Geoscience Australia 20 June 2012 Hobart – two telescopes

Geoscience Australia 20 June 2012

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

Geoscience Australia 20 June 2012 Parkes

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)

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

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

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

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

Local tie Geoscience Australia 20 June 2012

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

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

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!

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

AuScope project densification 20 June 2012

Geoscience Australia 20 June 2012

Australian – New Zealand network Geoscience Australia 20 June 2012

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

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

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

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

Geoscience Australia 20 June 2012 ITRF2005 Velocity field

Hobart12 – X component Geoscience Australia 20 June 2012

Hobart12 – Y component Geoscience Australia 20 June 2012

Hobart12 – Z component Geoscience Australia 20 June 2012

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 =

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

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

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

Kath12M – X component Geoscience Australia 20 June 2012

Kath12M – Y component Geoscience Australia 20 June 2012

Kath12M – Z component Geoscience Australia 20 June 2012

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

Yarra12M – X component Geoscience Australia 20 June 2012

Yarra12M – Y component Geoscience Australia 20 June 2012

Yarra12M – Z component Geoscience Australia 20 June 2012

Geoscience Australia 20 June 2012

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

First catalogue (Ma et al., 1990)

ICRF1 defining sources Geoscience Australia 20 June 2012

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

ICRF2 sources

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

ICRF2 defining sources (295) Geoscience Australia 20 June 2012

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

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).

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

Earthquake in Japan – 11 March June 2012

UT1-UTC during March June 2012

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

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

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

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

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

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

Thank you! 20 June 2012

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

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

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

Hobart - Katherine, GPS data Geoscience Australia 20 June 2012

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

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

Earthquake in Chile – 27-Feb October 2010