JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 1

Extending ICRF to 24 GHz

C.S. JacobsJPL (Caltech/NASA)

P. Charlot, E.B. Fomalont, D. Gordon, G.E. Lanyi, C.Ma,

C.J. Naudet, O. J. Sovers, L.D. Zhang,and the KQ VLBI Survey Collaboration

11 Jan 2006

Extending the ICRFTo Higher Radio Frequencies:

24 GHz Astrometry

IVS General Meeting 2006

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 2

Extending ICRF to 24 GHz

• Motivation for a radio frame above 8 GHz (X-band)

• Game plan

• Observations

• Results

• Accuracy

• Future Plans/Conclusions

Outline

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 3

Extending ICRF to 24 GHzCollaborators on Astrometry

• P. Charlot Observatory of Bordeaux

• E. B. Fomalont NRAO-Charlottesville 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 O.J. Sovers RSA Systems/JPL L.D. Zhang JPL/Caltech NASA

This team is a subset of the larger KQ VLBI Collaboration which includes:

National Radio Astronomy Observatory -Socorro

U.S. Naval Observatory

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 4

Extending ICRF to 24 GHz

Motivation

• Astrometry, Geodesy and Deep Space navigation, now at 8.4 GHz (X-band)

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

Picture credit: SOHO/ESA/NASA

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 5

Extending ICRF to 24 GHz

Why Ka-band?

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, USA, 59pp.

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 6

Extending ICRF to 24 GHz

Schematic ofActive Galactic Nuclei

Redshift z~ 0.1 to 5Distance:

billions light yearsParallax = 0

Proper motion < 0.1 nrad/yr

Centroid of radiationGets closer to central engine (black hole)

As one goes to higherFrequencies, therefore,

K/Ka/Q better than X

AGN schematic

(Credit: C.M. Urry and P. Padovani ) http://heasarc.gsfc.nasa.gov/docs/objects/agn/agn_model.html

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 7

Extending ICRF to 24 GHz

-

Credits: X-ray (NASA/CXC/M. Karovska et al.); Radio 21-cm image (NRAO/VLA/Schiminovich, et al.),

Radio continuum image (NRAO/VLA/J.Condon et al.); Optical (Digitized Sky Survey U.K. Schmidt Image/STScI)

AGN Cen-A in X-ray, Optical, Radio

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 8

Extending ICRF to 24 GHz

Source Structure vs. Frequency

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 ----->

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 9

Extending ICRF to 24 GHz

Game Plan

• Long term - simultaneous 8.4 and 32 GHz (X/Ka-bands) at present instrumentation not completely operational

• Interim plan: Bracket 32 GHz with currently available24 GHz (K-band)43 GHz (Q-band)- Interpolate behavior at 32 GHz (Ka-band)

identifies likely detectable sources

• Ka-band - DSN 34m Beamwaveguide antennas: FRINGES! Goldstone California Madrid, Spain Tidbinbilla, Australia

- VLBA: 32 GHz proposal not funded at this time - Others??

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 10

Extending ICRF to 24 GHz

Initial Observations

• VLBA ten 25m antennas

8 sessions each 24 hours ~ 60 sources per session

3-5 snapshots, 2 min each

400 MHz spanned bandwidth

128 Mbps record rate

• Simultaneous astrometry and imaging

• more sessions planned for 2006

(photos credit NRAO/NSF/AUI http://www.aoc.nrao.edu/vlba/html/vlbahome/thesites.html)

Mauna Kea OVRO Brewster N. Liberty Hancock

Kitt Peak Pie Town Ft. Davis Los Alamos St. Croix

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 11

Extending ICRF to 24 GHz

Results: 24 GHz Celestial Frame

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 12

Extending ICRF to 24 GHz

Results: 24 GHz vs 2.3/8.4 GHz Frame

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 13

Extending ICRF to 24 GHz

∆RA accuracy: K (3 constraint) vs. S/X ICRF

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 14

Extending ICRF to 24 GHz

∆Dec accuracy: K (3 const.) vs. S/X ICRF

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 15

Extending ICRF to 24 GHz

RA-RA corr. vs. Arc: Effect of More Data

• 3-D orientation set by fixing 1.5 sources i.e. minimal constraint• RAs not well separated by least squares

• After 3 sessions After 8 sessions

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 16

Extending ICRF to 24 GHz

RA-RA correlations: Effect of constraints

• 3-D orientation set by fixing 1.5 vs. 4 sources

• RAs not yet well separated by least squares “fix” at cost of 5 external constraints

3 rotation constraints 8 rotation constraints

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 17

Extending ICRF to 24 GHz

∆RA accuracy: K (8 const.) vs. S/X ICRF

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 18

Extending ICRF to 24 GHz

∆Dec accuracy: K (8 const.) vs. S/X ICRF

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 19

Extending ICRF to 24 GHz

3 Constraint Zonal Errors: ∆Dec vs. Dec

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 20

Extending ICRF to 24 GHz

8 Constraint Zonal Errors: ∆Dec vs. Dec

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 21

Extending ICRF to 24 GHz

Conclusions

• ICRF now extended to K-band with sub-mas accuracy!

Observations: K-band (24 GHz): 8 VLBA sessions 259 sources, but unevenly observed

Accuracy:

~ 350 / 470 µas (RA/Dec) with 3 constraints

~ 200 / 300 µas (RA/Dec) with 8 constraints

Source parameters starting to separatewith only few days data - more data needed.

• Future Plans:More K-band data on the way.Make 8.4 / 32 GHz (X/Ka) operational

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 22

Extending ICRF to 24 GHz

Results: 43 GHz Reference Frame

JPL/Caltech NASA

11 Jan 2006, C.S. Jacobs Page 23

Extending ICRF to 24 GHz

How Does VLBI work?Extragalactic “nebulae” idea goes back to 18th c. ?

• Relies on point source at infinity -Active Galactic Nuclei Concept: Nav by “fixed” stars

• Advantages:Parallax unobservableProper Motions < 0.1 nrad/yr

BUT . . .BUT . . .

• Price to be paid isVery weak sources 1 Jy = 1.0E-26 watt/m**2/Hzneed lots of square meters => > 25m Antennalots of Hz bandwidth => 100 Mbps – 1Gbpslow system temp => Tsys = 20-40 Kelvin

Basis of VLBI: Point source at infinity

(Hubble Deep Field STScI/NASA)