Two years of ozone measurements from the Solar Mesosphere Explorer satellie satellite are compared to the results of a model of lower mesospheric photochemistry. The measured ozone mixing ratios are larger than those predicted by the model by as much as a factor of two at pressures near 0.1 mbar and 1.3 at 1.0 mbar using currently accepted reaction rate coefficients. The model is brought into good agreement with the measurements over a wide range of latitudes and solar zenith angles only if the efficiency of the odd hydrogen catalytic cycle which destroys odd oxygen is decreased by 30--50%.