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Over the past 20 years, gas filter correlation radiometers (GFCR's) have made important contributions to our knowledge of the atmosphere by providing remote measurements of a number of gas species from aircraft, balloon, and spacecraft platforms. Though GFCR's have many attractive features , these instruments are generally mechanically complex, often requiring rapidly moving mechanical parts. A new GFCR concept has been reported by Sachse et al. 1 According to this concept a polarization modulator is used in conjunction with a polarization beamsplitter as a solid-state optical switch to rapidly alternate the path of incoming radiation between the two GFCR's optical paths (i.e., the paths containing the gas correlation and vacuum cells). Because this concept does not require rapidly moving parts, it has several potential advantages for remote sensing from space, including high reliability, efficiency and long operational life time. |
