Current status of ASTE for submm VLBI

Transcription

1 Current status of ASTE for submm VLBI Mareki Honma (VERA/NAOJ) + ASTE submm-vlbi team member (T. Oyama, T. Hara, K. Hada, H. Nagai, T. Bushimata, S. Suzuki, N. Kawaguchi, Y. Kohno, H. Ezawa, H. Iwashita R. Kawabe, H. Ogawa et al.) in collaboration with the international sub-mm VLBI team

2 Sub-mm VLBI 2010 Chile will be a key station for Sgr A* observations good site in the southern hemisphere, long baselines CARMA SMTO Hawaii Pico Veleta Schedule 2010 fringe test 2011 major obs. ASTE/APEX Planned Array for Mar 2010 obs. ASTE: Atacama Submm Telescope Experiment (D = 10m) location: near ALMA site, 4860m main frequencies: 345GHz (single cartridge RX)

3 Block diagram for VLBI Required components 230GHz RX Local generator Down Converter Recorder Frequency Standard

4 Recent progress 1 Oct 2 Apr 2009 Oct 2010 Jan 2010 Mar kick-off of ASTE VLBI JSPS funding starts (- 2011) test of instruments in NAOJ 1st-round setup at ASTE 2nd-round setup + observations

5 230G-receiver & backends Receiver : ALMA cartridge-type receiver RX testing Specification Single pol. (1/4 plate) 1 x SIS Mixer (DSB) IF output of 4~8 GHz (f ~ GHz) RX test done on Oct 2009 T_RX ~ K (DSB) Cartridge Test includes nearly whole system (RX, local, analog backends, sampler) backends

6 230GHz system stability 230G-test-tone measurement is done on 2009/Oct/19 230GHz is down-converted to 100 MHz with IF/BB converters (i.e., stability test of the whole system) Test-tone source Receiver Test-tone injection 230 GHz phase for 2000 sec σy ~ 10 sec, excellent!

7 Frequency standard H-maser Kvarz H-maser may be shipped to Chile (Jan/2010), but there are some risks (troubles in transportation, power shut-down problem etc.) troposphere OCXO8607 An alternative OCXO 8607 (the best X tal) H-maser ASD comparison

8 OCXO 8607 test 5-8/Oct/2009 at Mizusawa H-maser 1.4GHz vs OCXO8607+ SG E4426B 1.4G (E4426B stability is already known and good enough) Coherence for 15 sec (multiplied up to 230GHz) is ~ 95% 1.4G phase (red), and 230G Phase after fringe search (green) 230G (red) ~95 %!! Fringe 230G (green)

9 VERA fringe with OCXO8607 Mizusawa H-maser was temporarily replaced with OCXO 8607 for test observations Frequency drift only in Mizusawa, originating from X tal s characteristics Delay (nano sec) Fringes successfully obtained from all VERA stations! IRK OGA ISG MIZ 1.5 hours

10 ASD analysis Short-term ASD: no difference between H-maser and X tal (i.e., dominated by troposphere) Long-term ASD (t>100 sec) is different, that for baseline with X tal is dominated by X tal frequency drift tropos 10^13 phere OCXO 8607 spec. Hma 10^14 ta X se r tro po sp he re l ft i r d MIZ-IRK (X tal & H-maser) IRK-ISG (H-masers)

11 Progress at ASTE in this month new container (for VLBI instruments) Inside of VLBI container 230 GHz RX installation Cabling through ground

12 Issues to be discussed for 2010 Backends two of K5, 2 x 2 Gbps, but with 2 of 512MHz band (no subbands) software correlator should be able to handle with different sub-bands data, but Mark 4 correlator not. We will borrow Mark 5B+ as well. HDDs (still under test at ASTE) 500 GB HDDs seem mostly OK at ~5000m Trouble probability is much higher for 1 TB or 1.5 TB strong limit of total recording time. How many hours of observations in 2010?

13 Future plans 2010 Testing fringes at 230 GHz 2011 Large campaign at 230 GHz at 4 Gbps? 2012? 8 Gbps and/or 345 GHz? (345G RX already exits, but needs 1/4-wave plate for polarization) We also started discussion of ALMA phase-up with ALMA-J team. Recently we got ~150 K$ for ALMA phase-up study. Our original plan was to develop to correlator-recorder interface for ACA, but we are happy to collaborate internationally to build a full ALMA phase-up system.

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15 Local System Synthesizer (~18G) + multiplier chain Synthesizer : Agilent E8257D-UNR Multipler: HXI for 75 GHz (x4) VDI for 230 GHz (x3) Synthesizer E8257D has a phasestability high enough for 230 GHz 70G x3 18G x4 Multiplier chain

16 ASD from 230 GHz test-tone σy ~ 10 sec, excellent stability ASD for 230 GHz test-tone

17 Trade-off of X tal Bad long-term stability compared to H-maser (frequency drift) 1PPS comparison with GPS allows to calibrate frequency drift of X tal within 1 Hz Green: long-term X tal phase (top) 1PPS comparison (bottom) Rate from phase (green) and 1PPS (red)