A comparison of satellite mass spectrometer data from Dynamics Explorer‐2 and Atmosphere Explorer‐C and ‐D provides new evidence supporting the hypothesis that NO2is the source of the observed continuum glow near ram‐facing surfaces of the space shuttle. Surface reactions of thermospheric N and O in mass spectrometer ion sources produce NO and NO2in amounts highly dependent on surface temperature and composition, with direct exposure of ion source surfaces to rammed gas a necessary condition for the production of large amounts of NO2. Initial orbit data indicate that a period of surface conditioning is necessary before these odd nitrogen molecules can be produced effi