无线电干涉测量中的像素化和动态范围
Pixelization and Dynamic Range in Radio Interferometry
摘要：
本研究探讨了一些后果，代表天空的一个矩形网格的像素的动态范围的图像来自无线电干涉测量。特别是，图像像素化的效果耦合到天空的CLEAN反卷积表示为一组离散的δ函数可以限制当表示明亮的发射不局限于网格上的像素时获得的动态范围。天空曲率对非共面阵列的影响将限制动态范围，即使强源以“蝇眼”表示中的像素为中心，当这样的像素不位于对应的小平面的切点时。由于电离层、大气层或其他影响，各个天线的响应函数以及实际数据的校准中的不确定性将限制动态范围，即使在使用位于观测视场内的强源的无网格减法（即在可见度域中）时也是如此。一种技术，以减少这些影响的描述和实施中的Obit包的例子。这种技术的应用导致显着优越的结果，而不会显着增加计算时间。
英文摘要：
This study investigates some of the consequences of representing the sky by a rectangular grid of pixels on the dynamic range of images derived from radio interferometric measurements. In particular, the effects of image pixelization coupled to the CLEAN deconvolution representation of the sky as a set of discrete delta functions can limit the dynamic range obtained when representing bright emission not confined to pixels on the grid. Sky curvature effects on non-coplanar arrays will limit the dynamic range even if strong sources are centered on a pixel in a "fly's eye" representation when such pixel is not located at the corresponding facet's tangent point. Uncertainties in the response function of the individual antennas as well as in the calibration of actual data due to ionospheric, atmospheric or other effects will limit the dynamic range even when using grid-less subtraction (i.e. in the visibility domain) of strong sources located within the field of view of the observation. A technique to reduce these effects is described and examples from an implementation in the Obit package are given. Application of this technique leads to significantly superior results without a significant increase in the computing time.
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