Ultraviolet imaging polarimeter for observing polar mesospheric clouds

George M. Lawrence; Gary E. Thomas; Richard A. Kohnert; James C. Westfall

doi:10.1117/12.187561

30 September 1994 Ultraviolet imaging polarimeter for observing polar mesospheric clouds

George M. Lawrence, Gary E. Thomas, Richard A. Kohnert, James C. Westfall

Proceedings Volume 2266, Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research; (1994) https://doi.org/10.1117/12.187561
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

To study the polarization of sunlight scattered from polar mesospheric clouds (PMC) and the Rayleigh scattering from the upper atmosphere, we designed, constructed, and flew an ultraviolet imaging polarimeter (UVIP). A rocket-borne experiment, the UVIP consists of: an f/2 baffled telescope with a focal length of 76 mm; a filter/polarizer wheel with spectral bandpass and UV polarizing filters; a diode image intensifier; a thermoelectrically cooled, self-scanned diode array; and driver-interface electronics. The three polarization measurements are at 265 nm (8 nm spectral bandpass). Also, an unpolarized filter at 190 nm (20 nm bandpass) provides the color ratio 195 nm/265 nm. The Earth's limb is imaged onto the 128 pixels of the detector, observing tangent heights of 40 - 150 km with a height resolution of approximately equals 2 km. Previous optical measurements of PMC ice crystals indicate the particle scattering is Rayleigh-like, suggesting very high polarizations. To measure PMC against the ambient Rayleigh scatter requires 1% precision in polarization. Since we accurately know the polarization of the Rayleigh background, the technique is self-calibrating. We present the design of this instrument and example data from two rocket flights.

Citation Download Citation

George M. Lawrence, Gary E. Thomas, Richard A. Kohnert, and James C. Westfall "Ultraviolet imaging polarimeter for observing polar mesospheric clouds", Proc. SPIE 2266, Optical Spectroscopic Techniques and Instrumentation for Atmospheric and Space Research, (30 September 1994); https://doi.org/10.1117/12.187561

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