The SAGE III experiment is the latest in a series of satellite-based instruments utilizing the self-calibrating solar occultation technique to monitor aerosols and trace gases in the atmosphere. SAGE III is being considered for flight on the Earth Observing System (EOS) NASA polar platform B and as a payload in non-sun-synchronous and lower inclination orbits. This paper will describe the SAGE III instrument and potential coniributions to monitoring global change and other EOS objectives. Uses of these data will be illustrated with SAGE I and II long-term ozone, aerosol, and water vapor data.The SAGE III instrument design is based on the previous SAGE-series instruments with the addition of a CCD linear array detector to provide sufficient spectral resolution for improving species identification, aerosol and cloud characterization, and wavelength calibration. This change and other design improvements allow nighttime measurements using lunar occultation geometry, atmospheric density measurements making the species retrieval independent of other data sources, and extension of the altitude range of the measurements into the lower atmosphere. Near global measurements will be made of aerosol and cloud characterisücs and high vertical resolution profiles of temperature and key chemical species such as ozone, water vapor, nitrogen dioxide, nitrogen trioxide, and chlorine dioxide. Investigations of the spatial and temporal variability of these species will be conducted to understand their role in biogeochemical and hydrological processes and atmospheric chemistry. The self-calibrating characteristic of the occultation measurement technique will also allow the determination of long-term trends in water vapor, aerosols, ozone and other species of key importance in understanding climate change.
The diffraction of a light beam by two orthogonal traveling ultrasonic waves in water under Bragg angle incidence is described. It is shown that under low index modulation, only the zero order (0, 0), the two minus one orders (−1, 0 and 0, −1), and the cross minus one order (−1, −1) predominate in the diffraction process. Equalization of the four beam intensities, which is required in a two-component cross-beam laser Doppler velocimeter system, can be achieved with the transducers being driven at low power levels.
SAGE III is part of the Mission to Planet Earth's (MTPE) Earth Observatory System (EOS) with a first launch in the summer of 1998. SAGE III will provide long term monitoring of atmospheric species such as ozone and aerosols which play an important role in global environmental and climatic changes. This paper will briefly describe the goal of the SAGE III experiment, the instrument design, and the development of the processing algorithm for routine data processing to produce scientifically important data products for the science community.
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