Thermospheric structure: Correlation of mass spectrometry and incoherent-scatter sounding

Results from a day-night pair of rocket flights launched in France in February 1969 to measure neutral composition between 100 and 400 km are analyzed and are compared with data on neutral temperature and density obtained simultaneously from ground-based incoherent-scatter observations. New evidence is thus given of the considerable importance of chemical reactions occurring within rocket-borne mass spectrometers of the type used, and affecting in particular the oxygen measurements. It is concluded that past model atmospheres, based on incorrect determinations of the relative density of oxygen using mass spectrometric data, underestimate O/N2 slightly, and O/O2 grossly, at least as far as middle-latitude solar maximum winter conditions are concerned.