TECHNICAL DEVELOPMENT CENTER NEWS No.9
International Earth Rotation Service - VLBI Technical Development Center News

published by

Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan
October, 1996

CONTENTS

Overview of the Ninth TDC Meeting : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2
Review of Reorganization of the IERS VLBI and APSG Work Shop : : : : : : : : : : : : : : : : : : : : 7
The Compatibility of VLBI Terminal in APT : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 8
The Extension of the Asia VLBI Networks by CRL (the Results in Japan-Urumqi
VLBI Experiments) : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9
Technical Reports
Current Status of the Key Stone Project (KSP) : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 14
Crustal Deformation Measurement in the Metropolitan Area
Real-Time VLBI System Software { RKATS : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 15
Current Status of the Gigabit VLBI Recorder System : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 17
GPS Meteorology in Japan and its Implications to VLBI : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 19
Radar Observations of Near Earth Asteroids : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 22
Current Status of Kashima Radio Spectrograph (KaRAS) for Observing
the Sun and Jovian Radio Wave Emissions at Low Frequencies (20-70 MHz) : : : : 26
Announcement
Technical Workshop for APT and APSG 1996 (TWAA96) : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 7

1

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IERS TDC News No.9

Overview of the Ninth TDC
MeetingFujinobu Takahashi, the vice-director of IERS
TDC at Communications Research Lab., opened
the meeting.

Tetsuro Kondo (kondo@crl.go.jp)

2. Progress Report on IERS Restructuring(Taizoh Yoshino)

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-0012, Japan

Taizoh Yoshino introduced history from the beginning of the IERS to the present. He also introduced topics, such as review of the IERS services,
The Ninth meeting of the Technical Development inclusion of the crustal movement monitoring, etc.,
Center was held on September 13, 1996 at the con- in this year's IERS workshop.
ference room of Communications Research Labo- During this year, there was restructuring of the
VLBI organization in IERS. There were 14 proposratory.
als from 10 countries for the Call for Proposals for
VLBI participation in IERS.
The Communications Research Laboratory had
Attendance
proposed to continue as a technological development center. This proposal was formally acceptedby the Directing Board of IERS in September,
CRL members
1996. The US National Earth Orientation Service(NEOS) was selected as the IERS VLBI CoordinatKuniaki Uchida, Taizoh Yoshino, Shin'ichi Hama, ing Center, with Dr. Chopo Ma as representative
Hitoshi Kiuchi, Akihiro Kaneko, Kohichi Se- in the Directing Board.
bata, Hideyuki Nojiri, Toshimichi Otsubo, Michito
Imae, Mizuhiko Hosokawa, Yuko Hanado, Fuji- 3. Activity Reports of Each Organization by
nobu Takahashi (KSRC: Kashima Space Research the Special Members
Center), Yukio Takahashi (KSRC), Noriyuki Kurihara (KSRC), Ryuichi Ichikawa (KSRC), Yasuhiro The special members reported on the current
Koyama (KSRC), Mamoru Sekido (KSRC), Ju- status of the activities of their organizations.
nichi Nakajima (KSRC), Eiji Kawai (KSRC), Tetsuro Kondo (KSRC)
National Astronomical Observatory (Nobuyuki
Special members

Kawano)Nobuyuki Kawano reported current status of
Nobuyuki Kawano (National Astronomical Obser- VSOP,VERA, and RISE, which are major projects
vatory), Kazuo Shibuya (National Institute of Po- in the National
Astronomical Observatory (NAO).
lar Research), Mikio Tobita (Geographical Survey Budgetary request
VERA for next scal year
Institute), Masayuki Fujita (Hydrographic Depart- (1997) could not be for
proposed
to the ministry ofment, Maritime Safety Agency),
nance.
Therefore
a
new
task
team consisting
Following special members could not attend: of represenatives from VSOP, VERA
and RISE
Noriyuki Kawaguchi (National Astronomical Ob- group will be formed for promoting VERA.
servatory), Kosuke Heki (National Astronomi- crete partnership with universities and RFP Con(Recal Observatory), Hisashi Hirabayashi (Institute quest for Proposal) must be clari ed to promoteof Space and Astronautical Science), Yoshimitsu VERA.
Okada( National Research Institute for Science and Launch schedule of VSOP was postponed from
Disaster Prevention), Teruyuki Kato (Earthquake September, 1996 to January or February, 1997.
Research Institute, University of Tokyo),
The FX correlator at Mitaka started processing,and 24-hour-operation in a day and 10 stations simultaneous processing became possible. CorrelaMinutes
tion results are being tested through comparisonswith data processed by the correlator NAOCO
which is already in operation.
A relay satellite and a laser altimeter will be
1. Opening Greeting
added to the RISE project, in addition to adelta VLBI mission using a lunar lander and a

October 1996

3

moon orbiter. The number of sta members at system being developed under KSP project because
NAO/Mizusawa dedicated to each project is as fol- it is designed to be able to measure SAR satellite
lows: 10 for VERA, 16 for VSOP, 2 for RISE, and position with this accuracy. He also proposed the
3 for others.
possiblity of the calibration of SAR data by usSeven years have passed since NAO was estab- ing Japanese VLBI antennas as ground targets oflised. We hope to establish a space measuring sec- SAR observations because those positions are welltion which combines a VSOP group and an earth determined through repeated VLBI observations.
rotation group in the 2nd stage of future plan thatwill start from the 10th aniversary of NAO (three National Institute of Polar Research (Kazuo
years later). Frequent personnel exchanges among Shibuya)
Mizusawa, Mitaka, and Nobeyama area are also
Kazuo Shibuya reported current status ofplanned.
Antarctic VLBI project.
Equipments necessary for VLBI will be shipped
Hydrographic Department, Maritime Safety
toSyowa Station, Antarctica next year (Nov. 1997)
Agency (Masayuki Fujita)
by the 39th Japanese Antarctic Research ExpediMasayuki Fujita reported operations of SLR tion (JARE-39). Each equipment test has been(both portable and xed types) and GPS in Hy- started using the 5 m antenna at GSI when availdrographic Department, Maritime Safety Agency. able. Antarctic campaigns are planned from FebruFixed SLR has been operated over 10 years at ary, 1998, with probable participation of the AusShimosato. The observation schedule is becoming tralia, South Africa, and the Chilean Antarcticdenser, because the number of satellites is increas- station antennas. The campaign will include an S2
ing. Tracking of RIS of ADEOS will be started recording system, and correlator processing withfrom October. Portable type SLR, whose purpose di erent systems is yet to be discussed and solved.
is to measure the rst-order control point, was op- Regarding other topics,
erated from January to March, 1996 at Choshi (1) A DORIS beacon and a superconducting
which is the 14th point, numbering from Chichi- gravimeter have been operating properly,
jima Island measured in 1988. Choshi was also (2) 2 years' continuous GPS data was recorded
the last point planned to be measured. Second with a TurboRogue system on the site, althoughround of measurements begins this scal year. The data transmission was limited to every 10 days'
order of measurement will be Chichijima Island, data,
Ishigakijima Island, Minamitorishima Island, then (3) PRARE ground station for orbit determinaWakkanai. Though upgrade of the SLR system is tion of ERS-2 will be shipped to Syowa Station thisstrongly desired, it is dicult due to budgetary rea- November,(4) ERS-1/-2 SAR Tandem Mission over Antarcsons.
tica
received 70-pass pairs, and covered 1/3 ofContinuous GPS measurements are carried out
Antarctica
for SAR interferometry.
at 7 points (Sagami Bay, Shimosato, Okayama,etc.).
Test operation of D-GPS (1.5-2 m accuracy) de- 4. Space Surveying in Asia
veloped by the Aids to Navigation Department iscarried out this scal year. It will be operated forpractical use since next scal year. Hydrographic The First APSG Workshop Report (Taizoh
Department plans to make geodetic observations Yoshino)using reference stations of D-GPS.
Taizoh Yoshino reported on APSG (Asia Paci c
Space
Geodynamics). Dr.Ye, the former director of
Geographical Survey Institute (Mikio Tobita) the Shanghai observatory, proposed APSG considdevelopment of space surveying in the WestMiko Tobita reported activities relating GPS, eringern
Pacic region and the importance of this region
VLBI and SAR as follows.
inthemeetingof experts at the ESCAP conferIGS pilot project which measures positions of ence in September,
It became one of the reGPS stations in the ITRF coordinate system was comendations of the1994.
conference,
was inistarted. A 32m antenna dedicated for VLBI will be tiated. The APSG workshop wasandheldAPSG
inShanghaiconstructed at Tsukuba, and it will be operational in May, 1996. He emphasized that it was necessary
in March, 1998. An accuracy of 2-3 mm in absolute for space geodetic observations in the Asia Paci csatellite position is required for the SAR analysis. region to be accompanied by the advanced infrasHe therefore expressed great expectations for SLR tructure improvement. And, there was a question

4

IERS TDC News No.9

on present state and prospect on observations in real-time VLBI is not only its immediacy but also
the increased reliability by not using a recorder
India.
(mechanical equipment). Moreover, there is no difAPT(Asia Paci c Telescope) Report (Yukio ference in the speci cations between a tape-based
VLBI correlator and real-time one, because uni Takahashi)
cation of the data was attempted from the point of
Yukio Takahashi reported on APT as follows. view of the correlator.
The purpose of APT is to establish a VLBI network in the Asia region that is useful for both as- Real-Time VLBI Software (Mamoru Sekido)
tronomy and geodesy. Therefore the compatibility of recorder systems becomes a problem. The Mamoru Sekido reported regarding the softwareorganaization of APT is not yet xed, unlike the R-KATS for real-time VLBI correlation processing.
APSG. Joint APT and APSG workshop, TWAA96 The R-KATS aims at semi-unmanned operation in(Technical Workshop for APT and APSG 1996) correlation processing, and it is still under developwill be held at Kashima Space Research Center in ment. Debugging of the software was entering its
December.
nal phase for practical use.
There was a question regarding earth rotation
parameters
used in the real-time VLBI correlation
5. Technological Development Reports
processing. The answer was that the predicted values of IERS were used.
5.1. Key Stone Project (Crustal Deformation Observation System in the Tokyo 5.2 Next Generation VLBI System
Metropolitan Area)
Current Status of VLBI (Noriyuki Kurihara)

A Plan of Development of Multi-ch HighSpeed Correlattion Unit for Exclusive Useof Geodetic Survey (Hitoshi Kiuchi)

Noriyuki Kurihara reported current status of
A development plan for a high-speed correlation
KSP VLBI as follows.
The construction of facilities was started in 1993. unit was shown by Hitoshi Kiuchi. It processes
Daily observations were started on the Kashima- 32 ch 2 64 Mbps data, and is designed exclusively
Koganei baseline in January, 1995. Miura joined for use with geodetic obseravtions. The correlation
the daily observations in December, 1995. In unit will be developed by using an extension of conSeptember, 1996, daily observation by the full net- servative technology. No custom made ICs will bework of 4 stations (Kashima, Koganei, Miura, and used for the planned correlator. As for the video
Tateyama) was started. Unmanned observations band width, it was shown that 32 MHz band width
are carried out at each station, except for the guard (corresponding to 64 Mbps when 1 bit samplingis adopted) was limiting, considering the atness(operator) performing tape changes.
There was a question whether there was any of amplitude-frequency characteristics. There were
trouble in the unmanned operation. He replied \No some comments from a special member as follows:
trouble so far". In addition, there was an inquiery the purpose of technical development was ambiguabout the daily observation schedule. The answer ous, and clear motivation and target are necessary
was that presently the observation local time range to obtain budget for development. Some discusis xed for 5 hours from midnight through the early sions followed, and are summarized as follows.
morning at present, as long as there are no special Why will it be developed for exclusive use withgeodetic observations? The answer was that \excircumstances.
clusive use with geodetic observation" means that
correlator should measure group delay accuReal-Time VLBI Hardware (Hitoshi Kiuchi) the
rately. This is di erent from astronomical appliwhich are mainly concerned with accurate
Hitoshi Kiuch reported regarding the hardware cations,fringephase.
on the present state of real-time VLBI. Main points There were requests for the technical developwere as follows.
as follows. Please consider comaptibility
It has already succeeded in test operations. It mentwhenthedata aquisition system is developed, bewas also used for fringe tests to check the system cause it becames
in international VLBI
performance. The improvement of the software for experiments. Alsoimportantdevelopaninfrastructure thatstable operation is being made. An advantage ofOctober 1996

5

includes data transfer through satellites, which is way to obtain this information is either to use ranecessary for a remote site as in the Antarctic. diosonde obseravtions, whose time resolution is 12
hours and space resolution is about 300 km, or to
Development of Gigabit Recorder (Junichi use radiometer data on board a satellite which observes the same ground point every several days.
Nakajima)
A highly dense GPS observation network may be
Junichi Nakajima introduced current status of able to realize water vapor observations with a higha fast-sampler and a high-density recorder under space-time resolution (horizontal 20km and about
10 minutes in time) which is never attainable bydevelopment.
In his report, the importance of achieving high any other method. This is expected to make clear
sensitivity by extending the bandwidth under lim- the mesoscale phenomena, and to improve numerical prediction models in meteorology. By applying
ited antenna diameter was indicated.
In addition, the recorded signal could be mon- an improved numerical model to compensation ofitored on a TV display, since the equipment was wet delay, improvement in the accuracy of geodetic
developed on the basis of that for TV. Therefore observations are expected.
an operator could check the system easily.
Following comment was given from a special Asteroid Radar Observation (Yasuhiro Koyama)
member. Since the price of the K4 equipment does
not drop, price might become a limiting factor for On the international cooperation radar observathe popularization of this equipment. The gist of tion of the asteroid (Near Earth Asteroid) which
the discussion concerning this matter is as follows: approaches the earth, the principle of observation
the cost becomes almost equivalent to that for the and results of last year were reported by Yasuhiro
VLBA recorder when peripheral equipment is in- Koyama. In the observation in last year radio wave
cluded. A key to future popularity is the future was emitted from the 70m antenna at Goldstone,
USA, and re ected wave from the asteroid was reprice.
There was a comment that increased sensitivity ceived by each antenna at Goldstone, Evpatoria
is an important factor, and is not a wrong direction in Ukraine and Kashima in Japan. The asteriod
was named Golevka which combines initial two or
for technological development.
three letters of 3 station names joined the obseravtion. There was a question from the special mem5.3 Others
ber about the re ection coecient of the radio wave
from the asteroid. There was the comment fromanother member as follows. Actual comaprison
GPS+VLBI Meteorology (Ryuichi Ichikawa) was made using the sample brought back from theby Apollo project. Regarding the measureRyuichi Ichikawa reported on GPS meteorology moonment
ofsize and shape, there was a question of why
by utilizing GPS observations as a meteorological radio wave
used. The repoter answered that the
instrument for measuring the water vapor content resolution ofis theradar was higher than that of theof the atmosphere. Evaluation of GPS observa- optical observation.
tions using the KSP-VLBI data, with feedback to
the VLBI data analysis toward higher precision was Expectation to VLBI Technological Develalso reported.
The importance of the consideration in the anal- opment (Mizuhiko Hosokawa)ysis of azimuth angle dependence of the water va- Mizuhiko Hosokawa proposed ideal way, signi por content was indicated from the comparison cance, and expectation to the development of VLBI
of VLBI and GPS observations in cases where by every objects, every purposes, and every devellarge anisotropy is seen in the neutral atmosphere. opment directions. He classi ed each item as folThere was a question from a specialist: Why are lows. Objects are classi ed into natural cosmic rahighly precise geodetic observations expected from dio source and arti cial radio source. Purposes are
GPS meteorology? The answer includes two major calssi ed into astronomy, geodesy, navigation, andpoints. One is improvement in the meteorological, physics. Development directions are classi ed into
while the other is the density of GPS observations. accuracy, sensitivity, and immediacy.
Further comment was given by the reporter after Up to present time natural cosmic radio sources
the meeting as follows.
major objects of the VLBI measurement. From
Information concerning water vapor with a high arenow
on arti cial radio sources will become imporspace-time resolution is indispensable for the com- tant objectives,a number of space vehicles
pensation of the wet delay. At present, the only will be launchedbecause
for the moon and for planets. As

6

IERS TDC News No.9

for the purposes, if it becomes possible to measure suro Kondo. Although the observation at lower
source position with an acuraccy of better than 10 frequency band became dicult due to arti cialmicro arc second, measurement of star mass and noises, it was shown that to some extent radio inuctuations of standard coordinates system which terferences could be removed by applying a simple
is predicted by CRL theory group will be veri ed. algorithm on a spectrogram. In the future, an inIt also becomes possible to make a 3-D map of our terferometer will be constructed between Kashima
garaxy which is an important astronomy problem. and Hiraiso (about 40km baseline length). The
As for the divelopment directions, he stressed special member pointed out that the purpose of
expectations as follows. Keeping the leading in KaRAS. The reporter replied as follows. The purthe present state with respect to the immediacy pose is to obtain data available to use theoreticallike real-time VLBI, TDC/CRL should promote work to evaluate proposed radio wave generation
not only sensitivity improvement by expanding the models of the sun and Jupiter. There also was aband width but also other technological develop- comment on possibility and signi cance of carrying
ment, in particular higher precision to examine the- out such observation in the polar region which canmonitor the objects for long time a day.
oretical prediction.
KaRAS (Kashima Radio Spectrograph for 6. Closing Greeting
Low Frequency Natural Radio Wave ObserThe greeting of the closing was addressed by Kuvation) (Tetsuro Kondo)

niaki Uchida, the director of IERS TDC at ComThe current status of KaRAS (Kashima Ra- munications Research Laboratory.
dio Spectrograph) (20-70MHz) which was installed After the conference a short inspection of SLR
at Kashima Space Research Center for monitor- and VLBI facilities of the KSP Koganei station was
ing the sun and Jupiter was introduced by Tet- carried out.

Special members (left) and CRL members (right) atttended the ninth TDC meeting held at
the headquaters of Communications Research Laboratory on September 13, 1996.

7

October 1996

Review of Reorganization of
the IERS VLBI and APSG
Workshop
Taizoh Yoshino (yosh@crl.go.jp)
Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan

Review of Reorganization of the IERS VLBIIn the beginning, the aim of reorganization of the
IERS VLBI is explained referring to the policy of
IERS to be discussed at the 1996 IERS Workshop
in October (See; Report on the IERS Directing
Board Meeting No.18). Reorganization and particpations were decided by the members of Directing
Board in a vote by correspondence after the meeting held at Baltimore in May, 1996. It is decided
that the VLBI Coordinating Centre is NEOS (National Earth Orientation Service) with Dr. Chopo
Ma as representative in the Directing Board. Then,
it is informed that the proposal of CRL to continue
to work as a VLBI Technical Development Center (TDC) is formally accepted by the letter fromProf. Ch. Reigber (Chairman of the IERS Directing Board) to Dr. Y. Furuhama (Director Generalof the CRL). The TDC consists of seven institutes
from six countries.
APSG Workshop

The APSG (Asian Paci c Space Geodynamics)
Project is based on a recommendation of the symposium on Space Technology and Applications for
Sustainable Development held during the ESCAP(Economic and Social Commission for Asia and thePaci c) Ministerial Conference on Space Applications for Development in Asia and the Paci c (1922 September, 1994). It is also recommended as
the IAG Resolution #4 adopted at the XXI General Assembly of the International Association of
Geodesy in July 1995.
The rst APSG workshop was held in Shanghai
in May 1996. Objectives of the APSG discussed
at the workshop is reported. As an APSG structure, it is decided to have a Program Secretariat, aTechnical Coordinating Center (TCC), and a Data
Processing and Archiving Center under a Management Board. The TCC consists of ve Technique
Working Groups (TWG). Since CRL is expected tocontribute to the APSG as a VLBI Technical Development Center of the IERS, T.Yoshino (CRL)
is designated as a convenor. In order to understand the tectonic condition surrounding Japaneseislands, we should cooperate with the countries in
Asia-Paci c region for the study of future earthquakes.

TWAA96
APT&APSG
Technical Workshop for APT
and APSG 1996 (TWAA96)
10-13 December, 1996 Kashima, Japan
hosted by
Kashima Space Research Center
Communications Research Laboratory

Kashima Space Research Center of the Communications Research Laboratory will host an international workshop which will highlight technicalissues related with Asia-Paci c Telescope (APT)and Asia-Paci c Space Geodynamics (APSG)
Project from Tuesday, December 10 through Friday, December 13, 1996. In the 4th APT workshop held in Australia last year, it was agreed
to hold general APT workshop every two years.
Instead of expanding the workshop interval fromoriginal one year to two years, it was also agreed
that technical work group members should begathered in between the biennial general workshops and Japan was suggested as a venue of the
rst technical meeting of APT. It is our pleasure
to be able to announce that the meeting will actually take place with a full support from Science and Technology Agency (STA) and Japan
International Science and Technology Exchange
Center (JISTEC). Since there are many technicalrespects which are common for APT and a VLBI
part of APSG, we decided to make the meeting toa joint technical workshop for APT and APSG.
More information is available on Web Site
\http://apollo.crl.go.jp/index.html#TWA
A96" or from Workshop Secretariat:
Workshop Secretary : Yukio Takahashi
e-mail : takahashi@crl.go.jp
TEL : +81-299-847136
Assistant Secretary : Yasuhiro Koyama
e-mail : koyama@crl.go.jp
TEL : +81-299-847143
Kashima Space Research Center
893-1 Hirai, Kashima, Ibaraki, 314 Japan
FAX : +81-299-847159

8

IERS TDC News No.9

IV is upper compatible with VLBA. These two systems use open reel tapes. In Japan, we have developed the new VLBI terminal which is available for
1 Gbps mode and uses cassette tapes.
There are many types of VLBI terminal in the
Yukio Takahashi (takahashi@crl.go.jp)
Asia and Paci c VLBI network. Australian VLBI
network is uni ed by S2 system. Japanese VLBI
Kashima Space Research Center
network is uni ed by K4 system (or VSOP sysCommunications Research Laboratorytem). However, the global VLBI experiments were893-1 Hirai, Kashima, Ibaraki 314-0012, Japan conducted by Mark-III, and in future Mark-IV willused. JIVE adopted Mark-IV system. VLBAIn 1980's, VLBI observations were conducted besystemis most popular now, and it is the stanusing Mark-II, Mark-III VLBI terminal, or the dard type
VSOP project. It is very complex
VLBI terminal which is completely compatible situation toinconduct
VLBI experwith Mark-III type. Therefore, the VLBI termi- iment in Asia and Pacitheccollaborated
network.
VSOPgroup in
nal is uni ed by Mark-III type in 1980's. In 1990's, Japan has the copy equipments among VSOP
K4,
many types of VLBI terminal have been developed. S2, VLBA system, and some institutes in JapanFirst is K4 VLBI terminal which was developed
plans to make a copy equipment. It is necesby CRL(Communications Research Laboratory) in havesary
to
an standard method how to conduct
Japan. This recording system is a cassette type the jointmake
experiment
copy equipment and toand it uses a rotating recording head. The tape establish the standardusing
formatof the future VLBI
running is very stable, and there is no bit shift and terminal.
the parity error is very small. The recording modes In this December, the technical workshop forof 64 Mbps, 128 Mbps and 256 Mbps are available APT and APSG will be held at Kashima, CRL in
now. The recording duration of each K4 tape is 50 Japan. These themes were discussed in this workminutes in the rate of 256 Mbps, and 200 minutes in shop.
the rate of 64 Mbps. The automatic tape changer
for 24 tapes is also available. Therefore, any operator for the tape change is not necessary in normal
VLBI experiment during 24 hours in the rate of Technical Workshop for
256 Mbps mode, and during about one week in the
APT and APSG 1996
rate of 64 Mbps. We have also developed the video (TWAA96)
converter and formatter. The size of K4 VLBI terminal is compact (1/3 of Mark-III type) and theweight is light (1/4). The K4 system is used in the
10-13 December, 1996 Kashima,domestic VLBI experiments in Japan, KSP systemJapanand mobile experiments. Recently, NAO (National
hosted by
Astronomy Observatory) set K4 system at Urumqi
Kashima Space Research Centerstation. VSOP terminal had been developed based
Communications Researchon K4 system. Recorder and formatter is the alLaboratory
most same as K4 system for KSP system. However, it needs the time control units. Japan has
See Page 7 for Detail!
ve correlation system for K4 system; 1)KSP correlater (6 baselines), 2) Kashima correlater (onebaseline), 3)GSI correlater, 4)NAO mizusawa correlater, 5)VSOP correlater.
S2 VLBI terminal developed by Canada. It combines a few home video decks, and the price ischeap. The maximum recording rate is 128 Mbps.
It is used in AT(Australia Telescope) VLBI network and in many countries. The correlation forS2 system is available in Canada, and at ATNF
in Australia. VLBA terminal whose maximum
recording rate is 256 Mbps is used worldwide.
APT&APSG
Mark-IV which will be available for 2 Gbps modeis developed in USA and the correlation center has
been established in JIVE and other country. MarkThe Compatibility of VLBI
Terminal in APT

TWAA96

October 1996

9The Extension of the Asia
VLBI Networks by CRL (theResults in Japan-Urumqi VLBI
Experiments)
Y. Takahashi1(takahashi@crl.go.jp), T.Iwata3,
N. Kurihara1 , J. Nakajima1 , M. Sekido1 ,M.Imae2, Y.Hanado2 , Y.Koyama1, Dong
You Suo and Urumqi VLBI group, andShanghai VLBI group
1 Kashima Space Research Center

Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314, Japan
2 Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan
3 Now at National Space Development Agency ofJapan(being appeared in the proceedings of APT'95(Asia Paci c Telescope meeting 1995))
1. Introduction

Figure 1. The deformation in the Asia and near
Japan Archipelago.

The Asia and Paci c VLBI network makes thewidest VLBI network which cooperation with Australia, China, Japan, Russia and Hawaii. The east Furthermore, we conducted the pulser VLBI oband central Asia is very interested to study the servation with Russia in 1995, and we will conduct
crustal dynamics. This area is on the Eurasian the VLBI observation in the spring, 1996 again.
Plate. The India Plate collides to the central Asia, We also have the plan to set the K4 VLBI termiand Himaraya Mts. are created on the front of nal to Shanghai in China, Kalyazin in Russia andthe collision. The central Asia are pressed by the Wettzel in Germany. Therefore, we can extend theIndia plate motion, and the East Asia is pushed VLBI network in Asia.
out toward the east direction, that is, toward theJapan archipelago. This movement is related withthe crustal deformation in Japan archipelago. It 2. Joint Experiments with Urumqi
is recently considered that the deformation of east
Asia makes the micro plate (Amur plate) on the The results of Japan and Urumqi experiments
Eurasian plate and the other micro plate (Ohot- in 1994 and 1995 are described. Table 1 shows
suku Sea plate) on the North American plate. the overview of the experiments in 1994, 1995.
Figure 1 shows the crustal deformation in Asia In 1994, the phase calibration is not good, andarea. Four plates, such as North American plate we do not used the phase calibration data. The(or Ohotsuku Sea plate), Eurasian plate (or Amur phase information among the channels was xed
plate), Paci c plate and Phillipin Sea plate, collide to the phase relationship of one observation near
together near the Japan archipelago, and the big the middle of experiment. The observation usedearthquakes occurred repeatedly. The deformation the strong source, and the SNR is very large andnear Japan archipelago should be studied as the the phase uctuation is stable for each channel. In
deformation of the whole Asia area.
this method, the other observations has pseudo deAs concerning that the Asia area is important, lay by the incorrect phase information. The phase
we promote the Asia and Paci c VLBI experi- relationship among channels is changeable duringment. The joint VLBI experiments with Urumqi the experiment, and its change was equal with theconducted in 1994 and 1995. The results in these clock change. We need many changes in clock. The
experiments are described.
residual was very large.

10

IERS TDC News No.9

Table 1. Residual of Urumqi experiment

Date
Remarks
GOOD/CORR. Residual Delay1994
1st 1994/2/28 PCAL NO GOOD
121/191590 ps2nd 1994/3/ 3 PCAL NO GOOD
165/222406 psShanghai1995
1st 1995/3/19 PCAL GOOD
166/215382 ps2nd 1995/4/18 PCAL GOOD
171/306
649 psit is averaged without the phase information between the segments. The ratio of two correlated
amplitudes means the coherence loss caused by thephase stability, such as atmospheric scintillation,
the stability of reference signal and the stability ofsystem. The noise a ects on the ratio of two correlated amplitude in the case that a single noise
ratio (SNR) is less than 10, and the pseudo coherence loss appears for the small SNR. Therefore, we
can estimate the coherence loss only for large SNR.
However, SNR for almost all observation in our experiments is large and our estimation of coherence
is correct.
In the 1st experiment, the coherence at X bandis almost greater than 85 % shown in Figure 3. Abscissa is sources in the experiment and ordinate is
the coherence. The coherence at X band is about
60 % in the second experiment shown Figure 4.
The coherence at S band is about 80 %. The coherence loss by the atmospheric scintillation is lessthan 5 % at X band. This large coherence loss inthe second experiment may be caused by the stability of phase calibration or reference frequency (5MHz) for the short period.
We show the position of Urumqi. Table 2, 3 showtheestimated position XYZ components and HorFigure 2. Residual of Delay in 1995.
izontal & vertical movements of Urumqi station in
ITRF93 (International Terestial Reference Frame
In 1995, the phase calibration was considered to 1993).
be well, but the residual was also large. Figure 2 The estimated vertical component of the second
shows the change in the clock of Urumqi in 1995. experiment in 1994 may be incorrect. The XYZ poThe change in clock was very large and we needed sitions of Urumqi station estimated by 1995 experiments may be correct in the precision of 2 cm. The
many changes in clock almost every hours.
The coherence loss was checked for these exper- position of horizontal component was measured iniments. The whole observation is divided into the the precision less than 5 cm. Figure 5, 6 show theseveral segments shorter than 1 minute (a few 10 horizontal position (easterly and northterly moveseconds). The correlated amplitude are calculated ment) in ITRF93 obtained from the results of thefor each segment. The coherence correlated ampli- experiments in 1994 and 1995.
tude is obtained from an average as the complex We corrected the movement of Urumqi station
values over the all segments to include the phase on Eurasian plate in ITRF93, and we obtained theinformation. On the other hand, we can obtain the position of Urumqi station at Epoch 1994.3.1 on
incoherence correlated amplitude from the average the Eurasian plate from the results of 1995 exof correlated amplitude for each segments, that is, periments. If the Urumqi station moves on the

11

October 1996

Experiment1994.2.28
1994.3. 3
mean
ITRF93
1995.3.19
1995.4.18
mean
Kashima1994.3. 1
1995.3.19

Table 2. Position of Urumqi station in ITRF93

X (cm)Y (cm)
Z (cm)L (cm)
22831077.668.7 463192287.0612.6 436706395.4611.9 448425745.166.9
22831083.763.3 463192273.96 5.8 436706394.96 5.5 448425746.963.2
22831082.962.9 463192276.26 7.0 436706395.06 0.3 448425746.661.0
22831077.365.0 463192286.56 5.8 436706403.66 5.6 448425747.164.4
22831074.963.7 463192284.16 4.3 436706407.76 4.2 448425744.863.2
22831075.861.6 463192284.96 1.6 436706406.26 2.7 448425745.661.6
0399764924.9
0399764925.7

327669075.2
327669073.6

372427887.0
372427887.1

Table 3. Horizontal and vertical position of Urumqi station

Experiment East (cm) North (cm)1994.2.28
1994.3. 3

6.169.1-0.663.4
0.263.1-6.363.1
2.161.7
0.265.0

1995.3.19
1995.4.18

6.465.2-0.968.2
4.364.7

0.061.7
2.863.1
0.661.7

mean
ITRF93

Vertical (cm)9.3616.9-0.36 7.8
1.46 5.2

14.66 7.8
13.1615.4
14.36 0.8

mean
Position at 1994.3.1 on Eurasian Plate from 1995 resultsmean
1.064.7
1.561.7
14.36 0.8
Reference position of Urumqi station
X=22831083.2 cm Y=463192275.6 cm Z=436706706.3 cm

Figure 3. Coherence of 1st experiment in 1995 Figure 4. Coherence of 2nd experiment in 1995
(The solid line means 85%)
(The solid line means 85%)

12

IERS TDC News No.9

Eurasian plate due to the crustal deformation, thiscorrected position becomes di erent with the results of 1994 experiment. These positions of horizontal components agreed the positions obtainedby the 1994 experiments in the precision of 1 cm.
This result might mean that the Urumqi station on
Eurasia plate and the deformation was not large
though the error was a few cm. The positions areshown in Table 3. Figure 7 shows the corrected
position obtained from 1995 experiments.
3. Japan-Russia Pulsar VLBI Experiment

We conducted the pulsar VLBI experiment since
the spring 1995. The station in Russia is Kalyazin
64m antenna. The purpose of these experiments
are to measure the precise pulsar position andproper motion of pulsar. We deliver K4 terminal
to Kalyazin, and we continue experiments for a few
Figure 5. Horizontal position of Urumqi station in years.
ITRF obtained from the experiments in 1994.

4. Conclusion and Future

We conducted the VLBI experiments with
Urumqi or Russia. We succeeded the rst experiment with Urumqi station. The Urumqi positions
can be estimated in the precision of a few cm. The
Urumqi station has some problems yet. However,
it is proved that Urumqi station can be used as the
VLBI station. We hope to extend the Asia andPaci c VLBI network step by step.
We have a plan to deliver K4 system to the station in the area, such as Kaliazin (Russia), Shanghai (China), Wettzel (Germany). NAO (Narional
Astronomical Observatory) delivered K4 system to
Urumqi (China) and Crimea. NIPR has a plan
to establish the anterctica VLBI network aroundsouther hemisphere using K4 system. Therefore,
we can conduct the VLBI experiments in Asia andPaci c area using K4 system.
We also have new VLBI network in Tokyo
metropolitan area. We observe sources everyday.
Figure 8 shows the change in the correlation amplitude on the baseline between Kashima and Koganei since 31th January 1995. If we nd the burst
change for some sources in our VLBI network, weFigure 6. Horizontal position of Urumqi station in will propose VLBI observation in this Asia and Paci c VLBI network.
ITRF obtained from the experiments in 1995.

October 1996

13

Figure 7. Horizontal position of Urumqi station on Eurasian plate at 1995.3.1 obtained from the experiments in 1995.

Figure 8. The change in correlated amplitudes in KSP new project since 31th 1995.

14

IERS TDC News No.9

Current Status of the Key
Stone Project(KSP)
Noriyuki Kurihara (kurihara@crl.go.jp)
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-0012, Japan

Communications Research Laboratory has beendeveloping a Crustal Deformation Monitoring System for the Tokyo Metropolitan Area named the
Key Stone Project \KSP" system. The four VLBI
stations, Koganei, Kashima, Miura and Tateyama,
are distributed around the Tokyo Metropolitan
Area to form the VLBI network dedicated to theprediction of earthquakes occur there. In August,
1996, construction of the fourth (and last) station (Tateyama) was completed. Since September, 1996, VLBI daily observation started including
Tateyama VLBI station. An antenna at Tateyama
and station building are shown in Photos 1 and 2.
Daily VLBI observation at the four station is autoPhoto 1. An 11 m antenna at Tateyam.
matically carried out by commands from the central control system at Koganei central station or at
the Kashima sub-central station. Daily operation ted from Kashima to Koganei central station using
is quite going well. In May, 1996, the rst real-time the optical ber link (see IERS TDC News No.8,
fringes were successfully detected between Koganei June 1996). The results of KSP daily VLBI oband Kashima station. The VLBI signal data (with servation were opened to public through the Worlda rate of 256 Mbps) were also successfully transmit- Wide Web (URL http://ksp.crl.go.jp/).

Photo 2. Tateyama VLBI station.

15

October 1996

Crustal Deformation Measurement in the Metropolitan Area
Real-Time VLBI System Software | RKATS
M. Sekido1(sekido@crl.go.jp), T. Kondo1 , Y.
Koyama1 , H. Kiuchi2 , M. Imae2 , and H.
Sato3

Satelite withrefrector
Signal from RadioＳＬＲ

Starts
Koganei (CRL)

Miura pninsura
Bousouo peninsura

ＶＬＢＩ
Kashima(CRL)

Philippin Sea Plate

Pacific Plate
North American

1 Kashima Space Research Center

Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314, Japan
2 Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan
3 Kety Co. Ltd.
Abstract: Real time VLBI data processing software RKATS is under the development by Communications Research Laboratory and Kety Co. Ltd.
It is designed as automatic VLBI data processing
management software. The overview is describedin this article.
1. Introduction

Plate

Figure 1. Overview of Key Stone Projectprocessing system, which controls real-time 6 baselines correlation, Bandwidth-synthesis treatment,
and Mark-III database creation.
2.
Functions of Real-Time-KATS(RKATS)The RKATS is developed from a tape base
Key Stone Project (KSP) is a trial to catch VLBI
data processing software KATS, which assist
the pre-seismic crustal deformation around Tokyo a operator
in the work of correlation processing,metropolitan area by using VLBI and SLR tech- database creation,
data backup. Both RKATSniques (Figure.1). Daily observation with 4 VLBI and KATS run on andHP-UX
workstation. Figure 2
stations has started as test run from this summer. shows a over view of the ow
data processing.
In normal VLBI experiment, the observed data The functions of RKATS are asoffollows:
have to be recorded on magnetic tapes and they
have to be correlated after transportation to central correlation center. In the earliest case in the 1. The observed data are sent to correlation
KSP, 1-2 days were necessary for data processcenter through ATM communication system.
ing and analysis of the data. Now the correlaRKATS has already loaded the schedule letion system of KSP is semi-automated by DMSof the experiment before the start time with(tape auto-changer) and data processing and analreferring to its workstation clock. The
ysis software, but it even needs a support by opertime of the workstation is synchronized withator for transportation of tapes, tape mounting toUTC(CRL) through ntp (Network Time Proauto-changer, and correlation setup.
tocol).
Recently, real-time data transportation by using
Asynchronous Transport Mode (ATM) with high 2. The RKATS collects clock information of eachobservation station and earth orientation paspeed optical ber link has become available in labrameter (prediction) through network. A few
oratory level. We have started Real-time VLBI
minutes before the start time of observation,
based on co-laboration between CRL and NTT
information for correlation (source and station(Nippon Telegraph and Telephone Corporation).
positions information, observation start time,
Data transfer with communication network gives
and so on.) are send to the correlators.
a possibility of full-automated VLBI observation
system. It release an operator from transportation 3. Output data from correlators are transferredof magnetic tapes and treatment of them.
to hard disk drive of the workstation with PCNow a software RKATS (Real-time KATS) is
NFS (Network File System) on Ethernet. Just
under development for full automated VLBI data

16

IERS TDC News No.9

Obseration staion

ÜïèKashima Üïè
Üïè
Miura
Tateyama Üïè

Correlation Center

Observed DataÜïè

Koganei

receiverSchedule File
Start Command

Cetral VLBI

Observation

äá
äá
äá
äá

Correlator
Correlator
Correlator
Correlator
Correlator
Correlator

Log Files
Command,Information
Schedule File

Real-time Data Processing
Software (RKATS)

Control Computer Earth Orientation

LOG Files Collection
Correlation Management
Band Width Synthesis MethodæêèÝ Data,
Data Base Creaton
Data Base Creation
Auto Data Backup
CommandDynamic Click Compensation
Auto Fringe SearchError report by E-mailParmeter

Analysis Computer

Data Base Creation
Baselne Analysis
ERP by E-mailBaseline
Determination

Figure 2. Real-time VLBI data ow

after that, Bandwidth synthesis treatment is 3. Summary
done on the data.
4. After the experiment has nished, the RKATS Automatic Real-time VLBI data processing softcollects weather data and delay calibration ware RKATS is being developed for Key Stone
data from each observation station through Project. It is expected to run from the end of thisnetwork. And invoke data base creation pro- year.
cedure.
5. RKATS return to the rst state and load the Acknowledgments
next experiment schedule. Then it wait for the We appreciate Dr. Watanebe, Dr. Uematsu, andnext experiment start time.
Dr. Hoshino in NTT Optical Network System labThe new data is analyzed by auto baseline anal- oratory for the assist of high performance ATM
ysis software. Then the baseline and station posi- system for this project.
tions are determined. Final analysis is performed
after the nal value of Earth orientation parameteris provided from IERS.
Additionally RKATS has automatic data backup
function by using DAT auto-changer. The capacityof it is about 12GB, which gives capability of morethan 10 days of 24 hour experiment data storage.

October 1996

17

The gigabit recorder UTC sync. recording test
was carried out with recorder company TOSHIBA,YEM (Yamashita Engineering Manufacture), NAO
and CRL sta in August. Two GBR-1000 units
are prepared. In this experiment test ramp genJunichi Nakajima (nakaji@crl.go.jp)
erators are used instead of noise from radio telescope. At de ned certain UTC 1 PPS, the genKashima Space Research Center
erated ramp pattern switched to the other. We
Communications Research Laboratory
are investigating the position of data change point893-1 Hirai, Kashima, Ibaraki 314-0012, Japan on the tape and con rming whether the recording is accomplished with correct UTC ame in thetape. The DRA-1000, VLBI interface is handlingthe 1024 Mbps data with 32 MHz clock 32 parallel
1. Introduction
signal lines. Thus we need 31.25 ns digital accuracy
for recording/play back logical sequence. This GiIn the end of 1994, joint Japanese VLBI devel- gabit Recorder does not depend on inserted time
opment group has decided to employ TOSHIBA code as well as K3 (Mk-IIIa), this function test
GBR-1000 recorder for the next generation VLBI is most important step though the other longtitusystem. The project started from 1995 and dal system does not need. Gigabit recorder refer
we have completed the rst 1-Giga-bit cassette (or generate) its tape UTC control track both intype data recorder in 1996. Prof. Chikada, longtitudal and helical tracks.
Prof. Kawaguchi, Dr. Miyoshi (NAO), Mr. Hama, Here I introduce the UTC sync. functional test
Mr. Kaneko,Mr. Kiuchi and Nakajima (CRL) are with photo. This will let you understand the next
the contributed persons in this recorder project. generation recorder system concept.
Photo 1 shows the test bench. GPIB command
PC, Ramp data generator, DRA-1000, digital os2. Gigabit Recorder System Function cilloscope and GBR-1000 are prepared for function
Test
test. Photo 2 is DRA-1000, the VLBI interface
is disassembled under the test. The interface receive GPIB commands from observation computer
The next generation recording system consists orcorrelation process control computer. This inof two major parts. One is VLBI data interface terface
convert the VLBI sampled bit stream andunit (DRA-1000) and another is Gigabit Recorder GBR-1000
format in both direction. Photoitself (GBR-1000). VLBI data from any kind of 3 shows theHDTV
changeramp patterns on
A/D samplers are connected to the VLBI data in- the tape. In this caseoftherecorded
assigned
REC start UTC
terface (DRA-1000). These data are transferred is located in the middle of the certain
GBR-1000
to the recorder(GBR-1000) according to its HDTV HDTV ame. Since the GBR-1000 is producedfordata recording procedure. The random data in- the high-de nition television originally. The data
cluding radio star noise are recorded as a part is visualized by PC multi-scan monitor during bothof uncompressed HDTV ame format. The 1024 in observation and correlation processing. This is
Mbps cassette recorder now available in the mar- one of great advantage. We will be able to checkket needed slight speed up modi cation. It has the recording condition through the monitor. For
been completed before summer. Currently we are example, an AD sampler is saturated and send bidebugging the VLBI data interface unit which is ased data, or an AD sampler is malfunction anddesigned for VLBI and other scienti c data record- no data, apparently the monitor screen will show
ing. The three major features of this DRA-1000 corresponding single color. This feature is usefularewhen non-skilled operator must diagnose the sys1. REC/PLAY BACK data conversion between tem in each VLBI station. In actual radio astronomical observation, the data should be seen as
VLBI bit stream and HDTV ame.
random pattern(like TV sand storm) from the as2. Data independent recorder UTC synchroniza- signed recording start point.
tion including rotary-head phase control.
In addition all kind of time line command are
examined.
\time line command" is a recorder
3. Time line command could be de ned for event command The
withde ned execute time. When
procedure control.
we carry out the observation, we need several
REC/STOP commands before a tape run comes toCurrent Status of the Gigabit
VLBI Recorder System

18

IERS TDC News No.9

Photo 2.

Photo 3.

the end. These sequence are programmed in DRA- Sampler and recorder interface test is planned
1000 CPU intelligent interface as time line events. in October. Samplers are already completed. We
When we correlate the data, also the same play will carry out 1 Gbps domestic VLBI experiment asback sequence are programmed several recorders soon as possible to obtain test correlation data forin advance. This will reduce communications be- 1 Gbps VLBI correlator. All equipment for 1 Gbps
tween recorders and controller .
VLBI hardware will be available by the middle of1997.
3. Future schedule

Photo 1.

October 1996

19

GPS Meteorology in Japanand its Implications to VLBI
Ryuichi Ichikawa (richi@crl.go.jp)
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-0012, JapanAt present, GPS meteorology are considered to
be a powerful method for an understanding of at- Figure 1. Comparisons of PWV obtained by roumospheric variations (Bevis et al., 1994). More- tine radiosonde data sets of JMA (circles andover, we expect that GPS meteorology will also squares) and that estimated from GPS analyses
contribute an improvement of the precision of space (solid lines) at Sapporo, Akita, Wajima, and Yongeodetic techniques.
Japanese cooperate study supported by Science ago (after Ohtani et al., 1996)
and Technology Agency of Japan, which is titled "Establishment of Water Vapor Information
a. Research and development of tropoDatabase by GPS Meteorology and its Applicaspheric path delay correction using nutions to Numerical Weather Prediction, Earthmerical prediction data
quake Prediction Research and Hydrology", haveb. Revision of GPS analyzing software
been started as feasibility study in 1996 Japanesebudget year. The main objective of the study is to 3. Development and maintenance of GPS water
improve the precision of both the numerical predicvapor information databasetion for mesoscale phenomena and the detection
a. Development of rapid GPS analyzingof crustal movement. Achievement of the objectechnique
tive is attributed to the interaction of two systems:
the dense permanent network of GPS sites of Geob. Development GPS water vapor informagraphical Survey Institute (GSI) and the numericaltion database
prediction data with high resolution (20 km gridc. Evaluation of the database by meteorointervals and 36 vertical levels) of Japan Meteorological, geodetic, and hydrological users
logical Agency (JMA). As of April 1996, there are
610 GPS sites of GSI. By the end of 1996 scal We are now planning to evaluate the tropoyear, 250 GPS sites will be added to the present spheric path delay correction based on numernetwork.
ical prediction data at KSP (The Key Stone
Ohtani et al. (1996) preliminarily reported the Project) sites of Communications Research Labestimation of precipitable water vapor (PWV) by oratory (CRL). KSP network is carried out toGPS. They con rmed that PWV can be estimated monitor the crustal movements around Tokyo
within 3 - 4 mm rms by GPS comparing with ra- metropolitan area, Japan. The network will bediosonde data sets as shown in Figure 1. However, equipped with three space geodetic facilities, i.e.
there are several study elds which must be car- VLBI, SLR, and GPS, routinely operated by theried out to realize the main objective. These are end of 1996. Precise correction of troposphericplanning in the cooperate study as follows.
path delay is indispensable to detect seismic preand coseismic movements by using KSP
1. Evaluation of PWV by GPS measurements cursors
network.
a. Estimation and Evaluation of PWV ob- VLBI geodesy can avoid uncertainties of satellite
tained by GPS data analyses
orbit determinations and can independently estib. Study on numerical prediction based on mate the tropospheric path delay at each site bylong distance measurements. Thus, it is expected
GPS PWVthe residual delay estimated by VLBI will bec. GPS PWV in continental and oceanic re- thatmore
precise using the correction based on numergion
ical prediction data. The estimated delay is avail2. Study on improvement of precision of space able in the analysis of GPS data as a priori delay.
As a result, we can reduce an unknown parameter
geodetic techniques

20

IERS TDC News No.9

in the GPS analysis. In addition, realtime VLBI water vapor variation caused by the typhoon moveanalysis is now under development. Consequently, ment though it is a roughly qualitative comparison.
more precise monitoring of crustal movements by For more detailed interpretation another investiVLBI and GPS will be carried out with sub-daily gations are required; comparisons with numericalprediction data and radiosonde data sets, recalcutemporal resolution.
We are now executing a feasibility study for esti- lations of parameter estimations in VLBI and GPS
mating the delay by KSP network and are prepar- analyses, and so on. The results of these investigaing for observations comparing with water vapor tions will be reported in another paper.
radiometer (WVR). Figure 2 shows time series ofthe zenith delay estimated by VLBI and GPS anal- References
yses at Koganei and Kashima during 8 - 14 July,
1996 (JST). Both plots by VLBI and GPS increase Bevis, M., S. Businger, S. Chiswell, T. A. Herring, R.
during 9 - 11 July (JST) and extremely decrease A. Anthes, C. Rocken, and R. H. Ware (1994): GPSduring 11 - 12 July (JST) in a similar manner. Ac- meteorology: Mapping zenith wet delays onto precording to the infrared images by a geostationary cipitable water, J. Appl. Meteor., 33, 379-386.
meteorological satellite of JMA (GMS5), a typhoon Ohtani, R., H Tsuji, N. Mannoji, J. Segawa, and I.
moved northward in the Western Paci c during the Naito (1996): Precipitable Water Vapor Observed
concerned period (see Figure 3). It seems that the by Geographical Survey Institute's GPS network,
variations of the zenith delay are attributed to the Tenki, in submitting (in Japanese).

Figure 2. Time series of zenith tropospheric delay estimated by VLBI and GPS analyses at
Koganei - Kashima baseline (about 109 km) during 8 - 14 July, 1996. Since a priori delay
is not used in this analyses for both VLBI and GPS, the absolute values are not con dent.
However, similar characteristics are shown for both plots by VLBI and GPS; increasing in
Exp.2 (July 9) and Exp. 3 (July 10), and decreasing in Exp. 4 (July 11).

October 1996

21

Figure 3. Infrared images by GMS5 of JMA. Arrows as shown in these gures indicate typhoon. It isinferred that the variation of water vapor related to the typhoon causes the temporal variations of zenith
delay as shown in Figure 2.

22

IERS TDC News No.9

The asteroid was a very good target of international bi-static radar experiment since it had ahigh value of declination when it approached earth.
Taking this opportunity, an international asteroid
radar experiment was organized as a collaboration
Yasuhiro Koyama (koyama@crl.go.jp)
between Japan, Russia, and the United States. In
the bi-static radar experiment, a high power radio
Kashima Space Research Centersignal was transmitted from 70m antenna at GoldCommunications Research Laboratorystone, and the radar echo re ected at the surface893-1 Hirai, Kashima, Ibaraki 314-0012, Japan of the asteroid was received by the 34m antennaat Kashima along with other antennae at Evpatoria in Ukraine, and at Goldstone. The radar echo
was successfully detected and the asteroid became
1. Introduction
the rst solar system object observed by meansof radar from Japan. The name of the asteroid
Planetary radar technique has revealed its was proposed to the Minor Planet Center of theunique capability to investigate geometry and sur- International Astronomical Union after the radar
face properties of various solar system bodies (Os- experiment to honor the success by taking two ortro, 1993). The radar technique has advantages three letters of three ground stations (GOLdstoneover optical techniques in its high spatial resolution EVpatoria-KAshima = GOLEVKA) and it was ofand ability to construct three dimensional images. cially approved in January, 1996 (Minor Planet
Recently, deep space spacecraft can make more de- Circular 26245, 1996).
tailed investigations, but the planetary radar is still In this report, the results of the Golevka radar
playing an important role since observation oppor- observations and the future prospects of asteroid
tunities are far more frequent than space missions. radar experiments will be discussed. The full deThe asteroid 6489 Golevka (= 1991 JX) ap- tail of the Golevka experiment can be found in the
proached Earth to the geocentric distance of 0.034 papers by Koyama et al. (1996) and by Zaitsev et
AU on June 9, 1995. The asteroid is an Apollo al. (1996).
object and has an earth-crossing orbit with perihelion and aphelion distances of 1:0098 and 4:0328
AU, respectively (Fig. 1).
Radar Observations of Near
Earth Asteroids

Venus

Mercury
Golevka
Sun
Earth
Mars

Jupiter

Figure 1. Orbits of the asteroid 6489 Golevka and planets and their positions on June 9, 1995.

23

October 1996

itized data were recorded on a DAT tape. Both
Right-Hand- Circular-Polarization and Left-HandCircular-Polarization data were recorded. A DAT
can record two data channels for two hours.
In the bi-static radar experiment, high power tapeTheconradio signal was transmitted at 470 kW towards in Fig. 3. guration of the observing system is shown
the asteroid 6489 Golevka from a 70m antenna Observations were made for two hours on Juneat Goldstone, which is one of the worldwide deep 15, 1995, about a week after the closest approach
space telecommunication facilities operated by Jet of the asteroid to the Earth. The geocentric disPropulsion Laboratory (JPL). The signals re ected tance to the asteroid at the time of observations
from the surface of the asteroid were then received was about 0:048 AU. After the observations, theby the 34m antenna at Kashima (Fig. 2). Since data recorded on a DAT tape were transferred toour objective was to detect the radar echo from an a UNIX workstation through a GP-IB interface.
asteroid for the rst time in Japan and to ensure Power spectrum P (1f ) of the signal was calculated
the feasibility of conducting international asteroid from 5 seconds of data duration at frequency resoradar experiments, a CW wave form was trans- lution of 0.2 Hz, and then integrated for the period
mitted in Left-Hand-Circular-Polarization without that the power of received radar echo was stable,
any modulation which makes time delay measure- which is a span of 54 minutes, by compensating thements possible.
(Fig. 4). The radar echo is apparent
At Kashima, the received signal was down- Doppler-shift
in
the
RHCP
spectrum. The echo signal
converted to about 10 kHz and sampled at 48 kHz spectrum has apower
broad
width in spite thesampling rate after a low-pass- lter. The low-pass- transmitted signal wasfrequency
a
pure
CW
lter is built-in in a DAT digital data recorder unit, of the rotation of the asteroid. signal because
which has a cut frequency at 20 kHz. The dig2.
Radar Experiment of the 6489
Golevka

AsteroidTransmission Signal
470 kW 8.51 GHz

Radar Echo

Figure 2. Principle of bi-static radar observations towards Near Earth Asteroids.
DAT Digital Data Recorder Unit

Cryo.Sys.

X-Band Receiver Feed
LHCP

20 K

LNA

BPF

429.99-431.99
0-2 MHz
IRM

LPF
A/D
0-20 kHz 48 kHz

8.18-8.6 GHz

DAT

90 K

LPF

BPF
RHCP

LNA

8.18-8.6 GHz

8080 MHzIRM
0-2 MHz
PLO

A/D
0-20 kHz 48 kHz

10 MHzH-maser

Figure 3. Block diagram of the observation system set-up used at Kashima.

24Power Spectrum (Signal-to-Noise Ratio)
05
10

IERS TDC News No.9

-10

-5

0

5

10

∆f (Hz)Figure 4. Power spectrum P (1f ) of the received signal integrated for 54 minutes with frequency resolution of 0.2 Hz.

(Mottola et al., 1995, Hudson and Ostro, 1995),sin = 0:40 6 0:02 km. This value places a lower
bound of about 0:4 km on the asteroid's maximum
pole-on breadth.
The total power of a radar echo signal is proportional to an e ective cross section, r A, of atarget asteroid where r is a radar albedo and A isa cross section of the asteroid. The relation can be
expressed as
D

Prec

2

tx Gtx Grec r A
= 4PR2 1 4R2 1 4 :
tx

rec

(2)

Here,  is the wavelength of the radar signal, Ptx
is the transmitting signal power, Gtx is the gainof the transmitting antenna, Rtx is the distance of
the asteroid from the transmitting station, Prec is
The maximum dimension of the asteroid perpen- the received signal power, Grec is the gain of thedicular to its apparent rotation axis D and its ap- receiving antenna, and Rrec is the distance of theparent rotation angular velocity ! can be related asteroid from the receiving station. On the other
hand, the standard deviation for power spectrum
to Doppler frequency width W as,of noise, N , can be evaluated by equation,
D! sin
r
W =
f0 :
(1)
c
B
N = kB Tsys;(3)where f0 is the frequency of the central frequency
tof the received echo signal, c is the velocity of light, where kB is Boltzmann's constant, Tsys is the sysand  is the angle between the apparent rotation tem noise temperature of the receiving station, B
axis and the direction towards the receiving station is the frequency resolution of the power spectrum,
seen from the asteroid (Fig. 5).
t is the integration time. The normalized total
From Fig. 4, by taking the threshold of signal andpowerspectrum of the received data obtained byexistence to be P (1f ) = 2:96 from a con dence integrating
P (1f ) can then be evaluated aslimit of 99%, the lower edge of the radar echoZsignal is between 01:8 Hz and 01:7 Hz, whereas(4)
P (f )df = PNrec ;upper edge is between 1:5 Hz and 1:6 Hz. Thus
the frequency width of the radar echo can be es- where the integration should be done for the fretimated as W = 3:3 6 0:2 Hz. If we employ quency range where radar echo signal is present.
6:02 hours as the rotation period of the asteroid
Figure 5. Geometric relation between the rotation
axis of the asteroid and the observation site.

25

October 1996

The total power of the radar echo signal was Hudson R. S. and Ostro S. J. 1995, Bull. Amer. Asevaluated2 as 20:5 2 N . This value gives rA = tron. Soc. 27, 1063
0:11(km ). This radar cross section shows good Koyama, Y., M. Yoshikawa, J. Nakajima, M. Sekido, T.
agreement with Arecibo 1991 results and monos- Iwata, A. M. Nakamura, H. Hirabayashi, T. Okada,tatic Goldstone 1995 results. The e ective diame- M. Abe, T. Nishibori, T. Nakamura, T. Fuse, S. J.
ter of Golevka has been estimated to be no greater Ostro, D. K. Yeomans, D. Choate, R. A. Cormier,than 600 m from a preliminary inversion of Gold- R. Winkler, R. F. Jurgens, J. D. Giorgini, K. D.
D. L. Mitchell, M. A. Slade, and A. L.
stone delay-Doppler images (Mottola et al., 1995; Rosema,
Zaitsev,\RadarObservations of an Asteroid 6489
Hudson and Ostro, 1995). Thus the estimated ef- Golevka,"() 1996fective diameter implies a radar albedo of at least
0:39, or several times larger than the typical values Minor Planet Circular 26245, Minor Planet Center, Inreported to date for small asteroids (Ostro et al., ternational Astronomical Union, 1996
1991; Ostro et al., 1996).
Mottola S., Erikson A., Harris A. W., Hahn G.,
From this result, it is expected that this object's Neukum G., Buie M. W., Sears W. D., Tholen D.
surface is unlikely to be porous, that is, it probably J., et al. 1995, Bull. Amer. Astron. Soc. 27, 1055
lacks a regolith.
Ostro S. J., Cambell D. B., Chandler J. F., Hine A. A.,
Publ. Astron. Soc. Jpn.

submitted

Hudson R. S., Rosema K. D., and Shapiro I. I. 1991,
Science 252, 1399

3. Future Asteroid Radar Observa- Ostro, S. J., \Planetary radar astronomy," Rev. Modern Phys., 65,pp. 1235-1279, 1993
tions
Ostro S. J., Jurgens R. F., Rosema K. D., Hudson R. S.,

J. D., Winkler R., Yeomans D. K., Choate
The success of the rst asteroid radar experiment Giorgini
D., et al. 1996, Icarus 121, 44
from Japan is quite encouraging. In the near future, radar observations to 1982TA and 1994PC1 Zaitsev, A. L., S. J. Ostro, Y. Koyama, D. K. YeoS. P. Ignatov, M. Yoshikawa, D. Choate, A.
are being considered. In these experiments, the mans,
Petrenko, R. A. Cormier, O. K. Margorin, R.
phase-modulated signal will be transmitted to the G.
V. V. Mardyshkin, R. F. Jurgens, O. N.
asteroids to make the ranging observations possi- Winkler,
Rghiga, J. D. Giorgini, V. A. Shubin, M. A. Slade,ble. Also, the technical feasibility of radar interfer- A. P. Krivtsov, Y. F. Koluka, A. M. Nakamura, A. L.
ometric observations will be investigated by using Gavrik, D. V. Ivanov, F. S. Peshin, \Intercontinental
two large antennas at Kashima and at Usuda.
Bistatic Radar Observations of 6489 Golevka (1991

References

JX)," Planetary and Space Sci. (submitted) 1996

26

IERS TDC News No.9

been completed and daily observations were started
in July, 1996. The object is selected automatically.
In the daytime, the sun is tracked. At present,
Jupiter is observed when it is in the sky during
nighttime. Receiving frequency range of spectrum
analyzer is also controled automatically according
to the target. It is set 20-70 MHz for the sun,and 25-35 MHz for Jupiter. This di erence comes
about due to the characteristics of each emission.
For Jovian decametric radio wave emissions, theTetsuro Kondo (kondo@crl.go.jp)
intrinsic lower frequency limit is about 38 MHz.
Observations of radio waves at lower frequencies
are becoming more dicult in recent years
Kashima Space Research Centerdue
tothe increase of man-made noise such as
Communications Research LaboratoryTVbroadcasts
and other telecommunication sig893-1 Hirai, Kashima, Ibaraki 314-0012, Japannals. KaRAS observations are also a ected by thisKashima Radio Spectrograph (KaRAS) was con- interference. To improve the signal-to-noise ratio
structed at Kashima Space Research Center for ob- of spectrograms under these dicult conditions,serving decametric radio emissions from the sun we have developed computer software which elimiand Jupiter. In particular KaRAS is designed to nates man-made interference as much as possible.
form an interferometer in combination with a sim- In this process, rst we subtract the backgroundilar system at Hiraiso located about 40 km north. from raw spectral data. Background level is calThe KaRAS consists of a wide band antenna sys- culated as a time average ( 1 hour) of each sweep
tem, two swept-frequency type spectrum analyzers spectrum data. Then we adopt the following 3and a video converter system for a future inter- sigma criterion to eliminate interference signals still
fereometer use (Fig.1). A wide band antenna is a remaining on a spectrogram (Fig.2). First, the runcrossed log-peri antenna mounted on the top of 15- ning average and standard deviation of a given frem high tower as an AZ-EL type mount. Its nom- quency span is calculated for each sweep. Any data
inal receiving frequency range is 25-70 MHz. Re- points with deviations larger than 3 sigma are received crossed linear polarized component signals placed by an adjacent data values. This simple
are fed to a hybrid circuit to form a right handed algorithm is considered to be working properly for
and a left handed circularly polarized component actual data as shown in Fig.3.
signals. Both right- and left- polarized signals areampli ed and then fed to the two spectrum analyzers. Data from spectrum analyzers are acquired bya system control computer (HP Vectra) throughthe GP-IB interface. The data are transfered toa UNIX workstation (HP9000/730) to produce aspectrogram and to perform further analyses.
Development of observation control software has

Current Status of Kashima
Radio Spectrograph (KaRAS)
for Observing the Sun and Jovian Radio Wave Emissions at
Low Frequencies (20 - 70 MHz)REMOVAL OF INTERFERENCES(3 Sigma Method)
System Block Diagram of KaRAS

BPF
25‑70MHz

if Level > 3σ then Level = Average

LNA

R

X

Video OutHYBRIDY

Level

L

Log‑Peri. Antenna
25‑70MHz
Antenna Control Unit

3σ
Average

Video Converter

Spectrum Analyzer
GP‑IB

System Control Computer
Data Acquisition &Antenna Control

3σ
Average

Figure 1. A schematic block diagram of KaRAS Figure 2. A simple 3-sigma method for removing
system.
noise.

27

October 1996

Figure 3. Raw (top) and processed (bottom) spectrograms.

28

IERS TDC News No.9

VLBI Technical Development Center (TDC) at the Communications Research Laboratory (CRL)
is 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 plan of technical developments. The TDC newsletter is published biannually by
CRL to inform the IERS community its current activities.
This news was edited by Tetsuro Kondo and Yasuhiro Koyama, Kashima Space Research Center,
who are editorial sta members of TDC at the Communications Research Laboratory, Japan. The
editors wish to thank Dr. O. J. Sovers for his kind help in the correction of the news 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.
Summaries of VLBI and related activities at the Communications Research Laboratory areavailable 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/

TECHNICAL DEVELOPMENT CENTER NEWS No.9, October, 1996
International Earth Rotation Service - VLBI Technical Development Center News
published by
Communications Research Laboratory, 4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan