Atomic oxygen number densities in the mesosphere–lower thermosphere region measured by solid electrolyte sensors on WADIS-2
Abstract. Absolute profiles of atomic oxygen number densities with high vertical
resolution have been determined in the mesosphere–lower thermosphere (MLT) region from in situ
measurements by several rocket-borne solid electrolyte sensors. The
amperometric sensors were operated in both controlled and uncontrolled modes
and with various orientations on the foredeck and aft deck of the payload.
Calibration was based on mass spectrometry in a molecular beam containing
atomic oxygen produced in a microwave discharge. The sensor signal is
proportional to the number flux onto the electrodes, and the mass flow rate in
the molecular beam was additionally measured to derive this quantity from the
spectrometer reading. Numerical simulations provided aerodynamic correction
factors to derive the atmospheric number density of atomic oxygen from the
sensor data. The flight results indicate a preferable orientation of the
electrode surface perpendicular to the rocket axis. While unstable during the
upleg, the density profiles measured by these sensors show an excellent
agreement with the atmospheric models and photometer results during the
downleg of the trajectory. The high spatial resolution of the measurements
allows for the identification of small-scale variations in the atomic oxygen
concentration.