Minutes of the IRIS Subcommission Meeting Held During the IUGG XXI General Assembly

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)


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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