A rocket-borne electron beam fluorescence probe (EBFP) has been developed for thermospheric diagnostics. The EBFP is capable of measuring vibrational and rotational temperatures as well as species concentrations by utilizing a spectrally selective electrooptical system for the detection of the electron beam of 2.5-keV energy and 4-mA current was employed. N2 concentrations were measured by observing the radiation from the (0, 1) and (0, 2) vibrational bands of the N2+ first negative system, B2&Sgr;u+→X2&Sgr;g+. For O2 concentrations the (1, 0) and (2, 0) band sequences of the O2+ first negative system corresponding to the b4&Sgr;g-→a4&pgr;u transition were used. Results from two flights from Fort Churchill, Manitoba (March 1971 and March 1972), yielded N2 concentration measurements in good agrement with the Cira 1972 model atmosphere from 90 to 150 km and O2 concentrations in reasonably good agreement with the Cira 1972 model atmosphere for the 85- to 115-km altitude range.