TECHNICAL DEVELOPMENT CENTER NEWS No.6
International Earth Rotation Service - VLBI Technical Development Center News

published by

Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan
April, 1995

In October 1990, the International Earth Rotation Service (IERS) designated the Communications
Research Laboratory (CRL) and Haystack Observatory, USA, as the Technical Development Centers(TDC). These centers are supposed to do1) the development of new observation techniques and new systems for advanced Earth's rotation
observations by VLBI and other space techniques,2) the promotion of research in Earth rotation by advanced methods in VLBI,
3) the distribution of new VLBI technology.
The TDC meeting, attended by the ordinary members from inside the CRL and the special members
from the outside, is held twice a year. The special members advise the committee, concerning the planof technical developments. The TDC newsletter is published biannually by CRL to inform the IERS
community its current activities.

The Sixth TDC Meeting
The Sixth meeting of the TDC was held on March 3, 1995 at the conference room of the Kashima
Space Research Center, CRL.

Agenda
1. Opening address by Fujinobu Takahashi, director of the Standards and Measurements
Division, CRL
2. Introduction of Technical Development Center
3. Activity reports by the special members
4. Technical reports
4.1 Keystone project
4.2 Other technical development activities
5. Discussion
6. Closing address by Akira Sugiura, director of the Kashima Space Research Center, CRL

Attendees
CRL members
Takahashi, Fujinobu
Imae, Michito
Kunimori, Hiroo
Sugiura, Akira (Kashima Space Research Center)
1

2

IERS TDC News No.6

Takahashi, Yukio (Kashima Space Research Center)
Takaba, Hiroshi (Kashima Space Research Center)
Iwata, Takahiro (Kashima Space Research Center)
Kurihara, Noriyuki (Kashima Space Research Center)
Kiuchi, Hitoshi (Kashima Space Research Center)
Koyama, Yasuhiro (Kashima Space Research Center)
Hanado, Yuko (Kashima Space Research Center)
Nakajima, Junichi (Kashima Space Research Center)
Gotoh, Tadahiro (Kashima Space Research Center)
Kondo, Tetsuro (Kashima Space Research Center)
Special members
Kawano, Nobuyuki (National Astronomical Observatory)
Kawaguchi, Noriyuki (National Astronomical Observatory)
Saito, Takashi (Geographical Survey Institute)
Kanazawa, Teruo (Hydorographic Department, Maritime Safety Agency)
Hirabayashi, Hisashi (Institute of Space and Astronautical Science)
Shibuya, Kazuo (National Institute of Polar Research)
Okada, Yoshimitsu (National Research Institute for Science and Disaster Prevention)
Teruyuki Kato (Earthquake Research Institute, University of Tokyo) could not attend the meeting.

Minutes of the Sixth TDC Meeting
3. Activity reports by the special members
Each special member reported current status and activities of each institute.
Current Status of IRIS-P Network (Nobuyuki Kawano)

VLBI measurements on the IRIS-P network will be continued. The K-4 aquisition terminals will be
distributed to stations in China, Tasmania, and Hawaii (or Alaska) gradually starting in June, 1995.
Correlation processing will use the VSOP correlator.

Q&A
Q: How often are you planning to conduct experiments?
A: So far, we don't have an answer, because it depends on the agreement made between the
countries involved.
Outline of VLBI System Development at National Astronomical Observatory (Noriyuki

Kawaguchi)

TCU (Timing Control Unit) has been developed. TCU enables timing control at recording and/or
replaying without use of any formatted data.
A VSOP type data aquisition system is developed on the basis of the sampler (DFC-2000) developed
by CRL.
A sampler with 4 GHz sampling rate and 2 bits resolution was developed and has been evaluated.
Test observations start.
Burst sampling system, consisting of 4 GHz sampler and 32 Gb memories, can take the data for only
4 sec for fuge amount of data such as required to 500 sec when K-4 is employed.

April 1995

3

Q&A
Q: Who determines the orbit of VSOP?
A: JPL and ISAS.
VLBI Observations at Geograpphical Survey Institute (Takashi Saito)

In FY1994, we conducted domestic VLBI observations on baselines Tonami-Kashima and KanozanKashima. Two sets of VLBI systems equiped with 3.8-m dish antennas are newly installed. One isused as a xed station at Shintotsugawa in Hokkaido. The other is used as a mobile station and is now
stationed at Tsukuba. A hundred and ten GPS receivers are distributed in Japan by GSI. Besides this,a hundred GPS receivers are deployed in the South-Kanto area.

Q&A
Q: Are GPS observations always carried out?
A: Yes for the whole Japan network. As for the South-Kanto area, observations are madefor 6 hours a day.
Q: Do you have a plan to install a super computer for GPS data analysis?
A: Under consideration.
Q: How about VLBI observations in the South-west islands.
A: Next year, a mobile VLBI will visit Okinawa island.
Q: What is a ground for the density of GPS receiver's distribution.
A: It is determined from the size of precursor for the South-Kanto area and from budgetary
reason for the whole Japan network.
Q: Do you summarize the each GPS site's data?
A: Yes.
Q: Do you have a plan to contribute GPS data to IERS?
A: Yes.


Introduction of SLR (Teruo Kanazawa)
Stations in the world, satellite itself, and evolution of acuracy for SLR is brie y introduced.

Q&A
Q: What is the lifetime of the satellite?
A: Degradation of the re ectors is the main lifetime factor. Twenty years have been pastsince the launch of Lageos, but the re ector is still in good condition.
Q: What is the reason for Lageos2 being launched?
A: To improve the accuracy by increasing the spatial coverage.
Current Status of VSOP (Hisashi Hirabayashi)
Current status is introduced.

Q&A
Q: How about foreign project for space VLBI?
A: There is the Radioastron project of Russia. The satellite is scheduled to be launched in
1997, but there is a possibility that this will not take place. In addition, there is a plan
proposed to NASA.

4


IERS TDC News No.6

Status Report of Geodetic Observations in Antarctica (Kazuo Shibuya)

There is no progress for the Antactic VLBI project. GSI made absolute gravitational measurements.
DORIS is installed at Syowa station and working well. A campaign observation promoted by Germany
was carried out from January 20 to February 10, 1995.

Q&A
Q: Is there any xed GPS station at Syowa station?
A: No. A pillar for a xed station is under the construction.
Q: What is the accuracy of DORIS results?
A: 62cm for each component.
Q: Are the results included in IERS?
A: From now on.
Q: Do you have detailed information concerning the 9-m antenna at Macmurdo station,
especially concerning installation of the VLBI system?
A: At the moment there is no plan to install a VLBI system.
C: GPS or DORIS will detect the plate motion of Antactica for the rst time.

Status Report of Borehole Observations at National Research Institute for Science andDisaster Prevention (Yoshimitsu Okada)Eearthquake activity in the Kanto area has been low for sixty years since the big Kanto earthqukae.
However M4-class earthquakes began to occur recently. Borehole observations are very useful to monitor
small-magnitute earthquakes in the Tokyo metropolitan area covered with thick loam. Four 3000m-depth
and twelve-2000m depth boreholes are now instrumented.

Q&A
Q: You say that daytime observation is often a ected by blasting. Is it possible to remove
these e ects from the data?
A: Yes. We actually remove such e ects from the data.
Q: How small does the noise become at 3000m depth in a borehole?
A: About 1/200.
Q: Do you have a plan to deploy borehole observation system to cover the whole of Japan?
A: No.
Q: What is the cost of a 3000m depth borehole.
A: About two billion Yen.
Q: Is interferometry technique applicable for seismic waves?
A: Array of seismographs at a point is already utilized for observation. However, interferometry is dicult since the wave-form itself usualy varies between distant stations.
Q: How do you relate the borehole observationss to prediction of earthquakes?
A: We detect small earthquakes considered as precursors of big earthquake.

4. Technical Reports
4.1 Key Stone Project

5

April 1995

Figure 1: Key Stone Project

Outline of the Key Stone Project (Taizoh Yoshino)

The system of Key Stone Project (KSP) is designed to monitor the crustal deformation in the Tokyo
metropolitan area every day by the VLBI and SLR techniques with the several mm precision.
1994 Central station for data processing was built at Koganei in Tokyo. VLBI stations wereconstructed at Koganei and Kashima.
1995 VLBI stations was constructed at Miura in Kanagawa. Daily VLBI observations started
between Koganei and Kashima. Real time VLBI using optical ber network is underdiscussion. Data delivery to the JMA (Japan Meteorological Agency) and CCEP (Coordinating Committee for Earthquake Prediction) was discussed.



Current Status of Project (Noriyuki Kurihara)

VLBI stations

Development of VLBI stations dedicated to the KSP including a new building started in FY1993.
The observation system consists of three parts, i.e., (1) data acquisitions (2) system monitoring, and(3) remote controlling. Current timetable of development of each KSP station is as follows.

6

IERS TDC News No.6

year
March,
1995

July, 1995
1996

KOGANEI
CenterData acquisition

KASHIMA
Sub-Center
Data acquisition

MIURA

System monitoring
Concentrated controlling

System monitoring

Data acquisition(Systemmonitoring?)

Concentrated controlling

System monitoring

TATEYAMA

Data acquisition
System monitoring

Data processing and analysis system

VLBI data are processed and analyzed routinly at Koganei Central station. New correlator dedicatedto the KSP is under development. So is software for data processing and analysis. Presently tests
combining both hardware and software are going on. We will enter the routine operation phase of thecorrelator in FY1995.
Test observations on the Koganei-Kashima baseline

We carry out test observations on this baseline to check the whole performance of the KSP VLBI
system. First fringes were succesfully detected on July 25, 1994. The rst full 24-hour experiment was
carried out on August 29, 1994. Daily observations, whose main purpose is system performance check,have been carried out since January, 1995.


Automatic Observation System (Takahiro Iwata)

VLBI is one of the most accurate technique for geodetic measurements. However, it is not suitablefor daily observations because much man-power is necessary for both observations and data processing. The purpose of the Keystone project promoted by CRL is to detect regional crustal deformations,considered as precursors of large earthquakes, therefore continuous daily observations are strongly desirable. Especially high reliability is required for the system to perform the continuous observations not
disturbed by instrument malfunctions. Fully automatic operation is also required. We have designed
the KSP system so as to meet both these requirement.
Stations

Each station is equipped with two kinds of computers. One is a controlling computer which controls
the observation instruments, such as an antenna and a recorder according to schedule prepared inadvance. The other is a monitoring computer which gathers basic data, such as meteorological data,sytem noise temperature, and status of each instrument.
Central station

Koganei and Kashima function as a central station and a sub-central station. Both stations areequipped with concentrated controlling computers which control and monitor systems at each station
via a computer network. An operator at the central or sub-central station can therefore know the statusof each station.
Computer network

A WAN (Wide Area Network), which is a dedicated digital communication link, connects Kashima,
Koganei, Miura and Tateyama. Furthermore we plan to have a backup digital link between Kashima
and Tateyama. Each station is also equipped with a telecommunication line for data transfer. Remote
operation through this line is planned to recover the computer system as a backup.

7

April 1995

Data recording

The data recording is performed by the K4 data recorder built in the DMS-24 automatic tapechanger. The DMS-24 enables operatorless observations for 24 hours. We aim to do real-time datatransfer to the correlator at the central station in the future.


Data Acquisition System (Hitoshi Kiuchi)

The local oscillator synthesizes the local frequency signal (500-1000 MHz : 10 kHz step) for the video
converter. The measured phase noise is better than 3 deg, which is calculated according to the value ofthe measured Allan variance. Coherence loss caused by this phase instability is less than 0.04%. The
local oscillator has now been fully developed and is in commercial use. The video converter converts
windows in the IF signal input (500-1000 MHz) to video signals (0 - 32 MHz). The input interface unit
samples the 16-channel (max.) video signal, and sends the sampled data to the data recorder following
a time data block, and produces a data train of up to 256 Mbps. The format does not include a timecode but only a digitized signal. It was designed to make the best use of the K-4 recorder's abilities atlevels of up to 256 Mbps. The anti-aliasing ltering is made in analog (32 MHz), and sampling is carriedout by an 8 bit A/D converter of 64 Msps. The quantization threshold level of the A/D converter isadjustable. After sampling, the 16 MHz, 8 MHz, etc. ltering and bit discriminations are accomplishedby digital lter. The digital lter is good for producing excellent phase characteristics, and for reducing
coherence loss. It is possible to select suitable coecients for the digital lter, for example, the digitallter is used as a band pass lter during line observations. The con guration for one- and two-bit
sampling is shown in the table. It is possible to support the Mark-III, the VLBA, and the VSOP dataacquisition modes. This Input interface unit is adopted to the VSOP data acquisition sub-system.
Sampling rate

Number of
input ch.
16 ch
8 ch
4 ch
2 ch
1 ch



[Hz]

1 bit (2-level)

Data recording rate [bps]/Recorder

256M
16M
32M
64M

128M
8M
16M
32M
64M

64M
4M
8M
16M
32M
64M

32M
2M
4M
8M
16M
32M

16M
1M
2M
4M
8M
16M

Sampling rate

Number of
input ch.
16 ch
8 ch
4 ch
2 ch
1 ch

[Hz]

2 bit (4-level)

Data recording rate [bps]/Recorder

256M
8M
16M
32M
64M

128M
4M
8M
16M
32M
64M

64M
2M
4M
8M
16M
32M

32M
1M
2M
4M
8M
16M

16M
0.5M
1M
2M
4M
8M

Correlation Processing System | Hardware (Hitoshi Kiuchi)

KSP correlator

In the multi-baseline correlation processing, all the output interface units are daisy-chain connected
via GPIB and a timing control line. Therefore, the tape position data and the status data of all the data
recorders can be exchanged via the output-interface units. The main replay system (the main output
interface unit and the data recorder) and the sub replay system (the sub output interface unit and thedata recorder) can be synchronized in one-bit steps. The delay adjustment is done by controlling theTrack set ID and subsequent programmable shift registers (PSR). The signal (raw data) is unformatted
instead of in the Mark-III format. We are developing an XF type VLBI correlation processor for theK-4 system by making use of a Field Programmable Gate Array. The outline of the correlator is;(1) Automatic bit synchronization during multi-baseline processing,(2) Network Filing System for storing correlated data,(3) 2-bit sampled data processing capability,(4) 16ch high speed (32 Mbps/channel) processing,8

IERS TDC News No.6

Figure 2: Block diagram of KSP correlator(5) Signal provided by VME back plane.
This correlator was specially designed for the Keystone Project, which is concerned with measuring
crustal deformation in the Metropolitan area. The project utilizes 4 stations in the Metropolitan area,and each station has a new K-4 system and an 11 m antenna. Using this new correlator, we can improve
the precision of the geodetic VLBI and also contribute to radio astronomy VLBI. A part of the multibaseline correlation processor has been developed. And we are now checking its performance. We plan
to produce a multi station (4 or 5) correlation processor and are also developing new software that will
be compatible with our current software.

Q&A
Q: What is the number of lags in a correlation unit?
A: 32 lags.
Q: Why are 16 units necessary?
A: For applications other than the KSP.

Correlation Processing Control Software (Tetsuro Kondo)

9April 1995

Figure 3: KSP correlation system

Figure 4: Coarse search function using KSP correlator out
We named correlation processing control software "KATS" (KAnameishi (= keystone) data processing Togo (= uni ed) Software). KATS uni es the steps from correlation processing to just before
the creation of database. It aims at realizing an easy operator interface. The function of KATS issummarized as follows:(1) Set up of parameters passed to correlator(2) Automatic clock search(3) Dynamic clock o set correction(4) Operatorless operation except for initial tape setting(5) Automatic execution of band-width synsthesizing software(6) Execution of database creation software(7) Archive correlation data
Presently debugging of the whole correlation system is being carried out.

Q&A

10

IERS TDC News No.6

Q: When the sampling frequency is 8 MHz, a 32 bit-lag window merely covers a range of 4
micro seconds. Is dynamic clock o set correction working well for such a narrow window?
A: At rst, clock search is carried out on extended lag windows by connecting 16 unit
correlators serially. Once fringes are detected, we think that change of clock o set is muchless than 4 micro seconds for time interval between scans (= about several minitutes).



VLBI Data Analysis Software System for Key Stone Project (TAKEMIKADZUCHI)(Yasuhiro Koyama)

After each site of KSP (Key Stone Project) network performes VLBI observations every day, recorded
data tapes are transported to the Koganei Processing Center and correlated with the KSP correlator
by KATS (KAnameichi data analysis Togo [= uni ed] Software). Once KATS nished the correlation
processing including the bandwidth synthesis, the remaining data analysis is done by the software
TAKEMIKADZUCHI. The role of the software is (1) to create and maintain databases, (2) toestimate site coordinates along with other model parameters, and (3) to interpret the estimated results
and make the results available on the network. This software is presently under development and is
expected to be ready for operation soon. The conceptual design of the software is explained in thefollowing sections.
Database

A database is created from a set of KATS output les to prepare for following data analysis procedures. Kicked o by a command executed in the last phase of KATS, TAKEMIKADZUCHI
extracts required information from the KATS output les, calcurates ionospheric calibrations andplanetary ephemerides, interporates meteolorogical data and then creates a database using the Mark-3
Database Handler developed by Goddard Space Flight Center (GSFC) of National Aeronautics andSpace Administration (NASA). TAKEMIKADZUCHI also updates these databases automaticallywhen it receives a bulletin (either Bulletin A or Bulletin B) issued from International Earth Rotation
Service (IERS) via e-mail.
AnalysisRight after a database is either created or updated, theoretical values of a time delay and a delay
rate for each observation and their partials with respect to the various parameters are calculated by
the CALC software [version 8.1] which has also been developed by GSFC. In the case of initial creationof the database, other software (called REMAMB and MRKOBS) resolve ambiguities and remove badobservations respectively. Then in the nal step, VLBEST is run to estimate site coordinates along withother parameters such as clock o sets and atmospheric delay in the zenith directions. In case the root
mean squared delay residual exceeds a certain threshold, the operator is noti ed before the results are
released. The operator then can look into the raw data and change clock epochs or remove bad data
points manually using a graphical user interface in an X windows / Motif environment.
Data release

Estimated site coordinates are interpreted as motions of sites in the horizontal and vertical components, and as rates of change in baseline lengths. These results are stored in text les and, at the sametime, graphic gures are generated. Any researchers on the Internet network can access these text les
and gures from their World Wide Web browser such as MOSAIC at the URL http://apollo.crl.go.jp/(the URL is preliminary and may change in the future). If the latest data exhibits a large o set fromthe linear trend of the site motion or baseline length change, the data points will be distinguished incolor to attract attention for a possible pre-seismic signal. The results are updated everytime when
TAKEMIKADZUCHI updates databases according to the new set of earth orientation parameters
in IERS Bulletins and they are reported to related organizations by daily e-mail messages. We are
expecting that these data will be used by earthquake prediction research communities worldwide.

11

April 1995

Q&A
Q: Please consider to release radio source ux density information along with geodetic resultsby means of WWW for Astronomical community.
A: We are already considering this issue, and the preliminary results from three experiments
can be accessed as a test.
Q: What is the version of CALC, you are going to use?
A: The version of CALC is 8.1 and is the latest available version at present.
Q: Are there any means of data distribution other than WWW?
A: We are thinking of using e-mail distribution to related organizations like Japanese Meteorological Agency.
Q: What is the policy on public availability of released data? Are you planning to givepriority to a restricted group to use your results?
A: We are expecting wide research communities to use our data for geophysical research.
Therefore the data should be freely available without any restrictions.

Q&Afor the whole of the KSP
Q: Is KSP antenna to be equipped with 22 GHz receiver in the future?
A: No.
Q: How about comparison with other techniques?
A: GSI will use VLBI stations as ducial points for GPS observation. Therefore the KSP
antenna is designed to permit easy connection of its AZ-EL axes intersection to groundmarker.

4.2 Other IERS Related Technical Development Activities


Introduction and Outline of the Activities (Michito Imae)

Change on the organization at CRL for TDC

A new section named "Space Geodesy Section" was established at CRL Koganei Headquarters inJuly 1994. TDC is managed by three sections, Space and Time Measurements Section, Space Geodesy
Section and Radio-astronomy Applications Section.
According to this change, the research eld for each section is categorized as followings:
Space and time measurements section:
Precise measurement of time and frequency in the space and time projectSpace geodesy section:
Precise measurement of space in the space and time project Research on SLRRadio astronomy applications section:
Observation and analysis using 34m antenna system and technical development
Research and development activities at CRL's VLBI TDC

a. Status of Kashima 34m
The repair of the 34m antenna was almost nished. CRL is making e orts to full automatic
VLBI observations by the K-4 VLBI system using cassette tape auto-changer (DMS-24).
b. Technical developments of VLBI system
New K-4 Input Interface for VLBI
The development of the new K-4 Input Interface was completed and it is applied
to the Key Stone Project observation system.

12

IERS TDC News No.6

New generation VLBI system
Design of the new generation VLBI terminal that will have Gbps class sampling
rate has started.
Milli-meter wave receivers
Development of a compact and low noise SIS 40 GHz band receiver for 34m antenna. It will be expand to the 100GHz band low noise receiving system.
High speed data transfer for real time VLBI.
Basic study of real-time VLBI using ultra-high speed ATM network, as a breakthrough for VLBI technique.
c. VLBI experiments
Earth rotation VLBI experiments
Once or twice a month VLBI experiments are performed under the cooperation
with the Mizusawa Earth rotation network center of IRIS-P.
Kashima-Urmuqi VLBI experiments using K-4 system
Japan-Russia pulsar VLBI experiments
Domestic VLBI experiments
Experiments for the movement after the eastern part of east-north Japan earthquake under the cooperation between Mizusawa VLBI station of National Astronomical Observatory are being performed.
Sea level monitoring VLBIVLBI experiments in cooperation with Geographical Survey Institute were performed.
Metropolitan Diamond Cross(MDX) experiments
VLBI experiments in cooperation with Geographical Survey Institute were performed for connection with KSP stations.
Domestic VLBI experiment with Nobeyama Radio Observatory and Usuda station of ISAS
Cooperation to the Japanese VLBI network
d. Related activities for TDC
Satellite Laser Ranging
International SLR symposium was held in Australia using the fund of STA (Scienceand Technology Agency). Infra-red SLR experiment has been performed with theinternational cooperation.
Pulsar study
Development of a precise timing observation system using AOS (Acoustic Optic
Spectrometer) has been performed and continuous observation will be started.
Pulsar VLBI with Russian station was performed.
Basic research for space VLBI
Research target is changed to only the transmission of reference signal to the ETS-6
satellite because of the failure of the ETS-6 satellite to achieve geostationary orbit.
Status Report of the CRL 34-m Antenna at Kashima (Hiroshi Takaba)

Antenna control system

Automatic antenna stow software was incorporated in the VLBI automatic observation software toprotect the antenna from the strong winds. A maximum wind speed of 20m/s or a mean wind speed of
13m/s limit antenna operation.
The ve axis sub-refrector controller is being replacing and will be available in April 1995.

13

April 1995

Receiver system

1.5 GHz Receiving Syetem
2/8 GHz Receiving Syetem
5/10 GHz Receiving Syetem
15/22 GHz Receiving Syetem
43 GHz Receiving Syetem

Good
Good
Problem on the vacuum of the Dewar. not available
Good
A new system using an SIS mixer was installed. Tesing.

Backend syetem

A new VLBA data recorder was installed. The Mark-IIIa mode C is available using the VLBA data
recorder.
An automatic tape changer system (Digital Mass Strage DMS-24) became available. Up to 24 K-4
tapes are automatically changed and about one week's automatic observation become possible with thenormal 64Mbps recording mode.

Q&A
Q: How earthquake-proof is the performance?
A: The speci cations state says seismic intensity 6 (about 400 Gal)

Milli-meter Wave Receiver Development (Junichi Nakajima)

The new 43GHz receiver have been completed. We employ an SIS device and wideband IF system
for high sensitivity observation. The receiver had been installed in the feed system of the Kashima 34m
antenna. The cryogenic system test is in progress.
Project status

There are strong requirements to move to higher frequency to achieve high-sensitivity observations
and avoid arti cial interference. Extension of VLBI technology to mm-wavelength is a very important
objective itself. Furthurmore, mm-VLBI capability will enable us to observe new kinds of astronomicalsources. The development of mm-wave receiver started in 1993.
The receiver is planned for use in KNIFE (Kashima Nobeyama Intere FErometer) VLBI cooporative
observations. We have developed a new compact GM-cryogenic and a cold head o set dewar with
Sumitomo Heavy Industries. Without beam transmission waveguide, the 4K cooled receiver is installedin the secondary focus of 34m telescope (Fig.5). The cooling capacity of the cryogenics is 0.4W andis still improving the performance. We have succeed to retain superconductive temperatures in any
elevation angle of the telescope.
The recever employs the SIS device produced in Nobeyama receiver group (Fig.6). The received signal
is down converted to 5-7GHz wideband IF. This enables high sensitivity observations, accompanied byan ultra high speed acquisition terminal which is being developed. Sensitive observations of QSO
relativistic jets, cores and the Galactic center become possible. SiO observation also throw light on thecircum stellar radio source nature and sources of extragalactic origin.
Currently, we have carried out the receiver cooling test. Local signal and downconversion system
will be equipped successively. After completion of the the electronics, we need to obtain sub-refrector
position parameters. Then the KNIFE operation with normal IF band width (0.1-0.6GHz) will bestarted from April 1995. In 1996 full range GUN-local souce and wideband IF transmission are planned.
This is a joint project of Nobeyama Radio Observatory, Ibaragi University and CRL. The project ispartially supported by Nobeyama Radio Observatory.

Q&A

14

IERS TDC News No.6

Figure 5: Photo of the receiver installed in the feed system

Figure 6: Receiver temperature data

15

April 1995

Q: Performance of cryogenics is a ected by change of the mount angle. How about yoursystem?
A: So far, we get good stability of perfomance with angle change.

Next Generation VLBI System (Hitoshi Kiuchi)

In developing new VLBI data acquisition system for astronomical applications, it is the most important to take into consideration the requirement of the multi-bit sampling, the high-speed (wide-band)data sampling. We are developing a new sampling system for K-4 data recorder: its sampling rate isincreased to 2 (or 4) Gsps, 8-bit quantization. The block diagram is shown in Fig.7. We are developinga real time VLBI system for the KSP system, which is shown in Fig.8.

Figure 7. A high-speed sampling head.

Figure 8. ATM data transfer system for KSP.

16


IERS TDC News No.6

Pulsar VLBI (Yuko Hanado)

Pulsar observation study at CRL

Timing measurement : Application of millisecond pulsars to frequency reference.
Pulsar VLBI
: Measure the pulsars' positions and proper motions, and comparisonof reference frames.
Survey: Search for the new observation targets.

Pulsar VLBI

Signi cance:
Information concerning the pulsar's position, proper motion and distance are required.
1By comparing the position de ned from VLBI and the position de ned from timing analysis,
di erent reference frames and connected.
1

Attention points in observation:
Pulsars' intensities are weak.
1Dispersion e ect causes pulse-smearing.
1#

Large antenna is required.
1Observation bandwidth and integration time must be considered.
1Signal processing is required for improvement of S/N ratio.
1

Observation at CRL up to now:
'91 34m(Kashima)-25m(Shanghai)'92 26m(Kashima)-64m(Usuda)'94 34m(Kashima)-64m(Usuda)

PSR0329+54
PSR0329+54
PSR1937+21

L-bandS-bandL-bandK-3 correlator
K-3 correlator
K-3 correlatorX
O(gating)
X

Japan - Russia pulsar VLBI

Pulsar VLBI is planned between Kashima 34m antenna (Japan) and Kalyazin 64m antenna(Russia). This project is carried out based on the international cooperation between CRL andPuchino Radio Astronomy Station Astro Space Center of P. N. Lebedev Physical Insitute.
Observation frequency is L-band. The K-4 VLBI system is transported from CRL and usedin Russia. The correlation processing will be done at CRL.
Experiments in 1995 (preliminary experiments):'95. 3. 4 Fringe test (= system check)'95. 3.15 1st pulsar VLBI (for rather strong pulsars)'95. 3.27 2nd pulsar VLBI (for rather weak pulsars)
Future plan:
Based on the preliminary results in 1995, observations will be carried out during 2 or 3 years.
They may be expanded to the Japan-Russia-Australia pulsar VLBI network.

Q&A

17

April 1995

Q:
A:



Why were fringes not obtained for the 1994 experiments?
Because the elevations of selected sources were low and S/N ratios were not highenough.

Space VLBI (Takahiro Iwata)(English version of documents is not available)

Q&A

Q: How do you cope with the time di erence between time of the frequency of up-link beingchanged and arrival time of returned signal from the satellite?
A: Not yet considered.



Asia Paci c Radio Telescope (Yukio Takahashi)(English version of documents is not available)

Q&A

C: GSI plans to conduct the Japan-Korea VLBI experiment.
Q: What kind of K-4 will the network be equipped with?
A: It is the National Astronomical Observatory version.
Q: What is the current status of antennas in India and Southeast Asia?
A: India has some antennas, but the receiver frequency is lower than that of usual VLBI.

The Status of SLR R&D Experiment (Hiroo Kunimori)Classi cation
Geodetic Observation and Analysis

International
Network
Next
R&D

Generation

KSP SLR System

Table 1. Summary of Activities
Project Name
Fiscal Year
Status Summary
Earthquake Predic- 1990-1995-Comparison Results of Coordinatestion Measurement infrom collocation of SLR,VLBI andMetropolitan Area
GPS in MDX exp.
Evaluation
1994-1996-Improvements of range bias calibraof Earthquake Potention -Short arc solution of station potial in East Edge ofsition by Ajisai tracking campaign in
the Japan Sea
east Asia network （Fig.9 and Table
2)
Western Paci c Laser 1994-WPLS Symposium at Canberra Network
Japan as Secretariat of WPLS (Australia, China Japan and Russia)
Synchronous Laser 1992-1994-Synchronous Timing Precision :Ranging System
70ns
Orbit Determination 1995-System Design of Laser Radar to
ADEOS satelliteof Remote Sensing
Satellite
Spin Observation of 1994-1995-Prototype system
AJISAI
Eye-Safe Laser Rang- 1994-Introduction of Raman-1.5um gening Systemeration and SPAD detector system(1995-）-Phase of Speci cation

18

IERS TDC News No.6

Figure 9. The stations participated in AJISAI tracking campaign (SLR-Japan)

Table 2. The short arc solution of station position in SLR-Japan.
Station
Coordinates Internal
Deviation Error in(Analysis)
Error from ITRF92 ITRF92
Tokyo(7308)
x -3942020.074
0.007
0.085
0.116 (Single-pass)
y 3368097.479
0.007-0.0670.112
z 3702191.094
0.007
0.044
0.138
Tokyo(7308)
x -3942020.066
0.015
0.093
0.116
(SRD)
y 3368097.464
0.017-0.0820.112
z 3702191.093
0.005
0.043
0.138
Shanghai(7837)
x -2831087.946
0.025-0.0040.011 (Single-pass)
y 4676203.317
0.024-0.0210.011
z 3275172.789
0.026
0.018
0.012
Changchun(7237) x -2674386.952
0.031-0.0480.084 (Single-pass)
y 3757189.569
0.026
0.067
0.068
z 4391508.492
0.024-0.1500.053
Komsomolsk(1868) x -2948543.462
0.850(Single-pass)
y 2774313.435
0.496
Not listed in ITRF92
z 4912307.097
1.026
Simosato xed
UNIT:METERS

Q&A
Q: Why do VLBI results (for Koganei) have larger errors than those from GPS?
A: No ionospheric correction is applied for this case. Moreover, VLBI measurements were
only made seven times in a span of 6 years, but GPS measurements were made only forthree days. Thus they can not be compared with each other directly.

--------------------------------------------------------------

April 1995

19

This news was edited by Tetsuro Kondo, Kashima Space Research Center, who is the current representative of TDC. The editer wishes to thank Dr. O. J. Sovers for his kind help in the correction of thenews translated from Japanese to English.
Inquires on this issue should be addressed to:T. Kondo
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314, Japan
TEL: +81-299-84-7137
FAX: +81-299-84-7159
e-mail : kondo@crl.go.jp---------------------------------------------------------VLBI and related activities at the Communications Research Laboratory is now available from the home
page of the Radio Astronomy Applications Section of the Kashima Space Research Center on the World
Wide Web (WWW). The URL to view the home page is : http://apollo.crl.go.jp/