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IVS General Meeting 2004

IVS General Meeting 2004. Extending the ICRF To Higher Radio Frequencies: 24 and 43 GHz Astrometry. 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 9 Feb 2004. Outline.

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IVS General Meeting 2004

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  1. IVS General Meeting 2004 Extending the ICRF To Higher Radio Frequencies: 24 and 43 GHz Astrometry 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 9 Feb 2004

  2. Outline • Motivation for a radio frame above 8 GHz (X-band) • Game plan • Initial Observations • Results • Accuracy • Future Plans/Conclusions

  3. Collaborators 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

  4. 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 plasmadown 16X !! at 32 GHz (Ka-band) compared to 8 GHz. Picture credit: SOHO/ESA/NASA

  5. Why Ka-band? Valleys are microwave windows 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. . 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. 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. Basis of VLBI: Point source at infinity 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 => 34 - 70m Antenna lots of Hz bandwidth => 100 Mbps – 1Gbps low system temp => Tsys = 20-40 Kelvin (Hubble Deep Field STScI/NASA)

  7. AGN schematic Schematic of Active Galactic Nuclei Redshiftz~ 0.1 to 5 Distance: billions light years Parallax = 0 Proper motion < 0.1 nrad/yr (Credit: C.M. Urry and P. Padovani ) http://heasarc.gsfc.nasa.gov/docs/objects/agn/agn_model.html

  8. AGN Cen-A in X-ray, Optical, Radio 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)

  9. Game Plan • Long term - simultaneous 8.4 and 32 GHz (X/Ka-bands) at present instrumentation not all in place • 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 • Now: Exercise short baseline Ka-band instrumentation at Goldstone California (DSS 13 - DSS 25) • Exploring potential single baseline Goldstone CA to Kashima • Ka-band Soon - Goldstone-Spain (March ‘04) and Goldstone-Australia (April ‘05) VLBA ?? Others??

  10. Initial Observations Mauna Kea OVRO Brewster N. Liberty Hancock Ft. Davis Los Alamos St. Croix Kitt Peak Pie Town • VLBA ten 25m antennas 5 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 2004 (photos credit NRAO/NSF/AUI http://www.aoc.nrao.edu/vlba/html/vlbahome/thesites.html)

  11. Results: 24 GHz Celestial Frame

  12. Results: 43 GHz Reference Frame

  13. ∆RA accuracy: K vs. S/X ICRF ext “1.5”

  14. ∆Dec accuracy: K vs. S/X ICRF ext “1.5”

  15. Internal consistency: K - Q ∆RA

  16. Internal Consistency: K - Q ∆Dec

  17. Zonal Errors: ∆RA vs. Dec

  18. RA-RA corr. vs. Arc: Minimal constraint • 3-D orientation set by fixing 1.5 sources • RAs not well separated by least squares • Only 3 days data

  19. RA-RA correlations: 4 source constraint • 3-D orientation set by fixing 4 sources • RAs now better separated by least squares • Still only 3 days data • Cost: Impose 5 pieces of external information from S/X ICRF

  20. Conclusions • ICRF now extended to K and Q-bands at sub mas accuracy ! 24 and 43 GHz observations: 5 sessions ~ 230 sources at K-band, 24 GHz ~132 sources at Q-band, 43 GHz ~ 250 µas formal precision systematics at 500 µas level or less Source parameters not yet well separated with only few days data - more data needed. • Future Plans More K and Q-band data on the way. Planning for simultaneous 8.4 / 32 GHz (X/Ka) data

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