Atomic oxygen concentration profiles in the 90-to 140-km altitude region were obtained by analyzing the radiation intensity of chemiluminous nitric oxide trails deposited by rockets [Golomb et al., 1965]. The extremely high radiation intensity observed was incompatible with the laboratory rate constant for the NO + O -• NO•. + hr reaction. Therefore, a rate constant had to be applied that was derived by accepting mass-spectrometric measurements of atomic oxygen at 120 km. Also, the gasdynamic model applied to estimate the reaction volume and concentration assumed spherical source flow to emanate from the two sideward pointing orifices. The difficulties with the gasdynamic model and the rate constant have been avoided by simulating the upper atmosphere NO release in a series of wind tunnel tests at the Arnold Engineering Development Center Aerospace Chamber (SV). As a result, the flight data can be reexamined, the arbitrary rate constant and gas-dynamic model can be replaced by experimental data, and the derived oxygen atom concentrations can be put on an absolute basis.The concentrations so found agree fairly well with those deduced earlier by a more indirect method; they are generally lower by a factor of 2 from our previous publishe d values. The profiles are now not forced to agree with the mass-spectrometric measurements at 120 km, and thus it becomes apparent that, during the course of the night, toward sunrise, the atomic oxygen concentrations increase above 110 km and decrease below that altitude. The peak concentrations occur between 100 and 105 km at Eglin AFB, Florida (87øW30øN).The chemiluminescent glow resulting when NO is injected from two orifices into a super-sonic airstream containing oxygen atoms is shown in Figure 1. The expansion of the NO jet against. the Mach 3 airstream creates a shock in the oncoming airstream as well as creating a matching shock in the NO flow. Between these two shocks there is the hourglass-shaped mixing region wherein the glow originates. Some experimental parameters are given in the figure caption; • detailed description of the tests is given by van der Bliek et al. [1966]. The wind tunnel experiment consisted simply of injecting NO against the airstream containing oxygen atoms and measuring the radiant power produced in the chemiluminescent reaction. The airstream was a mixture of 02 and N2 with atomic oxygen produced by microwave discharge of 02 upstream of the nozzle. The oxygen atom concentration was measured in the test section by a modified NO• titration technique. The reaction volume was determined from top and side view photographs that were also densitometered for absolute surface brightness. The radiant power was measured at various NO flow rates, tunnel pressures, and Reynolds number. A model, described below, was then developed to relate the variables and scale the measurements appropriately. The radiant power P (photons sec -1) is given by P: k f [O][NO] d Fwhere k is the photon emission rate constant in cm 8 particle -1 sec -1, V is the reaction volume, an...
