Measurements of atmospheric trace gases have been made during the first Spacelab mission, on board the Space Shuttle, from November 28 to December 8, 1983. The principle of the observations is absorption spectrometry, in the infrared, using the Sun as a light source during sunset or sunrise periods. The instrumental set-up is described. The scientific program has been executed in very satisfying conditions all along the mission. Spectral observations actually performed during 18 solar occultation periods are related to CO, CO 2, CH4, NO, NO2, H2O, HCl, HF and O3. The results presented are related to CO and CO2. The mixing ratio of carbon dioxide is homospheric (3*10-4) up to 90 km. At higher altitudes, it decreases rapidly and reaches 2*10 -5 at 130 km. For carbon monoxide, a large variability is observed with the latitude. The weakest concentrations are observed at high latitude in the southern hemisphere.