Gbps Radio Telescope Data Transfer,

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APAN Fukuoka
Gbps Radio Telescope Data Transfer, VLBI Network
Experiment in CRL
Junichi Nakajima, Yasuhiro Koyama, Tetsuro
Kondo, Mamoru Sekido Moritaka Kimura, Hiroshi
Okubo, Hiroo Osaki Communications Research
Laboratory Kashima Space Research Center
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Presentation

• Review Radio Astronomy, Gbps VLBI and Gbps
  real-time ATM-based VLBI
• Introduction of ongoing projects
• a) Radio-telescope agreed G-bps hardware
  interface VSI
• b) Recent international network experiment
  of between U.S., Finland and Japan
• c) Network dedicated Gbps small radio
  telescope using common PC technology to fill-up
  back-bone

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Review 10 minutes
(1) Gbps VLBI and realtime Gbps VLBI

• 1998, first-ever magnetic-tape based Gbps VLBI
  had succeeded
• 2000, Gbps ftp-VLBI fringe finding method without
  tape shipping established
• 2001, ATM-based 1024Gbps real-time VLBI
  (domestic)
• 2002, IP-based real-time VLBI, ftp-based near
  realtime VLBI (international, between U.S.,
  Finland)
• 2002 Network-experiment dedicated small radio
  telescope developed

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VLBI essential
Very Long Baseline Interferometer
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Final target establish Global radio
telescope nano-second order data epoch control
in network common interface
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Instruments (Tape System)
AD sampler
Data Recorder
01GHz (IF)
Data
0000000010010010 11110101 10011011 11010011
10010110 11100100 11010100 11000011
0000000210001001 11001011 01001111 00110011
00111000 01111001 11001000 11010110
0000000301111000 11111100 11001101 10001011
10001110 01000100 01110001 00100111
0000000500100111 10010100 10011110 10001110
01110010 01011100 00111101 10010111
0000000600100110 11100001 01111001 11000100
11001100 11100001 11011110 00111110
0000000801101100 11100011 00101110 10000100
01110100 01111011 10100010 11101001
0000000900000111 11000111 11000011 10100010
11111001 10110110 01001111 00110010
0000001101111101 00111000 11111100 00111011
00110100 01001101 10100100 11110001
0000001200000111 11001100 00111111 10000110
10010001 11110000 00111101 01101100
Data processing correlator
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Amount of VLBI data

• Example
• 1024 M sampling per second,
• (Nyquist 512 MHz bandwidth RF acquisition)
• 1024 Msps 1(2)bit 1(2)ch
• total data rate 2048 Mbps
• 1024Mbps 24H duty 50
• 10Tbyte/ telescope

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High Sensitivity Observation (scientific output)
Nobeyama 45m

• Aim
• compare total flux and correlated flux
• Measure brightness temperature
• Source Selection
• High Red Shift QSO zgt3.5 60 sources
• Total flux gt10mJy_at_22GHz
• Antenna
• NOBEYAMA(45m)-Kashima(34m)
• Frequency
• 22GHz
• We detected more
• than 50 QSOs!

Kashima 34m
Deceralation parameter of universe
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2Gbps tape-based VSI Fringe (top data)
1-second fringe

• Confirmed superiority in sensitivity
• Each observation will be reduce to a few seconds
• High-frequency VLBI possibility

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ATM-network (GALAXY Domestic NTT connection)
Still a few telescopes are reachable via network
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Collaboration NAOdigital serializer ISASUDSC
64m NTTATM and fiber CRLGbps VLBI
system and 34m
1Gbps real-time fringe
GALAXY-network
Usuda 64m

Kashima 34m
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1Gbps real-time transmitted data
0-512MHz normal spectrum in Usuda 64m and Kashima
34m
Unusual spectum caused by the ATM cell failure
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1Gbps realtime-VLBI Fringe
256ns window
Gbps fringe detection, Usuda 64m slew to on
source. The moment fringe appears. SourceNRAO530?
pp1sec
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(2) a) Ongoing Project 10minutes
VSI (Versatile Scientific Interface)
VSI concept
DAS
DPS
VSI-S
VSI-H
VSI-H
VSI-S
VSI-S
DTS
Most radio telescope will use this interface.
Internationally agreed
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Instruments

• PC-VSI system
• All recording function on PCI board
• Gbps real-time VLBI tool
• Burst VLBI,ftp-VLBI
• Software correlator
• Expect wide-spread community by
• VLBI _at_home, VLBI_at_ site, VLBI_at_ satellite dish
• General purpose data acquisition

PC-VSI2000-DIM (digitalink)
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Instruments
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(2) b) Ongoing Project
Japan-Finland Network Observation
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Japan-Finland Network Observation
22nd,October,2002 Helsinki University of
Technology (besides NOKIA) Metsahovi Radio
Observatory 14m Radio Telescope 22GHz Receiver
Noise Temperature 60K(Tsys150K?weather
condx.) Astronomical Object W3OH, Massive Star
Forming Region Observation Period 15 seconds
(2GB)
Stellar emission
Sprious?
Metsahovi telescope
FFT Spectrum of the first second ftp data,
confirm receiver setup
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Correlated radio spectrum from object
Cross Power Spectrum
Doppler Rate Residual
We have connected radio telescopes via the network
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KASHIMA-WESTFORD (Japan-U.S.)IP VLBI real-time
Experiment
(2) b) Ongoing Project
Kashima 34m, CRL
Westford 18m, MIT Haystack
Observations toward determine the Earth
Orientation Parameter in real-time by
referencing the distant quasars.
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KASHIMA-WESTFORD IP-VLBI Experiment

• Observation 9th October, 2002 1500-1800UT
• Data Rate Started at 40 kbps 1Mbps,bi-directional
  
• Real-time data transfer to Japan and correlation
  processing

Westford 18m, MIT Haystack
Kashima 34m, CRL
Time-tagged IP packet exchange between the
telescopes
Kashima
Westford(18m)
Haystack?
K5
K5
X-band IF
Observations toward determine the Earth
Orientation Parameter in real-time by
referencing the distant quasars
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High-Speed Network (U.S. domestic)
Via NTT-Musashino To Kashima 34m RT
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Obtained radio star correlation, the dual
frequency result enables ionosphere radio delay
cancellation to determine precise EOP
X-band(8GHz)
S-band(2GHz)
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(2) c) Ongoing Project
Dedicated small Telescope for network-based
VLBI
1m-dish Ambient K-band LNA(200K)
Ibaraki-univ.
Takahashi PC-controlled
equator mount
Last 1-mile us usually longer than 1-mile.
PC-VSI observation Package
Ubiquitous VLBI Package
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CARAVAN Compact Antenna of RadioAstronomy VLBI
Adapted for Network
Quasar detected!

• 65cm small dish for satellite TV
• Equational mount of optical telescope
• Guided with optical telescope
• A remote controller automatically track objects

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Japan Gigabit Network(JGN)
Backbone is filled by Small Gbps VLBI telescopes
data.
Telescope approaching to network
Scientific Network(SINET)
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1Gbps real-time transmitted data
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Conclusions

• Gbps VLBI and real-time VLBI is producing
  scientific results.
• Internationally approved VSI interface and
  growing network enables mutual experiment between
  the countries.
• Dedicated small VLBI telescope for network will
  activate network bandwidth soon
• The PC based VLBI system development will
  popularize the intrferometric technique wide
  spread.
• ----Potential users in universities,
  communication dish engineering and other
  scientific fields are invited to this research
  field.