s/x receiver for parkes geodetic vlbi program
DESCRIPTION
S/X receiver for Parkes geodetic VLBI program. О leg Titov ( Geoscience Australia). ATNF, Sydney 29 October 2012. 29 October 2012. IVS astrometric programs. - PowerPoint PPT PresentationTRANSCRIPT
S/X receiver for Parkes geodetic VLBI program
29 October 2012
ATNF, Sydney
29 October 2012
Оleg Titov (Geoscience Australia)
29 October 2012 Geoscience
Australia
IVS astrometric programs
International VLBI Service (IVS) supports several observational programs (Earth Orientation Parameters; geodesy; astrometry). All in S/X
Astrometric programs are designed for improvement and densification of the International Celestial Reference Frame (ICRF2, 2009)
Parkes participates in the IVS astrometric programs since 2004, and contributed to ICRF2.
29 October 2012 Geoscience
Australia
ICRF1 catalogue (1998)ICRF1 catalogue (1998)
Geoscience Australia
20 June 2012
1.212 defining sources with the positional accuracy ~0.25 mas
2.294 “non-defining” sources
3.102 “other” sources
608 sources separated into 3 groups
29 October 2012 Geoscience
Australia
ICRF2 catalogue (2009)ICRF2 catalogue (2009)
Geoscience Australia
1.295 defining sources with the positional accuracy ~0.04 mas
2.922 “non-defining” sources
3.1217 VCS sources
3414 sources separated into 3 groups
Geoscience
Australia29 October 2012
ICRF1
Geoscience
Australia29 October 2012
ICRF2
Geoscience
Australia29 October 2012
ICRF2
7 million group delays were measured for legacy since 1979
All done in S/X
Geoscience
Australia29 October 2012
Accuracy for 295 ‘defining’ sources
Geoscience
Australia29 October 2012
Accuracy for 1217 ‘non-defining’ sources
29 October 2012 Geoscience
Australia
ICRF2 catalogue (2009)ICRF2 catalogue (2009)
Geoscience Australia
295 defining sources with the positional accuracy ~0.04 mas
We have reached the limit of accuracy to
search for hidden systematic effects
Geoscience
Australia29 October 2012
The Galaxy
Geoscience
Australia29 October 2012
Centrifugal acceleration due to rotation of the Solar system around the Galaxy center
V
a
V
a
29 October 2012 Geoscience
Australia
Secular aberration driftSecular aberration drift
Geoscience Australia
Systematic proper motion (dipole effect) caused by the acceleration of the Solar system barycentre
P – angle between object and the Galactic centre
Psina 2R
GMa Gal
cossinsinsincos
cossincos
321
21
aaa
aa
03
002
001
sin
cossin
coscos
aa
aa
aa
Geoscience Australia
29 October 2012
directonvectoronacceleratitheof
ofscoordinate),( 00
sourcetheof
ofscoordinate),(
Analytical expression for the dipole proper motion
29 October 2012
Fanselow (1983) Observation Model and Parameter Partials for the JPL VLBI Parameter Estimation Software MASTERFITV1.0, JPL Publication 83-39.
Bastian (1995)Eubanks et al (1995)Gwinn et al (1997)Sovers, Jacobs, Fanselow (1998)Kovalevsky (2003)MacMillan (2005)Kopeikin and Makarov (2006)
References
year/as64
213103 seckma
year/as 64
40 sources observed in more > 1,000 sessions
29 October 2012
cossincos 21 aa
The dipole systematic is visually detected!
29 October 2012
Observed apparent proper motions
29 October 2012
a = 5.3 ± 1.1 as/yr toward = 268 ± 12°, = -30 ± 13°
The Dipole obtained from 643 radio sources
29 October 2012 Geoscience
Australia
Interim conclusion
We are able to detect a tiny systematic proper motion of the reference radio sources (up to 1 μas/year), free of the intrinsic motion caused by the relativistic jets.
Potentially, we could study the dynamics of the Universe by the same way as we used to study the dynamics of the Galaxy
29 October 2012 Geoscience
Australia
Redshift dependence
ALLALL(643)
0<z<0.64(128)
0.64<z<1.13
(120)
1.13<z<1.64
(132)
z>1.64(121)
Amplitude
(μas/y)
5.3 +/- 1.1
5.0 +/- 2.3 8.0 +/- 2.2 9.3 +/- 2.7 9.1 +/- 3.4
Direction 268 +/- 12
-30 +/- 13
275 +/- 30-27 +/- 30
295 +/- 20-50 +/- 16
226 +/- 19-37 +/- 18
244 +/- 21
+17 +/- 22
Weighted rms
(μas/y)
20.8 21.2 16.7 22.2 21.9
Quadrupole systematic (2012)
29 October 2012
Mean square mplitude ~ 4.3 ± 1.4 as/year
Redshift dependent
Astrometric stability: 0.2<z<1
Quadrupole sy
stematic
Dipole systematic
Covariance function
Consider correlation between two point in sphere, separated by the angular distance P
29 October 2012
ddcos)','(f),(f)P(K
One-dimensional covariance function
Correlation vs mutual angle
radian
0.0 0.5 1.0 1.5 2.0 2.5 3.0
corr
elat
ion
-0.2
-0.1
0.0
0.1
0.2
step 1 degree
29 October 2012
Correlation vs mutual angle
radian
0.0 0.5 1.0 1.5 2.0 2.5 3.0
corr
ela
tion
-0.2
-0.1
0.0
0.1
0.2
step 1 degreestep 2 degree
One-dimensional covariance function
29 October 2012
Correlation vs mutual angle
radian
0.0 0.5 1.0 1.5 2.0 2.5 3.0
corr
ela
tion
-0.2
-0.1
0.0
0.1
0.2
step 1 degreestep 2 degreesstep 5 degrees
One-dimensional covariance function
29 October 2012
29 October 2012
Spectra of two proper motion components
29 October 2012
Spectrum of vector proper motion
Geoscience
Australia29 October 2012
Accuracy for 295 ‘defining’ sources
643 measured proper motions
• DE>+40 117
• 0<DE<+40 247
• -40<DE<0 174
• DE<-40 83
• More observations are required, especially, in the southern hemisphere.
29 October 2012
Australian (AuScope) – New Zealand network
Geoscience Australia
29 October 2012
12m Antenna at Patriot12m Antenna at Patriot5 deg/sec in azimuth, 1.5 deg/sec in elevation
29 October 2012
Conclusions
• Positions of the reference radio sources are likely to be affected by positional instabilities, random or systematic
• Cosmologic signals may be presented.
• More observations are required, especially, in the southern hemisphere.
29 October 2012
Plans
• ICRF3 to be approved by IAU GA in 2018
• IVS is planning to run am intensive astrometric program since 1, July, 2013.
• Southern Hemisphere is the area of special attention
• AuScope network to play a key role
• Parkes (with S/X receiver) is very important for observing of weak quasars for ICRF densification
29 October 2012
Thank you!
29 October 2012
29 October 2012 Geoscience
Australia
Reference frames
Inertial – no acceleration of the origin, no rotation of reference axes
Non-inertial – non-zero acceleration, rotation of reference axes is permitted
Quasi-inertial – acceleration of the origin is permitted, no rotation of references axes
29 October 2012 Geoscience
Australia
ICRS definition
Assumption (1995)
“The reference radio sources have no measurable proper motion
[at the level of precision achieved to 1995]”
The secular acceleration drift (dipole effect) is not considered by the current ICRS assumptions and IERS conventions - tbd
29 October 2012
...]...)(2
1)(
)([
HueeEeuer
ehdt
de
Proper motion in the expanding Universe (Kristian and Sachs, 1966) “Observations in cosmology”
σ – Shear
ω - Rotation
E – electric-type gravitational waves
H – magnetic-type gravitational waves
The Dipole obtained from 555 radio sources
a = 6.4 ± 1.5 as/yr toward = 263 ± 11°, = -20 ± 12°29 October 2012
29 October 2012 Geoscience
Australia
Solution of 2010 [Titov, Lambert, Gontier, A&A
(2011), 529, A91]
555 sources
0.7 +/- 1.1 μas/y -5.9 +/- 1.2 μas/y -2.2 +/- 1.2 μas/y
Amplitude
6.4 +/- 1.3 μas/y
RA = 263 +/- 11DE = -20 +/- 12
chi-sq = 1.5
wrms = 23.0 μas/y
Solution of 2012
643 sources
0.2 +/- 1.0 μas/y -4.5 +/- 1.1 μas/y -2.6 +/- 1.2 μas/y
Amplitude
5.3 +/- 1.1 μas/y
RA = 268 +/- 12DE = -30 +/- 13
chi-sq = 1.3
wrms = 20.8 μas/y
Conclusions
• The dipole effect does exist and is aligned with the theoretical prophecy.
• More distant radio sources (z>1.134) look less stable. It is important for future radio ICRF realizations.
• Cosmologic signals may be presented.
• Spectroscopic observations are essential.
29 October 2012
Part II
•Spectroscopic observations of reference radio sources (mostly in the southern hemisphere)
29 October 2012
29 October 2012
Team members:
David Jauncey (ATNF, CSIRO)Dick Hunstead, Helen Johnston (Uni of Sydney)Tapio Pursimo (Nordic Optical Telescope)Zinovy Malkin, Kirill Maslennikov, Alexandra Boldycheva (Pulkovo Observatory)Laura Stanford (Geoscience Australia)
How to implement the effect?
29 October 2012
Two ways (at least)Two ways (at least)
1. Introduce non-zero systematic proper motion at the level of IAU Resolutions
2. Incorporate the galactocentric acceleration to the conventional group delay model (IERS Conventions)
29 October 2012
))((1
1
)2
)(1)((
1)(
2
21
)(
2
222
2
2
2
wVsc
c
sVVb
cc
wV
c
V
c
U
c
sbgrav
Conventional group delay model
))((1
1
)2
)(1))(((
1)(2
21
)(
2
222
2
2
2
wtaVsc
csV
taVbcc
wVc
V
cU
csb
grav
Titov, Astronomy Report (2011), 55(1), 9529 October 2012