Nighttime atomic hydrogen and ozone concentrations are derived from simultaneous measurements of the vertical profiles of upper mesospheric airglow emissions and atmospheric sodium. The airglow profiles were obtained in a sounding rocket experiment launched from Alcaˆntara (2.5 ¿S, 44.2 ¿W) on May 31, 1992. A lidar operating at the launch site was used to measure sodium at the time of the rocket experiment. A total of 10 airglow photometers, 6 forward looking and 4 side looking, observed the OI 557.7 nm, O2 Herzberg and O2 atmospheric (0,0) bands, sodium D lines, OI 630 nm, OH(8,3) band, and the airglow continuum. The simultaneous ground-based sodium lidar and onboard sodium airglow measurements made it possible to derive the ozone concentration at heights between 85 and 100 km. The hydrogen concentrations were then calculated from the O2 atmospheric (0,0), OH(8,3), and the ozone profiles. The results suggest that the hydrogen concentration varied from 1¿109 cm-3 at 85 km to 1¿108 cm-3 at 100 km, values much higher than those suggested by recent model atmospheres and by some rocket observations at middle and high latitudes. Although the method of obtaining the concentrations of the minor constituents in the upper atmosphere is an indirect optical technique, this is the first time that these concentrations have been measured by rocket in the equatorial region. ¿ American Geophysical Union 1996