GRAVITY-WAVE MODULATED AIRGLOW OBSERVATION FROM SPACECRAFT

During the STS-75 shuttle mission a special purpose electronic imager viewed the atmosphere below the shuttle orbiter in the wake direction with the objective of imaging gravity wave induced airglow modulation. A continuous sequence of images was taken with a picture repetition r ate of 4 per second. A narrow band (3nm) filter was used to select the O-2 atmospheric 0,0 band al 762 nm. The effectiveness of the filter w as demonstrated by comparing images of tropospheric clouds with and wi thout filter under full moon conditions. The test showed that the atmo spheric O-2 absorption combined with the filter was effective in suppr essing intensity variations of the bright full moon illuminated clouds and any other earth albedo. Therefore under conditions of low moonlig ht the filtered images truly represented the modulation of the airglow intensity uncontaminated by earthshine. Longer sequences of airglow d ata were processed to compensate for spacecraft motion and to dynamica lly integrate the signal into a latitude and longitude map of airglow modulations. Because of the intrinsic low pass filtering of the slant view observation geometry preferential enhancement of the higher frequ encies was needed to bring out waves in the wavelength range of <200 k m. Although the shuttle based limited operation of the imager did not permit to make large area global surveys, the results demonstrated tha t spacecraft based imaging of the airglow on a long duration flight wo uld produce a global data set much needed for the understanding of Mes osphere Lower Thermosphere dynamics.