The Ozone Monitoring Instrument (OMI) is a Dutch-Finnish contribution to NASA's EOS-Chemistry satellite, which is due to be launched in December 2002. The aim of OMI is to contribute to climate monitoring and atmospheric chemistry research by providing daily global measurements of the total ozone column, ozone profile, NO2 column, other trace gases like SO2 and BrO, aerosols, cloud fraction, cloud top pressure, and surface UV irradiance.The optical design of OMI is based on the heritage of GOME and SCIAMACHY, and is suitable to perform TOMSand SBUV-type measurements. The electronics of OMI has a heritage from GOMOS. OMI is an imaging spectrometer with a spectral range 270-500 nm, a spectral resolution of 0.45-0.6 nm, and a wide field-of-view (114°). For most wavelengths the groundpixel size is 13 x 24 km2 in the global mode. There are two channels: a UV channel, which is split into two parts to reduce straylight, and a visible channel. Both channels have a two-dimensional CCD as detector. Polarization of the incident light is scrambled. For in-flight calibration, OMI can measure sunlight, and onboard white-light and LED sources.

Specular and diffuse reflectance (BRDF) of black absorbing coatings, meant to be used for the HIFI instrument aboard the FIRST satellite, has been studied in the sub-millimetre region (0. l

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FLEX is a scientifically driven space mission to provide demonstration/validation of the instrumentation and technique for measuring the natural fluorescence of vegetation in the Fraunhofer lines. The payload consists of high spectral resolution (0.1-0.3 nm) CCD imaging grating spectrometer with two channels: one in the red (648-664 nm)and one in the blue (39 1-438 nm) for working with several Fraunhofer lines. The across track FOV is 8.4°; ground spatial resolution is better than O.5x0.5km2. To increase the SIN ratio a steering mirror will be used, if necessary, to "freeze" the image and also to provide 4° across track depointing. Calibration is made by viewing the sun via a diffuser plate switched into the telescope field of view. A separate CCD camera will allow cloud detection and scene identification. A TIR radiometer will provide simultaneous surface temperature measurements.The spacecraft, overall mass estimated at 200kg, is derived from the ASI-MITA bus which provides all the necessary subsystems and stabilized platform. By use of on-board storage, ground requirements for satellite control and data link are minimized; the possibility of local stations for real time reception/distribution is also envisaged. Provisional orbit characteristics are: LEO sun synchronous, 500-900km altitude. Priority will be given to highest revisit frequency on a sufficient number of selected test sites.Keywords: Fraunhofer line detection, imaging spectrometer, fluorescence. -INTRODUCTIONFluorescence of vegetation is directly linked to photosynthesis and thus to light transformation and utilization for biomass production. Since many factors act on photosynthesis efficiency and photosynthetic capacity, at short term (stress factors: temperature, water, nutrients, ..) and long term (environmental factors: global air temperature, available PAR radiation, atmospheric composition, ..) fluorescence signal is thus highly specific of vegetation function, stress and vitality 2, 3, 4, Observation and measurement of fluorescence from space would significantly enhance our capability to monitor vegetation state and quantify biosphere processes and interactions. Although solar induced fluorescence is a very weak signal, its detection is possible using the Fraunhofer lines of the solar spectrum, a method that can be used from a satellite, as was already suggested some 25 years ago 6, 7, 8, 9 Since this time, development in optical imaging spectrometers and space technology makes this technique feasible. In a companion paper (this conference) the rationale and scientific motivations for a fluorescence space mission -FLEX -Fluorescence Explorer -recently proposed in response to ESA call for Earth Explorer Opportunity Missions, are discussed. This paper addresses the technical characteristics and mission elements: instrument concept I spacecraftl mission operations and implementation of the FLEX project, focussing on the Fraunhofer imaging spectrometer. -GENERAL MISSION CHARACTERISTICS2.1 Scientific requirements: the scientific payl...

At present there is an increasing interest in remote sensing of aerosols from space because of the large impact of aerosols on climate, earth observation and health. TNO has performed a study aimed at improving aerosol characterisation using a space based instrument and state-of-the-art aerosol retrieval algorithms, based on requirements for up-to-date regional and global aerosol transport models. The study has resulted in instrument specifications and a concept design for aerosol detection from space. Based on the study the main requirements for a dedicated aerosol spectrometer are: a spectral range from 330-1000 nm with a spectral resolution from 2 nm (UV) to > 30 nm (NIR), observation in at least 3 polarisation directions (Stokes parameters) over a field of view (FOV) in swath direction of > 114 degrees and observation in at least 3 viewing directions (backwards, nadir, forward). The spectrometer design is a prism imaging spectrometer using a single detector array to measure the complete spectra for 2 polarisation directions. In this way the requirements for each viewing direction can be met with only 2 detector arrays. The system has a modular set-up, which makes the implementation of, for example, a change in the number of observation directions very simple. The basic requirements to discriminate between aerosol types are currently only met POLDER, that combines multiple view angles with polarisation. The DARE concept shows an attractive potential for the development of next generation aerosol sensors.