Atmospheric absorption in the near and middle UV at altitudes attained by stratospheric balloons.

Two stratospheric experiments were conducted in April 1974 by means of a balloon-borne stellar photometer. The first was devoted to the study of the effect of rotation on the ultraviolet photometry of a population of 12 hot stars, while the second was devoted to the measurement of the twilight variations of ozone. Both experiments used an electrophotometer system operating in the near UV and consisting of a 16-cm Cassegrain telescope and a photodetector. At the stratospheric altitude attained, oxygen and ozone are the only molecules capable of absorbing near UV radiation, oxygen because of its concentration and ozone because of its absorption coefficient. On the basis of this principle, the density and vertical distribution of ozone were determined after separating the oxygen absorption component from that of ozone.