TECHNICAL DEVELOPMENT CENTER NEWS No.5

International Earth Rotation Service { VLBI Technical Development Center News
published byCommunications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184,Japan

September, 1994

(Reproduced in June, 1998)

In October 1990, the International Earth Rotation Service (IERS) designated theCommunications 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 andthe special members from the outside, is held twice a year. The special members
advise the committee, concerning the plan of technical developments. The TDC
newsletter is published biannually by CRL to inform the IERS community its
current activities.
The Fifth TDC Meeting

Heki, Kosuke (Kashima Space Res. Cent.)
Kunimori, Hiroo
Hama, Shin'ichi
Kiuchi, Hitoshi (Kashima Space Res. Cent.)
Sekido, Mamoru (Kashima Space Res. Cent.)

The Fifth meeting of the TDC was held on December 17, 1993 at the conference room of the CRL
headquarters.
Agenda

1. Opening by Fujinobu Takahashi, director of the Special Members
Standards and Measurements Division, CRL
Yokoyama, Koichi (National Astronomical Ob2. Introduction of new committee members
servatory, Mizusawa)
Shibuya, Kazuo (National Institute of Polar
3. Report of the iRiS'93 international workshopResearch)
4. Technical reports
Okada, Yoshimitsu (National Research Insti4.1 Keystone projecttute for Earth Science and Disaster Prevention)
4.2 Other technical development activities
Kanazawa, Teruo (Hydrographic Department,Maritime Safety Agency)
5. Report on the working group on VLBI systemcompatibility
Other members, Nobuyuki Kawano (NAO, Mizu6. Discussionsawa), Noriyuki Kawaguchi (NAO, Nobeyama),
Makoto Murakami (Geographical Survey Institute), Hisashi Hirabayashi (Institute of Space andAstronautical Science), Teruyuki Kato (Earthquake Research Institute, University of Tokyo)
could not attend the meeting.

Attendees
CRL members

Takahashi, Fujinobu
Yoshino, Taizoh
Imae, Michito (Kashima Space Res. Cent.)
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IERS TDC News No.5

Minute of the Fifth TDC Meeting,Technical Reports1. Keystone ProjectOverview
Four tectonic plates (North America, Eurasia, Paci c, Philippine Sea) meet at the Kanto district,causing complicated seismic activity there. In addition to the Tokai Earthquake (M8), supposed at
the Suruga Trough and the Odawara Earthquake(M7), supposed at the western part of the Kanagawa Prefecture, it has been pointed out that theTokyo metropolitan area may su er from a medium
sized earthquake directly underneath in a near future. Crustal strains have been increasing since
they were reset to zero in 1923 by the great Kantoearthquake and the earthquake potential is now
large enough to cause an earthquake up to M7directly under the Tokyo metropolitan area.
The project to monitor regional crustal deformations in the Tokyo metropolitan area by using space
geodetic techniques has been started in 1993 byCRL. It is planned that four stations surrounding Tokyo are equipped with both Very Long
Baseline Interferometry (VLBI) and Satellite Laser
Ranging (SLR) facilities and daily routine geodetic VLBI/SLR observations are performed in thisnetwork to detect pre-cursory crustal movementthat may occur pre-seismically. These points also
provide positional references for the nation-wide
network of the Global Positioning System being
constructed by the Geographical Survey Institute(GSI), Japan. (Taizoh Yoshino)

VLBI systems
A new VLBI system is designed for the Keystone
Project, in which we emphasized (1) fully automatic observations/data processing, (2) high reliability and stability, and (3) high geodetic accuracy. Each VLBI station is composed of an 11 meter parabolic antenna, with a slewing speed as fastas 3 degrees per second, S/X band receivers, anH-Maser frequency standard and a new K4 VLBI
data acquisition system. The data recording is performed with the highest possible rate (256 Mbps)
of the DIR-1OOO, the K4 data recorder and awider receiving bandwidth (7.78.6 GHz) is used
for the X band, in order to enable highly accurate
determination of the group delays. Full automatic
operation can be achieved by using the DMS-24
automatic tape changer and a computer network
connecting the controlling computers at individual
VLBI sites. Daily geodetic VLBI experiments areto be done by remotely controlling the four VLBIstations from the central station at the Koganei
headquarters to detect short-term earthquake precursors. We also plan to build a new correlator
dedicated to the Keystone Project that can process
more than six baselines simultaneously. (MichitoImae)

SLR systems
An SLR system is to be installed at each of theKeystone Project stations in order to reinforce thevertical station position accuracies. 24 hour SLR
operation is possible for geodetic satellites as highas 50022000km with the ranging accuracies < 1cm. A new capability of this SLR system is to synchronize the ranging from the individual stations towithin 100 nanosecond. This enables precise timetransfer and reduction of the systematic errors inestimating the site positions.
A new SLR data analysis software, CONCERTO,
is under development in CRL and its parameter
adjustment part is now being written. We conrmed the precision of the orbits generated by
CONCERTO by comparing them with those produced by UTOPIA. The four SLR stations of theKeystone Project will have a large common view
and a variety of data analysis schemes including
the geometric method are possible. We plan tosolve for the site positions as common parameters
over a few successive passes and we expect theiraccuracies of <1 cm with 34 passes. (Hiroo Ku-nimori)
Q&A

Q: Is the currently available 3 meter mobile VLBIantenna at Koganei to be used for this project?

A: No, we build a new 11 meter antenna dedicatedfor the Keystone Project at each station. Please do
not confuse the Keystone Project with the MDX(Metropolitan Diamond Cross) VLBI network.

Q: How many hours do you plan to observe daily
in the Keystone Project?

A: We have a provisional plan of 4 hours a day.
It will yield a few recorded K4 tapes.

Q: How far is it possible to automate the SLR observations?

A: It still needs some help by an operator to catchthe satellite. This technique is advancing rapidly,
though. \24 hour observation" means that thestations are ready to observe whenever a satellite
passes over the stations.

Q: In order to reinforce vertical site position accu-

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September 1994

racies, one SLR station will do. Why do you plan
to have SLR at each station?

Development of the new K4 correlator
A new XF-type correlator, specially designed for

A: VLBI is still poor in estimating \relative" verti- K4 data recorders, is currently under development.

16 units are to be installed in a single compact
box (32kg, 45cm231cm246cm) together with thecontrol part. This new correlator can handle up to
32 Msps/channel 2 8 channels by using high-speed
programmable IC's. It can also handle multi-bitsampled data in each unit and the gating function
is implemented in order to correlate pulsar signals
eciently. This correlator is controlled by using
Q: How about the collocation plan between VLBI theVME system. (Shin'ichi Hama)and SLR in the project?
cal component which is highly correlated with clocko set and atmospheric delay. SLR coordinates givethe absolute position with respect to the geocenteras observed ranges are not biased by system delay
and target shape. SLR is also free from ionosphericdelays and turbulence by water vapor components.
That is why we need SLR at each station.

A: Local tie would be relatively easy because they R&D experiment No. 1 - Kashima-Usuda Pulsar
are installed closely. Subcentimeter precision is stilldicult, though.
2. Other technical development activities

Present status of the Kashima 34m antenna
A great amount of works have been done for theKashima 34m antenna since the end of 1992. Theworks include re-painting and anti-corrosion treatments of the whole body, replacement of the azimuth rails, reinforcing the backup structure of
the main re ector, and the improvement of the receiver/feeder systems. We put a cover over theazimuth rail to make its future corrosion slower.
We removed 300/600 MHz band receivers installed
beside the subre ector and replaced the IF signal
coaxial cables with highly reliable optical bers.
In September 1993, a typhoon hit the antenna anddamaged the subre ector controller. Now it has
been xed. We started the development of the mmwave receiver (40/lOO GHz) to be installed into the34m antenna as a joint project with the National
Astronomical Observatory, Japan. (Noriyuki Kuri-VLBI

A pulsar VLBI experiment is performed between
the Kashima 26m antenna and the Usuda 64m
antenna on Aug.7, 1992 and good fringes werefound for the pulsar PSR0329+54. We investigated
the relationship between the correlation amplitudes
and the widths of the signal gate in the K3 crosscorrelator by using its gating function, and conrmed that the amplitude reaches its maximum
when the gate is as wide as the pulse. With thenew K4 correlator, which has a higher pulsar gating function, we will be able to correlate millisecond pulsar signals as well as relatively slow pulsars
such as the one observed here. (Mamoru Sekido)

R&D experiment No. 2 - 22 GHz VLBI experiment

Conventional phase calibration signal generating
system can not generate suciently stable andstrong phase calibration signals for frequencies
higher than 10 GHz. We started to develop a newphase calibration signal generating system in order to enable geodetic VLBI in higher frequencies.
In the new phase calibration unit, phase calibrahara)tion signals are created at a lower frequency andthen up-converted by mixing them with a higher
frequency signal. We tested its performance andDevelopment of the new K4 backend
con rmed the signal strength and the long-term
The new K4 system is designed to enable high ac- phase stability. This new system is to be usedcuracies in all possible observing modes in VLBI by in the coming 22 GHz VLBI experiment between
employing wider bandwidths and multiple-bit sam- Kashima and Australia in 1994 March. (Hitoshi
pling capabilities. Present targets include 12 bit Kiuchi)
sampling, maximum sampling rate of 64 MHz, atness of the phase throughout the band, and so on. Q&AWe are currently developing a fast A/D converter
Q: Why is the new system not called \the K5"?
and a wide-band image rejection mixer. In the newK4 data recorder, we use a new data recording for- A: There should be a drastic improvement to do
mat where the time labels are not inserted in the so. For example, bandwidth synthesis techniquedata tracks but are written onto an independent was rst adopted when Mk2 becomes Mk3. Thecontrol track. This enables quicker data recorder new K4 does not have that kind of essential breaksynchronization in correlation processing. (Hitoshi through.

Kiuchi)

Q: Is the new K4 have compatible with the old K4?

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A: Yes, it is.
3. Report on IRIS-P and VLBI activities inNAO-MizusawaWe are going to purchase new K4 data recorders
and install them at the Hobart and the Fairbanks
stations next year. The Urumqi station, China, isexpected to join the IRIS-P network and we plan
to install another K4 data recorder there in 1995.
We also hope to install a new K4 recorder in 1996
at the Kokee VLBI station, Hawaii, so that it canjoin the IRIS-P experiments again. We have tostart thinking about the contribution to the world
VLBI community not only by R&D (Research andDevelopment) but also by D&D (Development andDeployment). The new 10 meter antenna at Mizusawa successfully participated in the IRIS-P experiment in July, 1993 for the rst time. We just nished the development of the bandwidth synthesis
software for the NAOCO (NAO correlator) and weplan to perform weekly or bi-weekly IRIS-P experiments by using the NAOCO at Mitaka, Tokyo.

IERS TDC News No.5

Kashima and to send tapes overseas to the foreign
data processing station. Except the time tag problem, data conversion is technically possible.
Following items are discussed for the next step.
(1) If we are to continue tape copying, we need atape copy center. Then we have to pay money forcopying.
(2) When we copy data, data rate is usually
selected to the slower one. It is hence timeconsuming.
(3) If we take the option of direct connection to acorrelator, we can avoid the above problems. We
can in uence the designers of the Mark IV and theEVN correlator so that they will take this into account. However, the number of data recorders to
be installed in the processing center would be unacceptable.

With only existing tools, what we can do would belimited. It is agreed to copy tapes as an immediate
action for VLBI compatibility. All the participants(Koichi Yokoyama)
also agreed on having a unique international VLBIsystem as a nal goal. The participants of theReport of the IRIS Working Group on
meeting agreed that Noriyuki Kawaguchi (NRO)
Compatibility of VLBI Systems
takes over Taizoh Yoshino (CRL) as the contact
The rst meeting of the IRIS Working Group person of the IRIS Working Group on Compatibilon Compatibility of VLBI systems was held on ity of VLBI systems at the end of 1993. (TaizohSeptember 9, 1993 as an ad hoc meeting of Yoshino)
VLBI'93 in Kyoto. The meeting was attended
by, A. Tzioumis (ATNF, Australia), W. Cannon
The New Representative of the VLBI(ISTS, Canada), R. Wietfeldt (ISTS, Canada),
Technical Development Center
B. Petrachenko (EMR, Canada), J. Cai (Xian, The space geodesy group of CRL has experienced
China), Qian Zhihan (Shanghai, China), Yea major restructuring in 1994 summer. Now weShuhua (Shanghai, China), J. Ulvestadt (JPL, have
two research sections at Koganei CRL headUSA), A. Niell (Haystack, USA), S. Lowe (JPL,quarters, i.e. Space and Time Measurements SecUSA),K. Heki (CRL, Japan), M. Imae (CRL,tion (chief: Michito Imae), Space Geodesy SecJapan). H. Kiuchi (CRL, Japan), H. Kobayashi
tion (chief: Taizoh Yoshino), and one section at(ISAS, Japan), T. Yoshino (CRL, Japan).
Kashima Space Research Center, i.e. the Radio AsFrom each institution, current status on VLBI tronomy Applications Section (chief: Yukio Takacompatibility was reported.
hashi). Future correspondence should be addressed
the following new representative of the group as
ISTS(Canada) Assuming MarkIII system, inter- to
the Technical Develop Center of IERS
face, to and from S-2 system, is developed.
Dr.Tetsuro Kondo, Radio Astronomy Applications
NAO(Japan) According to the agreement on the Section,
Kashima Space Research Center, ComVLBI generic interface, we are developing the in- munications Research Laboratory, 893-1 Hirai,
terfaces between VLBA and K-4, and between S-2
Kashima-machi, Ibaraki 314, JAPAN.
and K-4.
+81-299-84-7137
JPL(USA) Compatibility issue was discussed at Telephone:
Facsimile: +81-299-84-7159
Pasadena and Russia for space VLBI cooperation.
Internet: kondo@crl.go.jp
Haystack(USA) Compatibility between MarkIII This news was edited by Kosuke Heki, Kashima
and other systems are studied.

Space Research Center, who has been the represenCRL(Japan) Hybrid data correlation and tape tative of TDC during the last 12 months. I apolocopying are currently made to process data at gize the delay of the issue of the TDC News No.5.