Arctic ozone hole research. Night-time launch of a balloon & its experimental payload during the CHEOPS-3 project (CHEmistry of Ozone in Polar Stratosphere) near Kiruna, Sweden, during January & February 1990. Scientists from France, Germany & the U.S. conducted a number of experiments including measurements of atmospheric ozone & sampling various pollutants. This is a relatively small balloon (30,000 cubic meters), carrying an experiment to measure the concentration of nitric acid in Polar Stratospheric Cloud (PSC) formations. PSCs contain ice particles that are suspected as acting as substrates for the chemical reactions that destroy ozone.