The effects of incomplete resolution on surface distributions derived from strip-scanning observations, with particular reference to an application in radio astronomy

Abstract

A surface distribution can be measured by scanning in a number of directions with an observing instrument that has high resolution in only one direction. O‘Brien has describcd a met’hod which can be extended to reconstitute a two-dimensional distribution from a number of such ‘strip scans’. Because of the finite width of the strip and the associated lack of resolution, the ‘derived’ distribution differs, in general, from the ‘true’ distribution. But, because this method of measitring a, two-dimensional distribution is indirect and complex, the exact form such deviations mlty take is not apparent. It is shown that, the derived distribution is identical with that which would be recorded directly by two-dimensional scanning with a particular ‘spot’-instrument; the power response of this equivalent ‘spot’ has radial symmetry and is such that a line wan of it along any diameter is the same as the power response of the ‘strip’ in the dlrection of high resolution. An application of this to the determination of two-dimensional distributions of radio brightness over the sun's disc is discussed.