The Facility of Tsukuba 32-m VLBI Station
Yoshihiro Fukuzaki1, Keizou Nemoto1,
Michiko Onogaki1, Kouhei Miyagawa1,
Kyoko Kobayashi1, and
Geodetic Department,Geographical Survey Institute, Ministry of Construction |
Kitasato 1, Tsukuba, Ibaraki 305-0811, Japan
Geography and Crustal Dynamics Research Center|
Geographical Survey Institute, Ministry of Construction
Kitasato 1, Tsukuba, Ibaraki 305-0811, Japan
This report summarizes the specification of Tsukuba 32m VLBI station at the
Geographical Survey Institute (GSI). We present our history of VLBI activities and
the status. First of all, GSI developed three mobile VLBI systems and had repeated
observations with CRL. In 1998, GSI constructed a domestic VLBI network with five
permanent stations. A main station of the network is Tsukuba 32-m VLBI station (Fig.
1). It also becomes a key station in the international VLBI networks, especially in Asia.
Figure 1. Tsukuba 32m VLBI antenna.
Tsukuba station has a 32 m cassegrain parabolic antenna, which is made by NEC
Co. All of components are painted white color to protect the deformation by the
imbalance of temperature from sunshade. The main reflector is covered with thermal
insulator panels, then its temperature is kept between +/-3 degrees by using a
ventilation system in the back structures. The antenna structures have covers to
avoid direct sunlight. Table 1 shows the specification of the antenna, such
as the slewing speedand limit angles.
Table 1. The specification of antenna
|Year of Construction || 1998
| Radio Telescope || cassegrain
| Mount || Az-El
| Diameter of Main ref. || 32 m
| Surface Contour of ref. || +/-0.5 mm
| Azimuth Velocity || 3 deg/s
| Elevation Velocity || 3 deg/s
| Azimuth Limit || 10 - 710
| Elevation Limit || 5 - 88
Table 2. Station Configuration
| 8 letter || TSUKUB32
| 2 letter || Ts
| DOMES || 21730S007
| CDP || 7345
| Approx. Pos
| X (m) || -3957408.8
| Y (m) || 3310229.3
| Z (m) || 3737494.8
| Lat (deg.) || 36.1031
| Lon (deg.) || 140.0887
| Hight (m) || 44.7
| X-Band Tsys || 50 K
| S-Band Tsys || 75 K
| X-Band SEFD || 300 Jy
| S-Band SEFD || 360 Jy
Azimuth angle of the antenna is controlled by a wheel and track system. The
original azimuth rails, which weigh 73 kg per meter and are 10 cm wide, was cracked
because the stress between wheel and rail was larger than our assumption. In April 1999,
the rails have been replaced with larger ones (Fig.2).
Figure 2. The replaced rail (Left: before, Right: current).
For the moment, the significant
problem of the rail has not happened again. On the top of antenna, which is above
subreflector, a GPS antenna (Fig.3) is attached for the purpose of tie survey and
Figure 3. The replaced rail (Left: before, Right: current).
Table 3 shows front-end frequencies of Tsukuba 32m antenna. A cooled
HEMT receiver which was made by Nitsuki Co. was installed in X-band. First
local PLOs, which were made by CTI LTD., were installed. However, the phase
of the PLOs were unstable worse than a thousand degree per day due to change
the temperature variation in the front-end room. We installed a cover rack
for PLOs, and the PLOs are now always cooled by Peltier cooling system to
minimize effects by the temperature variations of the outside air. Three
intermediate frequencies (IF) at X-band were installed there.
Table 3. The front-end frequencies at Tsukuba station
|Input (MHz)||S band || X1 band || X2 band || X3 band
| 2100-2500 |
| 7780-8280 || 8180-8680 || 8580-8980
| PLO1 (MHz) || 1600 || 7280 || 7680 || 8080
| PLO2 (MHz) || 2000 || 7680 || 8080 || 8480
From front-end to back-end, signals are transmitted by optical fibers to avoid the
power loss. But we have troubles with the optical fibers since they often fails
to operate recently. We are now investigating the cause of the troubles. Mark IV and
K-4 systems have been installed there. We can record with both systems simultaneously.
Figure 4. Back-end equipment.
Two control systems have been installed in the station. One is the Field System
version 9 (FS9) developed by NASA GSFC. It is used for international experiments with
the Mark IV system. Another is the workstation GAOS (WS-GAOS) developed by CRL and
GSI. It is used for domestic experiments with the K-4 system. Recently, we can also
use the FS9 for domestic experiments because it now supports K-4 systems by a
cooperation with CRL Kashima and NASA GSFC.
Since 1999, a copy system, which can copy data from K-4 tapes to Mark-IV tapes,
has been installed to translate the data recorded at the stations only with the K-4
Figure 4. The diagram of copy machine (from K-4 to Mark-IV).
Updated on June 2, 2000.
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