Giga-bit Geodesy e-VLBI at 22GHz Ｈｉｒｏｓｈｉ Takaba Gifu University, Japan

Pacific Plate Philippine Sea Plate Gifu Univ. 11m Eurasia Plate North American Plate NAOJ Kagoshima 20m NTT Connection(2.4Gbps) JGN3 (10Gbps) Super Sinet(4.8Gbps) Future Plan GSI Tsukuba 32m NICT Kashima 34m Hokkaido Univ 11m NAOJ Mizusawa 20m ISAS Usuda 64m NAOJ Yakaguchi 32m NAOJ Nobeyama 45m e-VLBI network

鵜飼 Cormorant Fisher, a famous fishing method in Gifu 鮎（ＡＹＵ） From May 11 to Oct 1

Accuracy of the Geodesy VLBI Accuracy of delay time for one observation Δτ ∝ 1/ ＳＮＲ Δτ ∝ 1/Bandwidth ～ 1/(Radio Frequency) Accuracy of the Geodesy VLBI Formal Error ∝ Δτ/√(Number of observations) => e-VLBI with Higher Frequency!

Importance of Geodesy for Radio Astrometry For micro-arcseconds Astrometry => less than 1mm accuracy is required! VERA Project, NAOJ S/X, 22GHz, 43GHz

Status for ２２ＧＨｚ System of Gifu 11m antenna Install 22GHz receiver （ Dec ） Cooled LNA to 11K, Trec ～ 20K Tsys ～ 100K at zenith 2Gbps e-VLBI Tests （ April-Dec ） with NICT Kashima 34m antenna 1Gbps geodesy VLBI (Tape Recording) with NAOJ VERA (Oct. 2007)

Gifu 11m － Kashima 34m 22GHz Band e-VLBI ２ Gbps 、 16seconds integration SNR ～５ ８ （ Apr.2007 ）

Purpose of this Work Development of the Giga-bit e-VLBI system at 22GHz for Geodesy and Astrometry, 2Gbps x 2ch (Now) 2Gbps x 4ch (Next Step)

Giga-bit e-VLBI System Hardware A/D converter(ADS1000): NICT 1024Msps, 2bit sampling =>2.048Gbps Optical transceiver: NAOJ XF type 256 lags Correlator: NAOJ Software Observation Software: Gifu Univ. & NAOJ Analysis Software: Gifu Univ.,NICT & GSI

Giga-bit Realtime e-VLBI instruments at Gifu University Optical Transceiver 2.4Gbps×2 links A/D Converter 2 channels XF Correlator 3 Baselines Control Computer

Real time Correlator Optical Transceiver OC48(2.4Gbps)× ２ A/D converter 2Gbps×2ch Super-Sinet OC48(2.4Gbps) Super-Sinet OC48(2.4Gbps) Super-Sinet OC48(2.4Gbps) Fusion Research Lab. NAOJ （ Mitaka City ） High Energy Lab. Tsukuba Gifu Univ. 11m Telescope32m Telescope Gifu Prefecture’s Information Super Highway Tsukuba CATV Super- Sinet Super- Sinet Geodesy e-VLBI using the Super-Sinet Optical Transceiver OC48(2.4Gbps)× ２ A/D converter 2Gbps×2ch Real time Correlator S X SX SX 100km 7km 300km100km

Real Time e-VLBI, Gifu11m-Tsukuba 32m Sband was processed at Mitaka Correlator Xband was processed at Gifu Correlator Display the fringe pictures every 1 seconds Sband Xband

Geodesy VLBI with K4/K5 and e-VLBI Results of the K4/K5 and e-VLBI coincidents within 3mm !

Problems for Wide-Band VLBI (found from S/X bands e-VLBI) K4 or K5 uses Narrow Bands System with P-cal, video converters, and many samplers => Determine delay time by Band Width Synthesis Method Giga-bit system uses Wide Band IF with only one sampler! How can we determine Delay Time?

Tsukuba32m-Gifu11m e-VLBI data 1 second integration data 1024MHz sampling ＝＞ 1 lag ～ 1 ns Giga-bit e-VLBI data have very high SNRs, can determine delay time every 1 second! Delay time by Gaussian fitting 1ns 1 sigma 40ps, 100seconds =>4ps

Original data Rotate phases when gap exists Liner Fitting => delay time Delay time determination from phase gradient Frequency (MHz) Phase(degree)

Problem for the Phase Gradient Method Phase shift caused by the band pass filter

Accuracy of the delay time, Gaussian fitting vs Phase gradient => Gaussian fitting method is better Sigma of the delay time by Gaussian fitting [ps] Sigma of the delay time by phase gradient [ps] Strong Source Weak Source

High Speed A/D converter NAOJ is now developing 35GHz A/D => Direct Sampling should be possible at 22GHz with higher mode sampling mode => No Band Pass Filters, Down Converters! => Good phase stability for wider band width!

InP HBT AD Converter developed by NAOJ ADC DMX ＲＦ Ｓｉｇｎａｌ A 32-GHz signal was successfully digitized with 3 bits. (Kawaguchi, 2006)

Another Problem for Giga-bit e-VLBI Comparison of the delay time for K4, K5, and Giga-bit e-VLBI => large drift of the delay time exists only for Giga-bit e-VLBI!

Differences of the delay time for K4 and Giga-bit e-VLBI １ｎｓ Obs. # Xband pico-seconds K4 - Giga-bit e-VLBI 1day

Almost same as K4 Differences of the delay time for K5 and Giga-bit e-VLBI Xband pico-seconds K5 - Giga-bit e-VLBI

No large drift ！ Differences of the delay time for K4 and K5 Xband pico-seconds K4-K5 (JD0404)

X band S band K5 - Giga-bit e-VLBI

LNA P-cal Hydrogen Maser Down Converter VLBI Back end 5MHz signal by co-axial copper cable IF signal by optical fiber cable Observation Room Receiver Room More than 100m for large Antenna P-cal system cancels the delay time drift by using the same path for reference signal transfer with down converter!

Giga-bit e-VLBI system for 22GHz High Speed Sampler, working at 22GHz Eliminate band-pass filter and down converters Use digital filter for multi-channel analysis P-cal injection for Phase calibration and delay time correction

LNA P-cal Hydrogen Maser A/D Converter VLBI Backend 5MHz signal by co-axial copper cable VSI data by optical fiber cable Observation Room Receiver Room More than 100m for large Antenna Digital Filter

Conclusion Radio Astrometry needs Geodesy VLBI 22GHz e-VLBI system is under-developing Some Problems were fond for Giga-bit e-VLBI, but will be cleared by using the new RF A/D converter and P-cal system!