Diurnal variations in the thermosphere from a series of Marshall-University-of-Michigan probes

To investigate the diurnal variation in the concentration and temperature of molecular nitrogen, six Marshall-University-of-Michigan probes were launched from Cape Kennedy, Florida, on January 24, 1967. Omegatron mass spectrometers measured the N2 concentration from 150 to 320 km, and temperature was derived from the N2 scale height. Under the assumption of diffusive equilibrium, O2 and O concentration profiles were calculated so that the total mass of the N2, O2, and O would be in agreement with densities determined for satellite drag data above 300 km. The calculated concentration profiles of N2 and O2 are in excellent agreement with other direct observations but are in poor agreement with theoretical model atmospheres that are based on satellite-drag-determined densities. Diurnal variations in the constituent concentrations, temperature, and mass density are found to be completely reasonable with maximum values near 1400 hours and minimum values near 0400 hours. For rocket-borne mass spectrometer measurements, the wall loss coefficient is indicated to be near 1 for atomic oxygen. The well-known controversial factor-of-two difference between density determined from satellite-drag data and that obtained from mass spectrometers can be resolved when reasonable physical assumptions are made.