Continuity of UT1 Series from “Intensive” VLBI on Westford-Wettzell Baseline
Regular daily VLBI observations on Westford — Wettzell (W-W) baseline are performed since April 1985 as the part of International Radio Interferometric Surveying (IRIS) program (Campbell et al. 1992). During one hour observing sessions four radio sources are observed, each of them twice. The fixed observing schedule is repeated at the same sidereal time for approximately three months. Two high-declination sources 0212+735 and 1803+784 are included in each observing schedule, two low-declination sources (0°–39°) are different for different observing programs. The experiment is restricted to estimate only UT1-UTC and the differences in clock offsets and clock rates at the two observatories (Robertson et al.,1985). The necessary information about terrestrial pole and celestial pole positions is obtained from independent networks and is taken as a priori value. Limitation to single baseline and to only four sources makes the estimate of UT1-UTC high sensitive to the a priori EOP parameters, baseline orientation and sources positions. In this paper we analyze the discontinuities in UT1 due to baseline — source geometry changes associated with quarterly alteration of observing schedule. The expected effects are modelled and compared with the daily observation IRIS series.
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- Arias E.F., Feissel M., Lestrade J.-F. (1991). The IERS extragalactic Celestial Reference Frame and its tie with HIPPARCOS, IERS Tech. Note 7, Central Bureau of IERS, Observatoire de Paris.Google Scholar
- Campbell J., Carter W., Kawaguchi N., Ronnang B., Ye S., Yokoyama K. (1992). IRIS Earth Orientation Bulletin A, 104.Google Scholar
- Hefty J., Gontier A.M.(1993). Sensitivity of UT1 determined by single baseline VLBI to terrestrial and celestial reference frames,in press.Google Scholar
- IERS (1992). 1991 Annual Report. Central Bureau of IERS, Obs. de Paris.Google Scholar