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

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!


20 June 2012

Now

10 billon years

UT1-UTC


20 June 2012

1. 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)


20 June 2012

UTC TIME STEP on the 1st of July 2012

A positive leap second will be introduced at the end of June 2012. 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


20 June 2012

How IERS measures UT1-UTC?

20 June 2012

Using VLBI

Very Long Baseline Interferometry –

special astronomical technique


20 June 2012

Hobart – two telescopes


20 June 2012

;cos12 c

BTT

1T


20 June 2012

B

B = 10000 km,

= 0.03cos sec

2T


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: 0.110 Jy

Quasar 3C273B

20 June 2012

Point-like coreand 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


20 June 2012


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


20 June 2012

1. 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


20 June 2012

1989 - 26-meter dish in Hobart has been erected

2005 - 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 densificationAuScope project densification

20 June 2012


20 June 2012

Australian – New Zealand network


20 June 2012

12m Antenna at Patriot12m Antenna at Patriot5 deg/sec in azimuth, 1.5 deg/sec in elevation

20 June 2012

The 64-meter “dish” at workThe 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


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


20 June 2012

ITRF2005 Velocity field

Hobart12 – X component


20 June 2012

X - component

Year

2011.0 2011.2 2011.4 2011.6 2011.8 2012.0 2012.2 2012.4

met

er

-0.90

-0.85

-0.80

-0.75

-0.70

-0.65

Hobart12 – Y component


20 June 2012

Y-component

Year

2011.0 2011.2 2011.4 2011.6 2011.8 2012.0 2012.2 2012.4

met

er

1.12

1.14

1.16

1.18

1.20

1.22

1.24

Hobart12 – Z component


20 June 2012

Z-component

Year

2011.0 2011.2 2011.4 2011.6 2011.8 2012.0 2012.2 2012.4

met

er

-8.20

-8.15

-8.10

-8.05

Hobart12 (ITRF2005)


20 June 2012

Component VLBIGPS + local tie

(26-Nov-09)VLBI - GPS

X (meter)-3949990.683 +/-

0.004-3949990.675 +/-

0.004-0.008 +/- 0.005

Y (meter)2522421.181 +/-

0.0032522421.199 +/-

0.003-0.018 +/- 0.004

Z (meter)-4311708.161 +/-

0.004-4311708.170 +/-

0.0030.009 +/- 0.005

Reference epoch T = 2009.904

Hobart12 (ITRF2005)


20 June 2012

ComponentHobart26

(ITRF2005)Hobart12

Hobart26-Hobart12

VX (cm/y) -3.95 -4.1 +/- 0.8 0.2 +/- 0.8

VY (cm/y) 0.91 0.4 +/- 0.50.5 +/- 0.5

VZ (cm/y) 4.15 4.5 +/- 0.8 0.4 +/- 0.8

Tectonic velocities

Hobart12: error budget?


20 June 2012

Component X Y Z

σ (cm) 0.4 0.2 0.9

Weighted rms (cm)

2.4 1.3 2.2

External errors (positions of radio

sources) contribute to the total

geodetic error budget!

internal

external

Kath12M


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


20 June 2012

Year

2011.4 2011.6 2011.8 2012.0 2012.2

met

er

-4.70

-4.65

-4.60

-4.55

-4.50

Kath12M – Y component


20 June 2012

Year

2011.4 2011.6 2011.8 2012.0 2012.2

met

er

2.30

2.35

2.40

2.45

2.50

Kath12M – Z component


20 June 2012

Year

2011.4 2011.6 2011.8 2012.0 2012.2

met

er

-3.34

-3.32

-3.30

-3.28

-3.26

-3.24

-3.22

-3.20

Yarra12M


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


20 June 2012

Year

2011.2 2011.4 2011.6 2011.8 2012.0 2012.2

met

er

-6.20

-6.18

-6.16

-6.14

-6.12

-6.10

-6.08

-6.06

-6.04

-6.02

-6.00

Yarra12M – Y component


20 June 2012

Year

2011.2 2011.4 2011.6 2011.8 2012.0 2012.2

me

ter

9.85

9.90

9.95

10.00

10.05

Yarra12M – Z component


20 June 2012

Year

2011.2 2011.4 2011.6 2011.8 2012.0 2012.2

met

er

-1.00

-0.98

-0.96

-0.94

-0.92

-0.90

-0.88

-0.86

-0.84


20 June 2012

Internal vs external accuracy


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


20 June 2012

ICRF1 catalogue (1998)


20 June 2012

1.2/3 in the northern hemisphere

2.1/3 in the southern hemisphere

608 sources

ICRF2 sources

ICRF2 catalogue (2009)


20 June 2012

295 “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)


20 June 2012

degrees

-80 -60 -40 -20 0 20 40 60 80

as

40

60

80

100

120

140

160

180

cos

ICRF2 non-defining sources (922)


20 June 2012

degrees

-80 -60 -40 -20 0 20 40 60 80

as

200

400

600

800

1000

1200

1400

1600

1800

2000

cos

ICRF in the South


20 June 2012

1.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


20 June 2012

1.Boxing day earthquake and tsunami, 26-Dec 2004

2.27-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 2011

20 June 2012

UT1-UTC during 10-11 March 2011

20 June 2012

Earthquake, 11 March 2011

20 June 2012

P = 1.5 hoursP = 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)


20 June 2012

Year

2011.4 2011.6 2011.8 2012.0 2012.2

3431

870

+..

. (m

eter

)

8.96

8.98

9.00

9.02

9.04

Hobart12 - Katherine (alternative list of reference

radio sources)


20 June 2012

Year

2011.4 2011.6 2011.8 2012.0 2012.2

3431

870

+ .

.. (

met

er)

8.92

8.94

8.96

8.98

9.00

9.02

9.04

Hobart - Katherine, GPS data


20 June 2012

Hobart12 - Katherine


20 June 2012

Reference sources

Baseline rate (cm/year)

ICRF2 list

(2011-2012)-3.8 +/- 1.3

The alternative list (2011-2012)

-1.6 +/- 1.9

GPS

(2010-2012) -0.3 +/- 0.7

Baseline rate estimates

Tectonic impact on the Earth rotation


20 June 2012

1.Boxing day earthquake and tsunami, 26-Dec-2004

2.27-Feb-2010, Chile. VLBI site Tigoconc was effected – shifted on 3 meters

Earthquake in Chile – 27-Feb-2010

20 October 2010

Documents

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