Mass spectrometric measurements of minor constituents in the lower thermosphere

Abstract The feasibility of measurements of CO 2 , NO, N and H 2 O in the lower thermosphere by means of rocket-borne mass spectrometers with helium-cooled and with conventional ion sources is discussed. Three recent night-time experiments above Sardinia are described. They took place on October 13, 1970, at 0208 CET (payload SN5, helium-cooled ion source) and on February 7, 1971, at 0022 CET and 0445 CET (payloads ESRO S80-2 and -3, respectively, uncooled ion sources). Preliminary results indicate CO 2 to be mixed up to the turbopause and to be in diffusive equilibrium higher up. The ratio NO: N 2 was found to be in fair agreement with recent model calculations of Strobel (1971) for the altitute range 140 to 200 km.