For almost 50 years investigations of the Earth’s upper atmosphere have provided comprehensive knowledge about the subdiscipline of atmospheric science, now generally known as aeronomy. Since the advent of the space age observations made by spacecraft have made some of the traditional sciences into a “space science”. This is particularly true of the possibilities created for astronomical observations outside our Earth’s atmosphere with complex astronomical observatories, which have led to an unprecedented increase of information about stellar radiation sources beyond our own Sun.