e-VLBI WS
PC- VSI, PC adapted VLBI Standard Interface
and Ubiquitous Gbps VLBI
Junichi Nakajima,
Yasuhiro Koyama, Tetsuro Kondo, Mamoru Sekido
Moritaka Kimura, Hiroshi Okubo, Hiroo Osaki
Communications Research Laboratory
Kashima Space Research Center
Presentation
(1)ftp-VLBI in Gbps VLBI
and small telescope
observation (review)
(2)G-bit ATM real-time VLBI
toward PC-VSI
(3)PC-VSI, the PC based
VLBI system
development
(4)Ubiquitous (anytime
anywhere) VLBI for
network experiment in
pre-mature era
e-VLBI WS
Part 1
e-VLBI WS
Gbps VLBI review
• 1998, magnetic-tape based 1-Gbps VLBI had
succeeded
• 2000, Gbps ftp-VLBI fringe finding method without
tape shipping established
• 2001, ATM-based Gbps real-time VLBI
• 2001, 2-Gbps tape-based VLBI
• 2002, 2-Gbps real-time VLBI (plan)
Data Amount Example:
•1024 M sampling per second,
•512 MHz bandwidth RF acquisition
•1024 Msps × 1(2）bit × 1(2)ch
• total data rate 2048 Mbps
•
× 24H × duty 50％
•
～10Tbyte/ telescope/ session
High Sensitivity Observation and ftp-VLBI
•
Aim
– compare total flux and correlated flux
– Measure brightness temperature
•
•
•
Source Selection
– High Red Shift QSO z>3.5 60 sources
– Total flux
>10mJy@22GHz
Antenna
– NOBEYAMA(45m)-Kashima(34m)
Frequency
– 22GHz
Nobeyama 45m
Kashima 34m
First Observation have done at 1999/12/25
Second observation in 2000
Third observation in 2001
We detected more
than
50 QSOs!
- ftp-VLBI for fringe check is realized in these session
2Gbps tape-based VSI Fringe (2001 Dec.)
1-second
fringe
• Confirmed superior sensitivity
• Each geodetic scan will be reduce to a few seconds
• Expectation in high-frequency VLBI
Small telescope VLBI
•
Aim
– University owned VLBI station
– Single frequency wide and
•
•
•
Source Selection
– ITRF Sources 20 sources
– Total flux
>20Jy@8GHz
Antenna
– Gifu(3m)-Kashima(34m)
Frequency
– 8GHz
First Fringes January 2000
Gifu University ３m
Kashima 34m
Advantages of small telescope VLBI
• Continuum sensitivity √（Ｂ・τ）
• Minimum detectable sensitivity increase
• Small telescopes becomes spot lighted again
(University telescopes) ⇒τ
• Test bench for new observations
a) Higher order sampling
b) Wide-band absorption
c) Single frequency geodetic VLBI
Ubiquitous telescope idea
(how small we can go ?)
2002/4/12
Gifu 3m
Additional important topic : VSI
e-VLBI WS
VSI concept
DAS
DPS
VSI-H
VSI-S
VSI-S
DTS
VSI-S
VSI-H
Haystack, CRL and other components of the International VLBI
Service (Whitney et al. VSI-H2000, VSI-S2002?).
Achievement of VSI
・・The VSI compatibility will realize global telescopes
flexible collaborations.
Part 2
Gbps Real-time VLBI
GALAXY-network
Usuda
６４m Kashima 34m
Collaboration
・NAO:digital serialize unit
・ISAS:UDSC 64m
・NTT：ATM and fiber
・CRL：Gbps VLBI
system and 34m
7-sessions in 2001-2002,
seyfert-galaxies, pulsars and
other observation.
Kawaguchi, Uose and Iwamura.
presentation
1Gbps real-time transmitted data
0-512MHz normal spectrum in Usuda 64m and Kashima 34m
Unusual spectrum caused by the ATM cell transfer
1Gbps real-time VLBI Fringe
Gbps fringe detection,
Usuda 64m slew to on source.
The moment fringe appears.
Source=NRAO530、pp=1sec
What we learned from the Gbps real-time
e-VLBI WS
(1) It is huge work to running experiment both in network,
telescope and correlation same time.
(2) The network delay and behaviors in critical speed
introduces another difficulty in VLBI.
(3) For the case of no fringe, and confirmation,
simultaneous recording is prepared.
(4) Motivated network researchers helped us.
Ubiquitous telescope idea
(do we need simple dedicated telescope ?)
Part 3
PC-VSI system (simplified VLBI back-end)
PC-VSI
Gbps-AD
PC-VSI2000-DIM (digitallink)
– Capture All VSI data via PCI
board (66-MHz, 64-bit)
– Gbps real-time VLBI tool focused
TCP/UDP on GbE
– Burst VLBI, ftp-VLBI
– Software correlator
– Expect wide-spread to
community by
VLBI @home, VLBI@ site,
VLBI@ satellite dish
– General purpose data acquisition
PC-VSI board and experiment
PC-VSI observation with matured network
Let’s define the file format.
Gbps emerging new media
Part 4
Ubiquitous Telescope for VLBI and network 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
GALAXY network coverage
Still a few telescopes are reachable via network
Japan Gigabit Network(JGN)
Backbone is filled by
ubiquitous VLBI
telescopes data.
Telescope approaching to network
Scientific Network(SINET)
Network link of Gbps VLBI (summary)
Real-time
processing as
interferometer
Expect IPbased network
performance.
Off-line semireal-time
processing
Conclusions
e-VLBI WS
(1) Gbps VLBI, ftp-VLBI and real-time VLBI are on-going
project and produce scientific results.
(2) PC-VSI, the PC based VLBI system will become
popular as the sub-set of the Gbps VLBI. It will widely
spread interferometric technology .
(3) Ubiquitous portable VLBI telescope will stimulate
network experiment traffic, which can be placed near
backbone nodes.
----Potential users in university, communication dish engineering and other
scientific fields are being involved.