Crustal Deformation Measurement in the
Metropolitan Area Real-Time VLBI System Software -- RKATS
M. Sekido(sekido(AT)nict.go.jp), T.Kondo, Y.Koyama
Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314, Japan
Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan
Kety Co. Ltd.
Real time VLBI data processing software RKATS is under the development
by Communications Research Laboratory and Kety Co.Ltd.
It is designed as automatic VLBI data processing management software.
The overview is described in this article.
Key Stone Project (KSP) is a trial to catch the pre-seismic
crustal deformation around Tokyo metropolitan area by using VLBI and SLR
techniques (Figure.1). Daily observation with 4 VLBI stations has started as test run
from this summer.
Figure 1. Overview of Key Stone Project.
In normal VLBI experiment, the observed data have to be recorded on magnetic
tapes and they have to be correlated after transportation to central
correlation center. In the earliest case in the KSP, 1-2 days were necessary
for data processing and analysis of the data. Now the correlation system of KSP
is semi-automated by DMS (tape auto-changer) and data processing and analysis
software, but it even needs a support by operator for transportation of
tapes, tape mounting to auto-changer, and correlation setup.
Recently, real-time data transportation by using Asynchronous Transport Mode
(ATM) with high speed optical fiber link has become available in laboratory level.
We have started Real-time VLBI based on co-laboration between CRL and NTT
(Nippon Telegraph and Telephone Corporation).
Data transfer with communication network gives a possibility of full-automated
VLBI observation system. It release an operator from transportation of magnetic tapes
and treatment of them.
Now a software RKATS (Real-time KATS) is under development for full automated VLBI
data processing system, which controls real-time 6 baselines correlation,
Bandwidth-synthesis treatment, and Mark-III database creation.
2. Functions of Real-Time-KATS (RKATS)
The RKATS is developed from a tape base VLBI data processing software KATS, which assist
a operator in the work of correlation processing, database creation, and data backup.
Both RKATS and KATS run on HP-UX workstation.
Figure 2 shows a over view of the flow of data processing.
Figure 2. Real-time VLBI data flow.
The functions of RKATS are as follows:
The new data is analyzed by auto baseline analysis software. Then the baseline and
station positions are determined. Final analysis is performed after the final
value of Earth orientation parameter is provided from IERS.
- The observed data are sent to correlation center through ATM communication
system. RKATS has already loaded the schedule file of the experiment before
the start time with referring to its workstation clock.
The time of the workstation is synchronized with UTC(CRL) through ntp
(Network Time Protocol).
- The RKATS collects clock information of each observation station and earth
orientation parameter (prediction) through network. A few minutes before
the start time of observation, information for correlation (source and
information, observation start time, and so on.) are send to the correlators.
- Output data from correlators are transferred to hard disk drive of the workstation
with PC-NFS (Network File System) on Ethernet. Just after that, Bandwidth
synthesis treatment is done on the data.
- After the experiment has finished, the RKATS collects weather data and delay
calibration data from each observation station through network. And invoke
data base creation procedure.
- RKATS return to the first state and load the next experiment schedule.
Then it wait for the next experiment start time.
Additionally RKATS has automatic data backup function by using DAT auto-changer.
The capacity of it is about 12GB, which gives capability of more than 10 days of
24 hour experiment data storage.
Automatic Real-time VLBI data processing software RKATS is being developed for Key
Stone Project. It is expected to run from the end of this year.
We appreciate Dr. Watanebe, Dr. Uematsu, and Dr. Hoshino in NTT Optical Network
System laboratory for the assist of high performance ATM system for this project.
Updated on October 28, 1996.
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