Since the 1980s VLBI observations at two frequencies, 8.4 (X-band) and 2.3 GHz (S-band) have been used to locate the positions of compact radio sources with unprecedented accuracy. ... Observations of selected strong compact extragalactic radio sources, using this now mature technique, have been used to define and maintain a radio reference frame with sub-milli-arcsecond (mas) precision. ... Additionally, it will provide more reference sources for phase referencing VLBI observations. ... References . ...
metrologia The leap second: its history and possible future R. A. Nelson, D. D. McCarthy , S. Malys, J. Levine, B. Guinot, H. F. Fliegel , R. L. Beard and T. R. Bartholome w Abstract. This paper reviews the theoretica l motivatio n for the leap second in the context of the historica l evolutio n of time measurement . Th e periodic insertio n of a leap second step into th e scale of Coordinate d Universal Time (UTC) necessitates frequent changes in comple x timekeepin g systems an d is currentl y th e
... Twenty-Six Year Monitoring of Water Masers IAU Symposium 242, Alice Springs 1 Contents of the work A sample of H2O maser emission sources has been observed since 1980. ... Rudnitskij et al. ... Twenty-Six Year Monitoring of Water Masers IAU Symposium 242, Alice Springs 4 Maser in a protoplanetary disc (S255) Flux density, Jy S255: H2O line profile 5 February 2002 Radial velocity, LSR, km/s Rudnitskij et al. ... Twenty-Six Year Monitoring of Water Masers IAU Symposium 242, Alice Springs 12 ...
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