Citation
Abstract
The VLBI (very long baseline interferometer) cross-correlation procedure is analyzed for both a natural point source and a completely incoherent extended source. The analysis is based on a plane wave description of a radio signal that consists of stationary random noise. A formulation of the time delay is developed on the basis of plane wave phase. A brief discussion is devoted to small time delay corrections that are generated by relativistic differences in clock rates in the various coordinate frames. The correlation analysis, which includes electronic factors such as amplitude and phase modulation and the heterodyne process, leads to expressions for fringe amplitude and fringe phase. It is shown that the cross-correlation function for an extended source is identical to the point-source expression if one adjusts the fringe amplitude to include the transform of the brightness distribution. Examples of diurnal paths in the u-v plane are presented for various baselines and source locations. Finally, delay and delay rate measurement accuracy is briefly discussed.
Details
- Volume
- VII
- Published
- February 15, 1972
- Pages
- 37–50
- File Size
- 1.4 MB