VERA　 project

H.Kobayashi

NAOJ,VERA project

VLBA 10th Anniversary Conference

(Socorro, June 12, 2003)

Project members

13 scientists (NAOJ, Kagoshima Univ.) H.Kobayashi, S.Manabe, N.Kawaguchi, T.Omodaka, K.Shib

ata, O.Kameya, Y.Tamura, M.Honma, K.Hirota, Y.Kanya, T.Jike, H. Ishituka, M.Rijoha

7 technicians T.Miyaji, K.Horiai, S.Kuji, K.Iwadate, K.Satou, H.Sakai, T.

Bushimata

8 graduate students T.Oyama, T.Kurayama, R.Kamohara, H.Suda, S.Sakakibara,

K.Nakashima, R.Shimizu, Y.Che

Scientific goal

Astrometry with 10μarcsec. accuracy between background object and galactic object within 2.2 degree separation Proper motion and parallax measurements

3D map and velocity field of the Galaxy Detailed 3D velocity structure of molecular gas around evolved

stars and star forming regions

Phase referencing to improve sensitivity with long integration

Expected distance accuracy of VERA

Sun 10% error at the G.C 20% error at opposite side

Array configuration

Specifications

Antenna diameter ; 20m Observing bands ; 2GHz, 8GHz,

22GHz 、 43GHz Tape recording rate ; 1Gbps 2 beam system for phase referencing Path error between 2 beam; 100μm

Antenna （ Mizusawa station)

Construction of the antenna

Panel adjustment Surface accuracy

0.15mm rms Panel; 0.1 mm rms Panel adjustment; 0.1 m

m rms Sub ref.: 0.03mm rms

Cooled HEMT receiver

Trx = 60 K @ 22GHz

40K@22GHz

Trx=130K ＠ 43GHz

70K@43GHz

Discrete HEMT MMIC HEMT

Receiver platform for 2 beam

Antenna upper cabin

Radiator on the antenna surface

Noise source on the dish Symmetric distribution of

4 noise sources Instrumental phase error is

estimated by the average of 4.

Antenna （ Mizusawa station)

Instrumental 　 phase correction

Phase difference of surface radiator between 2 beams

Less than 1degree 　measurement accuracy is achieved

2B phase response from surface radiator depend on beam separation

First phase variations between 2 beams

Fringe phase of W49N,OH43 and difference

Allan variance of them

Coherence improvement

Coherence drop of 1B and 2B fringe

Fringe detection with 20 min. integration, GRB030329

Digital backend

•2.4Gbps transmit for each beam

•Digital filter is used for frequency selection

Spiral array feed for ＳＸ

Fringe detection by SX mode

Nov. 19th, 2002 between VERA mizusawa- Gifu

Geodesy observations

Combine with the world coordinate by SX observations Combined with Tsukuba 32m of Japanese GSI

Baseline determination Required accuracy 　　 2mm 22GHz wideband observations SX conventional observations

VERA first fringe on Feb. 20th, 2002

Orion-KL

H2O maser

１Ｇｂｐｓ recorder & correlation

•SONY 　 DIR2000 　 1024Mbps　

80 min/tape

•Mitaka FX correlator

5 station correlation with 1Gbps

Output to CODA system

Convert correlation data to FITS

First 1Gbps fringe among VERA 4 stations, Sep. 18th, 2002

Og ー Is Ir ーIs

Mz-IsMz-Ir

Test observations

Phase referencing check 22GHz

SgrB2-SgrA*, W51N, W49N, Orion-KL, W3OHVX-Sgr, VY-CMa, etc

43GHzOrion-KL

Fringe check and calibrators Strong H2O masers (>20Jy), Calibrator candidates

Antenna （ Mizusawa station)

Improvement of sensitivity ２２ＧＨｚ

Before improvement

After improvement

Atmospheric loss τ=0.2 66K τ=0.2 66K

Ground coupling 25K 25K

Fee dome loss -0.6 dB 54K -0.1dB 9K

Receiver 80K 112K 40K 50K

System noise Tsys* 232K 155K

Improvement of sensitivity 43 ＧＨｚ

Before improvement

After improvement

Atmospheric loss τ=0.15 49K τ=0.15 49K

Ground coupling 29K 29K

Fee dome loss -1 dB 90K -0.15dB 12K

Receiver 130K 190K 70K 84K

System noise Tsys* 358K 174K

Expected sensitivity 1

22GHz 43GHz

separation 0 deg. 2 deg. 0 deg. 2 deg.

Antenna aperture eff.

50%* 48% 45% 36%

Tsys 150 K 150 K 180 K 180 K

* Measured value

Expected Sensitivity 2

22GHz 22GHz 43GHz 43GHz

Continum Maser Continum Maser

Integ. Time

100 3600 100 3600

7σ

Sensitivity

0.1 Jy 1.2 Jy 0.25 Jy 1.9Jy

Integ. Time

3600 100 3600 100

7σ

Sensitivity

0.02 Jy 7.2 Jy 0.04 Jy 11.4Jy

VERA Mizusawa met a strong earthquake (Sanriku-minami jishin)

Vertical 0.2G, Horizontal 0.3G

Plan of VERA

2002 ：　 Fringe 　 detection / 2B fringe test

2003: Feasibility check of 2B interferometer

Test observations for astrometry

2004: Test observations for astrometry

Improvement of system sensitivity

2005: Complete

Ishigakijima

Iriki

Mizusawa

Ogasawara

VERA

KVN

VERA & KVN Network

16 VLBI stations in east Asia

Under operation

Under construction