The excitation of the Na airglow from Coqui Dos rocket and ground-based observations

On February 20 1998 two rockets were launched from Puerto Rico as part of the Coqui Dos campaign. Data from on-board photometers and ground-based data from a Na lidar and an airglow imager allowed an estimate to be made, using both the TIME-GCM and MSIS models, of the branching coefficient alpha for the Na airglow emission. Assuming the hydrogen density is within the range predicted by the two models the data are consistent with cu being less than 0.05. This value is well below a recent theoretical estimate of 0.67 and also below the nominally accepted value of 0.1 derived from previous aeronomic data.