4. Technical Reports

4.1 Key Stone Project


VLBI Data Analysis Software System for Key Stone Project (TAKEMIKADZUCHI) (Yasuhiro Koyama)

After each site of KSP (Key Stone Project) network performes VLBI observations every day, recorded data tapes are transported to the Koganei Processing Center and correlated with the KSP correlator by KATS (KAnameichi data analysis Togo [= unified] Software). Once KATS finished the correlation processing including the bandwidth synthesis, the remaining data analysis is done by the software TAKEMIKADZUCHI. The role of the software is (1) to create and maintain databases, (2) to estimate site coordinates along with other model parameters, and (3) to interpret the estimated results and make the results available on the network. This software is presently under development and is expected to be ready for operation soon. The conceptual design of the software is explained in the following sections.

Database
A database is created from a set of KATS output files to prepare for following data analysis procedures. Kicked off by a command executed in the last phase of KATS, TAKEMIKADZUCHI extracts required information from the KATS output files, calcurates ionospheric calibrations and planetary ephemerides, interporates meteolorogical data and then creates a database using the Mark-3 Database Handler developed by Goddard Space Flight Center (GSFC) of National Aeronautics and Space Administration (NASA). TAKEMIKADZUCHI also updates these databases automatically when it receives a bulletin (either Bulletin A or Bulletin B) issued from International Earth Rotation Service (IERS) via e-mail.

Analysis
Right after a database is either created or updated, theoretical values of a time delay and a delay rate for each observation and their partials with respect to the various parameters are calculated by the CALC software [version 8.1] which has also been developed by GSFC. In the case of initial creation of the database, other software (called REMAMB and MRKOBS) resolve ambiguities and remove bad observations respectively. Then in the final step, VLBEST is run to estimate site coordinates along with other parameters such as clock offsets and atmospheric delay in the zenith directions. In case the root mean squared delay residual exceeds a certain threshold, the operator is notified before the results are released. The operator then can look into the raw data and change clock epochs or remove bad data points manually using a graphical user interface in an X windows / Motif environment.

Data release
Estimated site coordinates are interpreted as motions of sites in the horizontal and vertical components, and as rates of change in baseline lengths. These results are stored in text files and, at the same time, graphic figures are generated. Any researchers on the Internet network can access these text files and figures from their World Wide Web browser such as MOSAIC at the URL http://apollo.nict.go.jp/ (the URL is preliminary and may change in the future). If the latest data exhibits a large offset from the linear trend of the site motion or baseline length change, the data points will be distinguished in color to attract attention for a possible pre-seismic signal. The results are updated everytime when TAKEMIKADZUCHI updates databases according to the new set of earth orientation parameters in IERS Bulletins and they are reported to related organizations by daily e-mail messages. We are expecting that these data will be used by earthquake prediction research communities worldwide.

Q&A

Q: Please consider to release radio source flux density information along with geodetic results by means of WWW for Astronomical community.
A: We are already considering this issue, and the preliminary results from three experiments can be accessed as a test.
Q: What is the version of CALC, you are going to use?
A: The version of CALC is 8.1 and is the latest available version at present.
Q: Are there any means of data distribution other than WWW?
A: We are thinking of using e-mail distribution to related organizations like Japanese Meteorological Agency.
Q: What is the policy on public availability of released data? Are you planning to give priority to a restricted group to use your results?
A: We are expecting wide research communities to use our data for geophysical research. Therefore the data should be freely available without any restrictions.

Q&A for the whole of the KSP

Q: Is KSP antenna to be equipped with 22 GHz receiver in the future?
A: No.
Q: How about comparison with other techniques?
A: GSI will use VLBI stations as fiducial points for GPS observation. Therefore the KSP antenna is designed to permit easy connection of its AZ-EL axes intersection to ground marker.




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