Experimental determination of absolute intensities in the solar XUV spectrum

Abstract

Experimental problems of absolute intensity measurements of solar electromagnetic radiation in the extreme ultra-violet (EUV) and soft X-ray region of the spectrum (designated cumulatively as “XUV” for brevity) are reviewed. From an evaluation of existing rocket and satellite data together with existing projects and goals of future observations from space vehicles, it is suggested that the numerous associated practical problems be devided into two major areas, namely (a) the general experimental art of heterochromatic absolute XUV spectrophotometry in the laboratory and (b) specific problems characteristic of the objectives of solar physics as well as existing restrictions of space technology. Within the first area (a) emphasis is placed on recent progress toward justified reliance on ionization detectors without necessary connection to source standards. For the second area (b), emphasis is placed on the immediate need to have existing exploratory observations followed by a new phase of more systematic experiments of increased accuracy.