Taizoh Yoshino
Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan
Date : July 10, 1995 18:00-19:20
Place: Engineering Center CR1-7, University of Colorado at Boulder
chaired by Taizoh Yoshino (Communications Research Laboratory)
Attendance:
Brent A. Archinal(USNO)
John M. Bosworth (NASA/GSFC)
James Campbell (Univ. Bonn)
William E. Carter (NOAA)
M. Cattaneo (University of Genova)
Thomas A. Clark (NASA/GSFC)
Eva Claudio (University of Genova)
Martine Feissel (Obs. Paris)
Dennis D. McCarthy (USNO)
Douglas S. Robertson (NOAA)
Harald Schuh (DGFI)
Bob E. Schutz (University of Texas)
Yoshiaki Tamura (NAOM)
Alan W. Whitney (Haystack Obs.)
Shu-Hua Ye (Shanghai Obs.)
1. Status Reports
1.1 NEOS (former IRIS-A) and NEOS Intensive (D.D. McCarthy)
New antennas have been set up at Green Bank, Hawaii and recently in
Florida. The latter is a replacement for the Richmond antenna destroyed in
a hurricane. The clock operations at Richmond will be moved to Colorado
Springs.
The correlator at USNO is operated for 5 days a week on two shifts plus a
third shift on two days. This is an increase over the previous situation, but
the number of VLBI experiments that can be scheduled by USNO is still limited
by the available correlation time. The funding by NASA of correlation at
Haystack has decreased to a very low level (only for R\&D).
The VLBI networks of NEOS (weekly) and NEOS Intensive (daily) are operated
for Earth rotation and polar motion as well as for establishing and
maintaining the celestial reference frame. The NEOS network is formed by
Fairbanks, Green Bank, Richmond, Hawaii, Fortaleza, and Wettzell
stations. Algonquin and Onsala occasionally join the NEOS observations. The
Intensive operations are continued using the Green Bank-Wettzell baseline.
1.2 IRIS-S (J. Campbell)
IRIS-S is operated once a month with Wettzell and Westford/Green Bank
including the southern hemisphere stations of Hartebeesthoek (South Africa),
Fortaleza (Brazil). Santiago (Chile) took part in IRIS-S from mid 92 to mid
93. The frequency of IRIS-S experiments is low, but they provide high
precision data
owing to extreme baseline length for the study of long-term effects in Earth
orientation.
The correlator at the MPIfR in Bonn is working at the saturation level,
the personnel situation being the limitation. The MkIV correlator will
supplant the present MkIIIA correlator in 1997 (financial support from IfAG,
Geodesy).
1.3 IRIS-P (Y. Tamura)
IRIS-P is not in operation since last year because of lack of funding
for correlation time in USNO and the problems with operational budgets at
several
stations.
A K4 type single-baseline correlator is running regularly in Mizusawa.
It is mainly used for astrophysical purposes, but it has the capability for
geodetic use. A ten-baseline correlator is under construction in the Mitaka
headquarters of the National Astronomical Observatory. It is originally designed
for space VLBI. Hence it does not have phase calibration. Plans are to modify
its hardware for geodetic applications.
A joint project with China will start soon. A K4 type backend system will
be installed at Urumqi station in China this year.
Plans to use the Syowa station in Antarctica are still being pursued,
although the necessary funding has not yet been secured.
1.4 China (S. Ye)
The Status of the Shanghai Observatory was reported with a written
memorandum. Several experiments of China-Germany-South Africa-Italy and
China-Japan
were described. A joint project between China and Japan was explained, and
a new IRIS network, named IRIS-E (Eurasia) was proposed.
(for more detail, see memorandum by Ye)
1.5 NASA/GSFC (T. Clark)
The NASA is conducting global VLBI campaigns for plate motion, celestial
and terrestrial reference frames. It carries out R\&D work on the further
development of
the VLBI DAS and correlator systems. The new MkIV correlator is under
development with the cooperation of Haystack and the JIVE institute in
Europe.
1.6 Other topics
M. Feissel (IERS): One copy of the new MkIV correlator will be built at
Dwingeloo within the Europe-Haystack cooperation in MkIV development. It
will be used mainly for astrophysics, but a smaller share of geodetic work is
also possible. Plans are to schedule some European geodetic experiments on
the basis of France's financial contribution to JIVE. The correlator is
expected to be operational by the end of 1997.
T. Yoshino: To monitor the crustal deformation, four VLBI observation
sites are being built in the Tokyo metropolitan area. The project is named
Key Stone Project. The system is operated fully automatically to obtain daily
solutions.
H. Schuh: The future of VLBI as a high precision geodetic technique should be
ascertained by developing further VLBI technology, aiming at a high
degree of automation and a replacement of tape recording by using wide
band communications links (prospects of real-time VLBI). European VLBI
group has proposed direct data communication by optical fiber network or
satellite links.
T. Yoshino: In the Key Stone Project by CRL, real time data processing
connecting four stations via optical fiber link is under development.
2. General Discussion
The topic of the optimal size of the radio source catalogue as the
realization of the celestial reference system for the geodetic VLBI campaigns
was brought up by Dr. Carter who stressed that the source list should not be
much larger than the 100 or so core sources, and that other purposes
(astronomical research goals on larger samples of geodetically less important
sources) should not be supported by geodetic means. Agreement was reached on
a set of 100 to 200 core sources to be large enough for geodetic reference
frame purposes.
In view of the reorganization of the CSTG under Comm.8, a change in the
title of the IRIS-subcommission was discussed. It now seems appropriate to
change the title to the "VLBI-Subcommission" in accord with the usage for
the other techniques, e.g. SLR-Subcommission.
3. New president
All the participants agreed to accept the nomination of
Dr.Thomas A.Clark (NASA/GSFC) as the Chairman of the
VLBI subcommission under CSTG for the next four year term.
Updated on November 2, 1995.
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