We thank T. Clark, C. Ma, and J. Ryan for permission to use data from astrometric and geodetic VLBI-observations, made under the support of NASA (USA). We are grateful to the staff of NASA Goddard Space Flight Center and the National Radio Astronomical Observatory (Socorro) for kind assistance in working with the data. This research has also made use of the United States Naval Observatory (USNO) Radio Reference Frame Image Database (RRFID). The University of Michigan Radio Astronomy Observatory was partially supported by the US National Science Foundation. The Boston University effort was supported in part by U.S. National Science Foundation grant AST-9802941, and by NASA through CGRO Guest Investigator Program grants NAG5-2508, NAG5-3829, and NAG5-7323. The St. Petersburg State University effort was supported in part by the Russian Federal program "Integration", grant #578, and a grant from the State Committee of Higher Education. The Institute of Applied Astronomy of the RAS research is supported by Russian Foundation for Basic Research grant 96-02-19177.
© European Southern Observatory (ESO) 2000
Online publication: June 8, 2000