Global ozone monitoring by occultation of stars: an overview of GOMOS measurements on ENVISAT
GOMOS on ENVISAT (launched in February, 2002) is the first space\ninstrument dedicated to the study of the atmosphere of the Earth by the\ntechnique of stellar occultations (Global Ozone Monitoring by\nOccultation of Stars). Its polar orbit makes good latitude coverage\npossible. Because it is self-calibrating, it is particularly well\nadapted to long time trend monitoring of stratospheric species. With 4\nspectrometers, the wavelength coverage of 248 nm to 942 nm enables\nmonitoring ozone, H2O, NO2, NO3, air density, aerosol extinction, and\nO-2. Two additional fast photometers (with 1 kHz sampling rate) enable\nthe correction of the effects of scintillations, as well as the study of\nthe structure of air density irregularities resulting from gravity waves\nand turbulence. A high vertical resolution profile of the temperature\nmay also be obtained from the time delay between the red and the blue\nphotometer. Noctilucent clouds (Polar Mesospheric Clouds, PMC) are\nroutinely observed in both polar summers and global observations of OClO\nand sodium are achieved.\nThe instrument configuration, dictated by the scientific objectives'\nrationale and technical constraints, is described, together with the\ntypical operations along one orbit, along with the statistics from over\n6 years of operation. Typical atmospheric transmission spectra are\npresented and some retrieval difficulties are discussed, in particular\nfor O-2 and H2O.\nAn overview is presented of a number of scientific results already\npublished or found in more detail as companion papers in the same ACP\nGOMOS special issue. This paper is particularly intended to provide an\nincentive for the exploitation of GOMOS data available to the whole\nscientific community in the ESA data archive, and to help GOMOS data\nusers to better understand the instrument, its capabilities and the\nquality of its measurements, thus leading to an increase in the\nscientific return.