Photographic Spectrometry and Radiometry on Distant Field Sources

Abstract

Field spectrometry and radiometry on rapidly moving objects customarily utilize imaging instruments. The applicability of such instrumentation in radiometry is discussed with particular emphasis on photographic cine spectrographs, ballistic spectrographs, and ballistic and cine cameras. Appropriate radiant energy transfer equations for distant point, line, and area sources are given in order to clarify photographic signal interpretation and to define suitable calibrations and reduction procedures. Various types of photographic signal transfer functions are discussed. An example of source parameters derived from actual field measurements is presented to illustrate the degree of consistency among different types of measurements. Laboratory studies indicate that absolute intensities may be measured photographically under field conditions to within a factor of 2 accuracy.