1 / 20

Multi-frequency Phase Referencing: with the KVN and beyond

Multi-frequency Phase Referencing: with the KVN and beyond. R.Dodson 1,2 T.H. Jung 1, M. Rioja 2,3 KVN, Korea: ICRAR, UWA, Australia: OAN, Spain. Alternative Tropospheric Calibration in mm -VLBI. Conventional Phase referencing to a calibrator source ( requirements difficult to meet ).

blondelle-kayson
Download Presentation

Multi-frequency Phase Referencing: with the KVN and beyond

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Multi-frequency Phase Referencing:with the KVN and beyond R.Dodson1,2 T.H. Jung1, M. Rioja2,3 KVN, Korea: ICRAR, UWA, Australia: OAN, Spain

  2. AlternativeTroposphericCalibrationin mm-VLBI Conventional Phase referencingto a calibratorsource (requirementsdifficulttomeet) • Observe at lowerband (e.g. 21.5 GHz) • Applytohigherband (e.g. 43 GHz) fast 43 43 GHz Different source Multi-frequency: phase ref. to a lowerfrequency Same source fast

  3. Target Basics of new method: SOURCE/FREQ. phase referencing fast slow slow X A,GEO + A,TRO + STA,STR+nA High: A,GEO + A,TRO + STnA RRA,GEO + A,TRO + STnA) Low: High: R  A,TRO- R *A,TRO= 0 A,XYZ- R *A,XYZ= 0, Antennaerrors cancel!  - R*= (R-1/R)  … slow slow RSTR+ 2c (D . A,shift)+ ST Frequency Phase Transfer

  4. Basicsofnewmethod:SOURCE/FREQ. phasereferencing Introduce a SecondSource B R2c (D . B,shift)+ ION NST Same as for A Source/freq. referencedVisibilityphase: A,STR + 2c  D (A,shift - B,shift)

  5. Importantpoints • “Perfect” Tropospheric calibration • Non-integer ratio betweenfrequenciesproblematic (Introducesphasejumpsrelatedtophaseambiguities) • Frequency agility crucial: VLBA (switching); • Best simultaneous observations: KVN (Yebes-40m) • Direct Astrometric measurement of “core-shifts”, even • at the highest frequencies, > 43 GHz • Errors in station coordinates no problem (for cont. VLBI) …… 2π (nA - nB+ R(nA - nB))

  6. KVN 3x 21m Antennas in S. Korea With 4 band simultaneous mm-wave receiver system: 22, 43, 86 & 129 GHz http://kvn-web.kasi.re.kr/en/en_obs_information.php

  7. 1st KVN 4-band Fringes (2012 April) KUS-KYS Fringe Phase (deg) 86GHz 43GHz 129GHz Fringe Amplitude (Jy) 22GHz IF13 IF14 IF15 IF16 IF1 IF2 IF3 IF4 IF5 IF6 IF7 IF8 IF9 IF10 IF11 IF12 16MHz x 16CH

  8. Delay K-band Rate K13015a Jan 15, 2013

  9. Delay Q-band Rate K13015a Jan 15, 2013

  10. Delay W-band Rate K13015a Jan 15, 2013

  11. Delay D-band Rate K13015a Jan 15, 2013

  12. MFPR applied Visibility Phase @ Q-band (Rate Corrected) MFPR applied with K-band solint 0.1 Bad weather at Yonsei MFPR applied with K-band solint 0.3 K13015a: Jan 15, 2013

  13. MFPR applied Visibility Phase @ W-band (Rate Corrected) MFPR applied with K-band solint 0.1 Low SNR at 22GHz Yonsei W-band v. high Tsys MFPR applied with K-band solint 0.3

  14. MFPR applied Visibility Phase @ D-band (Rate Corrected) MFPR applied with K-band solint 0.1 Low SNR at 22GHz Poor temp. control (±6oC) MFPR applied with K-band solint 0.3

  15. VLBA demonstrations • 86GHz (relative) phase referencing not first (Porcas&Rioja) but only practical Measured `core-shifts’ between 43&86 of <10μas Target is SiO maser alignment • 43GHz Absolute Astrometry 22 GHz conventional PR + 22/43GHz SFPR

  16. VLBA demonstrations FPT: Sources track each other SFPR: Phases are at `zero’ FPT: Sources have common residuals Image at phase centre SFPR: Astrometrically corrected phases Offsets from centre are the position difference btw frequencies

  17. Beyond KVN: Sim. mm-VLBI facilities VLBA has long baselines. KVN lacks these KVN uv-coverage: KAVA uv-coverage: Global uv-coverage: Potential to achieve~40μas with 2mm VLBI

  18. Consequence of Adding KVN to VERA KVN And VERA Array Much greater sensitivity to low(er) surface brightness

  19. Beyond SFPR: MFPR Can we find the corrections for ionosphere and instrumental terms in the data itself? Require ΔTEC → 0 In principle measurements at multiple frequency Should allow to solve for all the unknowns: ΔTEC Non-dispersive (Trop) Core-shift →Measure in delay →Measure in sim. mm freq. →Delay contribution*(k-1) With~0.1 nsec accuracy get ~0.1 TEC residual Obs. 4 freqs bracketing FPT observations Low frequency required: need L band

  20. Conclusions: • Source Frequency Phase Referencing is now an established method • both VLBA and KVN are demonstrating SFPR • We are extending into MFPR, and have VLBA observations made. But I have not seen the data yet.

More Related