VLBI Astrometry

9303527夏皮罗VLBI天文测量。超长基线干涉测量技术（VLBI）已被用于环绕地球的射电望远镜，以确定不确定度为1毫弧秒或更小的紧凑型射电源的天空位置和不确定度低至12微弧秒的邻近源的相对位置。夏皮罗博士和他在哈佛大学的同事们将继续使用这项技术：(a)确定银河系和星系外的距离，并估计哈勃常数；(b)测量或限定几个河外射电源的固有运动，以提高我们对这些射电源性质的理解，并改进河外参考系；(c)将这个坐标系与太阳系参考系联系起来。

9303527 Shapiro VLBI Astrometry. The technique of very-long-baseline-interferometry (VLBI) has been used with radio telescopes girdling the globe to determine the sky positions of compact radio sources with uncertainties of one milliarcsecond or less and the relative positions of neighboring sources with uncertainties as low as 12 microarcseconds. Dr. Shapiro and his colleagues at Harvard University will continue using this technique to: (a) determine galactic and extragalactic distances and to estimate the Hubble constant; (b) measure, or place bounds on, the proper motions of several extragalactic radio sources in order to improve our understanding of the nature of these sources and to improve the extragalactic reference frame; and (c) tie this frame to the solar-system reference frame.