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JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 1
Extending ICRF to 24, 32, and 43 GHz
C.S. Jacobs JPL/Caltech/NASA23 July 2009
Extending the ICRF to Higher Radio Frequencies:24, 32, and 43 GHz Global Astrometry
URS208977
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 2
Extending ICRF to 24, 32, and 43 GHz
• Motivation for a radio frame above 8 GHz
• Radio source structure/position/frequency effects
• Overview of Radio frames at 8, 24, 32, and 43 GHz
• K-band (24 GHz) frame
• X/Ka-band (32 GHz) frame
• Conclusions
Outline
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 3
Extending ICRF to 24, 32, and 43 GHz
Motivation
• Astrometry, Geodesy and Deep Space navigation have been at 8.4 GHz (X-band) with 2.3 GHz (S-band) plasma calibrations
Going to Higher radio frequencies allows
• Potentially more compact sources Potentially more stable positions • Higher Telemetry Rates to Spacecraft• Avoid 2.3 GHz RFI issues• Ionosphere & solar plasma down 15X !! at 32 GHz (Ka-band) compared to 8 GHz.
Drawbacks of Higher radio frequencies:• More weather sensitive• Weaker sources, shorter coherence times• Many sources resolved• Antenna Pointing more difficult
Picture credit: SOHO/ESA/NASA
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 4
Extending ICRF to 24, 32, and 43 GHz
The Atmosphere Effects Sensitivity
Murphy, R. et al., 1987, Earth Observing System Volume IIe: HMRR High-Resolution Multifrequency Microwave Radiometer. Published by NASA, Goddard Space Flight Centre, Greenbelt, Maryland 20771, USA, 59pp.
The three curves show absorption in a dry atmosphere, in the same atmosphere with 20 kg/m2 of added water vapour, and with both water vapour and 0.2 kg/m2 of stratus cloud added. .
Valleys are microwave windows
Murphy, R. et al., 1987, Earth Observing System Volume IIe: HMRR High-Resolution Multifrequency Microwave Radiometer. Published by NASA, Goddard Space Flight Centre, Greenbelt, Maryland 20771
Atmosphere Background:
3K/atmo @ 8 GHz
10-15K/atmo @32 GHz
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 5
Extending ICRF to 24, 32, and 43 GHz
Source Structure:
Natural radio sourcesat 8 to 43 GHz
are not point-like
Credit for this section:
E. B. Fomalont, NRAO. Charlottesville, VA
& C.S. Jacobs, JPL/Caltech/ NASA, Pasadena, CApresented at DDA meeting, Virginia Beach, May 2009
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 6
Extending ICRF to 24, 32, and 43 GHz
Structure vs. Frequency: scaled to beam
S-band X-band K-band Q-band2.3 GHz 8.6 GHz 24 GHz 43 GHz13.6cm 3.6cm 1.2cm 0.7cm
Ka-band32 GHz0.9cm
The sources become better ----->
Image credit: P. Charlot, Bordeaux Observatory & KQ VLBI Collaboration
0450-020 = J0501-0159
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 7
Extending ICRF to 24, 32, and 43 GHz
Structure vs. Frequency: Absolute scale
S-band X-band K-band K-band2.3 GHz 8.6 GHz 24 GHz 24 GHz6x3 mas 2x1 mas 2x1 mas 0.7x0.3masPk = 1.58 Jy Pk = 1.31 Jy Pk = 0.95 Jy Pk = 0.92 Jy
The sources becomes more compact ----->
Contours: -1, 1, 2, 4, 8, 25, 50, 75, 99% of maxAngular scale in milli-arcsec. Same scale for each diagram
0450-020 = J0501-0159
Credit: Petrov et al; Charlot et al., AJ, submitted Nov 2008.
Same resolutionas 8.6 GHz
Nominal resolution
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 8
Extending ICRF to 24, 32, and 43 GHz
Features of AGN (from Marscher)
Features of AGN: Note the Logarithmic length scale.Credit: Alan Marscher, `Relativistic Jets in Active Galactic Nuclei and their relationship to the Central Engine,’Proc. of Science,VI Microquasar Workshop: Microquasars & Beyond, Societa del Casino, Como, Italy, 18-22 Sep 2006.
View angleDoppler enhanced
One-sidedMost sources
>0.1 Jy
~1 masRs~
0.1 as
| |>100 2.3 GHz Radio Distant Radio Core Jets Lobes
JetBase
BlackHole
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 9
Extending ICRF to 24, 32, and 43 GHz
Overview of
Radio-based Celestial Frames
at 8.4, 24, 32, and 43 GHz
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 10
Extending ICRF to 24, 32, and 43 GHzS/X (2/8 GHz) ICRF1: 608
Sources
608 sources from S/X data up to 1995Errors Inflated: scale plus 250 µas RSS’edCredit: Ma et al, AJ, v. 116, 516, 1998.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 11
Extending ICRF to 24, 32, and 43 GHz
S/X Defining: 212 Sources
212 “Defining” sources determine conventional rotationErrors scaled plus 250 µas RSS’edCredit: Ma et al, AJ, v. 116, 516, 1998.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 12
Extending ICRF to 24, 32, and 43 GHzS/X-band (2/8 GHz): 3500*
Sources
*Plotted ~2400 sources with Declination uncertainty < 1 masGSFC-2008b-astro data to June 2008 (some K-band [22 GHz] data)Credit: Petrov, Kovalev, Fomalont, & Gordon, VCS-6, AJ, 2008, 136, 580.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 13
Extending ICRF to 24, 32, and 43 GHz
K-band (24 GHz): 275 Sources
VLBA Data 10 sessions 2002-07Formal errors with no inflationCredit: G.E. Lanyi et al, IVS meeting 2008, St. Petersburg
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 14
Extending ICRF to 24, 32, and 43 GHz
Q-band (43 GHz): 132 Sources
VLBA Data 4 sessions 2002-03Formal errors with no inflationCredit: G.E. Lanyi et al, AJ, submitted Nov 2008
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 15
Extending ICRF to 24, 32, and 43 GHz
X/Ka (8.4/32 GHz): 339 Sources
DSN 2005-09, Dec to - 45 deg. Credit: Jacobs & Sovers, 2008
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 16
Extending ICRF to 24, 32, and 43 GHz
K-band (24 GHz)Celestial Frame
based on VLBA Observations
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 17
Extending ICRF to 24, 32, and 43 GHz
Game Plan for Observations
• Phase I - Until 32 GHz available, bracket with VLBA’s closest bands 24 GHz (K-band) 43 GHz (Q-band) - Interpolate behavior to 32 GHz (Ka-band)
- identifies likely detectable sources at Ka, time variations - maps sources to provide structure information - accuracy cross-check of X/Ka during Phase-II
• Phase II - 32 GHz and 8.4 GHz (Ka/X-band) DSN observations 34m Beam-waveguide antennas, 2 baselines:
Goldstone California to Madrid, Spain 8,400 km Tidbinbilla, Australia 10,500 km
• Phase III - Add more antennas to the network - VLBA: 32 GHz proposal in the works
- Other sites have Ka, but none with X/Ka to cal plasma
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 18
Extending ICRF to 24, 32, and 43 GHz
• D. Boboltz USNO
• P. Charlot Observatory of Bordeaux
• A. Fey USNO
• E. B. Fomalont NRAO-Charlottesville
• B. Geldzahler NASA HQ
• D. Gordon Goddard/NASA
• C. S. Jacobs JPL/Caltech NASA
• G. E. Lanyi JPL/Caltech NASA
• C. Ma Goddard/NASA
• C. J. Naudet JPL/Caltech NASA
• J. Romney NRAO-Socorro
• O. J. Sovers RSA Systems/JPL
• L. D. Zhang JPL/Caltech NASA
KQ VLBI Collaboration institutions:
JPL, GSFC, USNO, NRAO, and Bordeaux Observatory •
Phase I: KQ Collaborators
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 19
Extending ICRF to 24, 32, and 43 GHz
24 & 43 GHz Observations
Mauna Kea OVRO Brewster N. Liberty Hancock
Kitt Peak Pie Town Ft. Davis Los Alamos St. Croix
(photos credit NRAO/NSF/AUI http://www.aoc.nrao.edu/vlba/html/vlbahome/thesites.html)
• VLBA ten 25m antennas
10 sessions each 24 hours
83K delay/rate obs. pairs
~65-180 sources /session
3-5 snapshots, 2 min each
400 MHz spanned band
128 Mbps record rate
• Simultaneous astrometry and imaging
• No Southern Stations
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 20
Extending ICRF to 24, 32, and 43 GHz
Results: 24 GHz Celestial Frame
Credit: G.E. Lanyi et al, IVS meeting 2008, St. Petersburg
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 21
Extending ICRF to 24, 32, and 43 GHz
∆RA, ∆ Dec: K vs. S/X
Accuracy tested vs. S/X ICRF-2 proto-type
RA: 108 µas = 0.5 nrad Dec: 207 µas = 1.0 nrad
ICRF-2 Credit: Ma et al, IERS Tech Note 35, in prep. 2009.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 22
Extending ICRF to 24, 32, and 43 GHz
K-band zonal Errors: ∆Dec vs. Dec
K-band vs. S/Xtilts vs. Declinationdue to uncalibratedIonosphere and other effects
No Dual-bandPlasma cals,No stations inthe south
Without Ion cals-10 +- 0.3 µas/deg
With GPS Ion cals-5 +- 0.3 µas/deg(shown at right)
Credit: G.E. Lanyi et al, AJ, 2008, in prep., Ma et al, in prep, 2009
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 23
Extending ICRF to 24, 32, and 43 GHz
X/Ka Frame
from Deep Space Network 8.4/ 32 GHz observations
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 24
Extending ICRF to 24, 32, and 43 GHz
Phase II: X/Ka
• Phase I - Until 32 GHz available, bracket with VLBA’s closest bands24 GHz (K-band)43 GHz (Q-band)- Interpolate behavior to 32 GHz (Ka-band)
- identifies likely detectable sources at Ka- maps sources to provide structure information
• Phase II - 32 GHz and 8.4 GHz (Ka/X-band) DSN observations 34m Beam-waveguide antennas, 2 baselines:
Goldstone California to Madrid, Spain 8,400 km
Tidbinbilla, Australia 10,500 km
• Phase III - Add more antennas to the network - VLBA: 32 GHz proposal in the works
- Other sites have Ka, but none with X/Ka to calibrate plasma
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 25
Extending ICRF to 24, 32, and 43 GHz
X/Ka Observations
Deep Space Network 34m Beam-waveguide antennas
• 44 sessions, 9390 delays/rates, ~2K parameters very small data set by S/X standards of 5 x 10^6 delays
• nominally 24 hours each to cover full range of RA
• Record rate: now 112 Mbps (MkIV mode A) future 896 Mbps (Mk5-A) = 3X sensitivity
• 360 MHz spanned bandwidth (receiver 500 MHz, VC limited)
• 1-2 snapshots, ~2 min each
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 26
Extending ICRF to 24, 32, and 43 GHz
Reference Frame Modelling
X/Ka cannot achieve the results which follow without S/Xmodels! Thus, we cannot get rid of S/X for years to come!
• Rotational alignment set to S/X ICRF
• Nutations: MHB model tuned to S/X VLBI
• Tidal models tuned to fit S/X VLBI
• UTPM: GPS + S/X VLBI data
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 27
Extending ICRF to 24, 32, and 43 GHz
X/Ka results: 339 Sources detected
DSN data 2005-09 Dec to - 45 deg
Ecliptic
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 28
Extending ICRF to 24, 32, and 43 GHz
∆RA, ∆ Dec: X/Ka vs. S/X
Accuracy tested vs. S/X ICRF-2 proto-type
RA: 185 µas = 0.90 nrad Dec: 260 µas = 1.27 nrad
ICRF-2 Credit: Ma et al, in prep. 2009.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 29
Extending ICRF to 24, 32, and 43 GHz
Zonal Errors: ∆Dec vs. Dec
Slope=1.76 sig
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 30
Extending ICRF to 24, 32, and 43 GHz
Results limited by Ka-band SNR
log10( SNR(Ka) )
Solution:
1) More bits
Mk5-A: Gbps3X SNR increase
2) Ka pointing
Potential for50% increasein SNR fromImproved pointingcalibrations
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 31
Extending ICRF to 24, 32, and 43 GHz
Results limited by No Ka-band Phase cal
Problem:180 psec~diurnal effect
Solution:
Ka-bandPhasecalPrototypeDemo’d --- >
Operations~2010
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 32
Extending ICRF to 24, 32, and 43 GHz
Troposphere Solution 2: Better Calibration
• JPL Advanced Water Vapor Radiometer ~ 1 deg beam better matches VLBI improved gain stability improved conversion of brightness temperature to path delay
• Initial demos show 1mm accuracy Goldstone-Madrid 8000 km baseline using X/Ka phase delays (Jacobs et al, AAS Winter 2005).
• A-WVRs deployed at Goldstone & Madrid Seeking funding for Tidbinbilla, Australia
• A-WVR not used yet for X/Ka catalog
-1.5
-1
-0.5
0
0.5
1
10 10.2 10.4 10.6 10.8 11
VLBI Delay Residuals DOY 200 Ka-Band DSS26-DSS55
VLBI Residuals
AWVR Calibrated VLBI
Time(hrs)
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 33
Extending ICRF to 24, 32, and 43 GHz
X/Ka Error Summary
• 339 sources north of -45 Declination
∆RA ~ 185 µas wRMS (0.9 nrad) ∆Dec ~ 260 µas wRMS (1.27 nrad)
• Potential for better than 100 µas accuracy: SNR: Mk-5A Gbps allows 3X sensitivity increase better pointing is realizing 50% better SNR
Instrumentation: Ka-band phase cal scheduled for ~2010, Digital Back End (RDBE)
Troposphere: Estimation with spatial/temporal correlations Advanced Water Vapor Radiometer cals
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 34
Extending ICRF to 24, 32, and 43 GHz
Conclusions: High Frequency ICRF
• ICRF now extended to 24 and 32 GHz ~200 µas accuracy!~300 sources north of -45 Declination
Sources unevenly observed both in numbers and geometry Caveat: models & cals still rely on S/X; still need S/X!
Observations: 24 GHz: 10 VLBA sessions, 43 GHz: 4 VLBA sessions32 GHz: 44 DSN sessions
Current Accuracy: 100-300 µas wRMS (0.5 - 1.5 nrad) Future Accuracy: 50 µas? Better?• Current limiting errors: Lack of southern stations: all bands Troposphere fluctuations: all bands Ionosphere: 24 GHz Instrumental calibrations: 32 GHz SNR: 32 and 43 GHz
Copyright 2009 California Institute of Technology. Government sponsorship acknowledged.
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 35
Extending ICRF to 24, 32, and 43 GHz
Troposphere Solution 1: Better Estimation
Day
few km
Night
12 3 CorrelatedFluctuations:Temporal &Spatial!
• Modify Least Squares to account for observation correlations -- both temporal and spatial
• Use Kolmogorov frozen flow model of Treuhaft & Lanyi (Radio Sci. 1987)
• This model increases the information available to the estimation process thereby enabling both 1) Reduced parameter biases 2) Reduced parameter sigmas
• Validation: Improves agreement of X/Ka vs. S/X catalogs by about 10% in Declinations (less in RA)
JPL/Caltech NASA
23 Jul 2009, C.S. Jacobs Page 36
Extending ICRF to 24, 32, and 43 GHz
Dec-Dec inter-source correlations