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| Paper: |
Astrometry and Geodesy |
| Volume: |
180, Synthesis Imaging in Radio Astronomy II |
| Page: |
463 |
| Authors: |
Fomalont, Ed B. |
| Abstract: |
Astrometry deals with the precise measurement of the absolute and relative position of celestial objects. High quality imaging of these objects, the main concern of many of the other lectures, is less important unless the object is large compared with the resolution of the observations. Since radio measurements are made from the Earth surface, the complicated motion of the Earth in space, the distortion and slippage of the Earth surface (geodesy) and the properties of environment through which the radio waves travel, can also be measured. This lecture will describe: the measurement of the total phase delay, the fundamental astrometric equation, simple examples of the determination of astrometric and geodetic information. For VLBI observations, the measurement of the group delay, with all of its foibles is described in some detail. A typical astrometric experiment and its reduction are illustrated. Finally, there is a discussion of astrometric and geodetic endeavors at the milliarcsecond level. |
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