COMMUNICATIONSCOMMUNICATIONSRESEARCHRESEARCHLABORATORYLABORATORY

Serial No. 23

November 2003

CONTENTS
The 3rd CRL TDC Symposium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Proceedings of the 3rd CRL TDC Symposium (Kashima, October 8, 2003)
Use of Ultrahigh-Speed Network in GALAXY Project...... 2

Hisao Uose, Sotetsu Iwamura, and Kazunori Kumagai
Transmission of VLBI Data with a TCP/IP Parallel Transmission System...... 6

Kazunori Kumagai, Sotetsu Iwamura, and Hisao Uose
High-temperature superconductor ﬁlter of 2.2GHz, Operating status against . . . . . 10
RFI
Eiji Kawai, Junichi Nakajima, Hiroshi Takeuchi, Hiromitsu Kuboki, and TetsuroKondo
2-Gbps PC Architecture and Gbps data processing in K5/PC-VSI. . . . . 12

Moritala Kimura, Junichi Nakajima, Hiroshi Takeuchi, and Tetsuro Kondo
Data ownership evolution and ﬂexible handling around PC VLBI

. . . . . 14

Junichi Nakajima, Moritala Kimura, Yasuhiro Koyama, and Tetsuro Kondo
Diagnostic tools for the K5 system. . . . . 16

Hiro Osaki, Tetsuro Kondo, and Yasuhiro Koyama
Current Status of the K5 Software Correlator for Geodetic VLBI

. . . . . 18

Tetsuro Kondo, Yasuhiro Koyama, and Hiro Osaki
Total VLBI data management system using database server –The organizer . . . . . 21
for VLBI@home–
Kazuhiro Takashima
Geodetic VLBI Experiments Using Giga-bit VLBI System
Hiroshi Takeuchi, Junichi Nakajima, Moritaka Kimura, Yasuhiro Koyama, andTetsuro Kondo(continued on inside front cover). . . . . 23

Evaluation of the K5 system in geodetic VLBI experiments. . . . . 26
Yasuhiro Koyama, Tetsuro Kondo, Hiro Osaki, Kazuhiro Takashima, Kazuo Sorai,
Hiroshi Takaba, and Kenta Fujisawa
An evaluation of VLBI observations for the positioning of the NOZOMI . . . . . 31
Spacecraft and the future direction in research and development of the deep
space tracking using VLBI
Ryuichi Ichikawa, Mamoru Sekido, Hiro Osaki, Yasuhiro Koyama, Tetsuro Kondo,
Takafuki Ohnishi, Makoto Yoshikawa, and NOZOMI DVLBI group
VLBI Application for Spacecraft Navigation (NOZOMI) – follow-up on Model . . . . . 34
and Analysis –Mamoru Sekido, Ryuichi Ichikawa, Hiro Osaki, Tetsuro Kondo, Yasuhiro Koyama,
Makoto Yoshikawa, and NOZOMI VLBI Observation GroupVLBI Observation by Receiving Narrow Bandwidth Signal from NOZOMI . . . . . 36
Fuyuhiko Kikuchi, Yusuke Kono, Ping Jinsong, Liu Qinghui, Kazuyoshi Asari,
Koji Matsumoto, Seiitsu Tsuruta, Hideo Hanada, Nobuyuki Kawano, and NOZOMI VLBI group
Orbit determination of spacecraft in deep space by Delta-VLBI technique: . . . . . 39
current situation and future
Makoto Yoshikawa, Takaji Kato, Tsutomu Ichikawa, Hiroshi Yamakawa,
Jun’ichiro Kawaguchi, Yasuhiro Murata, Takafumi Ohnishi, Shiro Ishibashi, Shigeo Tsujimoto, Katsutoshi Kurosu, and NOZOMI Delta-VLBI group
Present Status of Gravimetric Missions in SELENE/RISE. . . . . 43
Hideo Hanada, Takahiro Iwata, Noriyuki Namiki, Koji Matsumoto, Seiitsu Tsuruta, Toshiaki Ishikawa, Kazuyoshi Asari, Jinsong Ping, Qinghui Liu, Yusuke
Kono, Fuyuhiko Kikuchi, Hirotomo Noda, Kousuke Heki, Nobuyuki Kawano, and
RSAT/VRAD group
Black Hole Imager, Pre-Horizon Telescope In the Southern Hemisphere. . . . . 46

Makoto Miyoshi, Jose K. Ishitsuka, and Shinji Horiuchi
A 32 m Antenna Project in Peru
. . . . . 49
José K. Ishitsuka, Mutsumi Ishitsuka, Makoto Inoue, Masatoshi Ohishi, Kenta
Fujisawa, Takashi Kasuga, Masato Tsuboi, Keisuke Miyazawa, and Shinji Horiuchi
VSOP-2: a Proposal for a near future Space VLBI Mission. . . . . 51

Hisashi Hirabayashi
Developments for the next space VLBI mission, VSOP-2. . . . . 54
Yasuhiro Murata, Hisashi Hirabayashi, Inoue Makoto, and Next generation space
VLBI working group
Development of a primary feed system for the parabolic rectangular reﬂector . . . . . 57
antenna dedicated for planetary radio emission
Hiroaki Misawa, Riichi Kudo, Fuminori Tsuchiya, Akira Morioka, and Tetsuro
Kondo- News - News - News - News Smallest Backend in Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
100th meeting of the Geodetic Society of Japan was held at CRL . . . . . . . . . . . . . . . . . 60

November 2003

1

The 3rd CRL TDC Symposium

Tetsuro Kondo (kondo@crl.go.jp)
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, JapanAs a Technology Development Center (TDC)of the IVS, Communications Research Laboratory(CRL) held the third IVS Technology Development Center Symposium on October 8, 2003 at the
Kashima Space Research Center. This symposium
was devoted primarily to presentations of the stateof-the-art technology developments in Japan regarding VLBI. Fifty-nine people attended the symposium, and 19 oral presentations and 4 poster presentations were given during the day.
Progress of the technical developments of VLBI
using the high speed network (e-VLBI) has beenremarkable these days. The discussions were developed actively involving the network researchers
attending the e-VLBI session.
The results of the relative VLBI observations of
the “NOZOMI” Mars explorer, which ﬁnished thelast earth swingby successfully in May, 2003 andis now heading towards Mars, were reported in thesession about the position determination of spacecrafts. Moreover, a plan of the relative VLBI observations of the “HAYABUSA”, which is undercruise towards the sample return from the surface
of an asteroid, was also introduced. A future space
VLBI (VSOP-2) mission was also introduced in thesession of future plans.

Pictures taking on the third CRL Technology Development Center symposium held on October 8,
2003. Top: at the registration desk. Middle andbottom: in the large conference room (aural session).

Left: poster presentations.

IVS CRL-TDC News No.23

2

Use of Ultrahigh-Speed Net- started to attract a great deal of attention withthe rapid improvement of research and education
work in GALAXY Project(R&E) networks funded by governments and parts
Hisao Uose (uose.hisao@lab.ntt.co.jp),
Sotetsu Iwamura and Kazunori Kumagai
NTT Laboratories
3-9-11, Midori-Cho, Musashino-Shi,
Tokyo 180-8585 Japan
Abstract: A joint research project on real-timevery long baseline interferometry (VLBI) called
GALAXY is being conducted by NTT Laboratories, the Communications Research Laboratory(CRL), the National Astronomical Observatory(NAO), the Yamaguchi University, and the Institute of Space and Aeronautical Science (ISAS) to
explore the eﬀectiveness of ultrahigh-speed communications technologies when applied to advanced
scientiﬁc research. Using an ultrahigh-speed network allows us to raise the bandwidth of the radio
signals used for the cross-correlation, so the performance of the observation system can be greatly
improved. This paper outlines the technical issues
related to communications in the project and current conﬁguration of GALAXY network.
1.

Introduction

In recent years, the application of ultrahighspeed networks to advanced scientiﬁc research hasof the private sector. Typical applications being tried include ones in the ﬁelds of high-energy
physics, astronomy, genetic engineering, and distributed computing. Among them, the leader isreal-time very long baseline interferometry (VLBI),
which creates a large-scale virtual radio telescopeand is a very precise system for measuring theearth s rotation parameters using multiple distantly located antennas. VLBI itself is an established technology developed in 1960s and many scientiﬁc discoveries have been made in astronomy
and geodesy using it.
The key point of our research project called
GALAXY is to remove the performance bottleneck of the conventional VLBI scheme by using an
ultrahigh-speed communications network to carryobserved data, which previously had to be physically transported on magnetic tapes [1]. This
was the ﬁrst attempt in the world to use a highspeed digital communications network for a VLBI
observation system. NTT s objectives for the
project are two-fold. One is to establish technologies for very-high-speed communications (gigabitper-second class) in preparation for commercial services in the future. The second is to explore andprove the eﬀectiveness of those technologies in advanced scientiﬁc areas, which are the ﬁrst actual
applications utilizing the capabilities of ultrahighspeed communications technologies [2].

Figure 1. Data transmission technologies for real-time VLBI.

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Figure 2. Conﬁguration of GALAXY Network.
This paper explains the communications aspect of GALAXY project. First we discuss thedata transmission technologies for real-time VLBI
then the network conﬁguration of GALAXY is described. Finally we mention future research plans.

organizations around the world at a small cost.
Therefore, in the phase-2 project started in 1998
we started to explore the use of IP technologies
extensively within our experimental network alongwith ATM taking into account the collaboration
with R&E networks around the world. Using IP for
2. Data transmission technologies for real- transferring very-high-speed data involves manytime VLBI
challenging issues. With IP networks, “best eﬀort”
is the norm, so we must take measures to assure
The requirements for the transmission technolothat the data streams are transmitted to the othergies for real-time VLBI diﬀer greatly depending on
end reliably without any degradation of the total
the style of the observation and the required bandthroughput. From this viewpoint, we developed awidth. Figure 1 explains suitable technologies forvery-high-speed VLBI data transfer system using
each case.
multiple IP stream.
In the phase-1 project started in 1996, we built a
dedicated experimental network for real-time VLBI
3. Conﬁguration of experimental network
and used ATM technology to carry the data. ATM
technology has a rigorous bandwidth management
Figure 2 depicts the current physical conﬁgucapability providing the very reliable data trans- ration of GALAXY network and Figure 3 shows
mission required for critical applications [3]. The the interconnections with other R&E networks
relatively high cost can be justiﬁed for a high net- with which we are collaborating. Last year, thework usage case such as KSP where regular obser- GALAXY network was integrated with GEMnet,
vations were conducted. In the medium to lower which is another NTT research network. At the
network usage cases, however, the use of dedi- moment, we are upgrading links among NTT recated bandwidth is not economical. To make the search centers with the latest wavelength division
real-time VLBI experiment more aﬀordable and multiplexing (WDM) technologies to augment thewidespread, IP technologies must be used eﬀec- capacity of GALAXY/GEMnet.
tively, because the R&E networks around the world
Connectivity with other research organizations
are rapidly increasing their capacities and those has been greatly improved by interconnecting with
networks are accessible from major public research other R&E networks. The connection to Super

IVS CRL-TDC News No.23

4

Figure 3. GALAXY/GEMnet and partner R&E networks.

Figure 4. Collaboration with Super SINET (4-Gbps real-time experiment) .
SINET operated by the National Institute of Informatics (NII) has greatly improved the connectivity with domestic research organizations, especially national universities. We have a direct linkto Super SINET at 600 Mb/s as well as 2.4-Gb/s
SDH links. Figure 4 shows the conﬁguration of
the 4-Gb/s observation experiment in collaboration with Super SINET. We also have a direct link
to Abilene, which is the backbone network of theInternet2 project in the United States. The col-laboration with Internet2 provides us with connections to research organizations in the US as well as
in other parts of the world via their internationaltransit service (ITS).
We are continually upgrading our experimental
network to adapt to our new requirements. One isto deploy more high-performance IP equipment topromote research on “Internet VLBI” and anotheris to use the latest photonic devices and transmission equipment developed by our laboratories inNovember 2003

5

our network. A high-capacity data storage andvideo conferencing system supporting the remote
distributed experiment have also been deployed.
To test the eﬀectiveness of multimedia conferencing systems in these distributed laboratory environments, we have started to deploy a high-quality
video conferencing system in the main experimental sites. The quality of both video and soundshould be as good as possible to capture the environment of other locations not only in terms of
the spoken words, but also the background noiseand visual atmosphere. We are using MPEG2 encoders/decoders, echo cancellers, and large-screen
plasma displays to create a high-quality cooperative working environment.

tribute observed radio signals to a large numberof cross correlators in the Internet, many of which
will be ordinary PCs equipped with mathematical software conducting necessary scientiﬁc calculations on demand. In combination with the multistream data transfer method described in the paper, very-high-speed distributed cross correlation
will be possible.

4.

[2] H. Uose, K. Irie, and S. Iwamura, “NTT s
ultra-high-speed networking experiment: a real-time
VLBI project,” Proceedings of SPIE Vol. #4845-08,
2002.

Conclusions and future plans

References[1] H. Uose, K. Irie, S. Iwamura, T. Kondo, J. Nakajima, H. Kiuchi, N. Kawaguchi, K. Fujisawa, Y.
Murata, and H. Hirabayashi, “GALAXY and KSP:
Real-time VLBI Trials in Japan,” Proceedings of
URSI, 2002.

In December 2002 GALAXY team successfully
achieved transmission and processing speeds of 2
Gb/s. The development of “Internet VLBI” sys[3] H. Kiuchi, M. Imae, T. Kondo, M. Sekido, S. Hama,tems and a distributed cross-correlation system usT. Hoshino, H. Uose, and T. Yamamoto, ”Real-Timeing networked computers are other targets. WithVLBI System Using ATM Network,” IEEE Trans.
the success of IP VLBI data transmission, the poson Geoscience and Remote Sensing, Vol. 38, No. 3,
sibility of making an international real-time VLBI
2000.
observation system appears realistic. In addition,[4] K. Fujisawa, N. Kawaguchi, J. Nakajima, H. Kiuchi,
the combination of distributed data analyses andT. Kondo, H. Uose, K. Irie, S. Iwamura,and Y. MuIP data transmission/packet routing should leadrata, “Astronomical observations with GALAXY, a
to a completely new type of VLBI observation.
real-time VLBI network”, Proceedings of SPIE Vol.
For example, IP multicast could be used to dis#4845-11, 2002.

6

IVS CRL-TDC News No.23

Transmission of VLBI Data the higher the deﬁnition of the image and the ﬁner
results.
with a TCP/IP Parallel Trans- geodesic
Previously, VLBI researchers transferred signals
mission System
to a correlator by recording them on magnetic
tapes and physically sending them to the facility
housing the correlator. We have developed methKazunori Kumagai
ods of transmitting such signals (observational(kumagai.kazunori@lab.ntt.co.jp),data) via computer networks. Because the volume
Sotetsu Iwamura, and Hisao Uoseof observational data is very large (Several terabytes for one observation) and the distances among
NTT Laboratories
our observatories are very long (see Figure 1), new
Nippon Telegraph And Telephone Corporation
data transmission methods are needed. We have
9-11, Midori-Cho 3-Chome Musashino-Shi,developed them in collaboration with the CommuTokyo 180-8585 Japan
nication Research Laboratory, National AstronomAbstract: Transmitting data from radio astron- ical Observatory of Japan, the Institute of Space
omy sites is an application that demands very high and Astronomical Science, and Yamaguchi University.
bandwidth and quality service(QoS). We have developed a parallel transmission system to transmit an extraordinary volume of observed data fromtelescopes to data processing sites. Not all the
astronomical facilities were connected with highquality networks, so to share data among many
telescopes and processing units, we had to make asystem that can work well even over IP networks
where there is background traﬃc. Additionally, theproblem of long fat pipes related to long-distancetransmission has a signiﬁcant impact because thesefacilities are located far apart. Parallel transmission can solve these problems by splitting the original data stream into multiple slower streams. In
existing parallel transmission systems, it is diﬃcult
to reconstruct split data needed for astronomical
purposes. We achieved such reconstruction by us- Figure 1. Our Research Network for VLBI, Abiing a rubidium oscillator to synchronize devices. lene, and MIT.
It can provide a frequency with enough stability
and accuracy for one observation and is cheaper
than a cesium oscillator. 256 Mb/s using 8 streams 1.2 Previous Achievement
was achieved by this system. This throughput is
We have already achieved 2 Gbps in our dedmuch higher than the ideal throughput of a single
icatednetwork by using asynchronous transfer
stream. Moreover, high throughput and high availmode(ATM)transmission device([1]). After thisability are achieved even where there is backgroundsuccess,
westartedto develop an IP transmission
traﬃc.
system in order to collaborate with other research
networks. For this purpose, we have to take into
1. Introduction
consideration the following points.
1.1 Background - VLBI
• Each observatory is quite separate from othIn order to develop new technologies capable ofers.(For example, MIT Haystack Observatory
handling very high-speed applications, it is essenis 10,000 kilo-meters away from CRL Kashima
tial to solve the problems arising in speciﬁc applicaResearch Center). Therefore, the long-fat pipe
tions in actual development. So, we tried to solve
problem heavily aﬀects the usability of netthe problems invoked in very long baseline interworks.
ferometry(VLBI). This technology produces highdeﬁnition images of a far galaxies or ﬁne geodesic
results by observing a signal from one radio source
at several observatories and correlating the signals.
The longer the distance between the observatories,• Not all the observatories are connected tohigh-quality networks, so packet losses happen.

November 2003
• Researchers sometimes want to use dedicatedcorrelators for VLBI[2],[3]. To use these devices, we must stably input data into thesedevices in real time. In the case of usual realtime transmission such as data transmission
in remote video conference systems, a certain
level of ﬂuctuation input is acceptable. But inthe case of VLBI, the ﬂuctuation of input isalmost unacceptable.

72.

Architecture of Our Parallel Transmission System

2.1

Components

Our system is composed of a parallelization device, a serialization device, transmitting PCs, receiving PCs, and a control PC. These devices areconnected as illustrated in Figure 2. The parallelization device is connected to a sampler with an
ID1 line and to the transmitting PCs with IEEE
In the transmission via TCP/IP, we can improve1394 lines. The serialization device is connected tothe usability of networks by increasing the wina correlator and to the receiving PCs in the same
dow size. But in this case, it is known that packet
way. The transmitting and receiving PCs are conloss is inevitable, so this method is not a complete
nected to the network by Ethernet.
solution[4]. Therefore, we decided to use a parallel transmission, which can achieve high throughput by splitting the original data ﬂow to multiple
slower ﬂows. This type of system has the following
advantages.
• Even when round trip time is large (for example, the round trip time between CRL
Kashima Research Center and MIT HaystackObservatory is 200-250 ms.) and packet loss
exists, a parallel transmission can achieve highthroughput which a serial TCP/IP ﬂow witha large window size cannot.
• Even if some ﬂows slow down, the eﬀect on thewhole of transmission is small.
Even though some parallel transmission systems
and software have already been made, they cannot
reconstruct the original data stream in real time.
Therefore, we had to develop a new system for our
purpose.
Initially, we made a UDP parallel transmission
system as a prototype. This system achieved 256
Mbps with 8 ﬂows[5]. We can achieve higher rateby increasing the number of ﬂows.

Figure 2. Diagrammic Inllustration of Our Parallel
Transmission System.

The system control module in the control PC
controls other modules in the transmitting and receiving PCs. Additionally, it controls the parallelization device via a parallelization device control
module, and the serialization device via a serialization device control module. The ﬂows of commands
and observational data are illustrated in Figure 3.
1.3 Our New Achievement
Our system can work either in on-line mode for
UDP does not re-transmit data packets, so the real-time correlation or in batch mode for oﬄine
UDP parallel transmission system cannot transfer correlation.
enough accurate data in the network where packet
loss too often happens. This time, we developed 2.2 Data Transmission Procedurea TCP parallel transmission system in order to
The procedure for transmitting data between
transfer accurate data over such a network. In
parallelization and serialization is composed of thean environment where there is packet loss or ACK
following phases.
packet delay is large, the throughput of a TCP ﬂow
usually oscillates because the window control algo1. Initialization Phase: The system control modrithm changes the ﬂow’s window size. In such anule initializes all other modules. At that time,environment, parallel transmission can quickly redata re-transform modules change there obsercover from a fall because the throughput of eachvational data receiving port to listening mode.
ﬂow is slow compared to serial transmission which
2. Connection Phase: The system control modachieves high throughput by itself. In this paper,ule commands the data transform modules to
we describe the results of a performance evaluationon our system.

IVS CRL-TDC News No.23

8

Once they have received a start command, all
the data retransmission modules transmit observational data to the serialization device via
IEEE 1394 lines.
The receiving PCs provide a buﬀer against ﬂuctuations in the IP packets arrival interval and distortions in arrival order.
2.3

Figure 3. Modules in Our System and Relation
among them.
make TCP connections to corresponding data
re-transform modules.
3. 1394 Receiving Phase: After the TCP connections have been established, the system control module sends start commands to the datatransmission modules and the parallelization
device.

Division and Reconstruction of Data
Flow

The data stream output from a down-converter istransmitted to a parallelization device and divided
into multiple data streams.
The serialization device combines the multiple
ﬂows and reconstructs a single ﬂow. This stream
is transmitted to the real-time correlator. In orderto accurately reconstruct a single stream, we must
synchronize the devices. We chose to use a rubidium oscillator because it has enough accuracy overa short time.
3.

Performance Evaluation

3.1

Purpose and Contents of the Experiment• On-line Mode: Data transform modules
receive observational data from the parallelization device via IEEE 1394 lines
and transmit it to corresponding data retransform module via the TCP connection, using the hard disks of transmitting
PCs as buﬀers. The data re-transformmodules save the received data in harddisks of receiving PCs until they reachthe volume designated at initialization(buﬀering).

In order to verify that our system can transmit
a high bit-rate stream when the round trip time
between the transmitting and receiving ends andpacket losses are not negligible, we carried out experiments.

• On-line Mode: When all the data retransform modules have received the designated volume of data, the system control module sends start commands to all
the data retransmission modules.

3.3

3.2

Experimental Environment

Our experiment network is illustrated in Figure 4. We made an experiment network where
we could control the round trip time with a delay generator and generate packet loss with a bit
error inserter. (If a packet has bit errors, it is• Batch Mode: At ﬁrst, the data transdiscarded. ) We generated bit streams with aform modules save all the received obpattern generator/error detector and investigatedservational data on the hard disks of thewhether the stream was transmitted correctly ortransmitting PCs. After that, they transnot, by inputting the output stream from the serialmit the data automatically.
ization device to the pattern generator/error detector, which compares the output and input streams.
4. 1394 Transmitting Phase
Results

The experimental results veriﬁed that our system
worked well even where the round trip time was
equivalent to trans-paciﬁc transmission and packet
loss was not negligible.

• Batch Mode: When all the re-transformmodules have received all the data sent 4. Conclusion of Experiments
by the corresponding transmission modExperiments veriﬁed that our TCP/IP parallelules send, the system control module
sends start commands to all the data re- transmission system can transmit a data stream
transform modules.

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Transmission Experiment ”, NTT R&D, Vol.
50, pp. 824-830, 2001.
[2] Y. Koyama, T. Kondo, M. Sekido, R.
Ichikawa, T. Yoshino, H. Kiuchi, J. Amagi, H.
Uose, S. Iwamura “Achievements of Real-timeGeodetic VLBI Experiments ”, NTT R&D,
Vol. 50, pp. 839-844. 2001.
[3] H. Kobayashi, N. Kawaguchi, K. Fujisawa,
H. Hirabayashi, Y. Murata “Experiments of
Real-time Space VLBI by Using a High-speed
Network ”, NTT R&D, Vol. 50, pp. 853-857.
2001.
Figure 4. Experimental Environment.
that has suﬃcient quality for real-time VLBI processing by buﬀering at each receiving PC and synchronizing devices with a rubidium oscillator.
5.

Unsettled Problems

Although our system has good performance , wehave to ﬁx the following problems in order to put
our system into practical usages.
• The behavior of IEEE 1394 on Linux is instable. This is caused by the instability of adriver software for IEEE1394.
• The operation is complicated for beginners.
• Although we synchronize receiving PCs and aserialization device, they may become out ofsynchronization. So, our system cannot continue transmission for a long time. This breakof synchronization is caused by interruption bysome processes and so on.
It is very diﬃcult for us to improve the driver forIEEE 1394. So, we have to wait the improvement
by open source community.
In order to make our system easier for beginners,
we should improve the user interface of a system
control module.
We can synchronize devices for a long time by using a real time operation system on receiving PCs.
(Now we use redhat Linux on transmitting and receiving PCs.)
We will try to solve these problems in order that
our system become useful for VLBI researchers.
References[1] N. Kawaguchi, K. Fujisawa, J. Nakajima, H.
Uose, S. Iwamura, T. Hoshino, T. Hashimoto,H. Takagi “Gigabit Data Acquisition and the[4] J. Padhye, V. Firoiu, D. F. Towsle, and J.
F. Kurose “Modeling TCP Reno Performance:
A Simple Model and its Empirical Validation” , IEEE/ACM TRANSACTIONS ON NETWORKING, Vol. 8 , pp. 133-145, 2000.
[5] S. Iwamura, H. Uose, S. Nakagawa, T. Kondo,
H. Kiuchi, J. Nakajima, K. Fujisawa “VLBI
Data Transfer Over IP” , NTT R&D , Vol.
50, pp. 831-838, 2001.

IVS CRL-TDC News No.23

10

High-temperature superconduc- veloped High-Temperature Superconductor (HTS)
to recover wide-band reception (Kawai et al.
tor filter of 2.2GHz, Operating ﬁlter2003). The HTS ﬁlter fabricated on MgO substatus against RFI
strate and YBCO-HTS ﬁlm structure showed ideal
Eiji Kawai (kawa@crl.go.jp),
Junichi Nakajima, Hiroshi Takeuchi,
Hiromitsu Kuboki, and Tetsuro Kondo
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan

passband. The unwilling out-band emissions aresuppressed below -80dB from its passband. The
S-band receiver regained full bandwidth required
for minimum redundant channel allocation of band
width synthesis.
2.

Continuous operation of external cooled
ﬁlter

Currently, the HTS ﬁlter cryostat is installed
separately beside the LNA dewar. Pulse tube type
cryostat is operated to sustain superconductivity
In S/X-band radio-telescope systems, Radio Fretemperature 70K. With a serial interface monitorquency Interference (RFI) had been occurred ining, the ﬁlter subsystem keeps temperature stable
S-band since IMT-2000 systems are introduced normally in the ﬁrst 3-month. During annual mainas the new mobile phone. As we reported intenance of 34-m telescope power down, the subsysprevious TDC News article (Kawai et al.,2002), tem is turned oﬀ. After its power up, the re-started
Kashima 34-m antenna experienced severe RFI subsystem cooled down to 70K within 2 hours.
from a closely located IMT-2000 base station. The
This is faster than LNA cryostat cool down. ActuIMT-2000 broad-band communication system emit ally cooling ability of the pulse-tube cryostat varies
the relative strong transmission than previous diga little over applied inclination, no signiﬁcant sysital phones. The S-band receiver’s down-convertertem temperature change was monitored, since thewas saturated and observations were halted dur- HTS is not thermal generating component. This is
ing April 2002. The receiver system was restarted
the ﬁrst wide-band HTS ﬁlter in practical use.
by a narrow-band ambient ﬁlter installation after
the Low Noise Ampliﬁer (LNA). Then we have de1.

Introduction

Figure 1. Kashima 34-m telescope located in dense population area. The antenna is surrounded by more than ten IMT-2000 base station of two major companies. The telescope
can distinguish these base-stations by side-lobe coupling at low-elevation.

November 2003
3.

11

LNA overload measurement and ﬁlter
position

Though the post LNA HTS ﬁlter rejects current RFI in-comings to S-band LNA, increasing
RFI traﬃc in this frequency may completely saturate the LNA in future. In this case, to protect
the LNA, the HTS ﬁlter will be installed to in
front of the LNA. Evaluation of overloading levelis discussed as follows. We used a signal generator (SG) tone injection from a cross guide coupler
port of the receiver feed system where we usually
inject phase-cal tones. Under condition of receiver
feed connected to cold load, an SG is connectedto the port and LNA output is measured to obtain P(-1dB) compression level. Figure 2 shows
the measurement of -6.5dBm output. On the other
hand, pointing telescope toward the strongest component of IMT-2000 signal, we measured the levelof -17.6dBm by a power-meter. Thus roughly still
there is 11dB margin until the LNA saturation.
This measurement is done under initial deployment
of IMT-2000 service and the number of IMT-2000
user is expected to be increased rapidly. Thenthese base stations will equip additional transmitters. Another source is interfere by personal user
at close range. Observatory requests non-use ofmobile phones near facilities. Usually it is diﬃcult to turn oﬀ all mobile phones. These unwillingemission strongly interfered a few minutes observations. To avoid receiver overloading, We will monitor the RFI levels continuously. When the LNA
under monitoring is supposed to be near its saturation, we will install the HTS in front of the LNA.

Figure 3. HTS ﬁlter and ATC(Ambient Temperature Filter) comparison. Thick line shows ATC
ﬁlter passband limited in narrow-range and un suppressed strong RFI exists in nearby frequency. The
HTS passband is wide and its cutoﬀ shape is very
steep. RFI is completely suppressed. Higher edgeof the passband is determined by down-converter
characteristics currently.

4.

Summary

Figure 3 shows the S-band receiver RF spectrum by using normal ambient ﬁlter and HTS ﬁlter
combination. The HTS ﬁlter recover the receiving ability lower to 2193MHz and RFI components
from IMT-2000 system is completely disappeared.
The HTS ﬁlter system is practilally used in various VLBI experiment. S-band radio utilities are
increasing and the high performance ﬁlter subsystem is eﬀective to protect weak radio observation
under strong nearby emissions. Considering the
RFI level and LNA saturation tolerance, ﬁlter position are selectable in front of LNA or after LNA.
Since the IMT-2000 is strong RFI source, all VLBI
stations are recommended to monitor the RFI level
regularly to avoid unexpected observation failure.
References
Kawai.E. et al. S-band RFI problems at Kashima 34m antenna and a passive ﬁlter for mitigation. IVS
TDC News 21, Nov.,2002.

Figure 2. LNA overloading measurement by injecting CW tone. Comparing the measured P(1dB) compression level and strongest incoming
RFI, LNA margin until non-linear saturation is estimated.

Kawai.E. et al. Wide-band high-temperature superconductor ﬁlter on 2.2GHz RFI mitigation. IVS TDC
News 22, June,2003.

IVS CRL-TDC News No.23

122-Gbps PC Architecture andGbps data processing in K5/PCVSITable 1. 2Gbps Acquisition PC components
Mother board
PCI-bus
CPU
MemoryRaid

Moritaka Kimura (mkimura@crl.go.jp),
Junichi Nakajima, Hiroshi Takeuchi, andTetsuro Kondo

HD
Network
VSI-H
Price

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
1.

Introduction

Using high-speed PCs, PC-based data acquisition and processing systems are being developed.
After the completion of 1-Gbps per unit system, in
our experiment we have reached 2-Gbps per unit
in recent integration of K5/PC-VSI. This is thehighest PC recording speed ever performed andmaximum performance realized under high speed
PCI-bus architecture. Compared with 256Mbps
magnetic recorders, this is 8 times faster and theprice of the recording system is reduced to one
hundredth (200,000 USD to 2,000 USD). Not only
the system performance is drastically improved,
connection to Internet through the Giga-bit ether
ports are already equipped in the PC system. Anticipate the VLBI era of software correlation overthe network connections, one concrete PC architecture is determined. Successive correlation resources are also prepared by PCs over the network.
2.

PC Components selection of K5/PCVSI

K5/PC-VSI system consists of the VSI compatible A/D sampler [1] and PCI data capture board[2] that is used for capturing sampled data inmain memory. High-speed PCI bus and high-speed
RAID are required for PC-VLBI. The list of PC
components are shown in below table 1 . Thismother board was selected to utilize high-speed
PCI buses. One PCI socket (66MHz/64bit) is used
for data capturing from VSI sampler, another PCI
socket (133MHz/64bit) is used for RAID card fordata storage. Since, 1G-byte main-memory is used
as FIFO buﬀer, task switching overhead of OS, seektime of a disk and other process does not aﬀect
to continuous recording. Maximum data rate of2Gbps can be performed by 8-disks RAID-0 mode.
There is enough margin to perform RAID-5 to givehigh data reliability. Using two gigabit-ether ports,
almost all sampling data are transmitted to correlation PC. When we use 250GB x 8 disks of a goodbuy price, 8 hours / 512M-bps, 4 hours / 1024Mbps or 2hours / 2048M-bps recording is possible.
Each disk stored in simple removal case for media
transportation. Increasing disk capacity, 24 hours
Gbps observation without disk change become possible near feature.

3.

Rio-Works HDAMA
133MHz/64bit×2,66MHz/64bit×2
33MHz/32bit×2
AMD Opteron 240×2
2GbyteHighPoint Rocket Raid 1820
(8-port Serial ATA)
IBM-HITACHI Deskstar 250GB ×8
Gigabit ether ×2(on board)
PC-VSI2000DIM Interface card
2,000 USD (w/o HDDs and IF card)

Observation and Processing mode

Advanced from tape based system, ﬂexibility of
PC-VLBI enables researches various kind of observation modes. Show typical architecture in Figure
1, combination work of memory, hard disks, VSI
capture board, high-speed network and high speed
CPUs allow users this. They are used as both shortterm FIFO and storage. K5/PC-VSI currently supports following basic modes.
• Mode-1: Oﬀ-line stand alone observation
This observation mode is similar to conventional tape recorders. Sampling data of AD
unit is recorded to RAID, and disk-pack exchange is performed as if they are the tapes.
After Observation, removal disk-packs aretransported to the correlation PC. This observation mode is used in all usual VLBI stations
to substitute recorders.
• Mode-2: Fringe-Check observation
If observation station is connected to network,a part of observation data are transmitted toother site for immediate fringe check. In mostof the observation, real-time correlation is notessential requirement, low speed network andsampling inspection of the dataset satisfy theusers quicklook during observation period [3].
The K5/PC-VSI system is designed to recordand data transmission simultaneously.
• Mode-3: Real-Time observation
Where the observation station are connectedhigh speed network, all sampled data aretransmitted to network in real-time. If observation purpose does not require wide bandwidth, total data rate is compressed by resampling technique at CPUs. This mode is important in time critical observation like delta
VLBI observation for satellite positioning.
• Mode-4: Single dish observation
In spectroscopic observation, incoming raw
data is processed directly without disk recording. Though in severe RFI and switching observation, preserved raw data in the K5/PCVSI system can be applied to software processing algorithms of RFI removal and sensitivity
increase.

November 2003

13

Figure 1. K5/PC-VSI and observation mode conﬁguration. High speed PCI buses capability and highspeed CPU peripherals arrangement enables observation modes over the PC architecture. Sole PC I/O
performance is limited below 2-Gbps in present bus architecture.
Table 2. Requirement of ﬂoating point operation speed for real-time processing with n-stations, 1k-point
FFT with 1Gsps sampling rate
Number of station
n
2
3
4
5
6
7
8
9
10

Number of baselines
1
3
6
10
15
21
28
36
45

Total operation
speed [Gﬂops]
60
96
136
180
228
280
336
396
460

Operation speed
per PC [Gﬂops]
30
32
34
36
38
40
42
44
46

Table 3. The number of ﬂoating point operation for ample, the requirement of PC speciﬁcation for realtime correlation of 1Gsps and 1024 FFT points andn-stations, m-point FFT with m-samples.
Processing term
floating point
number of station n are shown in Table 2. ToFFT(real-FFT)
5/2m log2 ×m × n
tal amount of operation is summed up from funcDelay tracking and fringe rotation
3m × ntions that are used in FX correlation, operation
Cross correlation and Integration
4m × n(n − 1)/2
cost of each function are presented in Table 3. Actually, there are some data copies between memory
to registers in each function, the required PC performance is roughly 3 times larger than table 2. As
4. PC Correlation Resource Estimationa consequence, 1Gbps multi-baseline real-time corWhen we process VLBI data stored in disks, even relation, several high speed PCs that has capability
a slow PC can process whole data by spending of 100Gﬂops are required. Typical performance oflong time. On the other hand most severe case recent CPU is 12Gﬂops, PC system equips 8-CPUsis the real-time processing. This section deduce reach the ability. However, the software perforprocessing capability of multi CPUs system being mance is highly depend skill in programming, aplanned at CRL. All data processing of K5/PC- slight ﬂaw in software code and code without highVSI system is performed by software. The software speed technique can not be a correlation core of thedeveloped at CRL uses Single Instruction Multi- high speed software correlator.
ple Data (SIMD) functions which are equipped inrecent CPUs such as Intel Pentium-3, Pentium-4, References
AMD Athlon and Opteron. In addition, the soft- [1] Nakajima, J et. al. IVS CRL-TDC News
ware is scalable to multi-CPUs and multi-PCs [2].
No.17,pp.18,NOVEMBER 2000.
Since the software correlation employs FX algorithm, multi-baseline correlation is performed by [2] Kimura , M et. al. IVS CRL-TDC News No.21,
pp.31,NOVEMBER 2002.
increased number of PCs corresponding to number of station without vastly speed down. Using [3] Nakajima, J et. al. IVS CRL-TDC News
these characteristics, the performance of software
No.16,pp.15,JUNE 2000.
correlation reached hardware correlation. For ex-

IVS CRL-TDC News No.23

14

Data ownership evolution and decks. In observation, one of a station starts to use
PC-VLBI system as DIM (Data input module).
flexible handling around PC the
The data is transferred over Internet (or VSI-E in
VLBI
future) and corresponding PC-VLBI unit will work
Junichi Nakajima (nakaji@crl.go.jp),
Moritala Kimura, Yasuhiro Koyama, andTetsuro Kondo

as DOM (Data Output Module). The DOM acts
like a tape deck. Then the hardware correlator will
be able to work with the PC-VLBI system. During
tape system are the majority, this is a preferredstyle for uninterrupted VLBI operation.

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
1.

Introduction

Huge VLBI raw data has been a matter diﬃcult
to handle. The data written on magnetic tapes
can be used only by synchronized playback. Mostof the VLBI users could not touch the data until
they are processed at correlators. Recent improvement of PC-based VLBI technique (here after generally PC-VLBI) allows researchers to access the
raw VLBI data directly. By the ﬂexibility of ﬁleimage transfer between the systems researchers canintroduce their idea scheme into VLBI. As the examples, we have proved simple mutual data transfer over the Internet. Between Haystack observatory Mk-V and Kashima K-5 system accomplishedﬁle based compatibility (Koyama el al. 2003).
The data transfer is expected to develop to VSIE (VLBI Standard Interface -Ethernet). FinlandMetsahovi observatory PC-VSIB and the Kashima
PC-VSI (K-5 family) system achieved G-bps Internet observations and data compatibility throughthe VSI-H (VLBI Standard Interface Hardware,
Whitney et al 2001, Kimura et al. 2003). As theseeﬀorts, using compatibility of PC-VLBI over the
VSI-H and Internet (VSI-E), current VLBI system
will be able to change over the key components
from legacy units to the PC-VLBI smoothly. In
addition, future VLBI applications will have beneﬁt in its integration. In following sections, several
evolution cases are written brieﬂy.
2.

PC based VLBI and Tape based VLBI
coexistence

2.1

PC system introduction to tape based
VLBI system and coexistence

Though the PC-VLBI systems realized ideal
data handling environment, it is obvious fact thatexisting VLBI operation are running with tape systems. These systems are still important to support
regular observations. Thus, smooth introductionof PC-VLBI system as a part of the tape system isthe initial work. Figure 1 shows a scheme of partial
PC-VLBI system installation in the place of tapeFigure 1. PC-VLBI introduction step to the existing tape VLBI system. VSI-H will be used to keep
the compatibility of DIM and DOM. Tape transportation is disappeared for the PC-VLBI system.

2.2

PC-VLBI data ownership with remaining tape units

After a while, the tape system will be graduallyreplaced to PC-VLBI systems as in Figure 2. In
the observation system, most of the data transfer
will be done over the broadband network. Correlations are performed at high speed software. The
software correlator is running at each acquisition
PC or at massive calculation resources like GRID
network. But it should be recognized that several remote sites as in separated islands will not
be reached by high speed optical ﬁber in near future. Thus these stations in remote location will
use tape or other kind of media. To handle theseremaining media, VSI-H compatibility will be used
to introduce data into the computer network. Since
the correlation is done by software, the data delay
from a few stations does not aﬀect correlation set
up. The software correlator carry out processing ofexisting baseline data ﬁrst, then they will processrest of baselines.

November 2003

Figure 2. Once the PC-VLBI system get a majorityof the VLBI system, software correlator shows advantages in VLBI data processing. Remote stations
not connected via network will use transported media. The software correlation system accept the delayed media and accomplish correlation of remaining baselines.

2.3

15

VLBI scheme, most of the observations are arranged to the hardware speciﬁcation of VLBI terminal and correlator. In other word, there wassome limitation in observations and processing. In
software centric PC-VLBI, the system will change
this situation and researchers can integrate own
observation system around PC bus architecture.
As a typical case, Figure 4 shows wide/narrow
band multiplex data acquisition system planned in
K5 for observation of orbit determination VLBI.
A single PC will acquire G-bps data (PC-VLBI)
and narrow band data (IP-VLBI). Applying reliable high-speed software-core, observer integrate
post-processing system too. All observation results are processed over network resources. Thus
the researches can concentrate their scientiﬁc target without system integration from scratch.

Data recorder as a VLBI data archive
unit

Once the PC-VLBI system is introduced to the
VLBI observation network, unused tape decks andtapes will be left over. These systems are utilizedagain as a data archive units. Though the PCVLBI system will be the next VLBI facilities, theirability to store data in long period is not matured
yet. Optical media up to a few Tera byte will be
realized in future. But until the ideal optical media
coming, VLBI researchers can archive fringe test
and special observation session from the PC-VLBI
to the familiar magnetic recorders. Using the VSIH, the data will be retrieved to data ﬁle in PC at
the moment when they need. Figure 3 shows thisapplication.

Figure 4. PC-VLBI enables ﬂexible integration of
new VLBI system.

4.

Summary

Using the common hardware interface VSI-H andInternet data transfer which advance to VSI-E,
VLBI community with matured magnetic tape system can smoothly change over to PC-based VLBI
system. For a certain period, magnetic tapes canserve as T-byte order data archive unit. Once the
PC-VLBI system is introduced, their ﬂexibility allows users to introduce own new idea to its dataacquisition and data processing.
References
Kimura.M. et al. “First detection of 2-Gbps wide-band

Figure 3. Behind increasing PC-VLBI terminal,
fringes between two PC-based VLBI”, IVS TDC
remaining recorders are used as data archive units
News 22, June,2003.
to keep important observation data.
Koyama.Y. et al. “Rapid UT1-UTC estimation from
Westford-Kashima e-VLBI experiment”, IVS TDC
News 22, June,2003.

3.

Support new observation system

Flexibility of PC-VLBI is well given at integration of new VLBI observation system. In former

Whitney.A. “VLBI Standard Interface - Hardware
Speciﬁcation”,International VLBI Service, 2003,
http://ivscc.gsfc.nasa.gov

IVS CRL-TDC News No.23

16

Diagnostic tools for the K5 sys- In addition, the functionality of the system canbe easily checked by software programs because thetemsystem is constructed on the PC system. In theconventional VLBI system, it is not easy to checkproblems in the A/D samplers because it requires adata recorder, a data sampler, and a data processor
to check the data, and not all of them is available
Kashima Space Research Center
every time. In case of the K5 system, such capaCommunications Research Laboratory
bilities can be realized all in one in a PC. More893-1 Hirai, Kashima, Ibaraki 314-8501, Japan over, it is possible to check the data by comparing
or correlating with that of some other station, by
1. Introduction
transferring the data via computer network.
These examples illustrate outstanding capabiliK5 is a personal computer (PC) based VLBI obtiesof the K5 system for its easy diagnosing posserving and data processing system. Recently itsibilities.
Functionalities of the IP-VLBI sampler
has been used in various observation experiments,
board,
remaining
HDD disk space, and some othersuch as Koganei-Kashima baseline geodetic experissuesofthesystemcan be checked by using a set
iments, “Nozomi” spacecraft positioning observadiagnostic
tools . These toolsofsoftware-based
tions, a multiple baseline geodetic experiment inwill notify the operator if there is a potential probwhich ﬁve VLBI stations participated, and e-VLBI
observations with Kashima and Westford VLBI lem in the system. This will ensure the successstations to determine UT1-UTC within 24 hours. of the observation session. Therefore, we are now
In these observations, it has been shown that K5 developing such diagnostic tools for the K5 system.
system has great advantages comparing with con2.1 Current status
ventional VLBI recording system. One reason isthat K5 has computer network capability. It is
Some of the diagnostic tools for the K5 systemeasy to run and monitor an observation session re- have been developed. In this section, we will intromotely using network. The data can be transferred duce these tools.
via network after the observation session.
First, there are tools to show the amplitude disTo make use of the K5 VLBI system in a routine tribution of the sampled data. Figures 1 and 2
experiment, it is important to develop a suit of di- show the resultant plots of such tools. These ﬁgagnostic tools which checks the performance and ures are obtained by feeding 700mV peak-to-peak
functionality before the observations. Because K5 9kHz sinusoidal wave to this sampling board. The
is a system developed on PC, it is possible to use board was set to sample the data on 4-MHz, 8-bit,many advantages of PC systems. By using software and 1-channel sampling mode. Figure 1 shows the
programs it is possible to ensure there is no prob- amplitude distribution of the -full to +full range.
lem when VLBI data are being recorded. In this This plot shows a Gaussian-type distribution of thereport we present current status and future plans sampled data around the center. If the distribution
for such diagnostic tools, using the advantages that of the resultant plot suggests the signal level is too
the system is constructed on PC. This will ensure strong or too weak, the operator should adjust thethe functionality of the system when K5 system is level of the signals by adjusting ampliﬁers and atused in an observation session.
Hiro Osaki (osaki@crl.go.jp),
Tetsuro Kondo, and Yasuhiro Koyama

2.

Concept of the diagnostic tools

As the K5 system is developed on PC, we have totake care a few possible mis-settings peculiar to PC
systems. For example, observation data will not
be recorded if there is a conﬁguration error of thehard disk drives (HDD) of the PC. For instance,
if the write permission of the data storage directory is not suﬃcient to the user account the data
write will fail. There may also be other cases thatthe HDD used for the data storage is not mounted
on the PC by mistake. Such errors can be easily
checked and can be corrected by simple software Figure 1. Amplitude distribution of the sampled
programs which check the write permission and the data.
remaining HDD space.

November 2003

Figure 2. Frequency of occurrence of each 8-bit
sampled data.

tenuators. Figure 2 shows frequency of occurrenceof each 8 bit sampled data. Using these tools functionalities of the sampling board and the level ofthe input signal can be checked.
Second, there is a tool that can detect 1 PPS and
10 MHz signals. These signals are essential for the
IP-VLBI sampler board to work. Using this tool,
the operator can check whether these signals aresupplied to the board, even if accessing and monitoring the system from a remote place via network.
Third, there is a program that sums up thedata recording time of observations in a scheduleand shows the total recording time. This programshows three candidates of the required data storage area, calculated with the total data rate of 64,
128, or 256 Mbps. The remaining disk space of themounted drives is also shown. So the operator cancheck whether the remaining amount is enough forthe observations. In a near future this program will
be developed to calculate the actual required disk
space and notify the operator whether the remaining disk space is enough.
As shown in these examples, it is possible to create various diagnostic tools for the K5 system, using PC-based facilities. In the next section we will
introduce future plans of such diagnostic tools.
2.2

Future plans

Because PC-based system is ﬂexible, there are
more rooms for another kind of diagnostic tools.
Here we will show the ideas of the diagnostic tools
we are now planning to develop.
The ﬁrst category of the tools will diagnose thesystem itself. K5 system is assembled using the IPVLBI board and a PC. Generally the data writing
performance depends on the amount of RAM, thespeed of the bus, the linear density of the HDD,
the rotating speed of the HDD, and so on. These

17

factors must vary from PC to PC. Therefore thewriting performance should vary from system tosystem. This determines the limit of the stabledata-sampling rate. Therefore, it is important tomeasure the writing performance of the system byaltering the data-sampling rate. The performanceof the HDD also varies when the inside of the disk isused or the outside of the disk is used. Therefore,
it is better to check the performance by altering
the remaining HDD space too. In addition, HDD
may have some bad sectors. Such sectors should
be checked before the observations and should bemarked so that they will not be used. These capabilities will also be realized by making software
using PC facilities. In another case, the operator
may want to check whether the time of the sampler board is correct. If the PC is connected to a
network, it is easy to check the time and, if necessary, to synchronize the time of the board with theaccurate time, by accessing to an NTP server.
The second category of the tools analyzes thegiven signal, including the experiment data, 1 PPS,
and 10 MHz signals. Analyzing the data, it is possible to check whether there are phase calibration
signals and whether the intensities of the phasecalibration signals are appropriate for the experiment. Spurious signals and DC oﬀsets can also
be checked by analyzing the data. The operator
can diagnose the linearity of the sampling by feeding controlled sinusoidal waves to the K5 system, if
multiple bits are used for the observations. Usingsuch diagnostic tools, the operator can check thedata thoroughly and can ensure the functionalityof the system.
3.

Summary

In the present paper we described about diagnostic tools for the K5 system. These tools arebeing developed using the advantage of PC-based
system. Using PC-based facilities, functionalityof the system can be diagnosed easily comparedwith conventional VLBI recorder systems. Someof the diagnostic tools have been realized, and weare planning to develop the other diagnostic tools
in the near future. By completing such tools, thereliability of the PC-based observation system will
become robust.

IVS CRL-TDC News No.23

18

Current Status of the K5 Soft- 1000 series mini-computer (e.g., 45F, A900, etc.).
took about 8 hours to obtain 64 lag correlation
ware Correlator for Geodetic It
function by processing 16 Mbit data in the HPVLBI
1000 45F. The CCC was used in the actual fringe
Tetsuro Kondo (kondo@crl.go.jp),
Yasuhiro Koyama, and Hiro Osaki
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
1.

Introduction

In the genesis of VLBI, correlation processing
was performed by a software program, however routine processing of such as a 24-hour observation
data was impossible due to less computing power.
A hardware correlator was hence developed and has
been used for a long time. Recently the progressin computing power is remarkable, and computing
speed of a recent PC is much faster than that of
the mini-computers and workstations of ten years
ago.
Kashima VLBI group used to develop the “Software Correlator” named CCC (Cross Correlation
in a Computter) for a fringe test of domestic VLBI
observations [Kondo et al., 1991]. The CCC performed correlation processing using the data prepared by the K-3 (or Mark III) decoder in the same
way as a hardware correlator. The substance of
CCC was a FORTRAN program running on an HP-

test of a domestic VLBI measurement in 1985, andwe could get fringes. Although processing time was
improved by a factor of 3 by use of the HP-1000
A900, it was not practical from the reason that
not only data processing but also data transmission
took time too much (typical transmission speed via
telephone line at that time was only 1200 bps!). We
had to wait for progresses of both computing speed
and data transmission speed to put a software correlator in pratical use.
We have been developing a PC-based VLBI dataacquisition terminal named K5 dedicated to transmitting the data through the Internet [kondo etal., 2000, Kondo et al., 2002, Osaki et al., 2002]
since 2000. In parallel with the development of
K5 hardware, a software correlator written in C
language has also been developed for K5 data processing for geodetic use. The past experience of the
CCC development was employed eﬃciently in thedevelopment of K5 software correlator. At present
time, K5 software correlator can process 4 Mbps
data in real time when it runs on a PC equippedwith the Pentium III 1GHz processor or faster one.
The K5 software correlator is now used for processing geodetic VLBI data as well as delta VLBI data
observing a spacecraft such as “NOZOMI” (see it
Ichikawa et al., [2003]). Current status of the performance of K5 software correlator is reported here.

Figure 1. Two types of correlators.

November 2003

19

Figure 2. Schematic block diagram of the KSP correlator (XF type).

2.

K5 Software Correlator

There are two types of correlators (Figure 1).
One is the XF type correlator, which carries out
cross-correlation directly on the time domain, thenapplies a Fourier transform to a frequency domain
as required. The XF type corelator was developed
to achieve faster processing speeds by reducing thenumber of delay lags. Because the correlation function of white noise is represented by a sharp peak,
we can reduce the number of delay lags such as 32
or less. Thus an XF type correlator has been used
for geodetic VLBI system (e.g., KSP, K3, MarkIV correlators). The other one is the FX type.
Two stream of time domain data are ﬁrst Fouriertransformed to the frequency domain, then multiplied each other to obtain cross spectrum. Finallythey are inverse Fourie transformed to get crosscorrelation. This type of correlator can have longer
delay lags easily and is well used for data processingof astronomical application which requirs higher
spectrum resolution. VSOP correlator belongs tothis type. Both types have been developed as K5
software correlators.
Figure 2 shows a schematic block diagram of
the KSP hardware correlator. First we started
the development of an XF type software correlator to compare the correlation results with those
processed by hardware correlator. The same algorithm used in the KSP hardware correlator was introduced in the software correlator to assure geodetic results. Phase calibration (Pcal) signal detection was also implemented in the software. Thenan FX type software correlator was developed. The
substance of these correlators is a C program that

Figure 3. Current performance of K5 software correlator. Time required to process 1 sec data is plotted as a function of the number of delay lags for
XF (“cor”) and FX (“fx cor”) software correlators.
Data are 1ch or 4ch 1-bit-8MHz sampling data, andthe type of CPU type is Pentium-III 1GHz.

can run on FreeBSD, Linux, and Windows operating systems.
3.

Current performance status

Figure 3 represents the current status of the performance of K5 software correlators for geodetic
VLBI data processing. Times required to process
1 sec data of 1ch or 4ch 1-bit-8MHz sampling data
are plotted as a function of the number of delay
lags for XF (“cor”) and FX (“fx cor”) software
correlators. A PC equipped with a Pentium-III

IVS CRL-TDC News No.23

20

References
Ichikawa, R., M. Sekido, H. Osaki, Y. Koyama, T.
Kondo, T. Ohnishi, M. Yoshikawa, and NOZOMIDVLBI group, An evaluation of VLBI observations
for the positioning of the NOZOMI Spacecraft andthe future direction in research and development of
the deep space tracking using VLBI, IVS CRL Technology Development Center News, No. 23, pp.31-33,
2003.

Figure 4. Comparison of the processing speed forvarious kinds of CPUs and clock frequencies. Data
are 4ch 1-bit-8MHz sampling data and 32-lag correlation function is caluculated.

Kimura, M., J. Nakajima, H. Takeuchi, and T. Kondo,
2-Gbps PC Architecture and Gbps data processingin K5/PC-VSI, IVS CRL Technology Development
Center News, No.23, pp.12-13, 2003.
Kondo, T., J. Amagai, H. Kiuchi, and M. Tokumaru,
Cross-correlation processing in a computer for VLBI
fringe tests, J. Commun. Res. Lab., Vol.38, No.3,
pp.503–512, 1991.
Kondo, T., Y. Koyama, M. Sekido, J. Nakajima, H.
Okubo, H. Osaki, S. Nakagawa, and Y. Ichikawa,
Development of the new real-time VLBI techniqueusing the Internet protocol, IVS CRL Technology
Development Center News, No.17, pp.22-24, 2000.

1GHz CPU was used for these evaluations. The
processing speed of FX type is not so inﬂuenced by
the increase in delay lags, but that of XF type increases in proportion to the number of lags. Whenthe number of lags is less than 512, the processing Kondo, T., Y. Koyama, J. Nakajima, M. Sekido, R.
Ichikawa, E. Kawai, H. Okubo, H. Osaki, M. Kimura,
speed of the XF type correlator is faster than theY. Ichikawa, and GALAXY team, Real-time Gigabit
FX type.
VLBI System and Internet VLBI System, IVS 2002
We also tested the processing speed for various
General Meeting Proceedings, pp.142-146, 2002.
kinds of CPUs and clock frequencies, such as PenKoyama, Y., T. Kondo, H. Osaki, K. Takashima, K.
tium III, Pentium 4, AMD, Celeron, etc. Results
Sorai, H. Takaba, and K. Fujisawa, Evaluation ofare shown in Figure 4, where data used are 4ch
the K5 system in geodetic VLBI experiments, IVS
1bit-8MHz sampling data, and 32-lag complex corCRL Technology Development Center News, No.23,
relation function is computed. It is demonstarted
pp.26-30, 2003.
that real time processing is well possible when 1ch
Osaki, H., T. Kondo, and M. Kimura, Development ofdata are processed with a high performance CPUversatile scientiﬁc sampling processor (VSSP) – A(time required for 1ch data processing can be estipractical approach, IVS CRL Technology Developmated by dividing 4ch results by 4).
ment Center News, No.20, pp.7-9, 2000.
4.

Conclusion

The K5 software correlators (“cor” and “fx cor”)
were developed for geodetic VLBI data processing.
Processing speed was somewhat sacriﬁced in thesoftware development because we gave importanceto the attainment of the same algorithm used in the
hardware correlator in order to assure the geodetic
results. K5 software correlators are software package written in C language in which neither special
function intrinsic to CPU nor assembler program isused, so that it still has the room of improvement
for further speed-up. Software correlator actually
has the potential capability to process 1Gbps data
in real-time as reported by Kimura et al. [2003].
As it is shown by Koyama et al. [2003] that geodetic results using the correlated data processed by
K5 software correlator give reasonable results, wewill shift our improvement eﬀort to further speed
up of the processing speed.

November 2003

21

Total VLBI data management In VLBI community, we have the CATLOG system developed by NASA GSFC and USNO for thesystem using database servercorrelated data and Mark-III database. It s a good
–The organizer for VLBI@home–

tool to avoid missing data or wasting time to ﬁnd
speciﬁc data. We also have the TRACK web site
maintained by NRAO for the magnetic tape meKazuhiro Takashima (takasima@gsi.go.jp)
dia, Thin tape and Thick tape. With the help of
these utilities, VLBI data management has been
Geographical Survey Institutein order, because the data management is almost
Kitasato 1, Tsukuba, Ibaraki 305-0811, Japanequals to the management of magnetic tape media
so far. However, the recent introduction of disk me1. Introduction
dia to record VLBI raw observations might change
the data management into “CHAOS”. On disk meDo you:dia, it is easy to copy, move, or even delete the* Miss important deadlines at work?
VLBI data. We might lose important VLBI raw* Forget to return urgent phone calls?
data and/or attributes of those data such as loca* Lose papers that were “just here a minute tion, frequency, or source information. I d like topropose a total VLBI data management system inago ”?
* Have multiple layers of sticky notes on your this article.
computer?
2. System overview* Leave projects unﬁnished for days, weeks, oreven months at a time?
The management system is not the storage of
VLBI raw data or correlated data. The system
These questions were quoted from the advertise- overview is shown in Figure 1.
ment of the book named “ORDER from CHAOS”
The DB server stores only management inforby Liz Davenport published by Three Rivers Press. mation such as a schedule, observing log data or
Personally, my answers will include many “yes” to correlation status. An example of the management
these questions.
ﬂow is shown below.

Figure 1. The system overview of the total VLBI data management system. The light graypart is the system proposed and dark gray is the existing system.

IVS CRL-TDC News No.23

221) A scheduler registers a schedule ﬁle on the
management system.
2) Each ﬁeld system checks the observing schedule periodically.
3) If it ﬁnds the schedule assigned to the station,
it downloads the schedule ﬁle from server andset up its observation automatically.
4) Observation5) After observation, the ﬁeld system submits thelog ﬁle to the management system.

Figure 2. The development schedule.

6) The management system reads the log ﬁle andsets up the correlation information for eachstation.

development of e-VLBI or IP-VLBI, and in near
future recording medium, such as magnetic tapes
or hard disks, will become unnecessary. As a result
it s not enough to manage the medium for data
7) Each correlator checks the correlation inforhandling because VLBI data is in a ﬁle on PC. Thismation on the management system.
data management system should keep up the infor8) If it ﬁnds the uncorrelated data, it downloads mation of each data ﬁle instead of disk medium.
the data from each station via network, and3rd Step : Hookup VLBI@home
then correlates those data.
If software correlator is developed, the data pro9) A data analyst receives a data correlation re- cessing task can be easily broken up into pieces
port from the management system, and then that can be worked separately and in parallel.
he/she downloads and analyzes the data.
The processing method is similar to that of the
SETI@home project which is a scientiﬁc eﬀort to10) Release the results to public.
seek answer whether there is an intelligent life form
outside the Earth. Following this, we call the3. Development schedule
project VLBI@home. In such a parallel processing
The developing schedule consists of four steps, scheme, the host computer should manage manyi.e. disk management, data management, hookup client computers and the data processing. ThereVLBI@home and total management system devel- fore, this management system with database server
can help VLBI@home projects.
opment (Figure 2).
1st Step : Disk management
This is the management system of PC hard disk
module to record raw data. It s similar to thecurrent tape management system “TRACK . The
data disks are preassigned the eight digit ID e.g.
“GSI12345 . The system should keep up the status
of disks such as the information of current location,
experiment name, station name, correlation status,
etc. by using ID as a key. The diﬀerent point fromTRACK is that it also keep up the speciﬁcation of
hard disks because there are a lot of kinds of harddisks in the market and the speciﬁcation aﬀects thewriting rate or data capacity, compared to only two
kinds of the magnetic tapes (Thin or Thick). In
case of hard disks, the management system has animportant role to prevent a theft of disks because
there are general values in a PC hard disk, although
it was not in VLBI-speciﬁc magnetic tapes.
2nd Step : Data management
The high-speed communication network urges the

4th Step : Total Management
Finally, the total management system is built tounify the above-mentioned 3 steps. We expect that
this total management system reduces the burdenof VLBI scientists.
References
K5 (IP-VLBI) disk management system (in Japanese)
http://vldb.gsi.go.jp/sokuchi/vlbi/tape depot/
Database server (PostgreSQL)
http://www.postgresql.org/
Web Service (SOAP/XML) W3C
http://www.w3.org/2002/ws/
SETI@home
http://setiathome.ssl.berkeley.edu/
NRAO TRACK
http://track.nrao.edu/

November 2003

23

Geodetic VLBI Experiments several Giga-bit geodetic VLBI experiments haveand improved gradually [Koyama et al.,Using VSI-based Giga-bit VLBI performed
2000]. At the most of these experiments, relatively
Systemshort-baselines about 100 km had used. In order toHiroshi Takeuchi (ht@crl.go.jp),
Junichi Nakajima, Moritaka Kimura,
Yasuhiro Koyama, and Tetsuro Kondo
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
1.

Introduction

Communications Research Laboratory (CRL)
has been developed Giga-bit VLBI system to improve the sensitivity of geodetic VLBI observations.
There are a lot of advantages to use the Gigabit VLBI system for geodesy. The band-width of
512MHz, which is four times wider than the currently operating conventional VLBI systems, enables us to use weaker radio-sources for geodetic
observations, or to shorten the integration time
when the ordinal radio-sources are used. The highsensitivity of the system allows us to use smalldiameter antenna as a VLBI telescope. We hadalready reported on a compact VLBI system using 0.65-m antenna CARAVAN [Yonezawa et al.,2002]. As another beneﬁt of the Giga-bit system,
we can point out that single-channel system is usable for it. Currently, most of the existing geodetic
VLBI systems equip multi-cannel down-converters
and phase calibration (PCAL) signal generators.
Single-channel backend system can be installed easier than multiple channel system and the maintenance cost will be reduced. Moreover, complicatedband-width synthesis process is not necessary, sothat simple and fast algorithm can be applied todata analysis process.
The development of the Giga-bit VLBI system
at CRL started in 1996 [Nakajima, 1996]. At ﬁrst,
it is used for radio astronomical observations totake advantage of its high sensitivity. Since 1999,

conﬁrm the accuracy of the Giga-bit VLBI systemused in relatively-long-baseline, we did comparison
experiment between K-4 and Giga-bit VLBI system
at Kashima-Tomakomai baseline. Details of theexperiment and initial result of Giga-bit system arereported in this paper.
2.

Experiments

In order to evaluate the performance of the Gigabit VLBI system, two experiments were performed
from July15, 2003 to July 16, 2003. The experiment named GEX-12 done at July 16 was comparative experiment between K4 and Giga-bit VLBI
system. It was scheduled in time with the 24hours geodetic experiment, JADE-0306, which was
performed by Geographical Survey Institute (GSI).
Domestic six stations using the K-4 system took
part in the experiment. The Giga-bit VLBI system
was also installed at Kashima 11-m and Tomakomai 11-m stations, both were part of the six stations. In the case of the K-4 system, X-band
signals and S-band signals were recorded to correct the ionospheric propagation delay, but only
the X-band signal was recorded with the Gigabit VLBI system. In the experiment, integration
time of each observation was conﬁgured to achieve
enough signal-to-noise-ratios for the narrow-band
system. However, the integration time was unnecessarily long for wide-band Giga-bit VLBI system.
For this reason, we also carried out experiment inwhich integration time was optimized for a sensitivity of the Giga-bit VLBI system. This experimentnamed GEX-11 was performed at July 15 between
Kashima and Tomakomai for 6 hours. Though thetotal observation time of GEX-11 was one-fourthof that of GEX-12, the number of observations wasalmost same (180 observations).

Figure 1. Schematic diagram of the down converter and recording system for the Giga-bit
geodetic VLBI.

IVS CRL-TDC News No.23

24

Figure 2. Correlator conﬁguration of the Giga-bit VLBI system

Table 1. Results of the Experiments
Observation
Band
Numberof Baselines
RMS Delay
Residual [ps]Baseline
Length [mm]Baseline
Vector [mm]3.

GEX-11 (6 hours)

GEX-12 (24 hours)

GEX-12 + K-4 (S-band)

K-4 System

X bandX bandS,X bandS,X band

1

1

1

15

81

138

89

120

749810998.9±5.0749811039.6± ± 8.8749810980.44± ± 7.3

749810979.86 ± 4.4

x:−3680586331.0 ± 10.1
y: 2917515834.5 ± 8.5
z: 4300987705.3 ± 10.7

x:−3680586312.2 ± 18.9
y: 2917515785.0 ± 16.1
z: 4300987716.8 ± 19.7

x: −3680586346.2 ± 17.3
y: 2917515802.98 ± 15.1
z: 4300987669.9 ± 16.2

x: −3680586342.0 ± 9.3
y: 2917515815.1 ± 7.7
z: 4300987680.4 ± 9.9

Giga-bit VLBI System

The Giga-bit VLBI system used in these experiments consists of four components. A schematic
diagram of the system is shown in Figure 1. The
A/D sampler ADS-1000 has a capability to output
2-Gbps (1Gsps/2bit) VSI-H data. In the experiments, we used only the MSB data from ADS1000. The 1-Gbps recorder GBR-2000D records
VSI-H data from ADS-1000. The memory unit
DRA-2000-VSI is used for fringe tests in the experiments. DRA-2000-VSI has a function to freeze
sequential 1-second data from the continuous data
stream and one can get the data as a ﬁle from thebuilt-in FTP sever. The Giga-bit correlator GICO2 is used for correlation process. GICO-2 has twocorrelation ports. Figure 2 is a schematic diagramof the baseband conversion system. A 500-MHz local oscillator signal leaks to the base-band output
signal of the mixer and a low pass ﬁlter is used at
the subsequent to reduce the leak. Despite using
the ﬁlter, we can use the leaked 500-MHz CW tomonitor a phase stability of the AD system. At theone of the GICO-2 correlator cores, a delay tracking and a fringe rotation are applied to obtain theastronomical fringes and at the other core, signals
from two stations are simply multiplied to monitor
phase variations of 500-MHz signal.

4.

Results

The results of the experiments are listed in Table 1. They were calculated with Calc/Solve developed by NASA GSFC. Although the total observation time of GEX-11 was one-fourth compared with
GEX-12, the obtained results are better than thatof GEX-12. The advantage of the schedule optimization for the Giga-bit system can be conﬁrmed
from the result. To correct the ionospheric propagation delay for GEX-12, we used S-band dataobtained by the K-4 system (The third row in Table 1). The result is very consistent with a multibaseline result of the K-4 system (The fourth row
in Table 1). In Figure 3, phase ﬂuctuations of
500-MHz tone signal are shown. During the experiment GEX-12, a steep phase change occurred
about 20:00 UT. We suspect that it is due to thechange of the ambient temperature around AD. An
accurate temperature regulation is required for the
Giga-bit VLBI system.
5.

Future Plans

At the present, only an X-band signal is recordedby the Giga-bit VLBI system. To establish a selfcontained geodetic system by the Giga-bit equipments, we are developing a dual-band baseband
conversion system for the Giga-bit geodetic VLBI.

November 2003

25
Table 2. Lineup of Giga-bit A/D samplers
ADS-1000

ADS-2000

ADS-4000(developing)

Figure 3. Phase ﬂuctuations during the experiments. A steep phase change occurred about 20:00
UT during the experiment GEX-12.

Up to 1Gsps/2bit sampling.
Recorded with a Giga-bit
recorder. Using a PC-VSI
board, a 1Gbps recording to
HDD is also available.
Multi-channel sampler (16ch),
64Mbps/ch, 1-bit or 2-bits
sampling.
Up to 2Gsps/2bit sampling.

References
Nakajima, J., Current Status of the Gigabit VLBI
Recorder System, CRL IVS TDC news No. 9, pp.
17-18, 1996.

In the system, both S-band and X-band signals Koyama, Y., Kondo, T., Nakajima, J., Sekido, M.,
Ichikawa, R., Kawai, E., Okubo, H., Osaki, H., Takare combined at down converter and recorded byaba, H., Yoshida, M., and Wakamatsu, K., Geodetic
a single channel 1Gsps A/D sampler. To achieve
VLBI Observations Using the Giga-bit VLBI system,eﬃcient geodetic observations, we are developing
CRL IVS TDC news No. 16, pp.11-14, 2000.
a 2Gsps A/D sampler and planning its future upYonezawa,I., Nakajima, J., Ohkubo, H., Tsuboi, M.,
grade to 4Gsps. The lineup of the Giga-bit A/Dand
Kasuga,T., Development of compact VLBI syssamplers is listed in Table 2.
tem, CRL IVS TDC news No.21, pp.29-30, 2002.

IVS CRL-TDC News No.23

26

Evaluation of the K5 system in tem with the results from the conventional VLBI
systems such as the K4 VLBI system. For this purgeodetic VLBI experiments
pose, two geodetic VLBI sessions were carried out
Yasuhiro Koyama1 (koyama@crl.go.jp),
Tetsuro Kondo1 , Hiro Osaki1 ,Kazuhiro Takashima2 , Kazuo Sorai3 ,Hiroshi Takaba4 , and Kenta Fujisawa5
1

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
2
Geographical Survey Institute3
Hokkaido University
4
Gifu University
5
Yamaguchi University

to evaluate the performance and functions of theK5 VLBI system. The ﬁrst session was performed
for about 24 hours from January 31, 2003 by using
Kashima34-Koganei baseline. The second experiment was performed for about 24 hours from July
14, 2003 by using ﬁve VLBI stations at Kashima(34m), Tsukuba (32m), Tomakomai (11m), Gifu
(11m), and Yamaguchi (32m). The details and results of these experiments will be reported in thispaper.
2.

K5 VLBI system

The K5 VLBI system is designed to perform
real-time or near-real-time VLBI observations and1. Introduction
correlation processing using Internet Protocol over
After the prototype models of the K5 VLBI sys- commonly used shared network lines. Various comtem were developed, the systems are beginning ponents are being developed to realize the tarto be used for various VLBI observations such get goal in various sampling modes and speeds.
as the precise orbit determination of the space- The entire system will cover various combination
crafts Nozomi and Geotail [Kondo, et al., 2002; of sampling rates, number of channels, and numIchikawa, et al., 2003; Sekido, et al., 2003] and ber of sampling bits by selecting subset of thethe demonstration of international e-VLBI obser- available systems shown in Figure 1. For observations through close cooperations with Haystack vations with low data sampling rates, the outObservatory [Koyama, et al., 2003]. Therefore, it put signal of the base-band converters are samis very important to ensure that there is no prob- pled with the IP-VLBI board and the sampled
lem with the performance of the K5 VLBI system data are directly processed with the PC sysby comparing the results from the K5 VLBI sys- tem to which the IP-VLBI board is installed.

Figure 1. Concept of the entire K5 System.

November 2003

27

Figure 2. Developments of K3, K4 and K5 VLBI systems.

All the conventional geodetic VLBI modes of total data rate up to 512 Mbps with 16 channels
are covered with this conﬁguration. For a single wide frequency band (512 MHz) observations,
ADS1000 data sampler unit is used as an A/D sampler and the sampled digital data are transferredto the PC system through VSI-H (VLBI Standard
Interface - Hardware) interface with the PC-VSI
board. ADS2000 data sampler unit is used for 16
channel observations with the total data rate of1024 Mbps with 1 bit sampling mode or 2048 Mbps
with 2 bits sampling mode. The sampled digital
data from ADS2000 are also transferred to the PC
system through VSI-H interface with the PC-VSI
board. The same PC-VSI board will support data
output function from the PC systems. Both IPVLBI board and PC-VSI board is installed in the
PCI (Peripheral Component Interconnect) bus of
the PC systems.
As shown in the Figure 1, the K5 system is characterized by the use of conventional PC systems
and the shared network based on IP (Internet Protocol). The data correlation can be performed byhardware correlators which support VSI-H speciﬁcations, but the target will be to perform correlation processing by the PC systems using software
correlator programs. Similarly, the K4 system canbe characterized by the use of rotary-head, cassette
type magnetic tape recorders and the dedicatednetwork based on ATM (Asynchronous TransferMode). Similarly, the K3 system can be characterized by the use of open-reel magnetic tape recorders(Figure 2).
The name of the K5 system is frequently used for
the Versatile Scientiﬁc Sampling Processor (VSSP)
system which is designed for geodetic VLBI sessions. Figure 3 shows the picture of the prototype
system of the VSSP. It is consist of four UNIX PC
systems. Each UNIX PC system has one IP-VLBI
data sampling board, or also called as a VSSP
board, on its PCI interfacing bus. Table 1 lists the
speciﬁcations of the board. The board can sample 4 channels of base-band signals at various sampling rates ranging from 40kHz to 16MHz. The
timing of the sampling is controlled by the provided 10MHz and 1-PPS reference signals so thatprecise timing information can be reproduced fromthe sampled data. Quantization bits can be set
from 1, 2, 4, and 8. Because the board has thesemany sampling modes, it has many possibilities tobe used not only for VLBI observations but also
for various other scientiﬁc researches which requireprecise timing information in the data. Device
driver software of the board has been developedon LINUX, FreeBSD, and Windows2000 operating
systems, and FreeBSD is used in the prototype K5
data acquisition terminals. Two prototype K5 dataacquisition systems have been conﬁgured. Four PC

IVS CRL-TDC News No.23

28

systems are mounted in the lower part of the 19inch standard rack. A signal distributor unit for 1PPS and 10 MHz signals and 16-channel base-band
signal variable ampliﬁer unit are mounted in theupper part of the rack. The monitor and the keyboard on the top of the rack are connected to thefour PC systems by using a four-way switch. Each
PC system is equipped with four removable harddisk drives of the data capacity of 120 GBytes each.
The sampled data can be transferred to the network by using TCP/IP protocol or can be recorded
to internal hard disks as ordinary data ﬁles. The
maximum recording speed is currently restricted by
the speed of the CPU and the speed of the PCI internal bus. Currently, the total recording speed of
512 Mbps has been achieved. It can be expected torecord data up to 1024 Mbps by using faster PCI
bus and faster CPU in near future. To process thedata sampled with the K5 data acquisition system,
software correlation processing program is also under development on FreeBSD and Linux PC systems. The correlation processing program receives
data from K5 data acquisition systems over the network using TCP/IP protocol and then calculates
cross correlation functions in real-time. It can also
read data ﬁles on internal hard disks. These capabilities allow to transfer observed data in real-time
if the connecting network is fast enough, or in near Figure 3. Picture of the prototype K5 VLBI system
real-time if data buﬀering is required. Since eas- (VSSP) conﬁgured with IP-VLBI boards.
ily re-writable software programs and general PC
systems are used, the processing capacity and thefunction of the correlator can be easily expanded
Table 2. Comparison of baseline lengths estimatedand upgraded.
from the data obtained with K4 and K5 systems.
Table 1.
board.

Speciﬁcations of the IP-VLBI (VSSP)

Reference Signals
Number of Input Ch.
A/D bits
Sampling Freq.

10 MHz (+10 dBm) and 1-PPS
1 or 4
1, 2, 4, or 8
40 kHz, 100 kHz, 200 kHz,500 kHz,
1 MHz, 2 MHz, 4 MHz, 8 MHz,or 16 MHzPCIFreeBSD, LINUX,or Windows2000

K4
K5

No. of
valid
data
112
159

Baseline Length(mm)109099657.0 ± 6.7109099641.2 ± 3.2

RMS Residual
Delay
Rate
(psec) (fsec/sec)
76
136
33
92

internal hard disks as the data ﬁles. The data ﬁleswere read by the software correlation program andBus Interface
the cross correlation processing was performed afOperating Systemter all the observations ﬁnished. Then the bandwidth synthesis processing was performed and theobtained data were analyzed by CALC and SOLVE
software developed by Goddard Space Flight Center of National Aeronautics and Space Adminis3. Experiments
tration. During the observations, tape-based K4
After completing two prototype K5 VLBI data
data acquisition systems were used at both sites
acquisition terminals, 24 hours of geodetic e-VLBI
in parallel to compare the results. The data obexperiment was performed using two 11-m antentained with the K4 systems were processed withnas at Kashima and Koganei from January 31 to
the K4 correlator at Kashima and analyzed simiFebruary 1, 2003. Eight channels were assigned tolarly with the data obtained with the K5 systems.
both X-band and S-band and the total data rate
The results are compared in Figure 4 and Table 2.
was 64 Mbps. Observed data were stored in theNovember 2003

400

psec

200

0

-200

-400

(a) Group Delay
0

5

10

15

20

Hours from 09:00 UT on Jan. 31, 2003

400

200

fsec/sec

Figure 4 shows the diﬀerence in group delay anddelay rate obtained by the K4 VLBI system andthe K5 VLBI system. The constant oﬀset of thegroup delay can be absorbed as a part of the clock
diﬀerence estimated through the data analysis processing and therefore it does not cause any problem
in the data analysis. The RMS of the diﬀerenceis calculated as 72.7 psec for delay rate and 118
fsec/sec for delay rate, and it can be concluded that
the K4 and K5 systems are consistent with eachother. Table 2 shows the estimated results fromthe data analysis. From these comparisons, it canbe concluded that the estimated baseline lengths
are consistent with each other within two time theestimated uncertainties. In addition, the comparison of the RMS residuals of delay and delay rates
suggests the performance of the K5 systems is better than the K4 systems. The part of the reason of
the improvement can be considered that the phasecalculation of the phase calibration signals by thesoftware correlation processing uses precise formulawhereas the K4 hardware correlator uses a threelevel approximation for sine and cosine functions
for faster processing and to make the design of the
hardware correlator very simple.
Then the opportunity of a domestic regular
geodetic VLBI experiment performed by Geographical Survey Institute (GSI) was used for theevaluation of the K5 VLBI system. The experiment
JD0306 was performed for 24 hours from July 16,
2003. As a regular domestic experiment, four VLBI
stations operated by GSI at Tsukuba (32-m), Shintotsukawa (3.8-m), Chichijima (10-m), Aira (10m) participated with the K4 VLBI systems. At
Tsukuba station, K5 VLBI system was used in addition to the K4 VLBI system. By using the sameobserving schedule, Kashima (11-m), Tomakomai(11-m), Gifu (11-m) participated in the experimentby using K4 VLBI system and K5 VLBI system intandem. In addition, at Yamaguchi (32-m) station,
K5 VLBI system with two PC units were used toperform observations only in X-band with 8 channels. At three stations (Kashima, Tomakomai, andTsukuba), K5 prototype models shown in Figure 3
were used while PC systems conﬁgured with IPVLBI boards were used at Gifu and Yamaguchi
stations. Table 3 shows the comparison between results obtained from K4 VLBI system and K5 VLBI
system for six baselines. Since the K5 VLBI system at Kashima and Gifu stations stopped recording for about six hours and 12 hours respectively
during the observations, the number of valid datafor baselines including Kashima and Gifu stations
are fewer than the data from the K4 VLBI system. The comparison suggests that the estimatederror obtained from both systems are comparable

29

0

-200

-400

(b) Delay Rate
0

5

10

15

20

Hours from 09:00 UT on Jan. 31, 2003

Figure 4. Diﬀerence of (a) group delay and (b)delay rate obtained from K4 and K5 systems. Horizontal axis is the time of the scan in hours fromthe beginning of the session while the vertical axis
is the diﬀerence of group delay and delay rate.
The error bars are one-sigma errors evaluated from(sK 42 + sK 52 )1/2 where sK 42 and sK 52 are standard deviations of the data estimated from K4 andK5 systems, respectively.

considering the number of available data and theestimated baseline lengths are consistent with eachother considering the estimated error.
In Table 4, preliminary results of estimated coordinates of the Yamaguchi 32-m station based on
the ITRF97 reference frame are presented. In thedata analysis, site coordinates of the Tsukuba 32-m
station was used as the reference and the X-band
group delay data between Tsukuba-Yamagichi
baseline were used. Since ionospheric correction
can not be performed because only X-band data
were taken at Yamaguchi station, it have to be
noted that there might be a systematic error in
the estimated coordinates.

IVS CRL-TDC News No.23

30

Table 3. Comparison of baseline lengths estimated from the data obtained with K4 and K5 systems.
Baseline

Tsukuba-Kashima
Tsukuba-Gifu
Tsukuba-Tomakomai
Kashima-Gifu
Kashima-Tomakomai
Gifu -Tomakomai

SystemNo. ofvalid data

K4
K5
K4
K5
K4
K5
K4
K5
K4
K5
K4
K5

176
130
184
55
124
169
174
48
171
108
154
49

Table 4. Estimated coordinates of the Yamaguchi
32-m VLBI station.
X:
Y:
Z:

4.

−3502544258.3 ± 22.1
3950966396.9 ± 25.8
3566381164.9 ± 22.0

Conclusions

Baseline Length(mm)53811894.9 ± 2.1
53811891.6 ± 3.1
311067474.0 ± 2.9311067483.3 ± 4.0740526116.3 ± 4.4740526119.4 ± 5.1
358799168.6 ± 2.8358799174.7 ± 4.5749810979.9 ± 4.4749810985.5 ± 5.5902668931.2 ± 4.8
902668930.6 ± 6.1

RMS Residual
Delay
Rate
(psec) (fsec/sec)
53
158
81
121
98
189
58
136
103
165
103
146
72
191
92
144
115
125
106
143
135
125
116
138

for orbit determination of deep space spacecraft Group delay measurements of GEOTAIL and NOZOMI telemetry signals -, IVS CRL TDC News, No.
21, pp. 18-21, 2002.
Sekido, M., R. Ichikawa, H. Osaki, T. Kondo, and Y.
Koyama, VLBI application for spacecraft navigation(NOZOMI) Part II, -Delay model and analysis-, IVS
CRL TDC News, No. 22, pp. 12-15, 2002.
Ichikawa, R., M. Sekido, H. Osaki, Y. Koyama, T.
Kondo, and NOZOMI VLBI group, VLBI application for spacecraft navigation (NOZOMI) Part I, Overview-, IVS CRL TDC News, No. 22, pp. 10-11,
2002.

The results from two geodetic VLBI experiments
between K4 and K5 VLBI systems were compared
to ensure that the K5 VLBI system has expected
Koyama, Y., T. Kondo, H. Osaki, A. Whitney, and K.
capability and performance similar or better than
Dudevoir, Rapid turn arround EOP measurements
the K4 VLBI system. The results from two diﬀerby VLBI over the Internet, Proceedings of the IAG
ent systems are consistent with each other considerG02 Symposium in the 23rd. IUGG General Asseming the estimated error. From these comparisons, itbly, Sapporo Japan, July 2003 (submitted).
can be concluded that there is no problem in using
the K5 VLBI system for precise VLBI observations.
Acknowledgment: The authors would like to express sincere appreciation to many members of Geographical Survey Institute, Hokkaido University,
Gifu University, Yamaguchi University, and Communications Research Laboratory for supporting
observations of the VLBI experiments described inthis report. We also would like to thank Geographical Survey Institute for allowing us the other stations to participate in the JD0306 session.
References
Osaki, H., Advancement of Versatile Scientiﬁc Sampling Processor (VSSP), IVS CRL TDC News, No.
21, pp. 16-17, 2002.
Kondo, T., R. Ichikawa, Y. Koyama, M. Sekido, and
H. Osaki, VLBI ovservations using IP-VLBI system

November 2003

31

An evaluation of VLBI observa- nal for several baselines using a software correlation
We provided 15 VLBI group delay data
tions for the positioning of the procedure.
sets to the Institute of Space and Astronautical SciNOZOMI Spacecraft and the ence (ISAS). In this short report we describe thefuture direction in research and results of the experiments and future plans.
development of the deep space 2. NOZOMI VLBI experiments
The ﬁnal products obtained from the VLBI extracking using VLBI
periments were available with approximately 20
hours latency as shown in Figure 1. The several
Ichikawa, R.1 (richi@crl.go.jp), Sekido M.1 ,tens of gigabytes data sets were acquired at each
Osaki H.1 , Koyama Y.1 , Kondo T.1 ,station on the K5 system within 3-5 hours VLBI
Ohnishi T.2 , Yoshikawa M.3 , and NOZOMI experiment. After the completion of each VLBIDVLBI groupexperiment, the data sets at Usuda, Gifu, and Koganei were transferred to the Kashima using a high1
Kashima Space Research Center
speed optical ﬁber network on TCP/IP protocol in
Communications Research Laboratory
under 3 hours. Correlation processing was com893-1 Hirai, Kashima, Ibaraki 314-8501, Japan pleted at Kashima about 10-15 hours later. The
2
Fujitsu Limted
estimation of clock parameter based on the quasar
1-9-3 Nakase, Mihama-ku, Chiba 261-8588,
group delays was completed at Kashima 1 hours
Japan
later. On the other hand, the removable data hard
3Japan Aerospace Exploration Agency
disks at other stations (Tomakomai, Tsukuba, YaInstitute of Space and Astronautical Sciencemaguchi, and Algonquin) were mailed to Kashima.
3-1-1 Yoshinodai, Sagamihara,Thus, the latency to product the group delays usKanagawa 229-8510, Japaning these satation data were up to several days.
The obtained group delays were compared with
1. Introduction
the NOZOMI orbit using range and range rate
We preliminary reported the results of the VLBI (R&RR) observables. Preliminary results demonexperiments for the NOZOMI spacecraft naviga- strate that the VLBI delay residuals are consistenttion before the second earth swingby on June 19, with R&RR observables. However, the rms scat2003 [see Ichikawa et al., 2003[1] and Sekido et al., ter between them are relatively large up to several
2003[2] in detail]. NOZOMI is the Japan’s ﬁrst tens nanoseconds as shown in Figure 2. The unMars probe. In these experiments, we successfully resolved trend for the Kashima (CRL) - Tsukuba
detected group delay fringes of NOZOMI range sig- (GSI) baseline are also represented. One candidate

Figure 1. Schematic image showing NOZOMI VLBI data ﬂow and analysis.

IVS CRL-TDC News No.23

32

possibility of the trend is uncertainty of the a prioridelay value predicted by the VLBI model. We arenow evaluating our VLBI group delays by comparing with the R&RR results more deeply.
According to the ISAS announcement the NOZOMI completed its ﬁnal Earth swingby operation
on June 19 2003, and is on its way to Mars. NOZOMI passed within 11,000 km of the Earth in amanuever. NOZOMI’s arrival at Mars is scheduledin the middle of December 2003.

Figure 3. HAYABUSA Image (after JAXA/ISAS)

epoch. A source geometry of the HAYABUSA
spacecraft and nearby quasars are illustrated in
Figure 4. The signal to noise ratios of the detectedquasar fringes are shown in Table 1. We are now
planning to perform a ﬁrst HAYABUSA VLBI experiment based on the signal intensity result.
Figure 2. Residual delays between determined position using R&RR data by ISAS and VLBI groupdelay observables

3.

Preparation of HAYABUSA VLBI experiments

Our main concern is to establish the diﬀerential
VLBI positioning technique for the interplanetary
spacecrafts in realtime. However, NOZOMI VLBI
experiments are insuﬃcient to develop the technique due to some problems such as signal weakness, narrow band width and so on. Thus, weare now preparing to perform another VLBI experiments. The one of the candidate targets is
HAYABUSA, which was developed to investigate
asteroids (see Figure 3).
HAYABUSA was launched on May 9 2003,
and has been ﬂying steadily towards an asteroid
named “Itokawa,” after the late Dr. Hideo Itokawa,the father of Japan’s space development program.
HAYABUSA is traveling through space using an
ion engine. It will orbit the asteroid, land on it,
and bring back a sample from its surface[3].
First, we evaluated the signal intensities of thecandidate quasars to perform the diﬀerential VLBI
experiments. We selected 24 quasars from the
ICRF catalog considering the HAYABUSA trajectory during September 1 to December 31, 2003.
The separation angles between the HAYABUSA
and the quasars are less than 10 degrees at each

Figure 4. Trajectory of the HAYABUSA spacecraft(circles) and nearby radio sources (solid squares)
from September 1 to December 31 2003.

4.

Planed Activities

We have to carry out additional works to achieve
our ﬁnal goal as follows:• Development of the analysis software for the
spacecrafts positioning using phase delay observables• Improvement of the ﬁnite distance VLBI
model to expand its capability in a positioningof the low earth orbit satellites

November 2003

33

Table 1. Signal to noise ratio of the detected quasar fringes nearby HAYABUSA spacecraft during Sep.
1 to Dec. 31, 2003. 3C454.3 and 3C84 are reference sources to check the quasar fringe.
source name
3C454.3(Ref.)
1748-253
1817-254
1908-201
1921-293
1920-211
1936-155
1958-179
2008-159
2037-253
2126-158
2128-1232143-156
2155-152
2229-1722216-038
2223-052
2227-088
2233-148
2243-123
2252-090
2254+024
2318+049
2320-035
2335-027
3C84(Ref.)

integ. time (sec.)
60
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
600
60

• Improvement of processing speed and eﬃciency for the VLBI data correlation using
multiprocessor and high speed network• Development of the diﬀerential VLBI software
package such as the antenna tracking for the
spacecraft, the automatic scheduling of the
VLBI observation, the propagation delay estimation, and so on• Validation of the NOZOMI VLBI experimentsby comparing with R&RR data obtained by
ISAS.

CH1
18.6
8.9
8.4
14.9
57
19.9
7.7
16.4
15
8.5
8.8
27
8.7
16.9
9.8
20.4
29.3
20.9
10
12.9
8.3
9.1
10.8
10.7
8.3
37.1

CH2
19
8.8
8.7
16
59.2
13.6
8
19.5
12.8
8.4
9.9
28.6
8.4
14.3
8.4
21.6
28.8
19.3
8.2
14.7
7.9
8.2
9.6
8.3
9.4
35.7

CH3
21.2
8.6
8.6
10.3
53.7
13.8
9.2
16.4
13.9
8.4
8.5
26.4
7.7
13.3
8.9
22
27.4
19.2
7.8
14
8.5
8.3
8.9
8.6
8
29

CH4
21.3
8.2
8
12.3
57.3
12.3
8.5
15.3
15.3
8.3
9.5
25.7
8.5
15.4
8.7
22.5
31
21.7
7.9
12.9
8.7
8
9.4
8.7
8.2
32.8

References[1] Ichikawa et al., VLBI Application forSpacecraft Navigation (NOZOMI) Part I –Overview–, TDC News, No.22, pp 10-11, 2003.
[2] Sekido et al., VLBI Application for Spacecraft
Navigation (NOZOMI) Part II –Delay Model
and Analysis–, TDC News, No.22, pp 12-15,
2003.
[3] JAXA web site, http://www.muses-c.isas.jaxa.
jp/English/index.html, 2003.

IVS CRL-TDC News No.23

34

VLBI Application for Space- 2. Delay Observable
craft Navigation (NOZOMI)For the VLBI experiments of spacecraft NOZOMI, several Japanese domestic VLBI stations– follow-up on Model and Anal- and Algonquin observatory in Canada had joined
ysis –
in the observations. The modulated signal (range
M. Sekido1 (sekido@crl.go.jp), R. Ichikawa1 ,H. Osaki1 , T. Kondo1 , Y. Koyama1 ,M. Yoshikawa2 , and NOZOMI VLBI
Observation Group3
1

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
2
Institute of Space and Astronautical Science
Japan Aerospace Exploration Agency
3-1-1 Yoshinodai, Sagamihara,
Kanagawa 229-8510, Japan
3
JAXA, CRL, NAO, GSI, Gifu Univ.,
Yamaguchi Univ., Hokkaido Univ.,
and CRESTech/SGL
1.

Introduction

Establishment of VLBI application technique forspacecraft navigation is one of our target of current
projects, as we reported in previous issue of IVS
CRL-TDC news [Ichikawa et al., 2003; Sekido etal., 2003]. We are going to brieﬂy introduce current
problems to be solved.

signal) transmitted from NOZOMI spacecraft has
not so wide bandwidth inherently. Consequently,
the accuracy of its group delay observable is not
so high, and long baseline observation is one of theways to increase the angular resolution of the observation.
Longer baseline VLBI observation requires
higher accuracy in a priori delay/rate predictions,since fringe rotates faster and deviation of source
coordinates aﬀects to delay/rate more greatly thanshorter baselines. Actually stable detection offringes on intercontinental baselines (Algonquin
and Japanese domestic baselines) suﬀered fromsome diﬃculty as reported previously [Sekido etal., 2003]. We will discuss more on this problem
in the next section. One of the causes of the problem was deviation of predicted orbit from true one,
although it is inevitable for spacecraft diﬀerently
from normal astrometric VLBI. To enable stable
fringe detection under large delay rate oﬀset, weneed to expand rate window by reducing the integration duration of each bin.
Even the bandwidth of radio signal from spacecraft is narrower than that of quasar, its phase delay observable can be measured with high resolu-

4e-10

Delay Rate (sec/sec)

3e-10
2e-10
1e-10
0

-1e-10-2e-10-3e-10-4e-1006/04 06/04 06/04 06/04 06/04 06/04 06/05 06/05 06/05 06/05 06/05
06:00 09:00 12:00 15:00 18:00 21:00 00:00 03:00 06:00 09:00 12:00

Time (UT)
Figure 1. Diﬀerence of delay rates between observed by Doppler frequency measurements
and theoretical calculation by CRL based on ﬁnite distance VLBI model (cross mark). The
data is on Kashima - Algonquin (9000km) baseline on June 4 2003. Solid line indicatesdiﬀerence of delay rate between predictions of CRL and ISAS.

November 2003
tion if we could resolve the ambiguity. It will provide a beneﬁt to achieve high angular resolution
even with combination of Japanese domestic VLBI
stations. Domestic VLBI stations do not always
have large diameter dishes, so signal to noise ratio(SNR) is not so high. To get higher SNR with weakline spectrum signal, frequency resolution has to be
increased. The simplest way to increase frequency
resolution is extending the time span in Fouriertransformation, although it takes longer time for
Fourier transformation to get higher resolution no
more than one Hertz. In addition, The frequency
received at observatory is drifting due to relative
motion of the spacecraft and observer, and this effect cannot be eliminated at such high frequency
resolution. For this purpose, we are developing acorrelation software speciﬁc for line spectrum tomeasure fringe phase.
3.

Delay rate comparison –CRL,ISAS, andDoppler measurements–

One of the caused of diﬀerence on delay rate between prediction model and observed delay rate,
which is computed by Doppler frequency measurements, had come from deviation of prediction orbitof NOZOMI. The orbit data we used in the previous report (Figure 3 of Sekido et al. [2003]) was
prediction orbit, which was propagated from determined orbit by range and range rate (R&RR)
measurements in February 2003. So the prediction
orbit at this time had larger error. Determined
orbit by R&RR measurements in June was provided afterward. The geocentric angular distance
between predicted and determined spacecraft coordinates diﬀered by around twenty arc seconds. After using the determined trajectory of spacecraft,the discrepancy of delay rates between observed
by Doppler measurements and the theoretical one
has reduced to the half of that before (Figure 1).
However the rate residual still remains about 1.e-10
sec/sec on 9000 km baseline.
ISAS also computed delay rate of VLBI observation based on numerical solution of light time equation for two legs from spacecraft to two observation
stations. The diﬀerence of delay rate between ISAS
and CRL is superimposed with solid line in Figure 1. These independent computations of delay
rate coincide within the order of a few psec/sec.
Since the theoretical computation of delay and delay rate are only for geometrical component, delay
due to radio wave propagation medium will me remain as residual. Although, the diﬀerence of observed delay rate and theoretical one at order of
1.e-10 sec/sec is too large to be explained by propagation medium. It may suggest that determined
orbit still might have error in order of several arc

35

seconds.
References
Ichikawa R., Sekido M., Osaki H., Koyama Y., KondoT., and NOZOMI VLBI group, 2003, “VLBI Application for Spacecraft Navigation (NOZOMI) Part I-Overview-”, IVS CRL-TDC News, No.22, pp.10-11.
Sekido M., Ichikawa R., Osaki H., Kondo T., andKoyama Y., 2003, “VLBI Application for Spacecraft Navigation (NOZOMI) Part I -Delay Model
and Analysis-” IVS CRL-TDC News, No.22, pp.1215.

IVS CRL-TDC News No.23

36

VLBI Observation by Receiv- Table 1. List of radio telescopes involved in the
ing Narrow Bandwidth Signal VLBI observation of NOZOMI.
StationAntenna diameter (m)from NOZOMI
Fuyuhiko Kikuchi (fuyuhiko@miz.nao.ac.jp ),Yusuke Kono, Ping Jinsong, Liu Qinghui,Kazuyoshi Asari, Koji Matsumoto,Seiitsu Tsuruta, Hideo Hanada,
Nobuyuki Kawano, and NOZOMI VLBI
group

USUDA
KASHIMA
MIZUSAWAMIZUSAWA

Table 2. The narrow bandwidth VLBI sampling
and recording system (S-RTP station).

Earth Rotation Division,
National Astronomical Observatory of Japan(NAOJ)
2-12 Hoshigaoka, Mizusawa,Iwate 023-0861, Japan
1.

Introduction

An orbit of a spacecraft (s/c) is usually determined by using coherent 2-way range and rangerate (R&RR) measurements. The range observables are obtained by measuring the round trip
light time between the s/c and the ground tracking station. On the other hand, the range-rate observables are obtained from measurements of the
Doppler shift of the radio signal on coherent 2-way
links by using an onboard transponder. In addition
to R&RR, the VLBI (Very Long Baseline Interferometry) technique can be also used for positioningof the s/c. By measuring the diﬀerence of arriving time of same wave front of radio signal fromthe s/c at two separated antennas, VLBI can determine the angular position of the s/c in space.
VLBI is sensitive to the direction perpendicular toline-of-sight (LOS) direction to the s/c from thetracking station in contrast to the R&RR. Combination of two kinds of observations can improve
the accuracy of orbit determinations.
The VLBI technique has been adopted forthe s/c positioning in the early stage of VLBI.
JPL/NASA VLBI group used VLBI for tracking
Apollo lunar missions and VEGA probes [1]. In
Japan, VLBI method was used to track the geosynchronous satellite in the 1980 s. Recently, in orderto improve this technique and to make it a common method for the s/c orbit determination, we
observed the ﬁrst Japanese Mars explorer ”NOZOMI” by using a regional VLBI network and a
new s/c VLBI tracking method. NOZOMI had
two swing-bys by the earth in Dec. 2002 and June
2003 so as to be injected into a Mars orbit in 2004.
During the period between these two swing-bys,
the onboard high gain antenna could not point to
the earth due to some operational problems. In
this period, R&RR measurements cannot be obtained with suﬃcient SNR. To overcome this problem, the NOZOMI team of ISAS (Institute of Spaceand Astronautical Science) and the VLBI group of
CRL (Communications Research Laboratory) col-

64
34
10
20

Sampling rate:
Quantization:
Number of channels:

200 kHz
6 bits4laborated to determine the NOZOMI orbit by using VLBI technique [2][3]. The s/c VLBI tracking
group of NAOJ (National Astronomical Observatory of Japan) also took part in the observationfrom 13 to 27 in May 2003. The radio telescopes
involved in this mission are listed in Table 1. In thispaper, the results of the analysis by the method ofcorrelating the NOZOMI carrier waves are shown.
2.

Back-end system and correlation software

In radio astronomical and/or geodetic VLBI surveys, usually wide bandwidth signals (from several MHz to GHz) are recorded by fast samplingrate systems, especially for obtaining the accurategroup delay, which depends on signal bandwidth.
In contrast with above systems, when applying the
VLBI technique for the s/c orbit determination, it
is not eﬀective for the s/c to generate and emitsuch a wide bandwidth signal or for ground system to record and real-time process such a wide
bandwidth signal. Usually, the s/c transmits narrow bandwidth downlink carrier wave and/or themodulated carrier wave. The group delay and delay rate should be obtained from the narrow bandwidth signals so as to get the instantaneous angle of the s/c and the angle variation in space.
For this reason, we have developed a narrow bandwidth VLBI sampling and recording system, called
S-RTP station, for the s/c VLBI tracking [4][5].
The detail performances of this system are listed inTable 2. This system has been used for NOZOMI
observations.
The sampling rate of our system is very slow,
therefore the amount of sampling data is smallenough for correlation by a common used PC. For
this system, correlation software has been also developed. The software is composed of modules of
VLBI delay estimation and cross-correlation which
includes the bit-shift and fringe- stopping. In a
conventional correlator, delay is calculated on anNovember 2003

37

assumption of plane wave coming from the radiosources. We modiﬁed the delay model of plane
wave by spherical one for tracking of the s/c nearfrom the earth[6]. The predicted propagation
time from the s/c to the reference station is expressed by following equation.
|Rsc (t − τref (t)) − Rref (t)|(1)τref (t) =cwhere Rsc (t) is the predicted position vector of thes/c every 1 minute which was distributed by ISAS,
and Rref (t) represent the position vector of the reference station. t is the time based on the reference
station, and c is the velocity of light. τref (t) is
obtained in iterative procedure as follows.

i|Rsc t − τref(t) − Rref (t)|
i+1
(2a)
τref
(t) =
c
|Rsc (t) − Rref (t)|
0
τref
(2b)
(t) =
c
0
τref
(t) is an initial value of τref (t). On the other
hand, the propagation time from the s/c to theslave station is expressed by following equation.
τslv (t) =|Rsc t − τref (t) − Rslv t − τref (t) + τslv (t) |c(3)where Rslv (t) is the position vector of the slave
station and τref (t) is given from the Eq.(1). τslv (t)is obtained in iterative procedure as well as τref (t).
Finally the geometric delay between the reference
and the slave station is obtained as follows.
τg (t) = τslv (t) − τref (t)3.

Signals of NOZOMI(4)

Figure 1. Block diagram of narrow bandwidth receiving system.
4.

Results of Correlation

4.1

Estimation of Residual Fringe Phase

The correlation was done by software of FX
mode. At ﬁrst, the signals of the slave station
were bit-shifted and fringe-stopped by using thedelay predicted by Eq.(4). Then, the signals of
the reference and the slave stations were crosscorrelated during each parameter period (PP). In
NOZOMI mission, a C/N of the signal recorded at
the ground station was too low, so we use only ±30Hz around the center frequency of the signals toincrease the signal-to-noise ratio (SNR). The resulted residual fringe phases of the carrier waves
and two range tones for USUDA64-KASHIMA34
baseline are shown in Figure 2. The residual fringe
phases of carrier wave were obtained every 1.3 second PP, and SNR was 21. Its standard deviation
was 10 degrees, which means that the position of
NOZOMI can be determined with an accuracy of
30m assuming that the baseline is 200km and the
distance between NOZOMI and ground station is
6×106 km. However, an ambiguity of 2nπ (n is integer) is still included in the residual fringe phase.
On the other hands, because the C/N of the range
tones were less than carrier wave, we could obtain
the residual fringe phase only for the USUDA64KASHIMA34 baseline. Moreover, the transmissionof NOZOMI was divided into 2 modes, A and B.
In the mode A, the ambiguity tones were added
to the range tones and decreased the C/N. So theresidual fringe phases of range tones were not obtained for this period of 60 seconds (see A of Figure2). On the contrary, the ambiguity tones were notadded in the mode B and the residual fringe phasesof range tones were obtained in this period of 40
seconds, and SNR is 13. Therefore the group delay
analysis could only be done during the mode B.

Between two swing-by events, the downlink signal from NOZOMI was modulated for R&RR measurements. In ranging mode, downlink signal was
consist of a carrier wave, two range tones, and someambiguity tones. The carrier frequency fcarrier of
NOZOMI is 8411MHz. The range tone frequencies are fcarrier ± fcarrier /212 (fcarrier /212 is about
515kHz). The ambiguity tones whose frequencies
are fcarrier ± fcarrier /2n+12 (n =1,2…) are added
every 100 seconds for 60 seconds to solve the ambiguity of the range tones. In order to resolve theambiguity of phase measurement by using groupdelay, the carrier wave and two range tones wereseparately recorded in 3 channels of S-RTP station.
Moreover, to compensate the phase diﬀerence between channels of the video converter, the phasecalibration signals at every 60kHz were mixed with
the IF signals in front of the video converter. For
calibrating the clock oﬀset and clock rate between
two VLBI stations, several QSOs with position precisely known were also observed before and after
the tracking of NOZOMI. The signals were also 4.2 Estimation of Group Delayrecorded with IP-VLBI system at the same time
Before analyzing group delay, the eﬀect of the[2][3]. Block diagram of narrow bandwidth receiv- separate band has to be removed from the residual
ing system is shown at Figure 1.

IVS CRL-TDC News No.23

38

Figure 2. Residual fringe phases of the carrier wave
and two range tones.

Figure 4. Group delays of NOZOMI signal.
The NOZOMI signal was too weak in this observation, however, it can be expected that the accuracy of the group delay would be improved to 9nsec
when the SNR of received signal is 100.
5.

Conclusion

The s/c VLBI tracking group of NAOJ participated in the VLBI observation of NOZOMI. In thismission we recorded three carrier wave signals byusing narrow bandwidth sampling and recording
system, and correlated these signals by using softFigure 3. Detected fringe of NOZOMI.
ware method. The group delay was obtained every
100 seconds with standard deviation of 41 nsec.
Due to the very low C/N, this result is not accufringe phase as following,rate enough for orbit determination of NOZOMI
precisely, but we conﬁrmed the validity of our new
ref

slv
∆φi = ∆φi − φpcal,i − φpcal,i (i = 1, 2, 3)(5) hardware and software VLBI systems. It is also
conﬁrmed that our new VLBI system has a capawhere ∆φi is the residual fringe phase of ith chan- bility of precise s/c tracking within the error of aslv
nel and φrefpcal,i and φpcal,i are the phase of phase few nsec when SNR is about 100.
cals of the channel, respectively. The group delayof the signals are given by,
References∆τgroup delay =∆φi+1 − ∆φi
2π(fi+1 − fi )(6)

where fi is the carrier frequency of ith channel.
The result of group delay is shown in Figures 3
and 4. Its standard deviation was about 41 nsec.
This error could be caused by the thermal noiseof all the R&RR systems including the low-passﬁlter. The clock oﬀset and clock rate were estimated from the observation of some QSOs by IPVLBI through the conventional correlation. The
estimated clock oﬀset was 8.1 × 10−7 seconds andclock rate was −2.6 × 10−13 seconds/second. After the corrections of clock oﬀset and clock rate,
we compare the geometric delay obtained by abovegroup delay analysis with the result of the VLBI
group of CRL [2][3]. It was noticed that an average diﬀerence of delay was 58 nsec. This diﬀerence
may result from the diﬀerence of video converter
used at KASHIMA station and the diﬀerent geometric delay models used by diﬀerent groups.

[1]Sagdeyev, R.Z, et al., Diﬀerential VLBI measurement of the Venus atmosphere dynamics by balloons:
VEGA project, A&A, 254, pp.387-392, 1992.
[2]Ichikawa, R., M. Sekido, H.Osaki, Y. Koyama, T.
Kondo, and NOZOMI VLBI group, VLBI application for spacecraft navigation(NOZOMI) part Overview-, TDC News No.22, pp10-11, 2003.
[3]Sekido, M., R. Ichikawa, H.Osaki, T.Kondo, andY. Koyama, VLBI application for spacecraft navigation (NOZOMI) part –Delay Model and Analysis–,
TDC News No.22, pp12-15, 2003.
[4]Kono, Y., H. Hanada, K. Iwadate, H. Araki, N.
Kawano, Y. Koyama, and Y. Fukuzaki, The diﬀerential VLBI Observation of Lunar Prospector, IVS
2000 General Meeting Proceedings, pp346-349, 2000.
[5]Kono. Y., Precise three-dimensional positioning ofspacecraft by multi-frequency VLBI and Doppler
measurements, Dr. thesis, the Graduate University
for Advanced Studies, 2002.
[6]Fukushima, T., Lunar VLBI observation model,
A&A, 291, pp.320-323, 1994.

November 2003

39

Orbit determination of space- because we can plan more ﬂexible missions. MoreNOZOMI has a serious trouble since April
craft in deep space by Delta- over,
2002, and we are under the situation that we have
VLBI technique: current situ- to establish a new method for orbit determination
for NOZOMI. That is the method using Deltaation and future
VLBI technique.
Makoto Yoshikawa1 (makoto@pub.isas.jaxa.jp),
Takaji Kato1 , Tsutomu Ichikawa1 ,Hiroshi Yamakawa1 , Jun’ichiro Kawaguchi1 ,Yasuhiro Murata1 , Takafumi Ohnishi2 ,Shiro Ishibashi2 , Shigeo Tsujimoto2 ,Katsutoshi Kurosu2 , and NOZOMI
Delta-VLBI group3

In this paper, we show the results of Delta-VLBI
observations for NOZOMI, and we mention about
our future plans.
2.

Delta-VLBI observation for NOZOMIThe Japanese Mars Explorer NOZOMI was
launched in July 1998. In the original plan, it
would have arrived at Mars in October 1999. The
original orbit plan is shown in Fig.1. However,1
Japan Aerospace Exploration Agency
when the spacecraft left from the earth to Mars,
Institute of Space and Astronautical Science
there occurred a problem and the orbit plan was
3-1-1 Yoshinodai, Sagamihara,
forced to change (Fig.2). In this new plan, NOKanagawa 229-8510, JapanZOMI will arrive at Mars at the beginning of 2004
2
Fujitsu Limted
after two earth swingbys. Anyway, at this schedule
1-9-3 Nakase, Mihama-ku, Chiba 261-8588,
change, there was no problem for the orbit deterJapan
mination of NOZOMI, and we were going to deter3
JAXA, CRL, NAO, GSI, Gifu Univ.,
mine its orbit by the conventional RARR method.
Yamaguchi Univ., Hokkaido Univ.,(At present, NOZOMI is on the orbit that arrives
and CRESTech/SGL
at Mars at the middle of December 2003.)
Another problem occurred in July 1999. The S
1. Introduction
band down link was stopped. NOZOMI has S andAt present, we are operating two interplanetary X bands, so X band was used for down link since
spacecrafts. They are “NOZOMI”, Mars explorer then. Therefore, this trouble was not so serious
of Japan and “HAYABUSA”, an asteroid sample for the communication with NOZOMI, but fromreturn mission. In order to determine their or- the point of the orbit determination, this trouble
bits, we use a conventional method using range and causes some problems. One of the problems is arange rate (RARR). In addition to this method, we small acceleration associated with the reorientation
have strong hope to use Delta-VLBI technique for of NOZOMI. X band uses the high gain antenna,
so we need rather frequent attitude maneuvers to
the orbit determination.
The orbit determination by using Delta-VLBI point it to the earth. Acceleration occurs at eachtechnique is very promising, because the accuracy attitude maneuver, and it makes the orbit deterof the orbit determination will be much better and mination rather diﬃcult.
There is another problem, which is much morediﬃcult. We found that in some period between the

Figure 1. Original orbit plan of NOZOMI.

Figure 2. New orbit plan of NOZOMI.

IVS CRL-TDC News No.23

40

tion (Fig.3).
We tried both RARR method and Delta-VLBI
method for the orbit determination for these twoswingbys. As the result, we managed to determine
the orbit of NOZOMI by RARR method accurateenough to carry out these swingbys. Because of theconstraint of the attitude control of NOZOMI, thetracking data was taken by using not main beam of
the high gain antenna but its side lobe for the mosttime. Therefore the Doppler data was not normal
and it has strange bias. We developed a special
technique to use such unusual Doppler data for theorbit determination by RARR.
As for the Delta-VLBI, we did many observations. And we were able to derive the delay timeby carrying out correlation analysis. However, theresults have rather large scattering (about several
10 nsec) and systematic error as shown in Figs.47. These ﬁgures show the O-C of the delay time,
Figure 3. The trail of NOZOMI at the second earth
where “O” is Delta-VLBI observation results whichswingby. This photograph was taken at June 19,
were analyzed by Communications Research Labo2003, 11:39:16 UTC by Mr. Akimasa Nakamura at
ratory (CRL) and “C” is calculated values based on
Kuma Kogen Astronomical Observatory in Ehime
the orbit determination result by RARR method.
prefecture in Japan. The trail of NOZOMI is seen
We tried to determine the orbit of NOZOMI by
faintly at the center. The ﬁeld of view is 12 arc
using these Delta-VLBI data, but the results wereseconds, and the exposure time is 12 seconds. The
not good. We think the reason is the large scattermagnitude of NOZOMI is about 15 or 16.
ing of the data. We will carry out further analyses
to solve this problem.
two earth swingbys it is diﬃcult to get the range
data, because we cannot make the attitude of NOZOMI to point its high gain antenna to the earth.
This is one of the reasons why we started to consider the use of Delta-VLBI technique to the orbit
determination of NOZOMI.
And then the most serious problem occurred in
April 2002. By strong solar ﬂare one of the power
units was stopped, and we could not get the telemetry from NOZOMI. Moreover we could not control
its attitude and orbit. After this trouble, many attempts were done and ﬁnally we were able to getsome information from NOZOMI and to control theattitude and orbit by some special methods. But
we could not put the attitude of NOZOMI at thedesirable one to get range and Doppler data. So
sometimes we could not get range and/or Doppler
data, and this made the Delta-VLBI method much
more important.
Under this very critical situation, the two earth
swingbys (on 21 December 2002 and 19 June 2003)
were carried out successfully. At the earth swingbys, we asked several observatories in Japan to observe NOZOMI. And at the second swingby, oneof the observatories succeeded to take the imageof NOZOMI. Fig.3 shows the trail of NOZOMI,
which was taken at the predicted time and posi-

3.

Future plans

Although the attempt to carry out the orbit determination of NOZOMI by Delta-VLBI technique
has not been successful yet, we would like to continue to try this method much further. Of course
ﬁrstly we are going to analyze the data for NOZOMI further. In addition to NOZOMI, we haveanother spacecraft, that is HAYABUSA (Fig.8).
HAYABUSA, which is the spacecraft for theasteroid sample return mission of Japan, waslaunched on 9 May 2003, and it will arrive at anasteroid in 2005. It has a special engine called “ionengine”. The thrust level of the ion engine is notlarge but it works continuously. Such low continuous thrust makes the orbit determination rather
diﬃcult. We would like to try Delta-VLBI technique for the orbit determination of HAYABUSA
as well as the RARR method.
We have another plan related Delta-VLBI. In
Japan, a new organization for space activity has
started since October 2003. This organization
is called Japan Aerospace Exploration Agency(JAXA). In JAXA, there is only one VLBI station, that is Usuda Deep Space Center. Up tonow, Delta-VLBI observations for spacecraft havebeen carried out in collaboration with other organizations, such as CRL, NAO (National Astro-

November 2003

41

Figure 4. O-C of delay time taken by IP-VLBI system on Dec. 21-22, 2002. The baseline is KashimaUsuda (above) and Kashima-Gifu (below).

Figure 5. O-C of delay time taken by K4 system on Dec. 21-22, 2002. The baseline is Kashima-Usuda(above) and Kashima-Gifu (below).

nomical Observatory of Japan), GSI (Geographical
Survey Institute of Japan), Gifu university, Yamaguchi university, Hokkaido university, and Canada(CRESTech/SGL). Such collaboration is very important and we would like to continue this wide
collaboration. However it is also important tohave Delta-VLBI facilities in JAXA itself, because
Delta-VLBI should be used in the daily tracking aswell as emergency tracking. Therefore, at present
we have just started to consider the possibility of
installing the Delta-VLBI facilities at Uchinoura
Space Center. If this is possible, JAXA has two
VLBI stations, Usuda and Uchinoura.
We studied how much the Delta-VLBI between

Usuda and Uchinoura can make the accuracy ofthe orbit determination better. One of the results
is shown in Fig.9. This is for a certain periodof HAYABUSA, where Doppler data is not eﬀective for the orbit determination. This result showsthat the Delta-VLBI with the baseline of UsudaUchinoura is quite eﬀective for the orbit determination.
As a summary, we say again that the Delta-VLBI
method is very promising for the orbit determination of spacecraft in deep space. We have done
many Delta-VLBI observations for NOZOMI, andwe were able to get delay time as the result. However, we have not been successful to use the Delta-

42

IVS CRL-TDC News No.23

Figure 6. O-C of delay time taken by IP-VLBI systemt on Jan. 10, 2003. The baseline is UsudaKoganei(◆),Usuda-Gifu(2), and Kashima-Usuda ().

Figure 7. O-C of delay time taken by IP-VLBI system on May 22-27, 2003. The baseline is KashimaTukuba (•), Kashima-Usuda (), Usuda-Tsukubai (■),Usuda-Yamaguchi (◆).

Figure 9. Analysis of position accuracy. The datalabeled “UDSC” indicates the accuracy obtained by
RARR method using only Usuda station. The datalabeled “1d”, “3d”, and “5d” mean that DeltaVLBI data is also included for the RARR orbit deVLBI data for the actual orbit determination. We
termination and the number is the number of data
will continue our work and we hope we can espasses of Delta-VLBI observation. The data latablish new orbit determination method by using
beled “udsc+snt” indicates the accuracy by RARR
Delta-VLBI technique.
method using Usuda and Santiago stations. FourWe are grateful to the many people and organidiﬀerent baselines were analyzed: Usuda-Kashimazations for their kind and devoted help.
(◆), Usuda-Mizusawa (×), Usuda-Uchinoura (),and Usuda-Canberra (■).
Figure 8. HAYABUSA (MUSES-C) mission. (byA. Ikeshita / MEF / ISAS).

November 2003

43

Present Status of Gravimetric
Missions in SELENE/RISE
Hideo Hanada1 (hanada@miz.nao.ac.jp),
Takahiro Iwata2 , Noriyuki Namiki3 ,Koji Matsumoto1 , Seiitsu Tsuruta1 ,Toshiaki Ishikawa1 , Kazuyoshi Asari1 ,Hirotomo Noda1 , Yusuke Kono1 ,Jinsong Ping1 , Qinghui Liu1 ,Fuyuhiko Kikuchi1 , Kousuke Heki1 ,Nobuyuki Kawano1 , and RSAT/VRAD
group
1

National Astronomical Observatory,
2-12 Hoshigaoka, Mizusawa,Iwate 023-0086, Japan
2
Japan Aerospace Exploration Agency,
2-1-1 Sengen Tsukuba, Ibaraki 305-8505, Japan
3
Kyushu University,
6-10-1 Hakozaki, Higashiku,
Fukuoka 812-8581, Japan
1.

Introduction

In SELENE project which is Japanese lunar exploration using H-2A rocket with the launch of
2005, we have two gravimetric missions, RSAT and
VRAD. RSAT mission consists of 4-way Doppler
measurement of a main orbiter through a relay
satellite in addition to 2-way Doppler and ranging measurements of the satellites and it realizes a
direct observation of gravity ﬁelds in the far side of
the Moon for the ﬁrst time. VRAD mission, on theother hand, consists of observations of orbits andgravity ﬁelds of the Moon by VLBI and it makes
three dimensional observations of orbits in cooperation with RSAT for the ﬁrst time. We will obtaina highly accurate lunar gravity model by the new
methods and will investigate property of the lunar
core and elastic property of the lunar crust referring to LALT (Laser Altimeter in SELENE) and
LLR (Lunar Laser Ranging) data as well as the
new gravity data.

Figure 1. Concepts of gravimetric missions. Upper: RSAT, lower: VRAD.

S to X-band at Rstar is measured at UDSC (4way Dopler measurement) in RSAT mission. Two
way Doppler measurement of the signal directly returned from Rstar as well as ranging of Rstar are
also carried out for determination of independent
motions of the two satellites.
Three carrier waves in S-band and one in X-band
which are emitted from Rstar and Vstar are used
for VLBI measurement of the satellites in VRAD
mission. A multi-frequency VLBI has been proposed for the purpose of precise positioning using
the phase delay and the optimum frequency spacing for three frequencies in S-band, 2212, 2218 and
2287 MHz, and one in X-band, 8456MHz, has beenobtained [Kono et al., 2002]. This method uses carrier waves of lower power consumption instead ofnoise and is appropriate for positioning of a space2. RSAT/VRAD Mission
craft. It has been shown by VLBI experiments usThere are two sub satellites, a relay satellite
ing carrier waves from Lunar Prospector that mea(Rstar) and VRAD satellite (Vstar) in SELENE
surement error of phase delay of the carrier waves
and they are separated from a main orbiter when
was possibly less than 10 degrees which was equivit has a semi-major axis of 3000km and 2,200km,
alent to positioning error of about 20cm on therespectively. Usuda Deep Space Center (UDSC)
Moon. Concepts of the gravimetric missions aretransmits S-band uplink signal to Rstar and a partshown in Fig. 1 [Iwata et al., 2002].
of it is returned and the rest is forwarded to themain orbiter. Doppler shift of the signal going from 3. Instruments for RSAT/VRAD Mission
UDSC to the main orbiter via Rstar and coming
Instruments used for 2-way Doppler and ranging
back in the same way but being converted frommeasurements are S/X-band cross dipole antennas,

IVS CRL-TDC News No.23

44

S-band transponders, S-band diplexers, S-band hybrids, telemetry and command units and they areonboard both Rstar and Vstar. We have also two
radio sources for VLBI onboard both Rsatr and Vstar. In addition to them, an S/X-band transponder, an S-band power ampliﬁer, an X-band power
ampliﬁer, S-band omini antennas, S-band switches
and S-band band pass ﬁlters on board Rstar andan S-band transmitter/receiver, an S-band diplexer
and an S-band hybrid onboard the main orbiter areused for 4-way Doppler measurement.
We have completed designing and manufacturing of ﬂight model for RSAT/VRAD mission andhave begun performance test combined with the
sub satellites Rstar and Vstar. S-band omni antennas newly developed for RSAT mission has experienced performance test under low temperatureand phase pattern test. Total system for 4-way
and 2-way Doppler measurements including instruments onboard and ground system was evaluatedin March of 2003 at UDSC and the expected accuracy was achieved. Rstar and Vstar themselves
have experienced mechanical and thermal test andno special problem was arose. A separation and rotation mechanism for Rstar and Vstar which was
also newly developed showed good performance onboard µ-Lab Sat.

5.

Observation Schedule

The gravimetric mission consists of 4-way
Doppler measurements (FWD), diﬀerential VLBI
observations (VRAD), 2-way Doppler and ranging observations (RSRD) and telemetry and command operation (TCM). Besides, there is a standby
mode (STBY) when battery power of the satellites
is not enough. Number of operations which canbe conducted at once is restricted due to supplied
power. We cannot do anything else when we carryout FWD operation. RSRD or TCM can be collaborated with VRAD operation provided that thesatellites is fully lit by the sun.
FWD has ﬁrst priority over any other mission
because a chance of communications among two
satellites and the Earth is very limited and because
it is operated only when the main orbiter is in thefar side. . Observation schedule is made considering the following conditions: 1) whether Rstar andVstar are seen from the Earth, 2) whether the main
orbiter is in the far side of the Moon, 3) whether
Rstar and Vstar are lit by the sun, 4) whether communications among the main orbiter, Rstar and theEarth are possible, 5) whether batteries are fully
charged, 6) whether temperatures in Rsat and Vstar are in an appropriate range, etc.
We make a plan to conduct double intensive observations
each of which consists of one month pe4. Ground System for VRAD Mission
riod under participation of foreign stations. The
Carrier waves in S and X bands received by domestic network VERA will take part in VRADa VLBI antenna are converted to video signals mission for the whole mission period of one year.
by a video converter in the K-4/Mark-III system We are developing an international network forand they are recorded either by the K-4/Mark-III VRAD mission from the points view of baseline
system like conventional VLBI experiments or by length in north-south and east-west directions, anda narrow band recorder especially developed for BKG Wettzell, Shanghai Astronomical ObservaVRAD experiments. The narrow band recorder (S- tory, Urumqi Astronomical Observatory and HoRTP Station, System Design Service Corp.), con- bart Observatory are expected to constitute thesisting of 4 channels for the video signals and one international network. It is necessary to make adfor a reference clock signal, samples and digitizes justments of machine time between the VLBI stathe video signals at 200kHz intervals with 6 bit res- tions including VERA.
olution. Seven narrow band recorders are prepared
for VRAD mission and they will be distributed to 6. Improvement in Gravity Modeldomestic stations belonging to VERA and foreign
There are serious problems in gravity models obstations which will participate in VRAD mission.
tained so far: 1) only 2-way Doppler measurement
We are developing software which controls local
is used, 2) there is no direct observation of gravity
frequencies in a video converter by 10kHz steps andﬁeld of the far side (Ill-posed problem). A-prioriattenuators by 1dB in order to put the video signals
constraint is necessary due to no far side data andwhich are aﬀected by Doppler shift into the narrowlarge error is expected in the far side accordingly.
band channels of 70kHz with appropriate levels.
Gravity anomaly near lunar rim, on the other hand,
Cross correlation procedure for determination of
may not be correctly estimated. It is because senphase diﬀerences is also developed and is evaluatedsitivity of Doppler measurement from the Earthby comparing results obtained by diﬀerent software
for motion of a satellite perpendicular to the lunar
with identical data.
surface is very low and there is no other Doppler
measurement in the direction perpendicular to thesurface in the rim region

November 2003

45

These problems will be solved and a new grav4) Development of software for operation andity model will be obtained by RSAT/VRAD miscorrelation of VLBI measurements,sion. Accuracy of the gravity ﬁeld will be im5) Development of data base system,
proved for wide range by tracking of 3 satellites
of diﬀerent altitudes, accuracy in the far side will6) Development of receiving and recording sysalso be improved by 4-way Doppler measurements,
tem for VLBI dataand gravity anomaly near rim region will be estimated correctly by three dimensional observations
cooperated with Doppler and VLBI measurements. References
Simulations show that accuracy of the new gravity
model is better than the present model by more Iwata, T., Sasaki, T., Kono, Y., Hanada, H., Kawano,N., Namiki, N., Results of the critical design for thethan one order [Matsumoto et al., 2002].
7.

Summary

selenodetic mission using diﬀerential VLBI methods
by SELENE, Proc. 2nd. IVS General Meeting, 377380, 2002.

For the gravimetric mission is SELENE, we have
Kono, Y., H. Hanada, N. Kawano, K. Iwadate, Y.
carried out the following items:
1) Performance test of instruments on board,2) Development of software for scheduling andtelemetry monitoring,3) Adjustment of schedule for VERA and international VLBI network,

Koyama, Y. Fukuzaki, Precise positioning of spacecrafts by multi-frequency VLBI, Proc. 2nd. IVSGeneral Meeting, 179-183, 2002.

Matsumoto, K., K. Heki and H. Hanada, Global lunar
gravity ﬁeld recovery from SELENE, Proc. 2nd. IVSGeneral Meeting, 381-385, 2002.

IVS CRL-TDC News No.23

46

Black Hole Imager,
Pre-Horizon Telescope
In the Southern Hemisphere
Makoto Miyoshi1 (miyoshi@miz.nao.ac.jp),
Jose K. Ishitsuka1 , and Shinji Horiuchi2
1

National Astronomical Observatory, Japan
2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan
2
Center for Astrophysics and Supercomputing,
Swinburne University of Technology
Mail stops 31 P. O. Box 218 Hawthorn,
Victoria, 3122 Australia
1.

Introduction

Imaging black hole systems is one of the ﬁnal
goals in VLBI astronomy. For this purpose, SgrA*,
the massive black hole at our galactic center is thebest target because of the apparent size of blackhole system is the largest of all, for example, theblack hole shadow (=about 5Rs) is more than 30
micro arc seconds in diameter, actually the largest
one among those of known black hole candidates.
Recent observations indicate 3.7 × 106 M as theblack hole mass of SgrA* (Schödel et al. 2002). If
accepted the value, the black hole shadow is morethan 45µ as in diameter. However the scattering
eﬀects by surrounding plasma have blurred the intrinsic black images and then previous cm-VLBI
observations of SgrA* could not reach the true face
so far. In order to escape from the eﬀects, weshould accomplish mm to sub-mm VLBI observations of SgrA*. Here we show uv- simulations forchecking imaging performance of several hypothetical arrays. First we show the case of 86GHz groundbased VLBI whose spatial resolution is quite insufﬁcient for resolving the black hole shadow but hascapability for imaging jet eruptions if occur, andthen show the case of 230GHz VLBI. The best array conﬁguration is the inversed VLBA location
at the southern hemisphere (called E-array here),
while the realistic sub-mm array composed of 5 stations show bad image results though important information will be obtained from visibility analysis.
We adopted here the previous estimated mass of
2.6 × 106 M (Ghez et al. 2000) and the corresponding shadow size of 30µas in diameter.
2.

Assumed arrays for simulations

Here we select the following 6 array conﬁgurations for simulations of testing performance for
SgrA∗ imaging.
• Array A: the present VLBA (NRAO) including 10 of 25-m dishes. The adopted sensitiv-

ities at both 86GHz and 230GHz are basedon typical system temperature ∼150K (except
MK, 100K for MK) and antenna eﬃciencies∼0.2 for real 86GHz conditions. Needless tosay, the actual VLBA antennas have neither
230GHz receivers nor suﬃcient antenna surface accuracy. This is only for conﬁguration
simulations.
• Array B: the VLBA plus a virtual station located at Huancayo in Peru. The virtual Huancayo antenna is 25-m in diameter with eﬃciency of 0.7 for both frequencies. The assumed system temperature is 100K. The location is in lat.12.0375 ◦S. in long. 75.2942 ◦W.
, 3375-m in altitude.
• Array C: the VLBA plus the Huancayo stationand the ALMA in Chile. As phased ALMA,
we adopted 70-m in diameter with eﬃciencyof 0.7 for both frequency. The assumed system temperature is 80K. The location is in lat.
23◦ S. in long. 67.4◦W. , 5000-m in altitude.
• Array D: the VLBA plus the Huancayo station, the ALMA and the SEST (ESO) in Chile.
SEST is 15-m in diameter with eﬃciency of
0.8 for both frequencies, which is better than
the real. The assumed system temperature is
100K, also better than the real. The location
is in lat. 29.25◦ S. in long. 70.733◦W. , 2400-m
in altitude.
• Array E: the SMA (CfA & ASIAA) in Hawaii,
CARMA in eastern California, the Huancayo,
the ALMA and the SEST (ESO) in Chile.
These except for Huancayo are actually realistic stations for performing 230GHz VLBI for
SgrA*. The SMA and the SEST are now operation, while the CARMA and the ALMA are
under construction. Here we adapted phased
SMA is corresponding to 25-m in diameterwith eﬃciency of 0.6. The system temperature
is assumed 100K here. For CARMA as phasedmode, 30-m in diameter with eﬃciency of 0.6,
and system temperature of 150K are assumed.
• Array F: the inversed VLBA, located at thesouthern hemisphere. Except locations of stations, all parameters are common as those of
Array A.
Figure 1 shows the uv-coverage of above 6 arrays
at 86GHz. The uv-coverage of VLBA (Array A)
in is notoriously worse in north-south direction for
SgrA*(Fig1. a). Adding stations in South America
reinforces the north-south coverage of the VLBA
alone (Fig.1. b, c, d). The uv-coverage of Array E
for SgrA* is large but quite sparse (Fig. 1 e). The

November 2003

47

Figure 1. The uv coverage of each array for SgrA* (86GHz).

Figure 2. The dirty beams of the arrays for SgrA*. The scale is 1.5mas (0.56mas) in each side for
86GHz (230GHz).
corresponding synthesized beams (or dirty beams)
are shown in Figure 2. As expected judging fromthe sharpness of main beam, the spatial resolutionsof array B, C, and D are about three times better indeclination than that of array A. The main beamof array E is certainly small but also exists side
lobes with quite high peak comparable to that ofmain beam. The array F shows high main beamand quite low side lobes as shown in Figure 2 (f).

sub-mm VLBI, we adopted the value as outer diameter while the same size is used for the blackhole shadow (elliptical shape with 30µas×24µas,
PA=80◦). This is a model image for 230GHz simulations (Figure 3a).
4.

Results from Clean

Figure 3 shows the clean results of the 6 arrays.
With each array we can recognized the jets eruption (0.5 mas in length) if occurs. Array A, namely
3. Image models for SgrA* at 86GHz andthe VLBA fails to recognize the cone shape that
230GHzwidening towards the end while other arrays deWe used two kinds of model images for SgrA*. tecting the widening though the performance difOne is for 86GHz simulation while the other is for ferences exist. From the lack of spatial resolutions,230GHz. From visibility analysis of VLBA obser- it seems impossible for ground-based array to ﬁnd
vations at 86GHz, the apparent shape of SgrA* the black hole shadow in SgrA* at 86GHZ evenare modeled as Gaussian brightness distributions without the scattering eﬀect. The adding station(Shen et al. in preparation). From the estimated in South America, Huancayo in Peru for example
size we here adopt Gaussian with major axis of 0.2 to the present VLBA, will improve the spatial resmas and minor axis of 0.15 mas ( PA=80◦) as outer olution three times in declination that is true foredge size. We also put the black hole shadow ( el- all frequencies.
liptical shape with 30µas×24µas, PA=80◦) at the
Figure 4 shows the results of CLEAN at 230GHZ
center. Further cone shape jets (0.5 mas in length) simulations. The images from array A and E are
are added in both sides. Such a jet may be observed not so good while there is a certain dip at the image
if something occurs in SgrA*(Figure 2a).
center from other arrays.
From primitive VLBI observations at 215GHz
the outer size is estimated about 0.1mas in di- 5. Discussions
ameter (Krichbaum et al. 1998). In order to
The best array for imaging of the SgrA* black
test for imaging the black hole shadow or not athole (shadow), at least from these simulations is

48

IVS CRL-TDC News No.23

Figure 3. Clean Results from several array conﬁgurations at 86GHz. The each square size is 1.5mas in
declination and 0.75 mas in right ascension.

Figure 4. Clean Results from several array conﬁgurations at 230GHz. The each square size is 0.25mas
both in declination and in right ascension.
Way, Nature 419, 694-696, 2002 Shen et al. in prepathe inversed VLBA (array F). Namely 8000km inrationextent, 10 in station number, sensitivity at least
the same of the performance 86GHz, location at Krichbaum et al., VLBI observations of the galactic
the Southern hemisphere are required.
center source SGR A* at 86 GHz and 215 GHz,
A&A, 335, L106-L110, 1998
The realistic array composing from 5 stationsSMA, CARMA, SEST, Huancaiyo, and ALMA is not insuﬃcient for imaging itself but visibility
analysis will be very important for detecting blackhole shadow.
We however must mention here that analysis ofsmall amount of visibility from like array E is important for measuring the diameter of black holeshadow and estimating the mass of the black holealthough the uv-coverage is insuﬃcient to get good
synthesis image from them. Actually we can begin
black shadow investigation with visibility analysis
from sparse array. We will report somewhere about
visibility analysis.

References
Ghez et al., The accelerations of stars orbiting theMilky Way’s central black hole, Nature , 407, 349351, 2000
Schödel et al., A star in a 15.2-year orbit around thesupermassive black hole at the centre of the MilkyNovember 2003

49

A 32 m Antenna Projectin PeruJosé K. Ishitsuka1 (pepe@hotaka.mtk.nao.ac.jp),
Mutsumi Ishitsuka2 , Makoto Inoue1 ,Masatoshi Ohishi1 , Kenta Fujisawa3 ,Takashi Kasuga4 , Masato Tsuboi5 ,Keisuke Miyazawa1 (∗) and Shinji Horiuchi6

Initially, the antenna will be tuned to receive
spectral lines of Methyl Alcohol at 6.7 GHz to survey and monitor Young Stellar Objects by smaller
modiﬁcations from the present system. As the surface accuracy of the main dish is better, observations at higher frequencies could be expected in the
future. On the other hand since the antenna location is unique in the southern hemisphere, geodetic
observations at S/X band should be done to measure plate tectonics in South America.

1

National Astronomical Observatory, Japan
Instituto Geofı́sico del Perú, Peru
3
Yamaguchi University, Japan
4
Hosei University, Japan
5
Ibaraki University, Japan
6
Square Kilometer Array, Australia(∗) retired
2

1.

Introduction

By adding a station in southern hemisphere like
Peru, a marvelous improvement in u-v coverage
could be obtained with the VLBA for sources nearequator. Currently a plan is being developed toconvert a 32-m telecommunications antenna used
for INTELSAT in the Peruvian Andes into a radio
astronomy facility operated by the Institute of Geophysics in Peru (IGP) and local universities withassistance from the National Astronomical Observatory of Japan (NAOJ).

2.

Location

The Sicaya antenna station (see Feigure 1) is located on a small hill in a beautiful open ﬂat valley that is similar to Owens Valley in California or
Nobeyama in Japan where world famous radio observatories are located. The Huancayo observatoryof IGP is just 5-km away from the Sicaya antenna
station. The antenna looks still in very good condition without no apparent rust probably due to its
location at 3375 m of high altitude and being far
away from sea side. The structure of the antenna
is well suited to upgrade receivers in future. The
receiver room is on the ground ﬂoor and connectedwith the main antenna dish and sub-reﬂector witha beam transfer reﬂector guide system. That allows us to install the receivers on the ground ﬂoor
and to work on these easily. Here is detail of theantenna that we got from the Japanese company
NEC who made it:

Figure 1. Estación Terrena de Sicaya, Huancayo - Perú.

IVS CRL-TDC News No.23

50

References
Horiuchi, S., D. Murphy, M. Ishitsuka and J. Ishitsuka,“Potential Improvements to VLBA uv-Coverages by
the Addition of a 32m Peruvian Antenna , Future
Directions in High Resolution Astronomy, A Celebration of the 10th Anniversary of the VLBA, Socorro, New Mexico, USA, June, 2003.

Figure 2. uv-Coverages Simulation adding the Peruvian antenna to the VLBA system. (Simulation
made by S. Horiuchi).

Latitude:Longitude:
Altitude:
Built year:
Antenna type:
Diameter of main dish:Frequency band:
Antenna mount:
Antenna moving speed:Surface accuracy:

3.

−12◦ 02 15−75◦ 17 39
3,375 m1984 to 1985
Cassegrain system
105 ft (32m)
6 GHz (transmittion)
4 GHz (reception)
Wheel Track type AZ-EL mount
0.3 degree/s for both AZ and EL
1.09 mm rms (without wind),1.26 mm rms (with 13 m/s wind)

Conclusion

The advantage of the addition of the Sicaya 32-m
telescope in the Peruvian Andes to the VLBA is remarkable especially for low declination and southern declination sources (See Figure 2). Discussions
are now taking place to investigate how to upgrade
this telescope so that both single dish and VLBI observations can be undertaken. However we believethat joining VLBA for VLBI observations is one of
the most exciting aspects of the project. Geodetic
measurements of plate tectonics in the active Andes region will be useful for geophysics and earthrotation sciences, and it would be also a grate contribution for the development of sciences in Peru.

November 2003

51

VSOP-2: a Proposal for a near tection of fringes on baselines to HALCA. Following the successes of VSOP, a near-term next
future Space VLBI Mission
generation Japanese space VLBI mission, curHisashi Hirabayashi (hirax@vsop.isas.jaxa.jp)
Institute of Space and Astronautical Science
Japan Aerospace Exploration Agency
Yoshinodai 3-1-1, Sgamihara, Kanagawa
229-8510, Japan
Abstract: HALCA, the ﬁrst dedicated satellite forspace-VLBI, was launched in February 1997, and
VSOP observations have been successfully undertaken
at 1.6 and 5 GHz. The VSOP-2 mission
bands of 8, 22,
is planned to have frequency
and 43 GHz, with dual polarization, a 1 Gbps
downlink bit-rate, and a phase referencing capability. The mission
proposal will be submitted to
ISAS/JAXA in October 2003, with the earliest
possible launch, if approved, in 2010.
1.

Introduction

The ﬁrst space VLBI experiment with a TDRSS
in 1986 (Levy et al.
satellite was successful1986), paving the way for a dedicated space VLBI
mission. The Institute of Space and Astronautical Science (ISAS) launched the ﬁrst space VLBI
satellite, HALCA, in 1997. HALCA’s orbit has
an apogee height of 21,400 km, perigee height of
560 km, inclination angle of 31 degrees, and orbital
period of 6.3 hours.
In June 1997, the ﬁrst 1.6 GHz images were generated and in July the ﬁrst 5 GHz images were
produced at the VLBA correlator. In April 1998,
22 GHz fringes to HALCA were ﬁrst detected at
Socorro for the ﬂaring water maser in Orion-KL(Kobayashi et al. 2000). HALCA has been operated for the VSOP (VLBI Space Observatory Programme) project in cooperation with many organizations and radio telescopes around the world.
HALCA’s status earlier in the mission has been reviewed by Hirabayashi et al. (1998), Hirabayashi etal. (2000a), and Edwards and Hirabayashi (2001).
Scientiﬁc observations are being routinely undertaken at 1.6 and 5 GHz. VSOP observations aremostly devoted to AGN. Parsec-scale jets and, insome cases, the shadow of plasma disks are visible with VSOP angular resolution. Hydroxyl (OH)masers, pulsars, and X-ray binaries are among
other objects observed. More information about
VSOP is available from the papers referenced above
and from http://www.vsop.isas.ac.jp.
2.

VSOP-2 PlanningA next-generation space VLBI mission Working Group was formed in May 1997 after the de-rently referred to as VSOP-2, is being planned(Hirabayashi et al. 2000b, 2001; Hirabayashi
2003) in collaboration with international partners.
A web page has been establishedat <http://www.vsop.isas.ac.jp/vsop2/> for the
VSOP-2 project.
The VSOP-2 science goals include: study ofemission mechanisms in conjunction with the next
generation of X-ray and gamma-ray satellites; fullpolarization studies of magnetic ﬁeld orientationand evolution in jets, and measurements of Faraday
rotation towards AGN cores; high linear resolution
observations of nearby AGN to probe the formation and collimation of jets and the environment
around supermassive black holes; and the highest
resolution studies of spectral line masers and megamasers, and circum-nuclear disks. Higher observing frequencies, cooled receivers, increased bandwidths and larger telescope diameters will resultin gains in resolution and interferometer sensitivity by factors of about 10 over the VSOP mission.
An angular resolution of approximately 25 microarcseconds at 43 GHz will be achievable, corresponding to about 10 Schwarzschild radii at the
distance of M87.
The VSOP-2 spacecraft will employ a 9 m oﬀaxis paraboloid antenna. The observing bands will
be 8, 22, and 43 GHz. The VSOP-2 satellite will beplaced in an elliptical orbit with an apogee height ofabout 25,000 km and a perigee height of 1,000 km,
resulting in a period of 7.5 hours. Unlike HALCA,
the VSOP-2 satellite will receive both LCP and
RCP, and use cryogenic coolers for the two higher
frequency bands to reduce the system temperature. Observing requires a two-way link between
the satellite and a tracking station, for a wideband
down link at 1 Gbps, and with the uplink used totransfer a reference signal.
The international cooperation and coordination
required for VSOP observations make it one of themost complex space science missions undertaken,
and a lot has been learnt for future space VLBI
missions. A similar level of collaboration will beessential for the success of VSOP-2. Submissionof the VSOP-2 proposal to ISAS will take place in
October 2003 and consequently launch on an ISAS
M-V rocket could be as early as 2010. By the timeof the launch of the VSOP-2 spacecraft a number of
new arrays and telescopes will also be in operation,with 1 Gbps and higher recording widely available.
Thanks to the VSI standard, and the simplicity
of DAT design, and the development of disk-based
recording, compatibility problems should not be as

IVS CRL-TDC News No.23

52

serious as they were for VSOP.
ISAS was merged with two other institutions
to form the Japan Aerospace Exploration Agency(JAXA) in October 2003. However, the VSOP2 mission proposal will be evaluated by the ISAS
Science Steering Committee as for previous ISAS
missions.
3.

could be achieved by adding GPS receivers with ahigh precision 3-dimensional accelerometer, or byusing both GPS and Galileo receivers, according
to simulations performed at JPL for the VSOP-2
orbit.
These new developments for VSOP-2 can be pursued further for the planning of following space
VLBI missions.

New Aspects for VSOP-2

The on-board radio astronomy antenna is oneof the most critical parts of the spacecraft. The
development of an oﬀ-axis mesh antenna with asegmented (modular) radial rib design has beenin progress over the last three years at ISAS. The
backup and deployment structure is based on the
ETS-VIII project antennas, which are scheduled tobe launched in 2006. To achieve a surface accuracy
as high as 0.3 mm (rms), radial ribs will help shape
the surface without too much cable structure. The
radio astronomy receivers for the 22 and 43 GHz
bands will be cooled, which will have appreciable
impact on the spacecraft design.
The frequency for the 1 Gbps VLBI data linkis 37-38 GHz (down-link), and for the (up-link)reference frequency is 40 GHz. The use of bothsenses of polarization will help for the maximum
use of the allocated band. Studies and trade-oﬀs
have been done taking into account both the quantization loss, circuitry complexity, and down-link
power.
Phase-referencing observations remove atmospheric phase ﬂuctuations and consequently can increase the coherence time. Although this capability
was not considered in the ordinal VSOP mission
design successful ‘in-beam’ phase-referencing observations have nevertheless been carried out with
the quasar pairs 1308+326 and 1308+328, separated by 14.3’ (Porcas et al. 2000) and 1342+662
and 1342+663, separated by 4.8’ (Guirado etal.
2001).
Furthermore the VERA array(see http://veraserver.mtk.nao.ac.jp/index.htm) of
the National Astronomical Observatory of Japan(NAOJ), which consists of four 20 m antennas withdual beam systems, will enable phase-referencing
technique to be explored in great depth. VERA isable to observe at all three VSOP-2 bands making
it be a good partner for VSOP-2 co-observing.
Nodding of the whole spacecraft quickly between the calibrator and target sources is possible with the addition of 2 Control Moment Gyroscopes (CMGs) to the 4 momentum reaction wheels(RWs). For phase-referencing observations, orbit
accuracies of 50 cm(8 GHz), 6.5 cm (22 GHz), and
1.8 cm (43 GHz) are required, and to detect watermaser proper motions in AGN requires a 2 cm accuracy. Orbit determination of a few-cm accuracy

4.

Further into the future

A multi-spacecraft mission is attractive for several reasons, providing better (u,v) coverage, better
angular resolution, and good coverage of observablesky. Also, a space-space interferometer would provide better coherence. A two-spacecraft mission,iARISE, has recently been studied in the U.S. (Fomalont et al. 2002). We think that the possibilityof a shared launch of VSOP-2 with another spacecraft, or with a second spacecraft launched separately could be possible options after the approvalof the VSOP-2 mission.
The desire to go to higher frequency bands toprobe the AGN central engine is natural because
the AGN core can be optically thin and also wegain in angular resolution. So, millimeter and submm space-VLBI are also very attractive long future
missions to prove relativistic phenomena related tojets and super-massive black holes. The potentialof sub-mm VLBI has, for instance, been illustrated
for observations of Sgr A* by Falcke et al. (2000).
So, as a near-term mission, launching a spacecraft for sub-mm VLBI with the phased ALMA
array on an experimental basis is another possibility, before a full sub-mm VLBI mission.
There are lots of new areas for space VLBI in thefar future. For space VLBI at sub-mm wavelengths
we need an on-board oscillator and good coherence,
and/or optical communication between the spaceelements, and/or direct correlation in space, etc.
VSOP-2 will serve as a good continuation, and extension, of space VLBI activity, and as the next
step towards more ambitious missions in the future.
References
Edwards, P.G. and Hirabayashi, H. 2001 in New Century of X-ray Astronomy (ASP Conf. Ser. 251) eds.
H. Inoue and H. Kunieda, p. 348
Falcke, H. Melia, F., and Agol, E. 2000, ApJ, 528, L13
Fomalont, E. et al. 2002, Whitepaper submitted toNASA’s SEU roadmap team, http://universe.gsfc.
nasa.gov/docs/roadmap/iarise whitepaper.pdf
Guirado, J.C., et al. 2001, A&A, 371, 766
Hirabayashi, H. et al. 1998, Science, 281, 1825 anderratum 282, 1995

November 2003

53

Hirabayashi, H. et al. 2000a, PASJ, 52, 955
Hirabayashi, H. et al. 2000b, in Astrophysical Phenomena Revealed by Space VLBI, ed. H. Hirabayashi,
P.G. Edwards, and D.W. Murphy (ISAS), p. 277
Hirabayashi, H. et al. 2001, in Galaxies and their Constituents at the Highest Angular Resolutions (IAU
Symposium 205), eds. R.T. Schilizzi, S.N. Vogel, F.
Paresce, and M. Elvis, p. 428

Kobayashi, H. et al. 2000, in Astrophysical Phenomena
Revealed by Space VLBI, eds. H. Hirabayashi, P.G.
Edwards and D.W. Murphy, p. 109
Levy, G.S., et al. 1986, Science, 234, 187
Porcas, R.W., et al. 2000, in Astrophysical Phenomena
Revealed by Space VLBI, ed. H. Hirabayashi, P.G.
Edwards, and D.W. Murphy (ISAS), p. 245

Hirabayashi, H. 2003, in Future Directions in High Resolution Astronomy: A Celebration of the 10th Anniversary of the VLBA (ASP Conf. Ser.) eds. J.D.
Romney and M.J. Reid, in press- News - News - News - News - News - News - News - News - News -Smallest Backend in Preparation
Junichi Nakajima (nakaji@crl.go.jp)
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan
Simply connect your satellite dish and a digital volt meter to the box. Then you will complete
an own smallest radio telescope. The tiny prototype box includes IF ampliﬁer, splitter, detector
and variable gain DC ampliﬁer.
Every summer CRL held scientiﬁc camp for nominated high-school students. The tiny telescope soldering construction is now one of the popular course. CRL received good reputations
to this teaching material, we will release the small backend both in kit and completed unit.
Details of the course and the material will be presented in the next issue of the TDC news. I
may add that the unit can be used instead of worn-out power meter in VLBI site.

IVS CRL-TDC News No.23

54

Developments for the next the cryogenic coolers to reduce the system temperThe onboard sampling frequency is more
space VLBI mission, VSOP-2 ature.
than 1 Gsps.
Sensitivity is ultimately limited by the coherencetime, which becomes increasingly aﬀected by atmospheric ﬂuctuations above the ground telescopes athigher frequencies. Several possibilities for “phasereferencing” to improve sensitivity by extending1
the coherence time are under study. The compariInstitute of Space and Astronautical Scienceson of the speciﬁcations of the VSOP and VSOP-2
Japan Aerospace Exploration Agency
satellites is shown in Table 1.
3-1-1 Yoshinodai, Sagamihara,
Observing frequencies up to 43 GHz will allow
Kanagawa 229-8510, Japan2high angular resolution observations of the optiNational Astronomical Observatory
2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan cally thin emission in many AGN cores. An apogeeheight is 25,000 km will allow an angular resolution
Abstract: As the presentation by Hirabayashi of 38 micro-arcseconds to be achieved at 43 GHz,
(2003) in this proceeding, we are planning VSOP-2 corresponding to around 10 Schwarzschild radii at
mission. We are making various kinds of develop- the distance of M87.
ments for the misson. We introduce the developments for the large antenna, fast switching scheme 2. Design of VSOP-2 satellite
using CMG, low noise receiver, gigabit data transA schematic view of VSOP-2 satellite is shown
mission, and high data rate sampling on board. We
in Figure 1. VSOP-2 satellite will be launched byalso study the system conﬁguration of the VSOPISAS M-V rocket. The orbit is 25,000 km apogee,
2 satellite and the orbit to ﬁt the expected roket,
1,000 km perigee, and the 7.5 hour period. The deM-V. VSOP-2 science goals include the imageing
sign of the satellite is changed from the last meetingthe accretion disk around the massive blackhole in
the nuclei of the active galaxies, studies of magnetic
ﬁeld orientation and evolution in jets, and the highest resolution studies of spectral line masers andmega-masers. Here we describe the developmentof the space antenna, high speed sampler, and thesatellite system.
Yasuhiro Murata1 (murata@vsop.isas.jaxa.jp),
Hisashi Hirabayashi1 , Inoue Makoto2 , andNext generation space VLBI working group1.

Description of VSOP-2 satellite

VSOP-2 satellite has the 10m-class antenna withthe low noise receivers and a downlink data rateof 1 Gbps. It will detect both LCP and RCP in
the band of 8, 22, and 43 GHz. The receivers of
22, and 43 GHz are cooled to around 30 K with

Figure 1. A schematic view of VSOP-2 satellite.

Figure 2. VSOP-2 satellite launch conﬁguration
with M-V faring interface.

November 2003

55

Table 1. Comparison of the speciﬁcation of VSOP, VSOP-2 and VLBA. There are other observing band
in VLBA. The sensitibity is related to the sensitivity of ground telescope. Sensitivities are calcurated
assuming to observe with VLBA.
VSOP
VSOP-2
VLBA
Antenna Diameter
8m
9m
25m
Apogee Hight
21,500 km
25,000km
0 km
Orbit Period (hour)
6.3
7.5
24
Polarization
LCP LCP/RCP
LCP/RCP
Data Bandwidth
128 Mbps
1 Gbps
512 Mbps*
Observing Band (GHz) 1.6, 5, (22)8, 22, 43 8,22,43,86 etc
Maximum resolution
0.36 mas
0.038 mas
0.096 mas
Sensitivity (5/8 GHz)
158 mJy
22 mJy7.9 mJy(22 GHz)
N.G.
39 mJy23 mJy(22 GHz phase ref.) impossible
9.1 mJy
5.3mJy(1.5 hour integ time)
Launch (earliest case)
1997
2010
* We adopt the maximum data rate of VLBA, this is not the operational case.
3.

Development for VSOP-2 satellite

3.1 Antenna Development
One of the technical challenges is be the requirement placed on the surface accuracy of the meshantenna by the highest observing frequency of 43
GHz (a wavelength of 7 mm). A 7-segment, oﬀset 10-m class antenna is under development. Thisantenna is has a lighter weight, and easier adjustment mechanism, than that of HALCA. The basic concept of this type of antenna was developedby NASDA (now JAXA) for the ETS-VIII mission.
However, the planned surface accuracy of ETS-VIII
is lower than that required for the VSOP-2 mission. We made the model of the full scale 1 segFigure 3. Picture of 2 gentlemen with a full scale ment model (Figure 3) to evaluate how accurately
model of the central part of a single antenna module the antenna surface can be adjusted. We conﬁrmed
to evaluate the adjustment of the surface accuracy. that we can get an accuracy of less than 0.2 mmrms.
to ﬁt it to the nose-faring of the M-V. The target
total weight is 910 kg. The image of the satellitewith the M-V nose-faring is shown in Figure 2.
The design of the VSOP-2 satellite is based on
HALCA design, but there is some new items wemust take account. 1) large oﬀ-axis paraboloid antenna 2) Cooler requres more power. VSOP-2 has
the total power of about 1.8 kW, which is about
double of HALCA supply. This means that wemust take care about the management of the thermal control. 3) Add 2 CMG s (control momentum gyro) for the fast switching observation, andGPS receiver and the accelarometer for the cm order accurate orbit determination, to carry out thephase-referencing observation.

3.2 High speed sampler radiation test
One of the problems for VSOP-2 is how to sample the data on-board, if we follow the same approach as HALCA. We assume a giga-bit rate ofdata sampling to obtain the desired sensitivity.
However, we can not ﬁnd any A/D sampler LSI
chips qualiﬁed for use in space. We tested a 10
Gbps, 1 bit sampler and a 1:16 demultiplexer, todemonstrate a possible solution for the on-board
high speed sampler. We carried out a 1000 krad total dose test and a single event test. We conﬁrmed
we can use those LSI’s on the VSOP-2 orbit.
3.3 Giga-bit data link
A giga-bit data transmission requires more than
1 GHz bandwidth frequency allocation. The only
possible band based on frequency allocation regu-

IVS CRL-TDC News No.23

56

Figure 4. Picture of the assembled GaAs MMIC
Q-band receiver.

lations is 37-38 GHz. The uplink frequency will
be moved to 40 GHz. We studied the link budget,and found that the condition is more severe thanthat of HALCA Ku link, but still it is possible.
We are developing the modulator and demodulator for the giga-bit data transmission. We adopt
the OFDM (Orthogonal Frequency Division Multiplex) method with 8 channel QPSK modulation,
to allow the CMOS type circuit for the modulator, and reduce the emisson in the outband of thetransmitting band.
3.4 Cooled frontend
43 GHz GaAs MMIC cooled receiver is developed using the commertial MMIC LSI for the room
temperature use (Figure 4). The current top dateof the noise temperature is about 40 K at 20 K
physical temperature, which is not the lowest but
enough charactaristic. We will develop the new
design with low power consumption,and small size
to ﬁt for the satellite limitation. We also developing the scheme how to cool the system to get theenough performance.

Figure 5. Simulation of the fast switching using
2 control momentums gyro and 4 reaction wheels.
Top gives the motion of the pointing direction from0 to 3.5 degree oﬀset. Middle and lower panel
shows the error of the attitude. Lower panel gives
the magniﬁed scele error.

on-board GPS system and accelerometer (Wu and
Bar-Sever 2001).
4.

Summary

We are now make a proposal of VSOP-2 mission
to be submitted ISAS/JAXA. There are some oftechnically charenging items, and we made development some of them. We have the prospect that
it is possible to realize this misson, in spite of somediﬃculties.
3.5 Possibility of the phase-referencing
Finally, we gratefully acknowledge all collaboraPhase referencing observations are a powerfultors
who have joined discussions about the VSOPmethod to determine accurate relative positions
2
mission.
This mission is planned based on disof radio sources, and longer integration times forcussionswithresearchers from JPL, NRAO, CfA
weaker sources. High speed switching between
(US),
DRAO,
SGL (Canada), ATNF (Australia),
sources less than 1 minutes period, and about 1,cm
JIVE(Europe),
Univ. of Ibaraki, Hosei Univ., Yaaccuracy orbit determination are required. We are
maguchi
Univ.,NAOJ,
and ISAS (Japan).
now studying the possibility of fast switching using the 2 control moment gyro s (CMG) which
References
is a higher torque actuator, with the combinationof 4 reaction wheels which are used for the norHirabayashi, H. 2003, in this proceedings.
mal attitude control. We succeed to make the fastswitching with 1 minutes period, 3.5 degree sepa- Wu, S.-C., and Bar-Sever, The Institute of Navigation,
14th International Technical Meeting, September 11ration (Figure 5). We are also studying the possi14, 2001 Salt Lake City, Utahbility of obtaining a higher orbit accuracy using an

November 2003

57

Development of a primary feedsystem for the parabolic rectangular reflector antenna dedicated for planetary radio emission
Hiroaki Misawa1(misawa@pparc.geophys.tohoku.ac.jp),
Riichi Kudo2 , Fuminori Tsuchiya1 ,Akira Morioka1 , and Tetsuro Kondo3
1

Planetary Plasma and Atmospheric ResearchCenter, Tohoku University
Aza Aoba, Aoba-ku, Sendai 980-8578, Japan
2
Network Innovation Laboratories, NTT
1-1 Hikarinooka, Yokosuka
Kanagawa 239-0847, Japan
3
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, Japan

1.

Figure 1. Panoramic view of the parabolic rectangular reﬂector antenna named IPRT. The aperturesize is 33m(azimuth)×31m(altitude).

Introduction

Tohoku University has established a meter todecimeter wave range radio telescope, named IPRT
(Iitate Planetary Radio Telescope), in 2001 at
Iitate, Fukushima, Japan. The antenna of theradio telescope is a fully steerable oﬀset-parabolatype with the physical aperture area of 1023m2,
and composed of a pair of same-shaped parabolic
rectanglar sections (16.5m×31m) installed on one
alt-azimuth mount (Figure 1). The radio telescope
has been dedicated for exclusive and regular observation of planetary radio emissions to investigate
electromagnetic environment of planets, particularly Jupiter’s inner magnetosphere [Misawa et al.,2001, Tsuchiya et al., 2002].
On the observations of planetary radio emission,
whose intensity is generally rather weak (at most
several Jy’s), polarization characteristic is one of
key parameters to investigate the electromagnetic
environment. It is therefore important to develop a
primary feed system suitable for this unique shaped
antenna with a high eﬃciency. We have developed
the feed system, which is installed at the primary
focus of IPRT and provided with a plane reﬂector (2.4m×2.4m), based on both numerical calculation and actual measurement of beam pattern. The
estimated aperture eﬃciencies for both horizontal
and vertical polarizations were ﬁnally achieved tobe nearly 70%. In this report, we introducef the
primary feed system brieﬂy with process of the development.

Figure 2. Calculated illumination patterns of thesimple half-wave dipole element with a plane reﬂector for horizontally (left panel) and vertically(right panel) polarized components. The height ofthe element from the plane reﬂector is set to be
0.1λ, where λ is a wave length (0.92m at 325MHz).
A quasi trapezoidal ﬁgure in each panel (bold line)
represents the parabolic rectangle reﬂector viewed
from the focus position. Contour lines represent
relative power in a unit of dB with respect to thebeam center. The estimated illumination eﬃciencies are 61% and 54% for horizontally and vertically polarized components, respectively.

2.

Illumination eﬃciency

The primary feed system for a parabolic circular
reﬂector antenna is generally composed of orthogonally crossed dipole antennas to measure polarization at a wave length of meter to decimeter. In caseof IPRT, since the reﬂector is rectangular whose

IVS CRL-TDC News No.23

58

Figure 4. Panoramic view of the new feed system.

Figure 3. Schematic illustration of the new feedsystem with parasitic elements and beam forming
rods. Major examined parameters are shown in thelower panel.

side lengths are not same each other (16.5m and31m), it is almost impossible to obtain same illumination eﬃciencies for horizontally and verticallypolarized components with simple crossed dipole
antennas. In Figure 2, we show a result of illumination patterns for a simple half-wave dipole feedsystem, where the length and position of dipole elements with respect to the plane reﬂector are set
to achieve almost maximum eﬃciency on IPRT; i.e,
61% and 54% for horizontally and vertically polarized components, respectively. Here the illumination patterns are numerically calculated with themoment method [Harrigton, 1968] for the observation frequency of 325MHz.
The reason of lower illumination eﬃciency of vertical polarization is mainly caused by larger leakageof illumination beam of vertical feed system. In order to reduce the leakage and revise illuminationeﬃciency, we modiﬁed the primary feed system byadopting the following two ideas; i.e. 1)addition ofa parasitic element: – adoption as the ‘Yagi’ antenna, to the half-wave dipole elements for bothhorizontally and vertically polarized components,
and 2)addition of beam forming rods to the elements for vertically polarized component. As forthe latter idea, eﬀectiveness of the beam forming
rods has been conﬁrmed for polarization measurement with a cylindrical parabola antenna by Kildal
and Sorngard [1980]. A schematic illustration anda panoramic view of the newly developed feed system are shown in Figure 3 and 4, respectively.
An illumination pattern for the new feed system was numerically calculated with the moment
method, and positions of parasitic elements andbeam matching rods, which enable high and al-

Figure 5. Illumination patterns of the new feedsystem measured using an approximately 1/6 scalemodel in the radio anechoic chamber. The display format is the sama as that of Figure 2. The
position parameters are selected to be 0.25λ and
0.35λ for hd and hy, respectively, and 0.49λ, 0.43λ,
0.65λ, and 0.76λ for hE1, hE2, XE1, and XE2,
respectively. The length of dipole and parasitic elements is selected to be 0.38λ and 0.39λ, respectively. Illumination eﬃciencies for both polarizedcomponents are achieved to be nearly 70%.

most same illumination eﬃciencies for the two polarized components, were investigated. In addition to the numerical calculation, the illumination
patterns were actually conﬁrmed using an approximately 1/6 scale model with the far-ﬁeld measurement system in the radio anechoic chamber of Communications Research Laboratory, Japan. As theresult, we have derived a suitable arrangement of
the elements and rods which enables the illumination eﬃciencies of almost 70% for both polarizedcomponents, and show the illumination patterns
measured in the radio anechoic chamber in Figure
5.
3.

Aperture eﬃciency

In this study, we derived an aperture eﬃciency(ηap ) by estimation based on i) evaluation of several characteristic parameters of the antenna, andii) actual measurement of signal intensities for ex-

November 2003

59

traterrestrial radio sources whose radio ﬂux densities are already known.
i) ηap derived by evaluation of antenna parameters: An aperture eﬃciency of a reﬂector antenna
is given by the following equation,
ηap = er ηi ηt ηrs ηbk(1)Here, er is a radiation eﬃciency which represents
a degree of signal conversion ratio from a radio
wave to an electric signal: – a degree of impedance
matching. We have achieved er ∼ 100% by adjusting height and length of the elements. ηi is
an illumination eﬃciency which we already introduced in the previous section. ηt , ηrs , and ηbk aretransmission loss eﬃciency, random surface error
eﬃciency and aperture brockage eﬃciency, respectively. The surface of the main reﬂector and planereﬂector of the primary feed system is made of astainless mesh with the pitch size of 2cm and 1cm
for the main and plane reﬂectors, respectively. The
total ηt value of the antenna is estimated to benearly 99.5% at 325MHz. The undulation of main
reﬂector surface was actually measured and the average surface roughness was estimated to be 8mmrms. This result gives ηrs ∼ 98.8% at 325MHz. As
for the aperture brockage, since IPRT is the typeof oﬀset parabola antenna, the aperture brockage
is considered to be negligible: – ηbk ∼ 100%. Thus,
based on the evaluation for each eﬃciency, apertureeﬃciency is ﬁnally estimated to be nearly 69%.
ii) ηap derived by actual measurement: When wemeasure some extraterrestrial radio source whoseradio ﬂux density is S, received signal power P isgiven by the following equation,
P = 0.5Ae G∆f S(2)

where G and ∆f are system gain and eﬀective band
width of a receiver system, respectively. Ae is eﬀective aperture area given by the product of physicalaperture area Ap (1023m2) and an aperture eﬃciency ηap . On the receiver system of IPRT, it isprovided with the gain calibration system which
consists of hot and cold loads at the front-end section, then G can be obtained with the so-called
Y-factor method, and ∆f is selectable at either 5
or 10MHz [Tsuchiya et al., 2002]. The ηap value
is therefore derived using known or measurable parameters as,ηap = 2P/Ap G∆f S(3)radio sources and the hot load temperature (seeTsuchiya et al. [2003]). Thus, it is conﬁrmed thatnumerically expected aperture eﬃciency is almost
achieved on the actual radio telescope system, andusage of a parasitic element and beam matchingrod is actually eﬀective for the parabolic rectangular reﬂector antenna.
4.

Summary

We have examined a primary feed system suitable for the parabolic rectangular reﬂector antennaof Iitate Planetary Radio Telescope (IPRT). The illumination eﬃciency of the feed system has been
investigated with numerical calculation with themoment method, and actual measurement using asmall scale model in a radio anechoic chamber. It issuggested that the usage of a dipole antenna combined with a parasitic element and beam forming
rods is one of the suitable feed systems to measureboth horizontally and vertically polarized waves
with high illumination eﬃciency. An actual measurement of an aperture eﬃciency of IPRT withthe developed primary feed system has been madeby means of extraterrestrial radio sources, and it
is ﬁnally conﬁrmed that the aperture eﬃciency isachieved to be nearly 70% for both horizontal andvertical polarizations.
Acknowledgment: The authors would like to appreciate Masato Tanaka and Yoshiyuki Fujii, Communications Research Laboratory for their assistanceon measurement of characteristics of the primary
feed system in the anechoic chamber and helpful
suggestions on development of a beam forming feedsystem.
References
Harrison, R. F., in Field computation by moment methods, Macmillan press, New York, 1968.
Kildal, P., E. Sorngard, Circularly polarized feed forcylindrical parabolic reﬂector antennas, IEEE Trans.
Antenna Propagat., AP-28, 210–215, 1980.
Misawa, H., A. Morioka, F. Tsuchiya, Y. Miyoshi,
T. Watanabe, R. Kudo, and T. Kondo, Newly developed meter to decimeter wave range radio telescope for the investigation of planetary environments, Proc. 34th ISAS Lunar Planet. Symp., 175–
178, 2001.
Tsuchiya, F., H. Misawa, Y. Miyoshi, T. Watanabe,
R. Kudo, A. Morioka, and T. Kondo, Performance
test of newly developed radio telescope and receivers
at the Iitate Observatory, Proc. 35th ISAS Lunar
Planet. Symp., 211–214, 2002.

We measured ηap by observations of intense extraterrestrial radio sources, such as 3C144(TauA), 3C405(Cyg-A) and 3C461(Cas-A). As the result, the actual aperture eﬃciency of IPRT was Tsuchiya, F., H. Misawa, R. Kudo, Y. Miyoshi, T.
derived to be 61∼71% based on the measurement
Watanabe, A. Morioka, and T. Kondo, First light ofof these radio sources. The somewhat large amJovian synchrotron radiation with the Iitate Planbiguity of aperture eﬃciency is mainly caused byetary Radio Telescope, Proc. 36th ISAS Lunar
uncertainties of absolute radio ﬂux density of thePlanet. Symp., 222–225, 2003.

IVS CRL-TDC News No.23

60- News - News - News - News - News - News - News - News - News - News - News -100th meeting of the Geodetic Society of Japanwas held at CRL
Yasuhiro Koyama (koyama@crl.go.jp)
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314-8501, JapanThe fall regular meeting of the Geodetic Society of Japan was held at the Headquarter of Communications Research Laboratory (Koganei, Tokyo) for three days from October 22, 2003. The society is
having regular meetings in fall and spring. The fall meeting of this year was the 100th memorial meetingand honorably CRL was awarded as the host. The ﬁrst meeting of the society was held in the nextcity of Koganei (Kodaira) in 1954 with only 11 presentations while there were 109 presentations andabout 200 participants in the 100th meeting. To memorize the meeting, a board was prepared and eachparticipant signed with short messages (see the picture below). The background design was taken fromthe cover page of the Journal of the Geodetic Society of Japan. It looks like the orbits of satellites andthe Earth, but some may feel it is associated with the Earth’s interior or the surface of the ﬂat waterwith ripples according to their interested research ﬁelds.
LOC Chair : Taizoh Yoshino
LOC members : Tetsuro Kondo, Yasuhiro Koyama, and Ryuichi Ichikawa

Photo 1. Collection of the writing and the participants of the 100th meeting.

“IVS CRL Technology Development Center News” (IVS CRL-TDC News) published by theCommunications Research Laboratory (CRL) is the continuation of “International Earth Rotation Service - VLBI Technical Development Center News” (IERS TDC News) published by CRL.
In accordance with the establishment of the International VLBI Service (IVS) for Geodesy andAstrometry on March 1, 1999, the function of the IERS VLBI technical development center was
taken over by that of the IVS technology development center, and the name of center was changed
from “Technical Development Center” to “Technology Development Center”.
VLBI Technology Development Center (TDC) at CRL is supposed
1) to develop new observation techniques and new systems for advanced Earth’s rotation observations by VLBI and other space techniques,2) to promote research in Earth rotation using VLBI,
3) to distribute new VLBI technology,4) to contribute the standardization of VLBI interface, and5) to deploy the real-time VLBI technique.
The CRL TDC newsletter (IVS CRL-TDC News) is published biannually by CRL.

This news was edited by Tetsuro Kondo and Yasuhiro Koyama, Kashima Space Research Center,
who are editorial staﬀ members of TDC at the Communications Research Laboratory, Japan.
Inquires on this issue should be addressed to T. Kondo, Kashima Space Research Center, Communications Research Laboratory, 893-1 Hirai, Kashima, Ibaraki 314-8501, Japan, TEL : +81299-84-7137, FAX : +81-299-84-7159, e-mail : kondo@crl.go.jp.
Summaries of VLBI and related activities at the Communications Research Laboratory are on theWorld Wide Web (WWW). The URL to view the home page of the Radio Astronomy Applications
Section of the Kashima Space Research Center is : “http://www.crl.go.jp/ka/radioastro/”.

IVS CRL TECHNOLOGY DEVELOPMENT CENTER NEWS No.23, November 2003
International VLBI Service for Geodesy and Astrometry
CRL Technology Development Center News
published by
Communications Research Laboratory, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan