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Novel ozone probe watches the Earth
Novel ozone probe watches the EarthKeywords: Ozone layer, Aerospace
The perfect launch of the European Space Agency's ENVISAT environmental monitoring satellite carried into orbit the GOMOS (Global Ozone Monitoring by Occultation of Stars) instrument containing no less than five light detection modules designed and built by Sira Electro-Optics. GOMOS has now been activated and scientists are already excited about its performance (see Plate 1).
Brian Teather, Sira Electro-Optics programme manager, says "Sira's contribution consists of near-infrared and visible/ultraviolet spectrometer detection modules, two star acquisition and tracking units, and a special fast photometer. Their high resolution and stability is crucial to the performance of GOMOS, which is designed to monitor the Earth's ozone layer."
Plate 1 The GOMOS ozone monitoring instrument, with its Sira Electro-Optics Ltd light detection modules, orbits the Earth aboard ENVISAT (illustration courtesy of ESA - J. Huart)
GOMOS observes preselected stars just before they pass behind the Earth. As their light travels through the atmosphere, certain wavelengths are absorbed and analysis of the resulting spectrum allows the amount of ozone to be deduced. In this way accurate three-dimensional maps of the ozone layer can be built up. Over the period of its mission, it will be able to measure changes in ozone concentrations as small as 0.1 per cent per year, well below the expected depletion rates.
In addition to monitoring seasonal, latitudinal and long-term trends in ozone levels, GOMOS will measure other atmospheric molecules and parameters, including NO2, NO3, water vapour, aerosols and vertical temperature distribution, to provide a better understanding of the depletion mechanism. It is expected to produce as much data as 360 ground-based stations.
Chislehurst-based Sira formed part of an international team headed by Matra Marconi Space, reporting to ESA's prime contractor, Dornier, now both part of Astrium.
The instrument is deployed on ENVISAT alongside MERIS, an imaging spectrometer in which Sira played a significant design role, used for monitoring land and water pollution.
Contact David Purll, Sira Electro-Optics Ltd, South Hill, Chislehurst, Kent BR7 5EH, UK. Tel: +44 (0)20 8467 2636; E-mail: David.Purll@siraeo.co.uk