Using cosmic radio sources to measure the deformation of the Australian plate: the AuScope VLBI...
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Transcript of Using cosmic radio sources to measure the deformation of the Australian plate: the AuScope VLBI...
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 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)
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 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
Geoscience Australia
20 June 2012
How IERS measures UT1-UTC?
20 June 2012
Using VLBI
Very Long Baseline Interferometry –
special astronomical technique
Geoscience Australia
20 June 2012
Hobart – two telescopes
Geoscience Australia
20 June 2012
;cos12 c
BTT
1T
Geoscience Australia
20 June 2012
B
B = 10000 km,
= 0.03cos sec
2T
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: 0.110 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
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 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
Geoscience 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
Geoscience Australia
20 June 2012
Australian – New Zealand network
Geoscience Australia
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
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
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
Geoscience Australia
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
Geoscience Australia
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)
Geoscience Australia
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)
Geoscience Australia
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?
Geoscience Australia
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
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
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
Geoscience Australia
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
Geoscience Australia
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
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
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
Geoscience Australia
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
Geoscience Australia
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
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 2012
1.2/3 in the northern hemisphere
2.1/3 in the southern hemisphere
608 sources
ICRF2 sources
ICRF2 catalogue (2009)
Geoscience Australia
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)
Geoscience Australia
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)
Geoscience Australia
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
Geoscience Australia
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
Geoscience Australia
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)
Geoscience Australia
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)
Geoscience Australia
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
Geoscience Australia
20 June 2012
Hobart12 - Katherine
Geoscience Australia
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
Geoscience Australia
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