Overview of the Twelfth TDC Meeting
Tetsuro Kondo (kondo(AT)nict.go.jp)
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-0012, Japan
The twelfth meeting of the Technical Development Center was held on March
10, 1998 at the Kashima Space Research Center of the
Communications Research Laboratory.
Fujinobu Takahashi (KSRC: Kashima Space Research Center),
Noriyuki Kurihara (KSRC),
Yasuhiro Koyama (KSRC),
Junichi Nakajima (KSRC),
Ryuichi Ichikawa (KSRC),
Tadahiro Gotoh (KSRC),
Tomonari Suzuyama (KSRC),
and Tetsuro Kondo (KSRC)
Noriyuki Kawaguchi (National Astronomical Observatory),
Hideo Hanada (National Astronomical Observatory),
Mikio Tobita (Geographical Survey Institute),
Masayuki Fujita (Hydrographic Department, Maritime Safety Agency)
Seiichi Shimada (National Research Institute for Science and Disaster
Kachishige Sato (Tokyo Gakugei University),
and Masayuki Takemura (Kobori Research Complex, Kajima Corporation)
Following special members could not attend:
Tetsuo Sasao (National Astronomical Observatory) and
Shuhei Okubo (Earthquake Research Institute, University of Tokyo),
1. Opening Greeting
Fujinobu Takahashi, the vice-director of IERS TDC at the
Communications Research Laboratory (CRL), opened the meeting.
2. Activity Reports by the Special Members
Each special member reported on the current status of the activities
of each organization.
National Research Institute for Science and Disaster Prevention
Seiichi Shimada reported on the effect of horizontal atmospheric asymmetry in
GPS data analysis. He mentioned that the estimated horizontal station position
had been improved but this is is not the case for the vertical position. He
also demonstrated water vapor distribution in a time-space domain obtained from
GPS data analysis.
Hydrographic Department, Maritime Safety Agency
Masayuki Fujita reported on the current status of SLR and GPS observations
carried out by the Hydrographic Department of the Maritime Safety Agency as
System improvement in accuracy targeting to 1 cm which is going on at the
Shimosato SLR station has entered a final phase.
Measurements using a mobile SLR station made at Chichijima Island on the
Philippine sea plate and which were separated by several years show motion of
the island at 6 cm/year, which is consistent with VLBI measurements. Last
summer the mobile station was located at Ishigakijima island. The measurements
could barely be carried out due to the system's age. Next fiscal year, the
mobile SLR station will be located at Wakkanai on Hokkaido.
The Hydrographic Department is planning to establish a fully automated GPS
observation station at Danjo islands located west of Kyushyu which uses a solar
battery and satellite communications link.
Deployment of the D-GPS network by the Aids to Navigation Department is going on
as scheduled. About 30 sites will be established by the end of FY 1998.
Nobeyama Radio Observatory, National Astronomical Observatory
Noriyuki Kawaguchi reported on the current status of the
VERA project and VSOP as follows.
The main aim of the VERA (VLBI Exploration of Radio Astrometry) project has been
slightly modified to emphasize the observation of invisible objects, that is,
the precise measurement of the attractive motion of maser sources due to the
gravitational field around black holes. An angle resolution (of better than) in
an order of 10 micro arcsecs is required for this purpose. To obtain this angle
resolution at least four, and if possible more than six, VLBI stations will be
necessary for the VERA network in Japan. Urmuqi station will be a key station
in improving the imaging ability of the VERA network. Furthermore, VERA can
have better continuum sensitivity than VLBA at millimeter-wavelength by having
wider observing bandwidth.
He also demonstrated the idea of a synthesis antenna by connecting a number of
antennas distributed throughout Japan using ATM optical links in a "writing
with one stroke" manner. He demonstrated that this idea would allow
observations at up to 8 Gbps, if the communication link has 10-Gbps speed and
five stations are connected.
As for the VSOP, Kawaguchi reported that "HALCA" is in good condition and space
VLBI observations are carried out almost everyday. He told us that he hopes to
compare VSOP results with high-angle resolution observation made by VERA at a
higher frequency in the future.
Finally, he requested the Technical Development Center (TDC) at CRL to maintain
the 34-m antenna as long as possible because of its importance to the Japanese
VLBI community and to continue the development of a reliable gigabit recorder.
He also hoped CRL would promote the development of a VLBI network in Japan
connected by optical fiber links like a KSP.
Tokyo Gakugei University (Kachishige Sato)
Kachishige Sato introduced his recent work on the model calculation of
rheological slip without friction at the subducting plate boundary. This study
was motivated by the measurement of postseismic crustal deformation measured by
GPS after the 1994 Sanriku-Haruka-Oki earthquake, he said. He evaluated two
types of rheological model for lower crust and uppermost mantle, the "Maxwell
model" and the "three-element solid model", by comparing the actual observation
results. He concluded that the "three-element solid model" better explains the
Kobori Research Complex, Kajima Corporation (Masayuki Takemura)
Masayuki Takemura reported on his recent work investigating the historical
seismograph records of the 1923 Kanto earthquake. He pointed out that what
happens after large earthquakes is important in predicting future earthquakes.
He said, we can learn many things from historically large earthquakes.
Geographical Survey Institute (Mikio Tobita)
Mikio Tobita reported that the Field System, which is VLBI system control
software developed by the US VLBI group, has been successfully installed at the
26-m antenna site at Kashima. A fringe test using the Field System was
successfully carried out on March 3, 1998, and good fringes were detected.
He also reported that the construction of a 32-m antenna at Tsukuba is complete.
A fringe test was done on March 20. This new antenna has a high-speed slewing
rate of up to 3 deg/sec. The reference point of the antenna was designed not to
vary over 5 mm per year. This will be monitored through a local survey.
Mizusawa Astrogeodynamics Observatory, National Astronomical Observatory
Hideo Hanada briefly reported on the current status of RISE (Research In
SElenology) in the SELENE (SELenological and ENgineering Explorer) project.
According to his report, SELENE will enter the PM phase in FY 1998. A workshop
relating to RISE was held at Mizusawa in January, 1998.
3. Technical Development Reports
3.1 VLBI Technology Developed at CRL
VLBI technology developed at CRL was reviewd by CRL members.
3.1.1 Automated Observations System
CRL has been developing automated observation/operation software for Japanese
VLBI since the early 1980's. These are "KAOS", "MAOS", "NKAOS", and
"KANAMEISHI" in chronological order. The latest one is for the Keystone
Project. The format of schedule files tends to be unified into the VEX format
in the case of international VLBI. Therefore our VLBI operation software should
be modified to accept the VEX format. On the other hand, the Field System,
which was developed by the US VLBI group, makes it possible to control hardware
developed by CRL, such as K4 and GBR recorders. Details are reported in this issue
(see page 6).
3.1.2 Antenna and Front-end System
CRL developed not only a receiver system for the 26-m antenna at Kashima but
also a GSI VLBI system. CRL has been cooperating with the National Institute of
Polar Research on the Antarctic VLBI project. We can say that CRL has
contributed to the progress of domestic VLBI stations. Thus CRL has the
potential of designing an antenna system up to 30-m and a high-quality and
reliable S/X receiver system. CRL can also evaluate the total performance of
3.1.3 Back-end and Recorder
We developed a K-3 back-end and a recorder system, which are compatible with the
Mark-III system. Then we developed a K-4 back-end and recorder which are more
compact than the K-3 system's and easy to operate. After the K-4 VLBI system, a
KSP recorder equipped with an automatic tape changer was developed. This
changer enables us to make observations for a long time without an operator. It
also makes observation very easy.
3.1.4 Real-time VLBI Technique
A real-time VLBI technique has been developed by CRL in collaboration with the
Nippon Telegraph and Telephone Corporation (NTT). High-speed optical fiber
links were constructed between four KSP stations by NTT. We also developed a
real-time correlation processing technique using data transmitted through
high-speed links. Now we are conducting routine VLBI observations using
3.1.5 Bandwidth Synthesizing Technique
The history of bandwidth synthesizing software in Japan was briefly reviewed.
Initially it took more than one hour to process only a single observation of
about six minutes. Now this has become less than one minute due to improvements
in software and computer hardware. One of the special members of TDC requested
the development of real-time bandwidth synthesizing software.
3.1.6 Data Analysis
Data analysis software dedicated to the geodetic VLBI developed by CRL was
reviewd. The software has been being updated year by year to reflect the latest
physical model and theory into analysis. The current software (for KSP) is
third generation in Japan. We plan to implement the following function in the
future, such as astronomical and geodetic applications, wide-band VLBI analysis,
differential-VLBI analysis, and phase synthesis analysis. One of the special
members hoped TDC/CRL would contribute to the data analysis of the VERA project.
3.2 Current Status of the Keystone Project (Crustal Deformation Observation System
in the Tokyo Metropolitan Area)
3.2.1 VLBI System
Kouichi Sebata reported on the current status of KSP-VLBI as follows.
Measurement accuracy has been drastically improved since last autumn due to the
change in observation tactics from a daily five-hour session to a 24-hour
session every other day. Even though KSP is designed for ease of use in
operation, sometimes recovery is difficult from R\&D experiments or unusual
accidents. We are compiling an operation manual as well as operation know-how
in our computer to allow special knowledge to be utilized and shared with
operator. As the KSP operator can access these manuals through the WWW, he/she
can cope with most difficulties without any specialist aid.
3.2.2 SLR System
Hiroo Kunimori reported on the current status of the KSP SLR system as
follows. The second observation campaign of Kashima and Koganei stations
was successfully carried out. Observations were made at all four stations.
KSP SLR started regular observations on February 16, 1998.
3.3 R&D Experiment Reports
3.3.1 Survey Observation of Radio Sources using KSP
Akihiro Kaneko reported on survey observation using the KSP VLBI facility. Last
autumn, KSP changed routine operation from an everyday basis to an every other
day basis. Survey observations were then carried out during the rest period of
routine KSP operation. The purpose of survey observation is to obtain
information about the angle size of radio sources available for VLBI. So far
120 candidates in the Parks catalogue have been surveyed, and fringes were
successfully detected on 57 sources.
3.4.1 Current Status of Kashima 34-m Antenna
The current status of the Kashima 34-m antenna was reported on by Eiji Kawai.
As almost ten years has passed since the antenna was constructed, deterioration
can be seen in every part. As the antenna is old, continuous upkeep is required
to maintain it in good condition. One of the special members of TDC appreciated
CRL's efforts in assisting and collaborating on VSOP. He requested CRL to keep
the 34-m antenna as long as possible. After Kawai's talk a general question was
raised concerning the lifetime of the antenna. Replying to the question, Mikio
Tobita of GSI commented that it was 30 years in the case of a new GSI 32-m
3.4.2 Current Status of Next Generation VLBI
Junichi Nakajima reported on the current status of the 43 GHz receiver currently
under development. He also reported on the interference problem at 1.6 GHz
expected to arise from the low altitude communication satellites to be launched
in the very near future. The effects and problems are now being investigated.
One of the special members commented that this might cause severe interference
for the VLBI station in space.
3.4.3 Current Status of NAOCO at Kashima
NAOCO, a simple correlator developed by the National Astronomical Observatory,
is temporarily being installed at Kashima to allow spectrum observations to be
made using the 34-m antenna. Tomonari Suzuyama reported that the installation
is going well.
4. Closing Greeting
The closing address was delivered by Kenichi Okamato,
the director of IERS TDC at the Communications Research Laboratory.
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