Rocket observation of atomic oxygen and night airglow: Measurement of concentration with an improved resonance fluorescence technique

Abstract. An improved resonant fluorescence instrument for measuring atomic oxygen concentration was developed to avoid the Doppler effect and the aerodynamic shock effect due to the supersonic motion of a rocket. The shock effect is reduced by adopting a sharp wedge-shaped housing and by scanning of the detector field of view to change the distance between the scattering volume and the surface of the housing. The scanning enables us to determine absolute values of atomic oxygen concentration from relative variation of the scattered light signal due to the self-absorption. The instrument was calibrated in the laboratory, and the numerical simulation reproduced the calibration result. Using the instrument, the altitude profile of atomic oxygen concentration was observed by a rocket experiment at Uchinoura (31°N) on 28 January 1992. The data obtained from the rocket experiment were not perfectly free from the shock effect, but errors due to the effect were reduced by the data analysis procedure. The observed maximum concentration was 3.8× 10¹¹ cm^–3 at altitudes around 94 km. The systematic error is estimated to be less than ±0.7×10¹¹ cm^–3 and the relative random error is less than±0.07× 10¹¹ cm^–3at the same altitudes. The altitude profile of the OI 557.7-nm airglow was also observed in the same rocket experiment. The maximum volume emission rate was found to be 150 photons cm^–3 s^–1 at 94 km. The observed altitude profiles are compared with the MSIS model and other in situ observations.