1. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 1 Extending ICRF to 24 GHz C.S. Jacobs JPL (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 ICRF To Higher Radio Frequencies: 24 GHz Astrometry IVS General Meeting 2006

2. 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

3. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 3 Extending ICRF to 24 GHz Collaborators on Astrometry P. CharlotObservatory of Bordeaux E. B. Fomalont NRAO-Charlottesville D. GordonGoddard/NASA C. S. JacobsJPL/Caltech NASA G.E. LanyiJPL/Caltech NASA C. Ma Goddard/NASA C.J. NaudetJPL/Caltech NASA O.J. SoversRSA Systems/JPL L.D. ZhangJPL/Caltech NASA This team is a subset of the larger KQ VLBI Collaboration which includes: National Radio Astronomy Observatory -Socorro U.S. Naval Observatory

4. 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

5. 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.

6. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 6 Extending ICRF to 24 GHz Schematic of Active Galactic Nuclei Redshift z~ 0.1 to 5 Distance: billions light years Parallax = 0 Proper motion < 0.1 nrad/yr Centroid of radiation Gets closer to central engine (black hole) As one goes to higher Frequencies, 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

7. 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

8. 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-band 2.3 GHz 8.6 GHz 24 GHz 43 GHz 13.6cm 3.6cm 1.2cm 0.7cm Ka-band 32 GHz 0.9cm The sources become better ----->

9. 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 available 24 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??

10. 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 OVROBrewsterN. LibertyHancock Kitt PeakPie Town Ft. DavisLos AlamosSt. Croix

11. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 11 Extending ICRF to 24 GHz Results: 24 GHz Celestial Frame

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 19 Extending ICRF to 24 GHz 3 Constraint Zonal Errors: ∆Dec vs. Dec

20. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 20 Extending ICRF to 24 GHz 8 Constraint Zonal Errors: ∆Dec vs. Dec

21. 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 separate with only few days data - more data needed. Future Plans: More K-band data on the way. Make 8.4 / 32 GHz (X/Ka) operational

22. JPL/Caltech NASA 11 Jan 2006, C.S. Jacobs Page 22 Extending ICRF to 24 GHz Results: 43 GHz Reference Frame

23. 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 unobservable Proper Motions < 0.1 nrad/yr BUT... Price to be paid is Very weak sources 1 Jy = 1.0E-26 watt/m**2/Hz need lots of square meters => > 25m Antenna lots of Hz bandwidth => 100 Mbps – 1Gbps low system temp=> Tsys = 20-40 Kelvin Basis of VLBI: Point source at infinity (Hubble Deep Field STScI/NASA)