AMON + AMON-RA: balloon-borne experiments, atmospheric compounds measurements, flight of 12 February 1999

AMON (Absorption de Minoritaires, Ozone et NOx) is a U/V-visible spectrometer which can be carried under stratospheric balloons, designed to obtain vertical profiles of ozone, nitrogen and chlorine molecules and the coefficient of aerosol extinction, at altitudes between 15 and 40 km. AMON data have been used for the ENVISAT validation campaigns.
It is composed of a 20-cm Cassegrain telescope with a 1-meter focal length, a grating spectrometer, and a CCD detector. The instrument is mounted in a stabilized gondola developed by the Geneva Observatory.
AMON observations are performed by the stellar occultation method, which consists in analyzing, during the setting of a star, recorded spectra that are affected by atmospheric absorption by the species that are present in the lines of sight of the star. At a balloon float altitude of 34-39 km, depending on the flight conditions, first a reference spectrum is recorded when the star is a few degrees above the horizon of the gondola in which the instrument is riding
In the frame of the preparation of the validation of the GOMOS instrument on board the European satellite ENVISAT, ESA has founded the development of AMON-RA (AMON-RApid), a low resolution spectrometer flying on board the AMON gondola which records ten spectra per second of the star observed by AMON. AMON-RA allows the study of the chromatic scintillation, a phenomenon that comes from the deviation of the star light rays through the atmospheric layers with different temperatures. This was the first flight of the instrument.