1 Gbps Disk-Based VLBI Observation for Future East Asia VLBI Observations Kiyoaki Wajima 18 March 2009 동아시아 VLBI 워크샵 Yamaguchi University Introduction Observation and Results Future Observation Plan Summary Contents Observation by K5/VSI with delight

I. Introduction

Wideband Observation in VLBI Minimum sensitivity for a continuum source in VLBI ⇒ S min ∝ B -1/2 –Expansion of bandwidth with high-speed sampling and data recording for better sensitivity Conventional VLBI recording system has a dedicated recorder with a magnetic tape drive 18 March 2009 동아시아 VLBI 워크샵 General-purpose instrument by commercial PC specification having VLBI data recording and correlation function

K5/VSI System Disk-based VLBI recording system developed by NICT VLBI Standard Interface (VSI)-compliant data recording with a data rate of 1 Gbps or higher –System configuration at low cost compared to dedicated recording system –Software correlation capability K5/VSI recorder (lower) and VSI-H compliant sampler ADS-1000 (upper) (image courtesy of NICT) We made test observations using K5/VSI for future EAVN observations 18 March 2009 동아시아 VLBI 워크샵

II. Observation and Results

Test Observation Summary Test Observations with K5/VSI –Date: 26, 27 June 2008 –Station: Yamaguchi 32 m, Kashima 34 m (baseline length: 850 km = 30 Mλ) –Frequency: 8 GHz –Target: 3C 273 –Observation made with three sampling modes (512 MHz bandwidth each) 1 Gsps, 1-bit sampling at each station 2 Gsps, 2-bit sampling at each station Mixed recording with 1-bit (Yamaguchi) and 2-bit (Kashima) Integration time: 1 ~ 10 seconds 18 March 2009 동아시아 VLBI 워크샵 Kashima 34 m Telescope Yamaguchi 32 m Telescope We are here!

Results Fringes were successfully detected in 27 June observation for all sampling modes Example of fringe search results. 1-bit quantization, 1 Gbps recording, and integration time of 3 seconds 18 March 2009 동아시아 VLBI 워크샵

Results (cont’d) Expected fringe SNR –1-bit sampling, B = 512 MHz, τ = 1 sec, T sys ~ 50 K (Yamaguchi), ~ 80 K (Kashima), S ν ~ 8 Jy (~ 30 Mλ) MOJAVE 15 GHz visibility plot for 3C273 on 17 July 2008 VLBA calibrator survey 8 GHz visibility plot for 3C273 on 14 July 2004 Consistent with our observation results 18 March 2009 동아시아 VLBI 워크샵

Results (cont’d) Effects of integration time and quantization for fringe SNR –Effect of integration time (upper) SNR ∝ t 1/2 –Sensitivity relative to the nonquantizing case 1-bit (2-level): 64% 2-bit (4-level): 88% 1/2-bit mixed correlation: 75% → sensitivity relative to the 1-bit quantization (lower) 1/2-bit mixed correlation: 117% 2-bit (4-level): 138% 18 March 2009 동아시아 VLBI 워크샵

Results (cont’d) Effects of integration time for fringe SNR Calculated and observed fringe SNR for each integration time relative to SNR for the integration time of 1 second in the same sampling mode 18 March 2009 동아시아 VLBI 워크샵

Results (cont’d) Quantization effects for fringe SNR Calculated and observed fringe SNR for each sampling mode relative to SNR for the 1- bit sampling in the same integration time 18 March 2009 동아시아 VLBI 워크샵

Results (cont’d) 27 June 2009 results (summary) Sampling mode Int. time [sec] SNRSNR ratio (int. time) SNR ratio (quantization effect) 1-bit －－ 1-bit － 1-bit － 1/2-bit mixed － /2-bit mixed /2-bit mixed bit － bit bit The results of each fringe SNR are consistent with theoretical values in terms of the integration time and quantization effects. 18 March 2009 동아시아 VLBI 워크샵

III. Future Observation Plan

EAVN Observations with K5/VSI Sampler with VSI-compliant output format (we suppose the ADS-1000 sampler) ⇒ VLBI observations with K5/VSI –Test observations and initial scientific results with KVN-internal baselines –International VLBI experiments with K5/VSI for EAVN KVN digital data acquisition system 18 March 2009 동아시아 VLBI 워크샵

Future Test Observation 22/43 GHz receiver installation at KVN Seoul and Ulsan station by June 2009 (Han-san’s talk) –Test observations with VERA and JVN in 2009 –K4/VSOP terminal with 256 Mbps (Miyazaki-san’s talk) Current development at Yamaguchi University –22 GHz cooled receiver system installation at Yamaguchi station –New K5/VSI instruments (my talk) Test experiments and scientific observations between Korea and Japan 18 March 2009 동아시아 VLBI 워크샵

Observation of Young Radio Galaxy 18 March 2009 동아시아 VLBI 워크샵 Spectral age, t syn, of young radio galaxies (CSO, GPS, HFP) Exploring the physical evolution of radio galaxies Multifrequency, wideband radio spectra for the lobes (ν br : Synchrotron break frequency) (Nagai et al. 2006, ApJ, 648, 148)

IV. Summary

Summary We made VLBI observations with K5/VSI at 8 GHz and fringes were successfully detected. The results of each fringe SNR are consistent with theoretical values in terms of the integration time and quantization effects. On the basis of test observation results, we are planning to carry out test experiments and to obtain scientific results. 18 March 2009 동아시아 VLBI 워크샵

为了东亚 VLBI … 동아시아 VLBI 를 위하여 … Thank you for your kind attention. どうもありがとうございました