Rocket Measurement of Molecular Oxygen Density in the Altitude Range 70-90 km at the Geomagnetic Equator

173-176Three instrumented rockets were flown from Thumba on 19 March 1970for measuring the concentration of molecular oxygen using absorption photometry technique. From the rocket data, the molecular oxygen density profiles were derived in the altitude range of 70-90 km. The density value derived from noon time and afternoon flights are found to be consistently lower than those given by standard atmospheric models by about 20%. These values can be made consistent with Groves’s model if the Lyman-alpha absorption cross-section of molecular oxygen is reduced by about 10% from the assumed value of 1 X 10-20 cm2. A comparison of the molecular oxygen density values for the three flights shows a possible diurnal variation with early morning value being the highest and the afternoon values the lowest