The authors report the results of a measurement of the Rayleigh scattering cross section of methane, nitrogen and carbon dioxide using a pulsed laser beam. In a similar study Skowronek and Alayli (1979) reported a variation in the cross section with the duration of the laser pulse. In this work the authors have been unable to reproduce Skowronek and Alayli's result and conclude that there is no effect due to the pulse duration. Their measurements agree with the classical cross section within the experimental error (+or-10% to 15%).
Large area (50cm2) thin film, band pass filters have been constructed to provide four wavelength bands for the Wide Field Camera telescope on the ROSAT satellite. The filters consist of a polycarbonate substrate coated with one of, carbon, beryllium, or aluminium, additionally a tin/aluminium filter is also available. These provide wavelength bands of mean wavelength 100, 140, 180, and 600 angstroms respectively. This paper describes manufacture, and qualification details in the context of filters launched at ambient pressure, with a very stringent requirement for opacity, at around 1800A, of better than 1O_8 of the filter area. Measures taken to protect filters against erosion by low earth orbit atomic oxygen are also briefly presented. Calibration procedures and results are discussed together with comparison of measured transmission profiles with those derived from published absorption coefficients over the range 40 to 2000 Angstrom.
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